vibrational spectra of some organometallic complexes

VIBRATIONAL SPECTRA OF SOME

ORGANOMETALLIC COMPLEXES

'/IB!V\TIONIŒ; SPEC7P-A OF sor-m . -

T Rl\N SI T l ON ME T i\L

ORGANOHE'I'ALLIC CmlP:r.JE~~;::S

Ph.D.

Gabriel George Barna

ABSTRc'\.CT

Chemistry

Department

The vapour phase and solution i. r. spectra of Mn (CO) 4NO

have been investigated in the 5250-33 cm- l region. The spectral data are in accord with a C3v trigonal bipyramidal geometry for

the molecule. Complete vibrational assignments have been

proposed. These assignments are supported in part by a simple

force constant calculation. The ionization potential of this

complex has been determined by mass spectrometry.

A ne,., route has been developed for the synthesis of

Fe(CO)2(NO)2. ~le soluLion i.r., far-infrared and Raman spectra substantiate further the previously assigned fundarnentals of

this species. Assignments are also proposed for the low

frequency modes of bm of the organophosphorus derivatives that

have been investigated. These assignments verify experimentally

the postulated frequency ranges of the Fe-C-O and Fe-N-O

fl.lndarnentals.

Partial vibrational assignments have been put forvlard for

the i. r. and P.aman spectra of the cyclic àiene Group VI 1~ !netal

complexes, (C7HaHl(CO)4· 'Ihe deviations in the observed spectra, in the v(C-O) regions, from what is expected on the basis of

J

C2v geometry, are explained by accidentaI degeneracies. Fermi

resonance arguments have unequivocally designated the coordinated

v (C=C) modes. The !'l-C-O fundamentals ha.ve been attributed to

certain frequency ranges, while the v (M-olefin) modes have been

assigned specifically. The norbornadiene ligand apparently

undergoes no change in stereochemistry upon coordination.

Limi 1:ed vibrational assignments have also been suggested

for the i.r. and Raman spectra of [(COD)RhCI]2' [(COD)CuCI]2

and (COD)2CuCI04' For the last compound, a novel structure

has been proposed on the basis of available spectral data.

The first vibrational assignments for thiocarbonyl complexes

have been achieved for CpMn(CO)2CS and Cp Mn (CO) (CS)2' The

Mn-C-S stretching and bending modes occur at similar positions

and with comparable intensities to the analogous Mn-C-O funda

mentaIs. ~A "slo~..," rotation of the rine; has been postulated ta

cause the apparent clecrease in the symmetry of both the Cp-Mn

and Mn(CO)2CS moieties in solution.

The vibrational spectra of transition metal carbonyl-

nitrosyl cOITlplexes have been investigated. For Hn(CO) 4NO,

in the vapour phase and in solution, a C3v molecular geometry

and complete vibrational assignments have been proposed. The

ionization potential of this cornplex has also been determined

by mass spectrometry. A new synthesis of Fe(CO)2(NO)2 has

been developed. The i.r. and Raman spectra of this complex

anà sorne of i ts organr)phosphorus deri vati ves, ha'le also been

s·tudied.

Partial vibrational assignrr.ents ha.ve been put fOr\vard

for the i.r. and Raman spectra of olefin complexes such as

(NBD)M(CO)4' [(COD)HCI]2 and (COD)2CuCI04. The C=C and metal

ole fin stretching fundamentals are discussed and assigned. A

structure is postulated for the last compound.

The first vibrational assignments for thiocarbonyl

complexes have been achieved for CpHn(CO)2CS and CpI1n{CO) (CS}2'

resulting in the identification of the IOvl-frequency Mn-C-S

fundamental vibrations.

RESUME

L'étude des spectres infra-rouge du 1'-ln (CO) 4NO en phase

vapeur ou en solution a été confinée dans la région 5250-33 cm- l

Les résultats concordent avec une géométrie trigonale bi-

pyramidale C3v de la molécule. On propose une attribution

compléte des vibrations, supportée en partie par un sirnple calcul

de constante de force. Le potentiel d'ionisation de ce complexe

fut déterminé par spectroscopie de masse.

Une nouvelle méthode de synthèse du Fe(CO)2(NO)2 fut mise

au point. Les spectres i.r., i.r. lointain et Raman sur

solutions supportent les attributions fondamentales précédemment

reporteés de cé composé. On propose également les attributions

correspondant aux modes de basse fréquence de deux des dérivès

organophosphorés qui ont été étudiés. Ces attributions vérifient

expérimentalement les intervalles de fréquence postulés pour les

vibrations fondamentales de Fe-C-O et Fe-N-O.

L'attribution de vibrations partielles est avancée pour les

spectres·i.r. et Raman des complexes cyclodiènemétal du groupe

VI A, (C 7Ha)M(CO)4. On explique les déviations du spectre

observé dans les régions v (C-O) , par rapport aux résultats

prévus pour une géométrie C2v ' par un phénomène de dégénérescence

accidentelle. La résonance de Fermi met, sans équivoque, en

relief les modes de coordination v (C=C). Les bandes fonda-

mentales M-C-O ont été attribuées à certaines régions de

fréquence tandis.que les modes V (M-oléfine) ont été attribuées

spécifiquement. Le ligand norbornadiéne semble ne pas changer

de stéréochimie lorsqu'il est coordonné.

Un attribution vibrationnelle limitée est suggérée pour les

spectres i.r. et Raman de [(COD)RhClJ 2 , [(COD)CuClJ 2 et

(COD)2CUCl04' Pour ce dernier composé, une nouvelle structure,

se basant sur les données spectrales à notre disposition, est

proposée.

La premiére attribution vibrationnelle des complexes

thiocarbonyles a été effectuée pour le CpMn (CO) 2CS et le

CpMn (CO) (CS) 2 . Les vibrations de valence et de déformation

du Mn-C-S apparaissent dans des régions similaires et avec des

intensités comparables aux vibrations fondamentales analogues

du Mn--C-O. Pour expliquer la diminution dans la symétrie des

deux composés Cp-Mn et Mn(CO)2CS en solution, on a postulé la

présence d'une "lente" rotation du cycle.

....

VIBR1\TION2\L SPECTRZI. OF SOHE

'l'Ri\..l\JSI'l'ION rrLETl'.L

O~(Gp.~'W:mThLLIC C0l-1PLEXES

Gabriel George Barna

.!-\. 'l'~1e3is Sllbmi t tcd to the FacuL:y cf

Graduate Studies and Research at

McGill University in Partial Fulfillment

of the Requirements for the

Degree of Doctor of Philosophy

Fro~ the Inorgru1ic Chemistry Laboratory

under the Supervision of

Dr. :;:.8. Butler

~lcGill University,

Montreal, Quebec.

@ Gabriel George Barna

----- - -------.

1973

"------ --

Septernber 1972

Î

To My Parents

TABLE OF CONTENTS

ACKNOHLEDGENENTS

LIST OF ABBREVIATIONS

LIST OF TABLES

LIST OF ILLUSTRATIONS

PART l

METAL CARBONYL-NITROSYL COMPLEXES

CHAPTER 1. INTRODUCTION

CHAPTER 2. LOt-J FREQUENCY VIBRATIONAL ASSIGN.1'-lENTS FOR

METAL NITROSYL CO!-1PLEXES

A. METlI-.L CARBONYL-NITROSYL COl-1POUNDS

B. OTHER METAL NITROSYL COMPLEXES

CHAPTER 3. NIT ROSYLTETRACARBONYIJ.1ANGANESE (0)

A. INTRODUCTION

B. EXPERIMENTAL

1. Vibrational Spectra

2. !-1ass Spectra

C. RESULTS AND DISCUSSION

1. Vibrational Assignments

PAGE

v

vi

vii

x

1

3

3

5

Il

Il

13

13

15

16

20

a. c-o and N-O Stretching Vibrations 20

b. Low Frequency Vibrations (700-

350 -1 cm ) 34

c. Low Frequency Vibrations Below

150 cm -1 29

i

2. Force Constant Calculations

3. Mass Spectroscopie Investigation

D. CONCLUSION

CHAPTER 4. DINI'I'ROSYLDICARBONYLIRON(O) AND SŒ-1E

DE RIVA'l'IVES

A. INTRODUCTION

B. EXPERIMENTAL

1. Syntheses


C. RESULTS fu~D DISCUSSION

D. CONCLUSION

PART II

SELECTED CYCLIC DIENE CŒ\1PLEXES OF

CHROHIUH, HOLYBDENUM, 'l'iJNGSTEN, IRON A.~D COPPER

PAGE

43

44

49

52

52

53

53

55

57

69

CHAPTER 1. INTRODUCTION 73

CH]I.PTER 2. REVIEiil OF VIBRATIONAL ASSIGNHENTS FOR METAL-

OLEFIN COMPLEXES 75

CHAPTER 3. TETRACARBONYL1.~ORBORNADIENEMETF_L (0) COHPLEXES 82

A. INTRODUCTION 82

B. EXPERH1ENTAI ..


1. Norbornadiene

2. Vibrational Assignrnents of Norbornadiene

83

84

84

Complexes 90

ii

a. C-O Stretching Vibrations

b. C=C Stretching Vibrations

c. Low Frequency Vibrations

PAGE

102

104

109

3. Geometry of Free and Complexed Ligand 113

D. CONCLUSION

CHAPTER 4. 1,5 -CYCLOOCTADIENE CO,l\1PLEXES

A. INTRODUCTION

B. EXPERHillNTAL


1. l, 5'-Cyclooctadiene

2. Vibrational l.ssignments for [( COD) RhCl] 2

and [ (COD) CuCl] 2

a. C=C Stretching Vibrations

b. H-Cl Stretching Fundamentals

c. M-L Stretching Vibrations

116

117

117

118

119

119

125

134

135

136

3. Vibrational Assignments for (COD)2CuCI04 137

D. CONCLUSION

PART III

7T-CYCLOPENTADIENYL!·1ANGANESE (I) THIOCARBONYLS,

CpMn(CO)2CS AND CpMn(CO) (CS)2

CHAPTER 1. INTRODUCTION

CHAPTER 2. EXPERH1ENTAL

CHAPTER 3. RESULTS AND DISCUSSION

A. RING VIBRA~IONS

B. Nn-C-O AND !-1n-C-S VIBRATIONS

iii

148

149

151

153

153

172

CHAPTER 4. CONCLUSION

BIBLIOGRAPHY

CONTRIBUTIONS TO KNŒ'iTLEDGE

ERRATA

iv

PAGE

182

183

192

194

AC1:N0l-1LEDGEI'lENTS

The author \'iishes to thank Dr. 1. S. Butler for his guidance

and encouragement, the latter being especially invaluable in

times of seemingly overwhelming crisis. His I,varm friendship

made the author's sojourn at I-lcGill most pleasant and rewarding.

The following are thanked for their specifie contributions

to this work:

Mr. W.A. Budd for the mass spectra,

Mr. A.E. Fenster for the componnds CpMn(CO) 2CS and

CpIvln ( CO) (CS) 2 '

Mr. R.J. Gale for the synthesis of (COD)2CuCI04'

t-1iss. D.A. Johansson for the (NBD) M(CO) 4 complexes.

The author is thankful to his wife, Betty, for her limitless

patience and perseverance in the typing of this thesis and the

arranging of the Figures.

The author reco9nizes the benefits he derived from tha

occasionally relevant, but perpetually stimulating discussions

with the other members of the laboratory.

The National Research Council of Canada is thanked for the

award of a Bursary and a Scholarship.

v

LIST OF ABBREVIATIONS

Spectral

\'1 - weak

lU - medium

s - strong

v - very

p - totally p01arized

p - polarized

dp - depolarized

p - depolarization ratio

m'i-v - millülatt

nm - nanometer

eV - electron volt

v - stretching mode

ë - bending mode

Chemical

HCBD - hexachlorobutadiene

COD - I,S-cyclooctadiene

NBD - norbornadiene

COT - 1,3,5,7-cyclooctatetra.ene

Cp - cyclopentadienyl

vi

J

LIST OF 'J'ABLES

T/I.BLE PART l PAGE

1. STRETCHING P.ND BEN DING FUNDAMENTJ\L FREQUENCIES OF

TRANSITION HETAL NITROSYL COtvlPLEXES (cm -1) • 8

II. DISTRIBUTION OF NORIl.t.AL 1-i0DES FOR l'ln (CO) 4~W 20

III. SYMHETRIES OF THE FUNDMlliNTAL MODES OF Mn (CO) 4NO

IV.

V.

(C3v

SYMHETRY) •

OBSERVED INFRARED ABSORPTIONS OF !lin (CO) 4NO

TEr1PERATURE STUDY IN THE v (C-O) AND v (N-O)

FUNDAf'.1.ENTAL REGIONS (cm -1) •

-1 (cm ).

VI. EXPECTED Fl~D OBSERVED OVERTONE Ai'\ID CŒIBINA'l'ION

FREQUENCIES OF Mn(CO)4NO IN THE 5250-3500 cm- l

22

23

32

REGION (CC14

SOLU'rION) • 33

VII. EFFECT OF SOLVENTS ON THE FREQUENCY OF v5

, THE al

Mn-N STHETCHING FUNDA!llENTAL (cm -1) • 36

VIII. CO!l'lPARISON OF THE FUNDAHENTAL FREQUENCIES OF -1

Hn (CO) 4NO J..ND Fe (CO) 5 VAPOURS (cm ). 40

IX. OBSERVED I~D CALCULATED v(C-O) FUND/ll1ENTALS (cm- l ). 43

X. C-O FORCE CONSTANTS OF CARBONYL-NITROSYL CŒ1PLEXES o

(mdyn/A) • 44

XI. ORDER OF DECREASING AB UN DAN CE OF Mn (CO) 4NO

FFAGMENTS

XII. FREQUENCY SHIFTS OF THE Fm~DAMENTAL MODES OF THE

Fe(NO)2(CO)L COMPLEXES (cm- l ).

XIII. VIBRF.TIONAL SPECTfu"\ OF THE PPh3

DERIVATI\I"ES OF -1

Fe(CO)2(NO)2 (cm ).

vii

45

62

63

TABLE

XIV.

XV.

INFRARED FREQUENCIES OF THE P(OMe) 3 DERIVATIVES

OF Fe (CO) 2 (NO) 2 (cm -1) .

-1 FUNDAHENTAL FREQUENCIES OF Fe(CO)2{NO)2 (cm ).

PART II

PAGE

66

70

XVI. ASSIGNED v(C=C) FUNDAHENTALS OF ETHYLENE COHPLEXES

(cm -1) • 76

XVII. SHIFT IN BANDS RELATED TO v(C=C) VIBRATIONS 78

XVIII. lI.8SIGNED FUNDAMENT1...LS OF f.lETlI.L-CYCLOOCTADIENE

SYSTEMS (cm-l ). BO

XIX. ASSIGNED FUNDAHEN'l'ALS OF VARIOUS HETAL-OLEFIN

COMPLEXES (cm- l ). 81

XX. VIBRATIONAL FREQUENCIES OF NORBORNADIENE (cm- l ). 88

XXI. INFRARED FREQUENCIES OF THE (NBD)M(CO)4 COMPLEXES

(cm-l ) . 95

XXII. -1

RlI.MA.N FREQUENCIES OF THE (NBDHl( CO) 4 COHPLEXES (cm ). 98

XXIII . SYH~,ETRIES OF THE FUNDAHENTAL I-IODES OF THE

(NBD)M(CO)4 COMPLEXES. 102

XXIV. FREQUENCIES RELEVANT TO THE FERMI PESONANCE

CALCULATIONS (cm-1 ). 108

XXV. ASSIGNMENT OF FUNDAMENTlI.L .MODES OF THE (NBD) N(CO) 4

COMPLEXES (cm- l ). 112

XXVI. MOLECULAR PAR1J-1ETERS FOR BONDED .P-.ND NONBONDED NBD. 114

XXVII. -1

VIBRATIONAL FREQUENCIES OF 1,5-CYCLOOCTADIENE (cm ). 121

XXVIII. DISTRIBUTION OF NOrurlAL MODES OF COD.

XXIX. SY~~ETRY AND ACTIVITY OF THE [(COD)RhCl]2 and

[ (COD) Cuel] 2 FUNDAHEN'rl'.LS.

viii

124

127

Tl\BLE PAGE

XXX. VIBRATIONAL FREQUENCIES OF [{COD)RhCl]2 AND -1

[(COD) CuCl] 2 (cm ). 131

XXXI. VIBRKfIONAL FREQUENCIES AND ASSIGN~œNT OF -1

(COD)2CuCI04 (cm ). 140

XXXII. NUMBER OF VIBRATIONAL MODES FOR 'l'IlE POSSIBLE

STRUCTURES OF (COD)2Cu(I) ION. 144

XXXIII. CORRELATION DIAGRk~ FOR THE Td h~D C3v PERCHLOP~TE IONS. 146

XXXIV. ASSIGNED FUNDl'J1ENTAL HODES (cm -1) OF [( COD) RhC1] 2

A..~ D [( COD) CuCl] 2 • 147

PART III

XXXV. SPECTRAL PREDICTIONS FOR CpNn(CO) 2CS. 154

XXXVI. INFRARED FREQUENCIES .Po.ND ASSIGNI1E~Jl'S FOR -1

[CpFe(CO) 3]BPh 4 AND [CpFe(CO) 2CS]BPh'1 (cm -) • 155

XXXVII. SOLID STATE IKFRARED AND RAI".J',N DA'l',,; (cm -1) AND

ASSIGNHENTS FOR CpMn(CO)2CS Jl..ND Cp?-ln(CO) (CS)2. 161

XXXVIII. INFRARED DATA AND COMPLETE VIBRATIONAL ASSIGNNENT

XXXIX.

XL.

XLI.

XLII.

FOR CpHn(CO)2CS IN SOLUTION.

CONPARISON OF THE RING VIBRATIONS (cm -1) OF

Cp!1n (CO) 3 A~D ITS THIOCARBONYL DERIVATIVES.

-1 COMPARISON OF \) (C-O) vJITH \)2 A..l\JD \)7 (cm ).

CORRELATION BETWEEN Mn (CO) 3 AND ITS CS

DERIVATIVES

VIBRATIONAL FREQUENCIES AND ;....sSIGNr-1EtYfS FOR -1

SOLID CpNn(CO) 3 (cm ).

XLIII. EFFECT OF SOINENTS ON SO~1E OF THE FUNDAHEN'TAL

-' MODES OF Cpr-1n(CO)2 CS (cm .L.).

ix

164

168

170

174

175

181

LIST OF ILLUSTRATIONS

FIGURE PART l

1. Possible trigonal bipyramidal structures for

Mn(CO)4NO •

PAGE

12

2. Polarization orientations in the spectrophotometer. 15

3. Infrared spectrum of Mn (CO) 4NO vapour (8 m.~ Hg) • 18

4. Infrared spectrum of ~~(CO)4NO (CS 2 solution). 18

5. Far-infrared spectrum of Mn(CO)4NO (benzene

solution) •

6. Infrared spectrum of Mn(CO)4NO illustrating the

3000-2200 and 1500-700 cm- l overtone and

combination regions (CS2

solution) •

7.

8.

Overton'e and combination spectrum of Mn (CO) 4NO

in the 5250-3800 cm- l region (CC14

solution).

Infrared spectrum of Mn(CO)4NO in the c-o and

N-O stretching regions (cyclohexane solution) .

9. c-o stretching modes for r-In (CO) 4~W (C3v symmetry) i

only one component of the doubly degenerate e mode

shown.

10.

Il.

12.

13.

Approximate description of the normal modes of

Fe(CO) 5 and Mn(CO)4NO.

+ Clastograms for three fragments of the Ivln (CO) 4NO

ion.

Plot of abundance vs. electron energy(eV) for

CS2

+ and Mn(CO)4NO+.

Infrared spectrum of Fe(CO)2(NO)2 (CS 2 solution).

14. Far-infrared spectrum of Fe(CO)2(NO)2 (benzene

solution) .•

x

18

21

21

21

30

37

48

50

59

59

FIGURE

15.

16.

Raman spectrum of Fe(CO)2(NO)2 (CS 2 and CC1 4 solutions) .

Solid state Raman spectrum of Fe(CO) (NO)2PPh3'

17. Infrared spectrum of Fe(NO)2[P(OMe) 3]2 (neat

liquide

PART II

18. Possible metal-olefin bonding schemes.

19. Infrared spectrum of norbornadiene (neat

liquid) .

20. Raman spectrum of norbornadiene (-196°C).

21. Infrared spectrum of (NBD)Cr(CO)4 (CS 2 and

C2 C1 4 solutions) •

22.

23.

24.

25.

26.

27.

28.

29.

30.

Raman spectrum of (NBD)Cr(CO)4 (solid state).

Infrared spectrum of (NBD)MO(CO)4 (CS 2 and

C2C1 4 solutions) •

Raman spect~um of (NBD)Mo(CO)4 (solid state).

Infrared spectrum of (NBD)lV(CO) 4 (Nujol and

HCBD mulls) •

Raman spectrum of (NBD)W(CO)4 (solid state).

Bar-graph representations of the (NBD)M(CO)4

infrared spectra. (M = Cr,Mo,W)

Bar-graph representations of the (NBD)M(CO)4

Raman spectra. (M = Cr,Mo,W)

Probable structure of the (NBD)H(CO)4 complexes.

Vapour phase structure of .norbornadiene.

31. Infrared ·spectrum of 1,5-cyclocctadiene (neat:

liquid) .

xi

",

PAGE

60

61

61

79

86

86

91

91

92

92

93

93

94

94

101

113

120

FIGURE

32. Raman spectrum of 1,5·-cyclooctadiene (-196°C)

33. Molecular structures for [(COD)RhCl]2 and

[ (COD) CuCl] 2 .

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

Infrared spectrum of [(COD)RhCl]2 (Nujol and

HCBD mulls) .

Raman spectrum of [(COD)PbCl]2 (solid state).

Infrared spectrum of [(COD)CuCl]2 (KBr pellet).

Raman spectrum of [(COD)CuCl]2 (solid state).

Bar-graph representations of the infrared spectra

of COD and its complexes.

Bar-graph representations of the Raman spectra of

COD and its complexes.

Infrared spectrum of (COD)2CUC104 (KBr pellet).

Raman spectrum of (COD)CuCl04 (solid state).

+ Five possible structures for the (COD)2Cu ion.

Postulated structure for (COD)2CuCI04.

PART III

Infr'ared spectrum of Cp Mn (CO) 2CS (vapour phase) •

Infrared spectrum of CpMn(CO)2CS (CS 2 solution).

46. Far-infrared spectrum of Cpr-1n (CO) 2 CS (benz~ne

solution) •

47.

48.

49.

Raman spectrum of CpMn(CO)2CS (solid state).

Infrared spectrum of CpMn(CO) (CS)2 (solid state).

Raman spectrum of CpMn(CO) (CS)2 (solid state).

xii

"

PAGE

120

126

128

128

129

129

130

130

139

139

143

145

158

158

158

158

159

159

'-

FIGURE PAGE

50. Bar-graph representations of the infrared

spectra of CpMn(CO) 3 and its CS derivatives.

51. Bar-graph representations of the Ra~an spectra

of Cp Mn (CO) 3 and its CS derivatives.

xiii

160

160

PART l

~ŒTAL CAill10NYL-NITROSYL COMPLEXES

- l -

CHAPTER J. INTRODUCTION

At the beginning of the research to be described in this

part of the thesis, several revie"ls on the physical and chemical

properties of transition metal nitrosyl complexes had already

1-4 been published . In the sections dealing \-Ji th the vibrational

spectra of these complexes, reference was frequently made to

the lack of Raman data. Although vibrational assignments can,

and have, been made solely on the basis of i.r. data, it was

pointed out that the current ava.ilability of commercial laser

Raman spectrophotometers would stimulate research into more

complete vibrational studies of these systems.

In the present work, i t ",as planned to carry out Raman

studies on a variety of transition rnetal ni trosyl cOTI!plexes.

The new spectral evidence so obtained would then be used to

confirm or reject sorne of the previous assignments that had

been made purely on the basis of i.r. data. It was also hoped

to extend the vibrational assignments of sorne simple metal

carbonyl-nitrosyl complexes of the type, M(CO)x(NO)y. Previously,

only Fe(CO)2(NO)2 5 and CO(CO)3N06-a had received any significant

attention.

Vibrational assignments have been proposed for a variety

of transition metal carbonyl complexes by a nurrber of independent

research groups. From these assignments, certain trends in the

low frequency modes have become apparent. Firstly, the rnetal

carbon'yl bending modes (8 (M-C-O)] generally occur at higher

9 '0 frequencies than the metal-carbon stretching modes [v(H-C)]- , .....

2

Second, the former modes are more intense in the i.r. while

the latter are more intense in the Raman. One aim of the

present study \vas to ascertain if there are sirnilar trends for

the low frequency modes of metal nitrosyls.

Before the results of the author 's own work on the spectra

of metal nitrosyl complexes are presented, the published

vibrational assignments for metal nitrosyl cornpounds are

reviewed briefly (Chapter 2). Next, the complete vibrational

assignment of Mn(CO)4NO, together with details of a force

constant calculation and a rnass spectroscopie investigation,

are given in Chapter 3. Finally, spectroscopie data for

Fe(CO)2(NO)2 and sorne of its derivatives are presented and

discussed in Chapter 4.

- 3 -

CHAPrrER 2. L01'J FREQUENCY VIBRl\TIŒJAL ASSICNr-1ENTS FOR

HETAL NITROSYL CŒ-IPLEXES

This revievl is divided into blO sections: metal carbonyl

nitrosyls and metal nitrosyl complexes containing ligands other

than CO. The approach \vill be an historical one. The review

is considered to be complete until June l, 1972. The proposed

vibrational assignments for the low frequency region (below

700 cm-l) are tabulated at the end of this review. The very

low frequency modes (in the 150-50 cm-l region) of the type

o (C-M-N) are not considered, owing to the scarcity of assignments in this region ..

A. METAL CJl.RBONYL-NITROSYL COMPOUNDS

The first complete vibrational assignment for any metal

nitrosyl complex was reported by MeDowell gt aZ. (MHy)6 in

1961. These workers investigated the i.r. spectrum of CO(CO)3NO in the vapour phase. Together with additional data from isotopie substitution (13 CO and 15NO) and supported by the vibrational

assignments for Ni (CO) 4' the follovTing results were obtained. The stretching fundamental, v (Co-N) , was assigned to the band at "594 cm-l, higher than -the bending mode, o(Co-N-O) ëit 565 cm- l

However, the normal coordinate calculation performed by the

vlilson FG method showed a marked diserepancy betvleen the

caleulated and observed values for these biO modes. Moreover,

the potential energy distribution indieated that the v(Co-N)

and the 0 (Co-C-O), as vlell as the 0 (Co-N-O) and v (Co-C)

- 4 -

fundamentals, are considcrably mixed.

The i. r. and Raman spectra of liquid Co (CO) 3NO were

investigated by Mann et aZ. 7 in 1967. On the basis of

admittedly indefinite depolarization ratios, the v(Co-N) mode

was reassigned to a medium intensity Raman band at 627 cm- l

A force constant calculation again shm'led considerable mixing

between the 6 (Co-N-O) and 6 (Co-C-O) modes.

The compound was also studied in the solid state by

Cataliotti et al. 8 in 1971. 'l'he i.r. active fundamentals were

assigned taking into account the observed solid state correlation

spli t·tings of the bands. In this s tudy, th C 0: 1 \) (Co-N)

-1 fundamental was assigned to a band at 612 cm , i. e. in agree-

-1 ment with the original vapour phase value of 594 c~ of MHY.

This assignment is not really inconsistcnt ,vi th the Raman data

of Mann because in Raman spectra al modes are generally found

to be the most intense. On this basis, i·c could have been

anticipated that the strong Raman band at 603 cm- l (594 cm- l in

the vapour) is indeed the a, ·v (Co-N) mode.

From the spectroscopie data of the three independent

research groups, it can be concluded that for the vapour phase

-1 v(Co-N) is at 594 cm ,while 6 (Co-N-O) is lower in energy at

565 -1 cm Furthermore, the intensity of the ô mode is more than

ten times grèater than that of the v mode.

The vibration al spectrum of the C2 carbonvl-nitrosvl v . -

complex, Fe(CO)2(NO)2' \'las assigned5 in 1968. For this species,

the al and b l v (Fe-N) modes ,';ere assigned to the vapour phase

bands at 619 and 658 cm- l respectively; ~ .. lhile the al' li l and b 2

- 5 -

6 (Fe-N-O) modes \Vere assigned to bands at 654, 648 and 614 cm-1

respectively. These assignments were based on i.r. data and

were supported by a complete force constant calculation. The

relative intensities of the absorptions due to the two types of

mode are again markedly different. Both the syrnmetric and

asyrnmetric stretching modes appear as \veak shoulders on the

sides of the very strong peaks assigned to the bending

fundamenta1s.

The on1y other carbony1-nitrosyl mo1ecu1e that has been

investigated is Na [Fe (CO) 3NO} 11. The s tretching mode l ',) (Fe-N) ,

was assigned te the band at 664 cm-1 in the solid state, at a

higher frequency than the ô (Fe-N-O) mode at 630 cm-1 . Both

these modes occur at a higher frequency ·than the corresponding

fundamentals of the isoe1ectronic molecule, CO(CO)3NO. Of course,

this is related to the effect of the negative charge on aIl of

the modes of this anionic species - the extra e1ectron enhancing

the Fe-N and Fe-C bond orders. A force constant ca1culation

yie1ded a' good fit between the observed and calculated values

for these modes. As in the previous cases, the stretching mode

appears as a very weak shou1der on the side of a very strong

bending fundarnenta1.

The data discussed in this section are summarized in Table I.

B. OTHER METAL NITROSYL COMPLEXES

12 In 1963, Fe1tham and Fate1ey assigned the fundamentals

of CpNiNO by ana10gy wi th those of Co (CO) 3NO. Thus, the H-N-O

- 6 -

-1 fundamentals \'Vere assigned as follows: v(Ni-N) 640 cm

6 (Ni-N-O) 570 cm-l. Raman data13 later eonfirmed that the

stretching fundamental \-las at 640 cm -l, while the bending mode

-1 had to be reassigned to a band at 490 cm •

Comprehensive studies have been carried out for a series

of HX5 (NO) complexes. In 1966, the al v (Ru-N) mode of

K2 [RuIS (NO)] was assigned14 to a band at 598 cm -l, while the

e 0 (Ru-N-O) fundamental VoTas assigned to a doublet at 573 and

552 em- l (the splitting caused by solid state effeets). Two

years later, Miki 15 prepared similar eompounds lof chromium and

ruthenium with normal isotopie abundances, and with enriched

l5NO • The· i. r. shifts betv!een the fundamentals of the two speeies

were eompared with those caleulated on two t~eoretieal three-body

models, M-N-O and M-O-N. The models indieated definitely that

the ni trosyl group \-las eoordinated to the mctal atom through

the ni trogen, \-lÏ th the stretehing mode al\vays oeeurring at a

higher frequeney than the bending mode. Prior to this work, the

linkage had been taci tly assumed to be M-N-O in ni trosyl complexes.

The validity of this model was/eonfirmed by applying it to

Co (CO) 3NO. Assuming HHY 1 S assignment of v (Co-N) and 0 (Co-N-O) ,

the calculated isotopie shifts based upon this thre.e-body model

\'Vere found to match elosely the observed isotopie shifts, as well

as the ones caleulated by MHY using the complete nine-body model.

Low frequency'metal nitrosyl fundamentals have also been

assigned 'for a series of [H (CN) 5 (NO) 1 n- complexes, chiefly on

the basis of i.r. data alone. In 1967, polarized icr.

- 7 -

measurements on a single crystal of Na2 [Fe(CN)S(NO)] 02H20, led

, l' 16 to unequlvoca asslgnments . The o(Fe-N-O) and v (Fe-N) modes

-1 were assigned to bands at 662 and 650 c~ , respectivelyo These

assignments are supported by two more recent studies (single

crystal Raman17 and lSNO substitution18). The bending mode

has a calculated and observed lSNO isotopie shift of 16 cm- l

while the shift in the stretching fundamental is only 2

The relative magnitudes of the isotopie shifts of these

-1 cm

f d 1 h b f ' d b h' t' ~ 19 un amenta save een con lrme y yet ot er lnves 19a~ors .

In K3 [Mn(CN) S(NO) ], the bending and stretching fundamentals

20 -1 were found to be accidentally degenerate at 660 cm 0 In the

dihydrate, perturbation spli ts this degeneracy: 6 (I-1n-N-O) is at

-1' -1 663 cm , and v (Mn-N) is at 653 cm 0 This assignment was

contradicted in 1971 by a more thorough study by Miki et aZ. 21

of the compounds K3 [Hn (CN) SNO] , K3 [!-ln (CN) s~JO] 02H 20 and

Ag2 [Mn(CN)SNO]. Using the same three-body calculaticns as

mentioned above lS , the M-N-O arrangement was again favouredo The ,

stretching modes, v (Mn-N) , were assigned at higher frequencies

than the bending modes, 0 (Mn-N-O) 0 In the unhydrated potassium

saI t, the bending and stretching fundamen·tals are accidentally

degenerate at 659 cm-li however, 15NO substitution splits this

degeneracy such that v(~~-N) is at 661 cm-1 and 6(Mn-N-O) is at

648 cm-l. In every case, the assignments were substantiated by

calculationo

AlI the assignments disGussed above are. sUInrnarized in 'l'able 10

Complex

K3 [Cr (CN) 5NO ] .H2 O

[Cr(NII 3 ) 5NO] C1 2

[Cr(NH 3 )5NO ] (CI04 )2

K3 [Mn (CN) 5NO ]

15 K3 [Hn (CN) 5 NO]

K3 [Mn(CNj 5NO ] .2H 2 O

15 K

3[Mn(CN)5 NO].2H 2 O

TABLE I.

STRETCHING AND BENDING FUNDAI-1ENTAL FREQUENCIES

OF TRANSITION METAL NITROSYL COMPLEXES (em- 1 ).

v (M-N) 15 (M-N-O) r-1edium

620 s 610 sh a,b ,e

573 s 535 m a,b,e

577 vw 531 s a,b ,e

659 s 659 s a,b ,e

660 s 660 s a,b,e

661 w 648 s a,b ,e

663 m 663 fi a,b ,e

653 663 a,b ,e

660 w 651 w} a,b ,e 646 m

Study Ref.

IR 15

IR 15

IR 15 00

IR 21

IR 20

IR 21

IR 21

IR 20

IR 21

J

Fe(CO)2 (NO) 2 619 sh(a1 ) 654 s (al) d IR 5

658 sh (b1 ) 648 sh (b1 )

614 s(b2 )

Na [Fe (CO) 3NO] 664 w 630 vs· bic IR Il

Na2 [Fe(CN)SNO] .2H2O 650 m 662 5 e IR 16

657 ms 666s e R 17

652 m 663 m e IR 18

K2

[RuC15

(NO)] 606 w 588 s a ,b ,e IR 15

K2 [RuBr5 (NO) ] 606 'Il 573 s a ,b ,e IR 15

[NEt 4 ] [RuBr5 (NO) ] 609 'Il 573 w a IR 14 '-0

K2 [RUI 5 (NO) ] 598 vw 573 vw} a IR 14 552 w

Co(CO)3NO 594 w 565 vs d IR 6

602 rn 564 s f IR 8

612 rn 568 vs g IR 8

627 m 566 'Il f R 7

CpNiNO 640 m 570 Vvl f IR 12

640 rn 484 m f R 13

640 vs 490 s g R 13

L_ --'

CS 2 [OsC1 5 (NO) ]

Cs 2 (OsBr5 (NO)]

K[IrC1 5 (NO)]

K [IrBr 5 (NO) ]

a Nujol mull

b HCBD mull

C KBr disk d vapour

e single crystal

f l' 'd J.qUl

g frozen solid

h microcrystalline solid

615 vw

612 (7)

617 w

615 (3)

567 ~l

560 (2)

562 w

558 (2)

595 w a

598 (2) h

586 m a

585 (1)' ·h

578 w a

580 w h

550 m a

550 w h

IR

R

IR

R

IR

R

IR

R

19

19

19

19

19

19

19

19

1-' o

j

- Il -

CH~.PTER 3. * NITROSYLTETRJ."\CARBONYU1J..NGJllJESE (0)

A. INTRODUCTION

During the past few years, several transition metal

carbonyl-ni trosyl complexes, isoelectronic vli th binary metal

carbonyls, have been discovered. A vast nunmer of the carbonyl

compounds and their derivatives have been investigated by means

of vibrational spectroscopy. In contrast to this, the spectra

of the carbonyl-nitrosyl complexes - with the exception of

Co (CO) 3NO, Fe (CO) 2 (NO) 2 and Ha [Fe (CO) 3NO] - have recei ved li ttle

attention. In particular, the i.r. spectrum of the five-

coordinate complex, ~ln (CO) 4NO, has been investigated only in

the C-O and N-O stretching regions 23 ,24 On the basis of three

C-O stretching absorptions observed in tetrachloroethylene

solution, a C3v trigonal bipyrarnidal structure, with the NO

group in one of the axial positions (Figure la) , has been

proposed for the complexe

A lm ... temperature (-110°) three-di!l1ensional X-ray study of

Mn(CO)4NO, frozen into its crystalline state, has been reported

25 recently • This study indicates that under these conditions

the most reasonable structure for the complex is a "trigonal

bipyramid wi th C2v rather than C3v symmetry, i. e. , 'id th the

NO group occupying one of the equatorial positions rather than

an axial one (Figure lb) •

* Part of the vlcrk described in this Chapter has already been

published22 .

(a)

o N

C3v

- 12 -

o

(b)

o c

oc;,,_f ,/ Mn ~~~ ~~-~ NO './ ------Cv-------

c o

Figure 1. Possible trigonal bipyramidal structures

for Hn(CO)4NO.

The purpose of the present study ~vas to obtain i. r. an.d

Raman data throughout the whole spectral region and to propose

a complete vibrational assignment for the molecule. In

addition, it was hoped to establish its molecular geometry in

the vapour phase and in solution.

- 13 -

B. EXP:CRHJENTAL

N-t t j'OS !lUe t Y'oc:aY'b oiZy Z manpanes e (0 )_' I-1n (CO) 4 NO, was

prepared and purified by the method of King26 The purity

of the deep red liquid \Vas established by the absence of any

impurity peaks in its mass spectrum and in the c-o and N-O

stretching regions of its solution infrared spectra.


The instrumentation used to record the vibrational

spectra of aZZ the compounds that are considered in this

thesis will be·described here. Solvents, unless otherwise

noted, were a1ways of spectrograde quali ty.

'rhe far-infrared spec·tra were recorded on a Perkin

Elmer FIS-3 spectrophotometer using 1.0 mm polyethylene

solution cells. The spectra were calibrated against the low

frequency spectrum of water vapour; the frequencies are

-1 precise to ±4 cm

Infrared spectra in the 4000-350 -1

cm region \'lere

recorded on a Perkin Elmer 521 spectrophotometer using the

1653.3 and 667.3 cm- l bands of water vapour as calibrations.

-1 '-1 The errors on the frequencies are ±4 cm (4000-2000 cm

region) and ±2 cm-1 (2000-350 cm-l region). The C-O ~~d

N-O stretching ::cegions were aiso recorded on a Perkin Elmer

337 spectrophotometer coupled to a Texas Instruments Servo-

Ri ter N.odel II expansion scale recorder. These spectra \vere

- 14 -

calibrated against the 2143.2 cn- l band of CO and the 1583.1 -1 cm

band of polystyrene i the observed frequencies are precise to

-1 ±l cm • A matched pair of 1.0 mm KBr solution cells were used

for all the spectra. The vapour spec·trum \Vas obtained using

a 10 cm gas cell, fi tted wi th KBr \',indŒvs.

The 5250-3800 cm- l region was recorded on a Perkin Elmer

350 spectrophotometer using 10 cm pyrex solution cells. The

4288.3 cm-l band of CO \Vas useCi to calibrate the spectrai the

precision of the frequencies is ±5 cm- l •

Raman spectra were obtained on a Jarrell-Ash Model 25-300

laser Raman spectrophoton.eter, equipped with a Coherent Radiation

krypton ion laser. Although the laser erni ts eight exciting lines,

only the 647.1 nm (red) and 520.8 nm (green) ones were used. The

maximum effective power of t.hese lines at t.he sample was about

100 and 50 rntJ, respectively. The plane of the incident beam was

always perpendicular to the plane of the slit. The polarization

of the incident and scattered beams are diagrammed in Figure 2.

The IIparallelll and "perpendicularll planes used for the depolar-

ization measurements are also shown in the Figure. To nullify

any orientational anisotropy in the rnonochromator~ depolarization

measurements were always obtained with a polarization scrarnbler

placed directly before the slit. The peaks were calibrated

against the 730.1 and 533.7 cm- l peaks of indene. Sar.lples were

rUl1 either as solutions in a quartz solution cell or as powdered

solids in capilla~J tubes.

.- 15 -

l Il

b

s

Figure 2. Polarization orientations in the spectrophotometer.

a - polarization of incident beam

b - plane of slit

i - incident beam

s - scattered beam

S - sample

l - plane of polarization for "perpendicular"

measurements

- plane of polarization for "parallel" measurements

2. M.ass Spectra

Mass spectra were obtained on an AEI MS902 mass

spectrometer. Samples ~lere generally run at a nominal energ-j

of 70 eV.

For the ionization potential (IP) determination, a

special procedure ~las employed. The voltage across the source

was monitored by means of a DANA Module 550 digital voltmeter.

Since this voltmeter was floating on 8000 volts, it was

insulated careiully to prevent it from grounding. The

'--'

- 16 -

vol t.meter \-ïas pmvered by a 12 V oc battery connected to a CDE

Powercon Model 12B8 AC generator.

The clast.ograms were obtained as follows. The compound

vias vapourized into a large bulb connected to the ionization

chamber through the cold inlet system. The amount of compound

leaking into the source was constant throughout the experi~ent.

The spectrometer was focused onto a given mie peak. As the

voltage across the source was varied, the nu~er of ions

arri ving at the analyser was read étirectly off the "Collector"

scale on the instrument. At given intervals, the voltage was

reset to sorne specific value to check the reproducibility of

numbers read off the IICollector". By this method, the nurnbers

were found to be reproducible (± 10%). Since the "Multiplier"

setting was kept constant, the relative abundances of the

different fragments are on the same scale.


~ving to the extreme air and light sensitivity and poor

scattering properties of the complex, aIl attempts to obtain

vapour phase, solution· or solid state laser Raman spectra

using the 647.1 nm krypton excitation, failed. Even when

frozen onto an evacuated cOld-finger at -196°, the compound

decomposed rapidly. However, despite the lack of Raman data,

vibrational and structural assignrncnts could be achieved for

this species.

The cow.mon structures for a five-coordinate molecule are

- 17 -

a square pyramid or a trigonal bipyramicl. The former can be

* eliminated on the basis of group theoretical arguments. The

latter is generally found in five-coordinate complexes. More-

over, the isoelectronic species, Fe(CO)S' has this configuration.

Two trigonal bipyramidal structures are possible for

Hn(CO) 4NO. The ~~O group can be axially or equatorially situated

giving rise to C3v and C2v molecular sYl®letries, respectively.

The twenty-seven normal modes, for both of these geometries, are

tabulatedaccording to their vibrational activities in Table II.

These fllildamentals are expected to appear in three spectral

regions:

(i) ·2150-1700 cm-l : v (C-O) and v (N-O)

(ii) 750-350 cm -1: v (!l'm-C) and \) (Mn-N)

o (1fu-C-O) and 0 (Mn-N-O)

(iii) below 150 cm- l c-r·ln-C and C-r.'In-N deformations

In addition to these fundamentals, è. number of overtone and

combination bands are expected, particularly in the 5250-2200

and 1400-700 cm- l regions.

The vapour phase and CS 2 solution i.r. spectra of Mn(CO)4NO

in the 4000-350 -1 region shm-m in Figures 3 and 4,. cm are

respectively. The far-infrared spectrum (400-33 -1 c~ ) in

benzene solution is sho\'1n in Figure 5. These spectra are in

* For C4v symmetry (apical NO group): 6al

(IR/R) + a 2 (inact.)

+ 4b l (R) + 2b2

(R} + 7e(IR/R). For Cs symmetry (eql1atorial NO

group): 17 a' (IR/R) + 10a 1/ (IR/R) •

- 18 -

(A) Figure 3. Infrared spectrum of Nn(CO)4HO vapour (8 mm Hg).

(B) Figure 4. Infrared spectrum of Mn(CO)4NO (CS 2 solution).

(C) Figure 5. Far-infrared spectrum of MnCCO)4NO (benzene

solution) •

J

r (A)

! i 1

j 1

L_

--~-_._~

(--.-

~-~ r~ -'--

1

1

1

r~

3~';'1l!"~~:----_. ___ .1 § <:

(B)

3:JNV lllWSN't/èil

(C)

o o ~

o o C\J

o o CV)

- 19 -

accord \vi th the general predictions made ab ove . Furthermore,

i t is readily apparent that the vapour phase and CS2

solution

spectra are remarkably simple and almost identical. A band

-1 count over the entire 4000-33 cm region yields about fifteen

bands which most probably can be regarded as fundamentals. In

view of this, the C3v structure is favoured for !-1n (CO) 4NO both

* in the vapour and in solution. It seems somewhat unlikely that

nine of the fundamentals expected for the C2v structure would be

too weak to be observed or accidentally coincident with other

fundamentals. In addition, almost aIl the i.r. active

fundamentals expected for the carbonyl-nitrosyls, CO(CO)3N07 and

5 Fe(CO)2(NO)2 ' are observ~ble directly. Presumably, crystal

packing forces are responsible for !J'm(CO) 41'W adopting the C2v

structure in the solid state.

Based on a C3v molecular geometrj, the symmetries of aIl

the fundamentals are collected together in Table III.

The observed frequencies for the vapour phase and solution

* Rapid intramolecular isomerization Ylithin this geometry, of 27 the type established by Udovich and Clark for the compounds

Mn (NO) (CO)4_x(PF3)x' has not been observed. For these PF3 derivatives, as \vell as some solvolysis products, the conclusion

that isomerization was occurring was based on the e:{Cess number

of v (C-O) and v (N-O) bands. No snch res'..ll t was observed for

~1n (CO) 4NO. It shoulà be noted that \"lhile this above mentioned

isomerization \"las developed for a model Ylith an equatorial NO

group·, the results can be explained as well, and for sorne cases

better, using a rnodel with an axial NO group.

Ho1ecu1ar Synunetry

- 20 _.

TABLE II.

DISTRIBUTION OF NORNAL HODES

FOR Hn (CO) 4NO

Symmetry of normal modes and their spectral activity

10al(IR/R) + 3a2 (R)

+ 7b l (IR/R) + 7b 2 (IR/R)

8a l (IR/R) + a2

(R)

+ ge (IR/R)

No. of i.r. active modes

24

17

i.r. spectra of ~~(CO)4NO, together with the assignments

proposed on the basis of C3v synunetry, are given in Table IV.

Typical spectra illustrating the various overtone and combination

regions are shown in Figures 6 and 7.

1. Vibrational Assignrnents

a. c-o and N-O Stretching Vibrations

Four i.r. active fundamentals [C-O stretching (2a1 + e)

and N-O stretching (al)] are expected for Hn(CO)4NO in the

-1 2200-1700 cm region. The i.r. spectrllm in cyclohexane

solution for this region is shm,m in Figure 8.

- 21 -

(A) Figure 6. Infrared spectrun of ~n(CO)4NO illustrating the

3000-2200 anQ 1500-700 crn- l overtone and

cornbination regions (CS 2 solution) .

(B) Figure 7. Overtone and combination spectrurn of Mn(CO)4NO

in the 5250-3800 crn- l region (CC1 4 solution).

(C) Figure 8. Infrared spectrurn of Mn(CO)4NO in the c-o and

N-O stretching regions (cyclchexane solution) .

-----=~-]

1 Lg I~

r ~o

o 'E

lis ____ ilr~

(A)

() o ,n

'"

5000 4500 4000 3800 cm-1 1

CB)

w u z <i tt--2 V)

z <t: 0:: t-

( C)

- 22 -

TABLE III.

SYNMETRIES OF THE r"UNI?PJ;iENTAL HODES

OF Mn (CO) 4NO (C3v SYMi'lETRY)

Fundamenta1 Symmetry No. i. r. bands

v (C-Q) 2a1 + e 3

v (N-O) al 1

v (lo·L'1. - C) 2a1 + e 3

v (Mn-N) . al 1

o (Hn-C,""O) al + a2 + 2e 3

o (Mn-N-O) e 1

o (C-Mn-C) 2e 2

o (C-r1n-N) al + 2e 3

-1 . The very strong band at 1766 cm ~s clearly due to v3 ,

the al N-O stretching mode. The weak band at 1730 cm-1 is

most probab1y the 15NO isotope band resulting from

15 . Mn(CO)4( NO), present in natura1 abundance (0.4%). The 15N_O

stretching vibration in Co (CO) 3 (15NO) is shifted dO\lm simi1ar1y

by 36 cm-1 from the 14N_O stretching vibration in CO(CO)3(14NO)6.

The position of the v(N-O) frequency indicates that it is a

Vapour (8nun Hg)

3546 w

c CS 2 soln.

3977 w

3942 vw

3861 v\'/

3503 m

TABLE IV.

OBSERVED INFRARED ABSORPTIONS

OF Mn(CO)4NO (cm-1 )a,b

CC1 4 soln.

5230 '.!w

4183 m

4103 s

4068 s

4026 m

3979 s

3943 w,sh

3864 w

3780 Vw

3715 vw

3503 vs

Cy c10hexane soln.

Assignment

3v3

2v1

N

vI + v 10 LoJ

v 1 + \12

2v10

\1 2 + v 10

2 \.1 2

v 1 + v 3

v 3 + v10

v 2 + v 3

2v3

j

2763 W 2761 W vI + vII

2747 W 2744 W vI + v 12

2679 w,sh v 10 + vII

2666 w 2666 w v 10 + 'J 12

2639 w 2631 w v 4 + v 10 ' v 2 + vIl

2609 vw 2602 vw vI + vS' v 2 + v 4

2566 vw 2560 ID 2558 ID vI + v 13

2522 V\v 2520 vw vI + v 14

2487 w 2477 fi 2476 ID v 10 + 'V 13

2444 w,br 2425 5 2426 5 V3 + VII

2400 vw,sh 2401 vw,sh v2 + v14 ' l'V v 3 + v 12 ,t>.

2372 'l-l,sh 2374 vw,sh v 2 + v6 ' v 7 + v IO '

v 3 + \'4

2325 vw,sh 2333 v\'/ ')2 + v 7

2310 vw,sh v 3 + vII - vIS'

v3 + vII - v16

2288 ID 2289 ID v3 + Vs

2206 vw 2202 ID v 3 + v13

2132 T,lW VI + V17 ' vI + v18

.J

21.16 vw,sh

2111 s 2098 s 2094 s

2092 sh 2087 sh 2082 sh

2020 vs. 2027 vs 2021 vs

1996 vs 1990 vs 1974 vs

1970 sh

196:; m 1946 sh 1945 w

1900 vvw

1870 vvw 1865 sh 1865 sh

1836 vw

1781 vs 1761 vs 1757 vs

1749 w,sh 1728 sh 1732 sh

1490 ID

J.445 sh 1450 w

2099 s

2088 sh

2058 vw

2023 vs

2018 sh

1982 vs

1947 w

1869 w

1766 vs

1730 w

v 10 + v 15 ' v3 + v 7 '

v 10 + v 16

vI

v(13C- O)

v2 + v 8

v10

vI - v 8

v2

vI - vIS' vI - v16 v (13C_O)

v10 - vIS' v 10 - v 16

v 3 + vIS' v3 + v16

v2 - v 8 v 3 v (15N_O)

vI - v 4

vI - v12

t\J U1

j

1420 sh

1365 sh

1356 w 1359 m

1313 vw 1318 w

1257 w 1260 m

1214 w 1214 w,sh

1187 m,br. 1186 m,br

10 B9 vw 1075 w 1069 m,sh

1047 w 1049 m,sh

10?1 moJ 1015 s 1019 s

990 w,sh

930 w,sh

907 vVl 899 m,sh 901 m,sh

B81 vw 875 m 880 s

815 mol 815 m

748 vw 751 w

914 vw

873 vw

820 vw

753 vw

vI - vII

v 10 - v 12

v 10 - vII

2v 11

2v12 , v 4 + v 12

2v 4

v 5 -1- vII

vII + v 14 ' v 4 + v 13

2v5 , \)6 + vII'

v 12 + v 14

v7 + vII

v7 + v 12

v5 ;- v 14

2v13

\)13 + v 14 ' v 5 + \)7

V 7 + v 13 ' v6 + v 14

vII + v15 ' vII + v 16 ,

V6 + V7

r.,) 0"\

J

715 w,sh

657 vs 653 vs 640 vs,br

641 vs

615 vl,sh

546 sh

. 524 m 523 s 532 m,br

489 w,sh

456 m 459 s} 456 s

417 vw,sh 417 w,sh

398 vw 398 w

357 \-1

308 m,br

270 m,br

647 vs,br

554 vw

531 s} 517 s

460 s} 454 s

428 sh

397 m

3:;9 m

2v 7 , v 4 + vIS'

v 4 + v 16

rl8

v 12

v 4

v 13 + vIS' v13 + v 16

Vs v13 - v 17 , v 13 - v18

v 13

v 14

v6

v-I

V14 - VIS' v14 - v16

v6 - vIS' \)6 - v 16

l'V -.J

j

L

102 m,br

66 w

52 w

v 15 ' v 16 \)

8

v17 ' v 18

a Where necessary each 1ist of frequencies has been divided into severa1 sections and the

intensities given are relative to the most intense peak within each section; s = strong,

TIl = medium, w = weak, sh = shou1der, br = broad, v very.

b The c-o and N-O stretching region (2200-1700 cm-l ) has a1so been recorded in n-hexane

solution. The observed frequencies are; 2097 m, 2088 sh, 2024 vs, 2018 sh, 1980 vs, 1947 w,

and 1767 vs.

c The far-infrared frequencies (below 350 cm- l ) given in this list were recorded in benzene

solution. N 00

- 29 -

* neutral NO group that is bonded to manganese.

-1 file three very strong bands at 2099, 2023, ruld 1982 cm

are assigned to vI' v lO ' and v 2 ' -i.e., the al (radial), e, and

a l (axial) C-O stretching modes, respectively (Figure 9).

These assignments are supported by the appearance of weak l3co

isotope bands due to Mn(CO)3(13 CO)NO molecules, present in

na-tural abundance (3% 13cO-radial a..'1d 1% l3co-axial). ~'i1hen

l2CO . ln an H-CO system is substituted by 13CO , a dmvmv-ard shift

-1 31 -1 of about 45 çm is expected for a frequency of 2000 cm •

This is the maxiumum shift anticipated, and vïOuld be obtained

only if aIl the CO groups involved in a particular vibr~tional

mode of the parent mole cule were substituted by l3co . When the

* Due to the three-electron bond in free nitric oxide, the

nitrosyl group can be coordinated in three possible valence

states: NOT, NO, or NO. A linear M-H-O bond is generally

viewed as being due to NO+, vlhile a coordinated NO- species

gives rise to a bent ~1-N-0 grouping. The stretching fundamental

of the coordinated ni trosyl group shmvs a marked dependence on

the electronic configuration of this group. The correlation is

evident from the comparison of X-ray data with the v(N-O)

frequency for. the follovJÏng three dihydrated species.

° M-N-O ~-l\; (l~)

Na2 [Fe (CN) SNO] .2H2O 178.3° 1.63

1<3 [Ivln (CN) SNO] .2H 2O 174.3° 1.66

K3 [V(CN) SNO] .2H2O 171.4° 1.66

N-O (A)

1.13

1.21

1.29

-1 (N-O) cm

1939

1725

1530

Ref.

28

29

30

The N-O bond 1engt..l1s and stretching frequencies are obviously

i!1dicative of the fact that in the -three molecu1es, the

ni trosyl groups are bonded as 1'10+, NO and IK'- respectively.

The M-N-O bond angles are a1so in line vii th the previously

postulated idea.

- 30 -

------------_._------------,

a, (axial) e

Figure 9. c-o stretching modes for Mn (CO) 4NO (C3v sylluuetry) ;

only one component of the doubly degenerate e mode shown.

parent molecule is only partially substituted, the shifts would be close to 45 -1 cm for those vibrations whi.ch involve mainly the substituted CO groups, near zero for those involving only

unsubstituted CO groups, and of intermediüte values for

32 vibrations involving.both types of CO groups .

The 35 cm-1 shift (44 cm- l in CS2

) between the band at

1982 cm- l and the isotope band at 1947 cm-1 indicates that the

1982 cm- l band is due mainly ta the vibration of the axial CO

group, i. e., the al (axial) c-o stretching mode ('v 2) .

vii th respect to the s·tructural assignment " there are hm

pie ces of information to be obtained from the spectrum in the

J

- 31 -

-1 2000 cm region. First, the three peaks observed in the v(C-O)

region are in agreement ",i th the nUIPber expected for C3v

geometry. Second, the observed 35 cm- l isotopie shift (44 cm- l

in CS 2 ) is in itself strongly indicative of ê_ symmetrically

unique CO group. For the molecule of C2v geometry, there are

two sets of two synunetrically equivalent CO groups. For the

monosubstituted l3 co species, all the vibrational modes

involving the 13co group would still con-tain a 12co group.

Th us , an isotope shift of 44 cm- l would not be expected for

any of the fundamental modes. This presence of a unique CO

group further corroborates the C3v structure.

The relatively low intensity of the 2099 cm- l band

-1 compared to the bands at 2023 end 1982 cm suggests that this

band is due to the al(radial) c-o stretching mode (vI) because

this mode is expected to exhibit tl1e weakest i.r. activity33

Horeover, such a totally syrnnetric c-o stretching mode is always

the highest of aIl tl1e c-o stretching frequencies of a metal

carbonyl complex of any stereochernistry33. 7he sma11 shift

(11 cm -1) observed between the 2099 cm-1 band and the isotope

b d 2088 -l, d f 13 ub 't' , an at co ~s expecte or mono- CO s st~ ut~on ~n a

vibration involving three equivalent CO groups. Therefore, this

-1 observation also supports the assignment of the 2099 cm band

as vl

•

-1 From the ?.bove discussion, the assignment of the 2023 cm

band to the e c-o stretching mode (v 10 ) follows automatica1ly.

A variable ter.!perature study was undertaken on the spectrllirL

hexane soIn.

2097

2024

2018

1980

1766

- 32 -

TABLE V.

TEHPERATURE STUDY IN THE \i (C-O) and \i (N-O)

FUNDAJ.1ENTAL REGIONS (cm-1 )

cy c10hexane soIn. (-82°)

2098

2022

2018

1977

1765

hexane solid (-110°)

2098

2023

2018

1977

1767

of J.VI'.n (CO) 4NO in solution. Spectra \V'ere obtained in the 2000-

-1 1700 cm region at room tempe rature , for the solution at -82°,

and for the sarrv1e frozen into a solid solvent matrix at -110°.

The data are presented in Table V. Except for the fact that the

spectral features are sharpened at 10wer temperatures, thus

making the 2018 cm-1 shoulder more pronounced, there is no change

in either 'the band structures or their relative intensi ties •

This implies that the molecular geometry of the species is

unchanged under the conditions emp1oyed.

'l'he consistenc..-y of these assignments is 'lerified by tl1e

-1 overtone and combination spectrum in the 5250-3500 cm region.

AlI the predic,ted frequencies are observed (Table VI). That

TABLE VI.

EXPECTED AND OBSERVED OVERTONE AND COMBINATION FREQUENCIES OF

Mn(CO)4NO IN THE 5250-3500 em-1 REGION (CC14

SOLUTION).

VCO

VNO

VI v 10 v

2 \)3 a

2094 2021 1974 1757

\)1 4188 ca1"c 4115 ca1c 4068 ca1c 3851 calc

2094 4183 w 4103 s 4068 s 3864 w

\)10 4042 ca1c 3995 cale 3778 ca1c

2021 4026 m 3979 s 'V3780 vw

\.12 3948 ca1c 3731 cale

1974 3943 m,sh 3715 vw

v 3 3514 ca1c

1757 3503 vs

a The third overtone of this mode is a11mved and is expected at -1 -1 5271 cm ; it is observed at 5230 cm

w w

J

- 34 -

there is a rather close fit between the calculated and observed

frequencies is a good indication that the c-o and N-O

stretching vibrations are not too anharmonic. This is also the

case for Co (CO) 3NO 7 but not for Fe (CO) 2 (NO) 2 5 . The weakest

bands in the 5250-3500 cm- l region result from the combinations

of the N-O stretching mode with the three C-O stretching modes.

A siw~lar situation exists for the overtones and combinations

of the C-O and N-O stretching modes in CO(CO)3N07 and

5 Fe ( CO) 2 (NO,) 2 •

The other bands which appear in -1

the 2200-1700 cm region

as shoulders on the main bands or as very weak bands, particularly

in the vapour spectrum, are assigned to combination or difference

vibrations (see Table IV).

b. Low Frequency Vibrations (700-350 cm- l )

The i.r. active fundamentals expected for Mn(CO)4NO in

the 700-350 cm- l region are: Mn-N-O bending (e), Mn-N

stretching (al)' Mn-C-O bending (al + 2e), and Mn-C stretching

(2a l + e). The assignments proposed here are supported by the

pub lished assignrnents for Co (CO) 3HO 7 , Fe (CO) 2 (NO) 25 , and Fe (CO) 534

which have been substantiated by force constant calculations.

In particular, the Mn-N-O bending and Mn-N stretching vibrations

should arise at higher frequencies than the I-1n-C-O bending and

Mn-C stretching vibrations. Horeover, the 1·1n-C-O in-plane

bending mode (v12) should occur at a higher frequency than the

5 Mn-C-O out-of-plane bending modes (v 4 and v 13 ) • AIse, the

- 35 -

relative intensities of the peaks can be used to give sorne

indication as to their possible origine It is now a weIl

established fact that the ô (lvl-N-Q) modes are generall~l more intense than the v(l.l-C) modes in the i.r. In the assigned i.r. spectra of the three carbonyl-nitrosyl systems considered in

the Review, (vide sup:r>a p. 9) a similar trend was noted for the metal-ni trogen vibrations vi z., the 0 (N-N-O) modes are much more intense than the v (M-N) modes.

On the basis of the preceeding arguments, the two fundamentals arising from the !-111-N-O g:.couping are expected at the high

frequency end of this region. Noreover, the v (lm-N) l'uode is anticipated to be one of the weaker bands. This particular

fundamental, however, can be assigned independently from other experimental evidence.

A solvent-effect study of the lm" freguency fundamentals

of Fe (CO) 2 (NO) 2 has s11mm that t..."1e Fe-N stre"cching modes shift to higher frequencies on going from the vapour to polar solvents, while the other modes remain alrnost unaffected or shift slightly

l . 5 to ower frequenc1es Infrared spectra of !-111 (CO) 4NO in CS 2, cyclohexane, CC1 4 , CHCI 3 , and acetone solutions indicate that

only the absorption at 524 cm- l in the vapour phase spectr~~ sho\'1s any appreciable solvent sensitivity. 'L'his band shifts to higher frequencies on going from ~~e vapour to polar solvents

(Table VII). Consequently, this rr.ode is assigned to the al ~m-N

stretching funda~ental (vS).

The highest frequency strong band in the vapour phase

1

a

- 36 -

TlillLE VII.

EFFECT OF SOLVENTS ON THE FREQUENCY OF VS'

THE al l'-1n-N STRETCHING FUNDAHENTAL (cm -1) .

Solvent V (Mn-N) V (vap.) -v (sol.)

Vapour 524

Carbon disulphide 523 +1

Cyclohexane 524 a 0

Carbon tetrachloride 532 -8

Chloroform- 537 -13

Acetone 573 -49

Average value of the bITO components of a doublet at 531 and

517 cm-l •

spectrum at 653 cm- l appears as a doublet (657 and 641 cm-l )

in the CS 2 solution spectrum. The 657 cm- l band is assigned

to the e Mn-N-O bending mode (Vll

) , while the band at 641 cm- l

is attributed to the e l'-1n-C-O in-plane bending mode (V12 ).

This last assignment is supported by evidence for the

isoelectronic and isostructural complex, Fe(CO)5. The e in

plane Fe-C-O bending mode (vll ) of this species, occurs at

646 cm- l • Observing the modes diagrarr@ed in Figure 10, it can

- 37 -

Figure 10. Approximate description of the normal modes of

Fe(CO)S and Mn(CO)4NO.

l

1

Fe(CO) 5 Mn (CO) 4NO Fe(CO)s !-1n (CO) 4NO

- 38 -

be seen that the axial groups do ~ot take part in this

fundamental vibration. Since the configuration of the

Equatorial plane is identical for the two species and

moreover, the masses of the iron and manganese atorns are

very similar, it is reasonable to expect that these modes

will occur at similar frequencies.

Theother Mn-C-O bending mode can similarly be assigned

by analogy with the bending modes of Pe(CO)r.. By comparison ::>

with the v7 mode of Fe(CO)5' the al (v 4) Hn-C-O bending mode

-1 i5 assigned to the weak band in the vapour spectrum at 615 cm

The three Hn-C st:cetching modes are expected to fall in

the region below 500 cm- l . The complimentary nature of the

C-O and M-C bond orders is weIl established. In vie\v of this,

the order of the al (radial) and the al (axial) Nn-C stretching

modes is expected to be opposite to that for the corresponding

C-O stretching modes. Moreover, both !1n-C stretching modes

should occur near 400 -1 cm • Consequently, the bands at 398

-1 and 357 cm in the CS 2 solution spectrum are assigned to v

6

and v 7 , respectively.

Since the e l-m-C stretching mode (v 14 ) of Hn(CO) 4NO is

similar to the e' Fe-C stretching mode (v 13 ) cf Fe . (CO) 5'

these two modes are expected te absorb in approximately the

same region. The v13 mode of Fe(CO)5 vapour falls at 431 cm-li

therefore, the weak band at 417 cm- l in the l\1...'1(CO) 4l\!û vapour

spectrum is assigned to v 14 •

- 39 -

-,1 By elimination, the 456 cm band is assigned to the e

(v13 ) Mn-C-O bending mode. This assignment is supported by

the expected position [higher than the v (r\1n-C) modes] and

intensi ty [greater than that of the v (r-1n-C) modes] of this

band. Also, it is split slightly into a doublet in CS 2 and

cyclohexane solution.

c. -1 Lmv Frequency Vibrations Below 150 cm

The i.r. active fundamentals expected for Mn(CO)4NO in

-1 the region below 150 cm are: C-Mn-C deformations (al + 2e)

and C-Mn-N deformations (2e). The far-infrared spectrum in

benzene solution (Figure 5) exhibits three bands in this

region at 102, 66, and 52 cm- l The 102 cm- l band is broad

and rather unsyrnrnetrical, ~vhile the other hw bands are

reasonably sharp.

The assignments proposed for this region must be regarded

as speculative because two of the modes expected are not

observed. By analogy with the v 14 ' vg , and vIS modes of

Fe(CO)S 33 which occur at 104, 72, and 68 -1 respecti vely34 , , cm

the three Mn (CO) 4NO bands are assigned in order of decreasing

frequency to vIS' v 8 ' and v17 • Since the e C-Mn-N.in-plane

5 ~ -1 deformation (V 16 ) is also expected ,1 to occur near 100 cm ,

the broad asyrnrnetrical band at 102 cm-l is attributed to this

mode as well as to vIS. The e C-Mn-N out-of-plane deformation

-1 (vIS) is anticipated in the neighbourhood of 50 cm '].'his mode

-1 is assigned tentatively, along with v17 ' to the band at 52 cm •

Normal mode

al Symmetry

v1 v2

v3

v 4 v 5

v6

v7

va

a" Symmetry û

v e 9

TABLE VIII.

COMPARISON OF THE FUNDAMENTAL FREQUENCIES

OF Mn(CO)4NO AND Fe(CO) 5 VAPOURS (cm- l ).

Mn(CO) 4NOa

Approx. Descrip.

C-O radial str.

C-O axial str.

N-Q str.

l'1n-C-O bend

~1rl-N str.

Mn-C axial str.

1-1n-C radial str.

C-Mn-C def.

Mn-C-Q bend

Freq.

2111

1996

1781

615

524

398

357d

66

Norma.l mode

al' Symmetry

vI

v2

v3 v4

a2

1 Symmetry

v 5

a2 " Symmetry

v6

v7

v 8

Fe(CO) b 5

Approx. Descrip.

C-O str.

c-o str.

Fe-C str.

Fe-C str.

Fe-C-O bend

c-o str.

Fe-C-O bend

Fe-C str.

Freq.

2117 "'" 0

1984

414

377

593c

2014

620

474

j

L

e Symmetry v9 C-Fe-C def. 72 f

v IO c-o str. 2020 e' Symmetry

vII Nn-N-Q bend 657 v IO c-o str. 2034

v 12 Mn-C-O bend 641 vII Fe-C-O bend 646

v 13 Mn-C-O bend 456 v12 Fe-C-O bend 544

\)14 . Mn-C str. 417 v13 Fe-C str. 431

vIS C-Mn-C def. 102 v 14 C-Fe-C def. 104

v16 C-Mn-N def. 102 g vIS C-Fe-C def. 68

v17 C-Mn-C def. 52 e" Symmetry

vIa C-Mn-N def. 52h V 16 Fe-C-O bend 487 c

vI? Fe-C-O bend 614

v 18 C-Fe-C def. 95

a Those frequencies below 150 cm- l are taken from the far-infrared data recorded in benzene

solution.

b Except \vhcre otherwise mentioned, the fundamental frequencies listed are those of

W.F. Edgell et aZ.~ Speatroahim .. 4ata~ 19, 863 (1963).

c From solid-state i.r. spectrum (ref. 34)

.f;:>.

f-'

.j

d In CS2

solution.

e This mode is i.r. inactive.

f From the laser Raman spectrum of the liquid [M. Bigorgne, J. Organometa~. Chem. 3 24, 211

(1970)].

g Presumable coincident with vlS •

h presumably coincident with v17 •

~ N

j

-- 43 -

TABLE IX.

OBSERVED AND CALCULATED

v(C-O) FUNDA1'1ENTALS (cm- l ).

Fundamental Observed Calculated

VI 2095 2093

vI ( l3CO) 2084 2086

v lO 2022 2022

v.., ... 1978 1979

v 2 ( l3CO) 1946 1946

The vibraticnal assignments proposed above for the

fundamentals in the three s2ectral regions are collected together

and compared with those of Fe (CO) 5 in Table VIII c

2. Force Constant Calculations

Force constant calculations were performed on the "CO

block" of Mn(CO)4NO, using the standard program of ., ,-

SchachtschneiderJo! modificd sligh tly by Dr. H.K. Spendjian

to run on the i-lcGill University IBH 360-75 computer. With

the nitrosyl group included in the calculation, convergence

cou Id not be obtained.

Using the assignment of the CO peaks proposed earlier

- 44 -

TABLE X.

C-O FORCE CONSTANTS OF

o Cl\Rl30NYL-NITROSYL COMPLEXES (mdyn/A).

1'-1n (CO) 4NO Fe (CO) 5 Fe (CO) 2 (NO) 2 Co (CO) 3NO

fC-O, eq. 16.69 16.57 } 16.92 16.55

fC-O, aXe 16.42 16.95

f 0.19 0.40 } CO,CO; eq. ,eq. 0.51 0.40 f 0.51 0.28

CO,COi eq. ,ax.

ref. 37 5 5

very good agreemen"t \.".as obtained betvleen the calculated and

observed frequencies. These l1urnbers are 1isted in Table IX.

No other assignment gave such a good correlation between the

t'VlO sets of frequencies. The resu1 ting force constants are

simi1ar to those obtained for re1ated species by more

sophisticated ca1cu1ations (Table X) .

3. ~ass Spectroscopie Investisation

F ' d' 38,39 d' 't' t t' 1* ragmentatlon stu les an lonlza lon po en la

* 'l'he term "ionization potentia1 11 shou1d strict1y be I!ionizaticn

energy" . However, since the former is the common1y employed

phrase, i t V/i1l be used in this thesis.

l

mie

055

169

83

141

197

85

41.5

113

III

55.5

69.5

139

- 45 -

TABLE XI.

ORDER OF DECREASING ABUNDANCE

OF !-1n (CO) 4NO FRAGMENTS

Ion

Mn+

[Mn (CO) 3NO] +

[l'ln (CO) ] +

Will (CO) 2NO] +

[Mn (CO) 4NO] +

[1-1nNO) +

[!-1n (CO) ] ++

[l'in (CO) NO] +

[Mn (CO) 2] +

[!-1n ( CO) 2] ++

[Mn (CO) ] ++ 3

[Mn (CO) 3] +

Relaotive Abundance

56

21

15

Il

10

7

5

4

3

2

2

1

determinations 40 have been carried out on several organometallic

complexes similar to Hn(CO)4NO. The ionization potentials of

CO(CO)3NO, Fe(CO)2(NO)2 and CpNiNO are 8.75, 8.45 and 8.50 eV,

respectively40. For both of the carbonyl-nitrosyls, the

- 46 -

[P - NO]+ ion concentration was negligible compared to that

of the [P - CO]+ ion.

The fragments obtained from electron bombardment of

Nn(CO)4NO, at 70 eV, are listed in Table XI in the order of

decreasing abundance.

As expected, the [P - NO]+ fragment is missing, in line

with other carbonyl-nitrosyls. Also, none of the doubly charged

ions contain the NO group. Two opposing trends are observed for

the order of the relative abundances of the two fragment types:

wi th and wi thout the NO group.

[Mn] + > > [Mn ( CO) ] + > > [!:4n ( CO) 2] + > [Mn (CO) 3] +

[Mn(CO)3NO]+»[Mn(CO)2NO]+>[~m(co) 4NO]+> [MnNO]+> [Mn(CO)N01+

The first trend is readily explained. As the NO group is

split off from the parent ion, the [Mn(CO) 4]+ ion fragments with

the successive 105s of the CO groups. The second trend cannot be

explained through the monotonic loss of any group. It seems to

suggest.that as long as the NO group is attached to the ionic

fragment, sorne other process, besides the simple loss of neutral

groups, may be occurring. Supportive of this suggestion are t.'l-te

non-characteristic clastograms obtained in the ionization

potential determination.

To obtain the IP of the parent ion, the ahundance of the

mie 197 ion was monitored as the voltage across the source was

gradually decreased. (The procedure is des cribed :).n detail in

the Experimental section). Whereas the resul ting curve was

- 47 -

expected to change monotonically, a condition for which the

Warren plot41 gives the value of the IP, well-defined sharp

peaks \vere observed. To determine whether this effect vIas

real or not, the s ame measurements \vere carried out for several

of the other ion fragments. The clastograms of the [P]+,

[P - CO]+ and [p - 2CO]+ ions are shown in Figure Il. It should

be noted that the ordinate represents the absolute, not the

fractional, abundances of the ions. A fresh sample, at a later

tirne, showed similar characteristic curves, indicating that these

curves are indeed reproducible.

There is indication for the step\vise unirnolecular decom-

position of Mn(CO)4NO. (Organometallic complexes, HMn(CO) 5 in

particular39 , have been shown to undergo such processes) •

* 2 r-ietastable peaks (m = rn2 Iml

) were found for the follmling steps:

[~ill(CO)4NO]+ --+ [Mn (CO) 3N01+ + CO

[Mn (CO) 3NO] + ~ [{\1n (CO) 2NO] + + CO

* rn = 145.0

= 117.6

The parallelism bet\veen the curves for the [Nn (CO) 4NO] + and

[Mn(CO)2NO]+ ions seems to be more than purely coincidental.

These curves suggest that there is sorne close interdependence

between these two fragments. There is not only a stepwise loss

of neutral CO groups as this -,vould gi ve rise to re lati ve

+ abundances of the three groups similar to those for the [Hn(CO) x]

fragments. It is felt that sorne unspecified secondary process

is responsible for the obvious intensi ty relationship bet"vleen the

two fragments. \'1h~ther this process is rea} , or just sorne curious

Figure 11.

- 48 -

+ Clastograms for three fragments of the Hn(CO)4NO

ion.

p+ - molecular ion, Mn(CO)4NO+

40

30 Q) u c 0 "0 C :J

..0 « 20

1 1

1 '10 1

1 1

1 1

1 1

1 1

1 1

1

1 1 1

10 30 50 70 Electron Energy (eV)

- t19 --

experiment.al artifact, remair.s to be established.

Further evidence for the fact that there is sorne other

process besides the straight loss of neutral CO groups, is found

in the value of the ionization poten·tial. The semilog curves

for the abundances of the parent ion, and. CS 2 + reference ion,

vs. the eV across the source, are shown in Figure 12. Carbon

42 disulphide has an IP of 10.1 eV • By inspection, the IP of

Mn (CO) 4NO is determined to be 11.5 ± 0.3 eV. This value is

considerably greater than the IP of other carbonyl-nitrosyl

systems ("'8.5 eV). This high value could also be an indication

of the fact that the appearance of the molecular ion is not due

to a simp18 ionization process.

These data, taken in conjunction, do indicate that further'

investigation is vlarranted into this phenomenon.

D. CONCLUSION

A complete vibrational assignment has been proposed for the

binary carbonyl-nitrosyl complex, .t-ln(CO)4NO. The i.r. data

obtained for the vapour and in solution dre interpreted best ih

terrns of a C3v trigonal bipyrarnidal structure rather than the C2v

one which is favoured for the complex in its crystalline state

at -110°C, on the basis of X-ray evidence. This conclusion is

based principally on the fact. that there are significantly fewer

fundamentals observed, than are expected for the C2v structure.

It is further supported by 13c-satellite evidence for a

syrrunetrically unique carbonyl group. A simple force constant

- 50 -

Figure 12. Plot of abundance vs. e'ectron energy(eV) for

CS 2+ and Mn(CO)4NO+.

p+ - rnolecular ion, Mn(CO)4NO+

w u z « o z

10

~ 1.0 «

9 Electron Energy (eV)

p+ !

14

- 51 -

calculation on the "CO block" of this molecule supports the

assignment of the v(C-O) modes and gives rise to force constants

in line with those of related species.

The ionization potential of Mn(CO)4NO has been determined

for the first time. The actual value is Il.5 ± 0.3 eV i.e. 1

significantly higher than the ionization potentials of related

carbonyl-nitrosyl complexes. A reproducible, but unexplained,

curious phenomenon has been observed for the fragmentation of

Mn(CO)4NO in the mass spectrcmeter. This process is postulated

to be one of the factors giving rise to such an unusually high

value of the ionization potential.

- 52 -

CHAPTBR 4. DINITROSYLDICl'-:.lffiONYLIP.ON (0) A~D SO!-lE DERIVA'J.'IVES

A. INTP.ODUCTION

As mentioned in the Review, there are fe\v Raman data for

metal nitrosyl complexes. From the author's own experience,

this is because metal nitrosyls generally give rise to po or

quality Raman spectra owing to their intense colour (usually

* deep red) and weak scattering properties.

In this Chapter, new vibrational data will be presented for

Fe(CO)2(NO)2 and a few of its derivatives. The Raman data are of

particular interest as they are the first ever obtained for iron(O)

nitrosyl complexes. In addition, the far-infrared spectrum of

Fe(CO)2(NO)2 has been recorded for the first time. The new

experimental evidence obtained provides support for the majority

of the previously published5 assignments for Fe(CO)2(NO) 2 but

places doubt on sorne others.

The low frequency spectra of four tertiary phosphine and

phosphite ceri vatives of Fe (CO) 2 (NO) 2 have been recorded in the

900-350 cm- l region. These data are among the relatively few

that have ever been measured in this spectral region. The general

practice in reporting the vibrational spectra of such compounds

is simply to list only the CO and NO stretching frequencies. A

* A Raman spectrum could not be obtained for the stable, y8llow

complex, [CPMn(CO)2NO]PF6. Since complexes of this colour are

usually ammeanable to Raman spectra, it appears that the

scattering property of this particular nitrosyl complex is the

limiting factor.

- 53 -

few vibrational assignments are proposed for the organophosphorus derivatives discussed here.

A new convenient route has been developed for the synthesis

of Fe(CO)2(NO)2. The method compares favourably with the most commonly used one of Hieber and Beutner43 •

B. EXPERIHENTAL

1. Syntheses

Di ni tY'OS 1/ Z. di c:aT'b ony Zi T'on (0), Fe (CO) 2 (NO) 2' was prepared b l th d . th [ ( , ] . 44 . t d' t Y a nove me 0 uSlng e Fe CU/

4H lon as an ln erme J.a e.

AlI operations were carried out strictly under nitrogen.

A mixture of 4 ml of Fe (CO) 5 (29 mmol) and 60 ml of

deaerated NH40H was stirred magnetically at room tempe rature

for 24 hr. The solution trJas then filtered and the [Fe (CO) 4H]

ion was precipitated by the dropwise addition of 5.1 9 of

(Et)4NCl (31 mmol) ~issolved in 30 ml of deaerated water. The resul ting pink precipi tate \\'as washed wi th t\rJO 10 ml aliquots

of deaerated water and an equal volume of pentane. This

precipitate was suction dried for 30 min.

To the solution of the [(Etj4N] [Fe(CO)4H] dissolved in 50 ml deaerated l ,2-dichloroethane, 13.3 9 of Diazald (N-methyl-N-

nitroso-p-toluenesulfonemide) (62 rnmol) was added. This

solution was then stirred magnetically for l hr., the excess

pressure being relieved through an oil-bubbler connected to the

flask. The flask was connected to a vacuum line and the solution was degassed by means of the usual vacuum line technique. A

- 54 -

dark red solution was distilled over into a-196° trap on

the vacuum line, from the room tempe rature reaction mixture.

This process resulted in a pure solution of Fe(CO)2(NO)2 in

1,2-dichloroethane. Performing this reaction step in chloro-

ethane instead of 1,2-dichloroethane, produces pure liquid

Fe(CO)2(NO)2 - the complex can be trapped out at -64°. Yields

of 60-75%, based on Fe(CO)5' can be obtained. The 1,2-dichloro

ethane solution can be stored, '>lithout any decomposition, for

weeks under vacuum in the dark.

DinitrosyZaarbonyZ(triphenyZvhosphineJiron(OJ, Fe(NO)2(CO)PPh3 ,

dinitrosyZbis(triphenyZphosphineJiron(O), Fe(NO)2(PPh 3 )2' and

dim: t ros.y Z aarb ony Z (tri me th'fll ph os phi te) i('on (0 J, Fe (NO) 2 (CO) [P (OHe) 3]

45 viere prepared according to published syntheses . The puri ty of

each compound \l7as estab1ished by t.l.c., its identi-ty by

comparison of the i.r. spectrum ,vith the pllblished one.

Dini-/;rosyZb1:'S (trimethl1Zphosphite)iron(O) 1 Fe (l-JO) 2 [P(OHe) 3]2'

was prepared by a method similar to the preparation of the mono-

trimethylphosphi te deri vati ve. A 5 ml solution of Fe (CO) 2 (NO) 2

('V2 rnrnol) in dichloroethane and 1.2 ml of P (Œ1e) 3 (9 mmol) was

stirred, under nitrogen, for 24 hr at 85°. During this time,

the starting material was converted, almost quantitatively, to

the bis-derivative. The resulting mixture \ojas purified by

chromatography on a silica gel coluœl. The first colourless

fraction (excess trimethylphosphite) was eluted WiL~ CH 2C12 •

The eluant was then changed to a 1:1 mixture of acetone and

hexane i this concentra.ted and eventually \l7ashed out a red band.

- 55 -

The resulting solution was rechromatographed on silica gel.

Finally, the solvent VIas removed at reduced pressure, leaving

the desired product as a red, oily material. This product • .,as

ShO\VD to be pure by t .1. c. r-t could be s tored in the dark,

under nitrogen, \.,ithout decomposition.

rt should be noted that a concerted effort to synthesize

similar PF3 derivatives, failed. The attempted synthesis was

similar to that used to prepare the tertiary phosphine

derivatives. In absence of tetrabutylammonium bromide as

catalyst, no reaction occurred. However, with the catalyst,

substitution of the CO groups did occur, as evide:1ced by

changes in the i.r. spectrum. The spectra aiso indicated the

presence of the tetrabutylammonium cation. n1is ion could not

be separated out by any chromatographie me ans . Conductance

measurements in nitromethane solution did indeed verify that

the reaction product was an ionic compound. Assuming a molecular

-1 weight of 400 g mole , the specifie conductance at 25° was

l l .... à t be 63 cm- l mhos- 1 M- l . E' . l l (C H) ca cu a ... e. 0 .Lemen-ca ana yses ,

failed to substantiate the molecular formula for any reasonable

compound that could be proposed. Mass spectroscopie analysis

also yielded no positive results. The dichotomy in the

behaviour of PF 3 and PPh 3 in their reactions with Fe(CO)2(NO)2

is not understood.


The i.r. spectrum of Fe(CO)2(NO)2 .in CS 2 solution was

-,

- 56 -

obtained using a pair of matched 1.0 mm KBr cells. The spectra

of triphenylphosphine, Fe (NO) 2 (CO) (PPh 3) and Fe (NO) 2 (PPh 3) 2

were recorded as Nujol mulls sand\oJiched bet\veen KBr plates.

The i.r. spectra of the two trimethylphosphite derivatives and

the free ligand, were measured for the neat liquids squeezed

between KBr plates.

The far-infrared spectra were obtained for benzene solutions,

and were run against pure benzene as reference in 1.0 mm Beckmann

polyethylene solution cells.

The Raman spectrum of Fe (CO) 2 (NO) 2 was obtained wi th the

647.1 nm exciting line at 50 mW power. OWing to the poor

scattering p.coperty of this compound, very \'Jide slits (9-10 cm- l )

had to be ernployed. Spectra were recorded for CS 2 and CC1 4

solutions. The regions of CS 2 solvent scattering 'VJere clear

for the CC1 4 solution spectrum. In this way, a composite Raman

spectrum in the 2100-1700 and 700-250 cm- l regions was obtained.

An attempt to record the Raman spectrum of the neat liquid,

failed.

The Raman spectrum of Fe(NO)2(CO) (PPh 3) was run for the

powdered solid in a pyrex capillary. Since the compound

decomposed in t.he laser beam at room temperature, a special low

temperature sample handling system, diagrarnrrled on the next page,

was constructed. With this system, temperatures down to -80 0

could easily be achieved. This sarnple was run at -10 0 using

the 647.1 nm exciting line at 80 roW power. A po or quality, but

reproducible, spectrum lIJas obtained. The spectrurn of Fe(NO)2(PPh3)2

- 57 -

p

i - incident laser beam

s - scattered laser beam

n - cold N2 inlet

p - pyrex capillary (sample)

t - ther~ocouple

e - evacuated

was also attempted at room and low temperatures. Although the

compound did not visibly decompose, only a very noisy baseline

was obtained and no peaks could be discerned.

Attempts to obtain the Raman spectra of the trimethylphosphite

derivatives also failed.


To facilitate the assignment of the fundamentals of

Fe(CO)2(NO)2 and its derivatives, certain trends noted for

other carbonyl-nitrosyl complexes will be introduced.

A good linear correlation can be obtained46 ,47 between

the shifts in the v(C-O) and v(N-O) fundamental frequencies

with changes in L for complexes of the type M(CO)x(NO)yL. The

shifts are dependent on the 1f-acceptor abilities of the

- 58 -

* ligands.

Assuming a significant TI-contribution to the bonding scheme,

a number of a priori predicitons can be made for Fe(CO)2(NO)2

and its derivatives. The 1T-acceptor abilities of the ligands

in question are generally accepted48 ,49 to be in the order of

CO>P (OR) 3>PR3 . On this basis, "through cornmon "rr-bonding

arguments, certain shifts in the fundamental modes can be

predicted (Table XII). It is evident from the assignments also

presented in this Table that these predictions are verified

experimentally ..

The solution i.r., far-infrared and solution Raman spectra

of Fe (CO) 2 (NO) 2 are shown in ?'igures 13, 14 and 15 respecti vely.

The Raman spectrum of the crystalline comple}{, Fe(NO)2(CO) (PPh 3),

is reproduced in Figure 16. A typical i.r. spectrQ~ of cne of

the organophosphorus derivative3 is also demonstrated in Figure

17. The frequencies relevant to these spectra, as weIl as to aIl

the other complexes discussed in this Chapter, are listed in

Tables XIII, XIV, and XV.

Although i.r. spectra of Fe(CO)2(NO)2 in the vapour phase

5 and liquid state have been published previously by Poletti et a~.

there are no reports in the literature dealing with the i.r.

spectrum in solution. In the present study, the i.r. spectrum

of Fe(CO)2(NO)2 in CS 2 solution has been recorded. This spectrum

* The author acknowledges the fact that cr-effects also play an

important role in metal-CO and metal-NO bonding. In particular,

they are concomitant to the TI-effects - a gcod 'IT-accepting ligand . . d . 48 belng slmultaneoulsy a poor a-donor an v~ae ~ersa

l

- 59 -

(A) Figure 13. Infrared spectrum of Fe(CO)2(NO)2 (CS 2 solution).

(B) Figure 14. Far-infrared spectrurn of Fe(CO)2(NO)2 (benzene

solution) .

w u z <! r-r-2 tJ) z <! 0:: r-

1

2000 1700

(A)

r

1

600 400 -1 cm

-,

w u z ;:! 1-

2 li) z <r Ct: 1-

300 100

(B)

- 60 -

Figure 15. Raman spectrum of Fe (CO) 2 (NO) 2 (CS 2 and CC1 4 solutions) .

Instrument 580-420b 700-580

c 2100-1980b

Controls a 350-250 420-360 1830-1730 Dnits ----

Excitation 647.1 647.1 647.1 nm

Power 50 50 50 mW

Slit 9.5 9.0 8.0 -1 cm

Sensitivity 5 10 2 x 10 10 -1 " sec

Time Constant 10 10 40 sec

Scan 20 10 5 cm -1 min -1

Chart 24 12 6 in/hr

a In the subsequently reproduced Raman spectra, for the sake of

brevity, the instrument controls will be named in short form and

the units will be ommitted.

b CS 2 solution.

c CC1 4 solution.

1 =s:~

-==--~ ~

-~ ~ ~

A1ISI'13.lNI

.-lE u

0 0 ~

0 0 <D

o o co ~-

o o o C\J

l

- 61 -

(A) Figure 16. Solid state Raman spectrum of Fe(CO) (NO)2PPh3.

Instrument Contro1s

Exc.

Power

Slit

Sens.

T.C.

Scan

Chart

920-350

647.1

85

5.5

5 x 10

40

5

12

2100-1680 -----647.1

85

4.4

5 x 10

40

5

12

(B) Figure 17. Infrared spectrum of Fe (NO) 2 [P (011e) 3] 2 (neat

1iquid) •

: f.

1

( A)

~------------------------------------------,~

=-

<

3:JN\t .1.11 V\JSNV'til (B)

lE u

o o ~

o o cD

.,

Mode

\l (C-O)

\l (N-O)

\l (Fe-C)

\l (Fe--N)

ô (Fe-N-O)

*

Predicted

* shift in mode

decrease

decrease

increase

increa.se

increase

TABLE XII"

FREQUENCY SHIFTS OF THE FUNDN~NTAL MODES OF

THE Fe (NO) 2 (CO) L CDr1PLEXES (cm -1) "

L= CO

2083 (al) , 2033 (h 2)

1806 (al)' 1763 (h 1)

659 (b 1)

647 (al)

610 (h 2)

Observed for Fe(NO)2(CO)L

P(OMe)3

2025 (a' )

1778 (a'), 1733 (a ")

669 (a ")

667 (a' )

619 (a' )

With L changing as CO, P(OMe)3' PPh 3 "

PPh 3

2009 (a' )

1759 (a'),1714 (a ") 0-, N

690 (ail )

669 (a' )

622 (a 1)

J

PPh3

IR

851 (6) b

753 (vw ,sh)

745 (v\'! ,sh)

741 (60)

ï~l (sh)

TABLE XIII.

VIBRATIONAL SPECTRA OF THE PPh3

DERIVATIVES OF Fe{CO)2{NO)2 (cm-1 ).

Ramanc

742 (8)

Fe{NO)2{PPh3 )2

IR

1712 (vs)

1667 (vs)

850 (7)b

843 (5)

a

803 (7,br)

750~ 744 (50)

740 J

723 (5)

Fe (NO) 2 (CO) (PPh 3 )

IR

2009 (vs) a

1759 (vs)

1714 (vs)

854 (10)b

849 ( 7)

748 (54)

724 (sh)

c Raman

2007

1742

1708

846 ( 6)

760 (5)

750 (5)

0'1 w

J

705 (32) 707 (30) 706 (8)

693 (63) 693 (sh) 693 (50) 696 (50) 692 (7)

679 (35) 685 (w,sh) 690 (w,sh)

672 (5) 669 (30) 660 (15)

627 (4)

620 {5} 616 (25) 617 (3) 622 (37) 617 (14)

618 (w,sh)

580 (20)

541 (3) 564 (3) 564 (20)

528 (3) 521 (70) 525 (52) 523 (6)

512 (45) 509 (sh) 505 (50) 507 (55) (l',

~

4981 495 (13) f (45) 490 490 (5) 489 (10)

466

1 458 (2) 458 (3) 458 (22)

441 (20) 450 439 (6)

430 (11) 429 (sh) 428 (5) 426 (12)

419 (12) 421 (16) 421 (s11)

396 (4) 403 (18) }

397 (2) 402 (3)

386 (10) 387 (:,)

J

396 (s) d

375 (3)

327 (3)

268 (sh) 268 (sh)

248 (m) 246 (90)

206 (m) 208 (50)

192 (sh) 1951 [(40)

185

a Spectrum obtained for CH2 C12 solution in the 2100-1700 cm- l region. b Spectrum recorded for Nujol. mull in the 900-350 cm- I region. c Spectrum run for a microcrystal1ine sample (at -lOoe for the iron complex) . d The far-infrared spectrum was obtained for the sample dissolved in benzene.

0) (JI

.J

P(OMe)3

851 (4)b

824 ( 10)

766 (sh)

726 ( 50)

512 (5)

- 66 -

TJ.I.BLE XIV.

INFRJl.RED FREQUENCIES OF THE P (OMe) 3

DERIVATIVES OF Fe(CO)2(NO)2 (cm-1).

2025 (vs)

1747 (vs) 1778 (vs)

1698 (vs) 1733 (vs)

853 ( 32)

801 (sh)

791 (46 ,br) 791 (28)

759 (sh) 754 (26)

737 (46)

678 (15)

667 (sh) 669 (s11)

663 (sh) 667 (17)

603 ( 21) 619 (20)

526 (33) 526 (10)

467 (sh) 475 (2)

420 (sh)

a

a -1 Samp1es ,.vere run as cyclohexane solutions in the 2100-1700 cm

region.

b Spectra were recorded

region.

for -1 the nE:at liquids in the 900-400 cm

,- 67 -

is of higher quali ty than the knO'.vn vapour and liquid spectra

bands previously appearing as shoulders are now distinctly

resolved.

The Raman spectrum of Fe(CO}2(NO}2 in the high frequency

-1 region (2100-1700 cm ) is in accord with the previous vibra'tional

assignment of this complex \vhich \Vas based on i. r. data alone 5 •

Unfortunately, reliable Raman depolarization ratios could only be

obtained for the CO stretching modes o";:ling to graduaI decom-

position of the complex in solution. Four Raman active modes

[v(C-O), al + h 2 ; v(N-O), al + hl] are expected in this region.

The highest frequency band in the CO strc=tching region at 2083 cm- l

is polarized, whereas the other CO band at 2033 cm- l is depolarized.

These data confirm the previous assignment of the two bands te the

* al (vI) and b 2 (')17) modes, rE'.!specti vely. 'l'he relative in tensi ty

-1 of the two peaks at 1806 and 1763 cm suggests they should be

associated with the al (v2 ) and hl (v 12 ) modes, respectively.

There is sorne evidence for reversing the previous assign-

ments of the v 5 a.né!. v 19 fundamentals. Bo t."L \',"ere assigned to

Fe-C-O bending modes. Based on the new Raman data, the s'tronger

560 cm -1 band ls reassignedto the al (v 5) bending mode, leaving

-1 the 477 cm peak as the h2

(v19 ) mode. This reassignment is

supported by a closer inspection of the available data. From

the published table of "Potential Energy Distribution Arnong The

* The fundamentals described by poletti et al. 5 have been re

nurnbered to conform to the more usual convention of decreas:i..ng in

frequency in each syn~~etry block.

"

- 68 -

Syrnmetry Coordinates ", i t can be seen that \) 18 and \) 19 nlix.

Using the reassigned value for \)19' a combination band due to

the interaction of these two fundamenta1s can be expected at

-1 482 + 614 = 1096 cm . 1>_ Il rather strong" band was observed aoc

1095 cm -1. Al though this band was previous 1y assigned to a

combination between 658 + 436 = 1094 cm-l, this seems somewhat

unlike1y because both of these bands are weak shou1ders, whereas

-1 the 614 and 482 cm bands are more intense. The stronger

fundarnentals would be more 1ike1y to give rise to a "rather

strong" combination band.

The previous assignment of the Fe-N-O and Fe-C-O funda

-1 mentals for Fe{CO)2(NO)2 to the 700-600 and 500-400 cm regions,

respectively, is substantiat~d experimentally. In the i.r.

spectra of the bis-P (OMe) 3 derivative, (Table XIV), for which

-1

the two CO groups have been re?laced, the peaks in the 500-400 cm

region disappear, while t.he others are only shifted. The shift

in the Fe-N-O fundarnentals in going from othe parent compound to

the mono-phosphite and phosphine derivatives is to higher

frequency, as predicted (vide supra, p.62). The relevant

assignments are shown in Table XII. To the best of the author's

knowledge, these are the first low frequency data that have been

used in such an argument. In general, only the \)(C-O) and \)(N-O)

high frequency fundamental frequencies ar.e considered owing to

the relative comp1exity of the low frequency region.

There is a strong band in the high reso1ution CS 2 solution

i. r. spectrum of Fe (CO) 2 (NO) 2 at 591 cm- l (Figure l3) , which

- 69 -

apparently was not observed in the published lower resolution

vapour phase or liquid state spectra. The Fe-N-O twisting mode

-1 of a2 symmetry (v 9 ) has been calculated to be at 590 cm •

Consequently, this 591 cm- l band is assigned tentatively to

either v 9 (made active by the solvent interaction) or to a

combination band (whose intensity has been enhanced by Fermi

resona.nce with the 610 cm- l mode) .

Four fundamentals (2al + b l + b 2 ) should appear in the

-1 100-50 cm region. The far-infrared spectrum of Fe(CO)2(NO)2

in benzene, down to 60 cm-l, was obtained. The only features

are a broad band centered at 87 cm -1 wi°th a weak shoulder at

-1 72 cm • rrhe former is in excellent agreement wi th the

-1 calculated value (86 cm ) for the N-Fe-N deformation mode (V 7 )

-1 and is tentati vely assigoned to this mode. The 72 cm band is

probably due to either v 8 or v 21 I.vhich are calculated to lie at

66 and 78 cm-l, respectively.

The proposed vibrational assignments for Fe(CO)2(NO)2 are

presented in Table XV. These assignments a.re based upon the

work on Poletti et aZ. S and differ only in the assignments of

D. CONCLUSION

The new far-infrared, i.r. and Raman spectra obtained for

Fe(CO)2(NO)2 substa~tiate the previously published vibrational

assignrnents for this co~plex. The only significant difference . is the assignments for the Vs and v 19 modes. The new vibrational

- 70 -

Tl.BLE XV.

-1 FUNDl'1-1ENTAL FREQUENCIES OF Fe (CO) 2 (NO) 2 (cm ).

Solutiona

Normal Mode Approx. Descrip. IRb Ramanc

al Syrrunetry

'\)1 c--o str. ~O83 2082

v 2 N-O str. 1806 1806

v 3 Fe-N-O bend. 647 647

v 4 Fe-N str. 624

v 5 Fe-C-O bend. 560 560

v 6 Fe-C str. 380 383

v 7 N-Fe-N def. 87

v 8 C-Fe-C dei. 72

a2 Syrrunetry

v9 Fe-N-O bend. 591

v 10 Fe-C-O bend.

v Il C-Fe-N def.

b 1 Symmetry

v 12 N-O str. 1763 1762

v 13 Fe-N str. 659

v 14 Fe-N-Q bend.

v 15 Fe-C-O bend. 436 426

v 16 C-Fe-N def.

Vapour

IRd

2118

1847

654

619

482

382

180H

658

648

436

J

- 71 -

h 2 Symmetry

"17 c-o str. 2033 2034 2061

"18 Fe-N-O bend. 610 614

"19 Fe-C-O bend. 476 477 559

"20 Fe-C str. 445 447

"21 C-Fe-N def. 72

a Other bands, not assigned to fundamental modes, were observed

at: 835, 324, 313, 272 cm-1 in i.r. and 322, 307, 270 cm-1 in

Raman.

b -1 The solvents used in the different regions are: 2100-300 cm -1 (CS 2), 300-60 cm (benzene) .

c Obtained for CS 2 solution in the 2100-1700 and 850-250 cm-1

regions. For the regions obscured by the solvent, the spectrum

was run for the CC1 4 solution.

d From reference 5.

J

- 72 -

data have a1so been successfu1ly used in correlc.ting bonding

effects in Fe(CO)2(NO)2 and its derivatives. In particular,

-1 sorne assignments in the low frequency (700-400 cm ) region

are uniquely based upon such arguments. The assignment of

the Fe-N-O and Fe-C-O fundamentals of Fe(CO)2(NO)2 to speciZic

frequency ranges, has also been experimental1y verified.

PART II

SELECTED CYCLIC DIENE COHPLEXES OF

CHRmnUM, 110LYBDENUM, TUNGSTEN, IRON AND COPPER

- 73 -

CHAPTER 1. IN'.L'?ODUCTION

Although a large number of metal-olefin compounds have been

synthesized since the early 1950'5, the vibrational spectra of

these complexes have received little attention. Complete

vibrational assignments have been achieved only for Zeise's

salt, K[Pt(C2H4

)C13

].2H20, and the corresponding dimer,

50-52 [Pt(C2H4 )C1 2 ]2' as weIl as for their palladium analogues •

However, even for these relatively simple systems, arguments

have been raised recently concerning the assignment of the

coordinated v (C=C) mode. Partial vibraticnal assignments have

been attempted·only for u few of the more complex metal-olefin

systems containing ole fins such as butadiene, 1,5-cyclooctadiene

(COD) , bicyclo[2.2.1]hepta-2,5-diene (norbornadiene, NBD) , and

1,3,5,7-cyclooctatetraene (COT).

In this \-'lOrk, i t was planned to obtain vibrational assign-

rnents for two sets of complexes containing t\\·o of the above-

mentioned larger ligands viz., NBD and COD. Ir. metal-olefin

complexes of the types to be discussed, there are two important

parameters that characterize the bond between the rnetal and the

ole fin. Firstly, the shift in the position of the v (C=C)

fundamental provides sorne clue as to the change in electron

density in the C=C group upon coordination. Second, the strength

of the metal-olefin bond is reflected in the position of the

* V (~l-I,)

*

stretching mode. For the (NBD)H(CO)4 complexes to be

In this Part, M-L will ahvays refer to a metal-olefin bO!1d.

- 74 -

considered here, only one v(C=C) vibration has ~een assigned53 ,

,.,rhereas two a.re expected. Furthermore, no mention has been made

of the v(~-L) vibrations. In the case of one of the COD complexes

that are also dealt with here, a partial vibration al assignment

54 was published when this vlork ha.d just been completed . Again,

only one \1 (C=C) mode \'las assigned, and the v (r.1-L) vibrations

were considered in a somewhat curious fashion.

The work describeë: in this Part of the thesis was undertaken

in order to furnish a unified approach to the problem of the

assignment of the v (C=C) and v (H-L) fundamentals of metal-olefin

complexes. These complexes a!?pear frequently in transition metal

chemistry,' They are often intermediates in the heterogeneous

reduction of olefins, they also appear in catalysis and as

intermediates in synthetic problems, ~-;rhile they have been widely

used, they have been li·ttle charvcterized. Before presenting the

results of the author's own work, the pres8ntly available

vibrational assignments for metal-ole fin complexes ':lill be

reviewed in Chapter 2. In Chapter 3, vibrational assigmnents

will be proposed for NBD and (NBD)f.1(CO)4 (1'1 = Cr,Mo,W) complexes.

Finally 1 in Chapter 4, vibrational assignrnents v]ill be suggested

for [(COD) RhCl] 2' [(COD) cuCl1 2 and (COD) 2CuC104' A molecular

structure is also offered for the last species.

1

- 75 -

CHAPTER 2. REvrmv or VIBHi"\TIONAL ASSIGNI'-ŒNTS FOR

!.ffiTAL-OLEFIN COHPLEXES

This review will be presented in historical sequence \oTith

emphasis being placed upon the published assignments for v (C=C)

and v (M-L) modes. There \.;ill be no attempt to try and duplicate

the several very comprehensive reviews on metal-olefin

55-58 complexes . The review is considered to be complete until

June 1972.

In 1958, Powell and Sheppard50 assigned the v (C=C) modes

for several ethylene complexes (T~le XVI) •

v (C=C) lies in the 1530-1500 cm- l region.

For these molecules,

-1 A weak band, at 410 cm ,

at the far limi t of the range of their instrument, \'las assigned

tentatively to the metal-ethylene s·tretching vibration, v (M-L) •

Subsequent work 51 on Zeise's salt, including a force constant

calculation, confirmed these assignments. Force constant

calculations have also been carried out on Zeise's dimer and its ··2

palladium analogue::>. The data from both these studies are also

presented in Table XVI. These force constant calculations

emphasize the need to consider the metal-olefin stretching force

constant for an accurate estimate of the C=C bond strength, since

the position of the v (C=C) band is strongly influenced by the

o(CH2) mode coupled to it.

A controversy arose in 1969 when Hiraishi 59 reassigned v (C=C)

in Zeise's salt to 1243 cm-l, on the hasis of Raman data. This

low frequency is consistent with a bonding scheme in which the

ethylene is bonded to ~he metal atom through sing~e bonds from

[Pd(C2H4 ) C1 2 ] 2

[Pt(C2H4 )C12 ]2

K[Pt(C2H4)C1 3 ]·H2O

K[Pt(C2H4)C13 ]

[Pt(C2H4 )C1 2 (NH 3)]

- 76 -

Tlill LE XVI.

ASSIGNED v (C=C) FUNDAMENTALS

OF ETHYLENE COHPLEXES a (cm-1).

V(C=C)50 v(C=C)52

1525 w 1527 w

1506 \'1 1516 w

1516 1526 b vw w

1516 vw

1520 w

v(H_L)52

427 s

406 s, 408 s (R)

407 sb

383

a Samp1es were aIl run in the solid state, cither as pressed

disks or as Nujo1 and HCBD mu11s.

b Re ference 51.

each carbon atome In view of this, tl1e two expected v (I\i-L) modes

were assigned to peaks at 493 and 403 cm- 1 . Sirni1ar1y, assign-

ments were proposed for the ais and trans-C4H8 analogues of

.', 1 60 Zelse s sa t • It was concluded that although there is no

definite experimental supporting evidence, it is at least possible

to assign the C=C stretching modes to bands in the 1260 crn-1

region. As in the case of the ethy1ene compOl ... nds f the v (toi-L)

modes were assigned to bands around 490 and 400 -1 cm

61 In an attempt ta reso1ve this controversy, Powell gt al.

- 77 -

carried out i.r. and Raman studies on a series of Pt-olefin and

Ag-olefin complexes and reported their results earlier this year.

In this work, they introduced the follovling formalisme The C=C

vibration in the 1500 cm- l region is labelled Band l and the

o(CH2 ) mode in the 1260 cm- l region is referred to as Band II.

These two modes are considered to be coupled, wi th the 'J (C=C)

vibration distributed among the two bands. The summed percentage

changes of Bands l and II, upon coordination, are related to the

metal-olefin bond strength. Also, assuming that "the maj or part

of the combined frequency change will be associated wi th the band

of greatest fractional v (C=C) character", i t is seen tha't Band 1,

-1 in the 150'0 cm region, is due mainly to the v(C=C) mode in all

the substituted Ethylene complexes ('rable XVII). For the Ethylene

complexes themselves, this work supports the assignrnent of

H' • h' 59 b 1 è' h . 1" f h ( ) __ .!.ra1S 1 , Y conc u .1n<] t at there 1S al: _ m1X.l.ng 0 t e v C=C

mode in Bands l and II.

Two extreme bonding possibilities for a metal-olefin bond

are shmvn in Figure 18. It is, of course, probable that the "real"

bonding picture is a mixture of the two. In the case of the

ethylene complexes, it seems that Figure l8B is a more accurate

description of the ethylenic bonding in view of the C=C

assignments. This implies that there should be two l-i-L stretching

fundamentals: a symmetric and asymnletric one, as diagrarr~ed below.

\ / C

M-: "c /\

L

ethy1ene

[Ag.L] +

K [PtCl3 .,L]

ais -2 -butene

[Ag. L] +

K [PtC13

.L]

trans-2-butene

[Ag.L] +

K [PtC1 3 • L] ,

- 78 -

'l'ABLE XVII.

SHIFT IN BANDS RELATED

TO v(C=C) VIBRATIONS

Band l Band II

1623 1324

1579 2.5 1320 1.5

1515 6.5 1240 7.5

1660 1255

1597 4.0 1250 0.5

1503 9.5 1242 1.0

ln 75 1308

1615 3.5 1302 0.5

1526 9.0 1263 3.5

4.0 275

14.0 493, 405

4.5 280

10.5 489, 404

4.0 290

12.5 493, 386

However, a1though two were assigned in the case of the p1atinum

comp1ex, (Table XVII), on1y one was assigned to the sil ver comp1ex.

The reverse bonding picture is indicated for the substituted

ethy1ene complexes. But there still seems to be a discrepancy

between the predicted single v(M-L) fundamenta1 assigned for the

sil ver complexes and the two such fundamenta1s assigned for the

platinlli~ complexes.

;'-

\/ c

M~II C /\

- 79 -

(A)

Figure 18. Possible metal-olefin bonding schemes.

(B)

54 In a study published six months ago, Powell and Leedham

extended their vibrational studies to a series of 1,5-cyclo-

octadiene complexes. The Band l and II formalism was used in

the same \vay as above. It was concluded 'chat the v (C=C)

-1 fundamental is again predominantlyassociated with the 1500 cm

band. The proposed vibrational assignments are given in Table

XVIII. There seems ta be an inherent contradiction in t.he way

the v (C=C) and v (H-L) modes are assigned. Naintaining that the

C=C vibrations are in the neighbourhood of 1500 cm-l, a bonding

scheme represented by diagram A in Figure 18, is implied. In

this case, for the palladium and platinum complexes, there should

be only two M-L vibrations, instead of the four that were assigned.

In addition, blO v (C=C) modes are expected for these C2v complexes,

and four for the D2h rhodium dimer. Only in the case of the

palladium complex was mention made of a second v(C=C} mode.

Vibrational assignments have been made for' a nurnber of o~~er

metal-olefin complexes. The proposed assignments are collected

together in Table XIX. For aIl of these complexes, except

(C4H6 }Fe(CO}3 and, (COT)Fe(CO}3' the same problem mentioned above

COD

(COD)PdC1 2

(COD)PtC1 2

[(COD) RhC1] 2

- 80 .-

TABLE XVIII.

ASSIGNED FUNDAl'ŒNT1\LS OF

HETAL-CYCLOOCTADIENE SYSTEMS (cm- 1).

'J (C=C) 'J (M-L)

IR Raman IR

1658 s 1644 s

1524 s 1522 vs 570 m, 464 vs 569

1511 rr....v 415 w, 350 w 413

1496 m 1500 vs 588m, 480 s 587

461 m, 378 \v 461

1474 m 1476 vs 583 \'1 , 490 vs 586

476 vs, 388 ms 480

Raman

mw, 464 TIl

vs 1 352 m

m, 482 m

vs, 385 m

rnw , 480 vs

vs, 393 s

is encountered viz. on1y one C=C fundamenta1 is assigned to a

meta1-diene system.

(NBD) Cr(CO) 4

(NBD) Mo (CO) 4

(NBD) W (CO)4

(NBD) PtC12

(NBD) RuC1 2

(NBD) RUBr2

2CuBr.NBD

2AgN03 ·NBD

(COT) Fe (CO) 3

[(COT) RhC1] 2

(C4H6 jFe(CO) 3

- 81 -

TABLE XIX.

ASSIGNED FUNDAMENTALS OF VARIOUS

HETAL-OLEFIN COMPLEXES (crn-1).

v (C=C) 'J (H-L)

IR Raman Raman Medium

1438 solution

1438

1420

1436 m mu11

1420 vw

1438 fil

1471 \I!

1470 m

1562 a 1562 a solution m m

1490 TIl 1460 5 330 vs

1630 wa mu11

1410 w

1439 m 1477 w 351 3 neat 1ig.

a Vibrationa1 mode of an uncomplexed C=C group.

ReL

53

62

63

64

65

- 82 -

CHJ..PTER 3. TETRACl\FŒONYLI.JORBORNADIENEj·;ETAL (0) COMPLEXES

A. INTRODUCTION

It appears from the Revie'i,v that vibrational assignments of

metal-olefin species have been restricted mainly to complexes

containing small olefins. In particular, little systematic

work has been done on metal-olefin complexes of the bicyclic

ligand norbornadiene (bicyclo[2.2.l]hepta-2,S-diene, C7H8).

\\1hen the syntheses of the Group VIII complexes, (NBD) RuC1 2 ,

[(NBD)RhCl]2' (NBD)PtC1 2 and (NBD)PdC1 2 were reported, a few

frequencies were reported but none were assigned66 . Infrared

data for (NBD) Fe(CO) 3 have been published but only the v (C-H)

and v (C-O) bands were assigned67 . P..l though t'flO v (C=C) modes

are expected for 1T-bonded diei1e complexes, on1y one has been

assigned for each of the following complexes in the region

indicated in parentheses: (NBD)PtX2 and (NBD)PdX 2 (1440-

-1 68 -1 62 1430 cm ) ,(NBD)HX2

(1470-1420 cm ) ,(ilBD)M(CO)4 (1438-

1420 cm- l )S3.

The work described in this Part of the thesis was initiated

in order to provide sorne definitive assignments for the vib-

rational spectra of the three (NBD)M(CO)4 complexe~ (M = Cr,Mo,W).

The focus of interest was the determination of reliable assign-

ments for both the v(C=C) and metal-olefin stretching vibrations.

Since no X-ray data were available on these compounds, i t "vas

also of interest to ascertain whether or not there is a

spectroscopically observable change in the geometry of the

- 83 -

ligand upon coordination. In addition, it was hoped to make

sorne tentative assignments for the vibrational spectra of the

free ligand itself.

B. EXPERIMENTAL

'l'etracal>DonyZnorboï.'nadienechromium(OJ, (NBD) Cr(CO) 4'

tetraaarbonyZnorbornadienemoZybdenum(OJ, (NBD) Mo(CO) 4' and

tetracarbonyZnorbornadienetungsten(Oj, (NBD)W(CO) 4 were prepared

by Miss. D. Johanssoni the chromium and molybdenum species by

the direct method of King69 , the tungsten complex through the

t ' t' t '1 d ' t' 70 h f tl "" r1.s-ace on1. r1. e er1. va 1. ve . Eac 0 le compounL<.s \"as

resublimed by the author before spectra were run. To ensure

that there was no polymerization of the free ligand, it was

vacuum distilled (125 mm IIg/33°) immediately prior ta use. The

resul ting liquid gave one sharp peak in agas chromatograph.

The i. r. of "the ligand was run as a neat liquid, the

chromium and molybdenum complexes were run as CS 2 and CC1 4

solutions in a pair of 1.0 mm KBr solution cells. The spectrum

of the tungsten complex was obtained for Nujol and hexachloro-

butadiene (HCBD) mulls.

The Raman spectra of the complexes were obtained for the

powdered solids in Pyrex capillary tubes, using the 647.1 and

520.8 nm laser lines for excitation. A partial solution spectruID

of (NBD)W(CO)4 in freshly dried and deaerated benzene was also

obtained in a qual:"tz solution cell (647.1 nm/40m~'1). The spectrum

of the free ligand was also obtained in this solution cell. The

- 84 -

solid state spectrum of NBD \'las recorded at liquid ni trogen

temperature using the apparatus sketched below.

s~

"'e r' \

c. RESt1'I~TS AND DISCUSSION

1. Norbornadiene

e - evacuated

i - incident laser bearn

5 - scattered laser beam

A partial spectroscopie investigation of this, olefin in the

solid, liquid and vapour phases has been carried out recently by

Baglin71 • On the basis of both i.r. and Raman data, aIl the

bands in the v(C-H) region were assigned. Furthe~more, the

antisymmetric v(C=C) mode was assigned tentatively to the i.r.

-1 band at 1543 cm •

- 85 -

The i.r. and solid state (-196°) Raman spectra of NBD

* recorded in the present \'lOrk are shown in Figures 19 and 20;

the actual frequencies are listed in Table xx. The data in the

v (C-H) region are in good agreement \Vi th those of Baglin. In

this work, the solid state Raman spectrum at -196° was also

recorded. Extremely good resolution \vas obtained throughout

the whole spectral region; peaks which appeared as shoulders in

the spectrum of the liquid \vere clearly resolved in that of the

solide

As Baglin pointed out, there are two extra polarized bands

in the v(C-H) region. He attributed these to Fermi resonance 72

between the v(C-H) fundamentals and the lower energy v(C=C) and

o (CH2 ) modes. It will be shown shortly (vide infra, pp.105) that

this suggestion i5 substantiated by the spectra of the (NBD) H(CO) 4

complexes. A comparison of the solid state and liquid Raman

spectra of NBD reveals two additional small peaks at 3085 and

-1 3050 cm • These are assigned tentatively to correlation field

spli tting. Baglin' s reasons for his assignments can be appre-

ciated but it is a little'difficult to see how he distinguished

50 readily between the various hl and b 2 modes without actually

seeing hi5 i..r. vapour spectrum.

The two v (C=C) fundamen'tals (a~ and b 1) are expected to J. ....

appear somewhere in the 1700-1500 cm- l region. The al mode

* Some of the subsequently shown Raman spectra are reproduced in

such a TJlay 'that the intensities of the peaks across the 2pectral

range are not relative to each other.

('or

- 00 -

(A) Figure 19. Infrared spectrum of norbornadiene (neat

1iquid) .

(B) Figure 20. Raman spectrum of norbornadiene (-196°C).

Instrument Contro1s 1680-20 3160-2830

Exc. 647.1 647.1

Power 55 80

Slit 4 4

Sens. 10 3 5 x 10 2

T.C. 2 2

Scan 20 20

Chart 24 24

(A)

.~.':..

o o

1 ~Q

t ~ ~~ 1

r 1

r~ 1

1

r

o c -----s;

(B)

.- 87 -

should be strong and polarized in the Raman, but weak in the i.r.

spectrum. The b l mode is expected to be stronger in the i.r • .....

spectrum. On this basis, the strong polarized Raman band for

-1 the liquid at 1574 cm , \.,i th no i. r. counterpart, is assigned

to the al v (C=C) mode. -1 The strong i.r. band at lS44 cm is

assigned to the corresponding b1

mode.

Certain other somewhat tentative conclusions may be inferred

73 74 from the assigned i.r. and Raman spectra ' of the C2v species,

cyclopentene (C5

H6). In the Raman spectrum of liquid C

SH

6, aIl

the strong bands are due exclusively to al fundamentals.

Similarly, the strong bands in the R~man spectrurn of liquid NBD

should also be due to al vibrations; this is indeed found to be

true on the basis of depolarization measurements. The very

intense polarized band a'c 1108 cm- 1 is assigned to an al ring

-1 mode by analogy with the al ring mode in C

SH6 at 1107 cm In

addition, the very strong totally polarized band at 937 cm- l is

also assigned to a symmetric al ring mode.

For C? syrnmetry, NBD should exhibit 31 i.r.-active modes _v

(12 al + 9b l + 10b2 ) and 39 Raman active modes (the above + 8a2 ).

Eight of these modes {3al + a2 + 2b l + 2b 2 } are accounted for

by the v(C-H) vibrations. As expected, nine polarized lines are

-1 observed in the 1600-400 cm regioni however, one of these at

1601 cm- l is most probably due to a cornbination band. Both the

i. r. and Raman spectra exhibi t fewer than the anticipated number

of fundamentals. However, since the molGcular geometry has been

, l' h d . h J 75,76. t ,., -estao 1.8 e as C2~ l.n t e vapour plase , l.t seems IllOS _].KeLy

IR

1iquid

3148 (sh)

3125 (11)

3105 (11)

3070 (32)

2991 (50)

2975 (sh)

2938 ( 44)

2873 ( 34)

1641 ( 4)

1600 (2)

1544 (34)

- 88 -

TABLE XX.

VIBRATIONAL FREQUENCIES

OF NORBORNADIENE (cm-1 ).

Raman

1iquid solid(-196°} Assignment

3148 (1) 3146 (3)

3125 (2) 3119 (5) vinyl b 2

3103 ( 14) 3098 (26) viny1 al F. R.

3085 (2) solid state sp1ito

3075 (sh) 3070 (25)

3065 ( 14) 3060 (24) vinyl al F.R.

3050 (5) solid state split.

2993 ( 13) 3001 (40) bridgehead al

2988 (52)

2970 (sh) 2973 (32)

2939 ( 8) 2934 (1.4 ) met,hy1ene al F.R.

2871 ( 6') 2867 (14) methy1ene al F.R.

* 1601 ( 7) P 1603 (2)

1574 (42) P 1575 (24) \) (C=C) al

1,560 ( 4)

\) (C=C) b 1

\) (C-H)

- 89 -

1450 (9) 1451 (4) op 1447 (10)

1391 (1)

1334 (sh)

1311 (50)

1269 (2) 1271 (3) dp 1274 ( 2)

1249 ( 1)

1240 (6)

1226 (20) 1230 (12) P 1228 ( 22)

1204 ( 18) 1209 ( 3)

1149 ( 8) 1150 (2) 1150 ( 12)

1104 ( 4) 1103 ( 77) P 1114 (26) ring al

1107 (sh)

1102 ( 88)

1071 (5)

1062 ( 4) 1062 (5)

1015 ( 4) 1018 (2) 1017 (9)

956 ( 24)

934 ( 15) 937 (72) P 934 ( 110) ring al

911 (6) 910 (sh) P 913 (25)

891 (sh) 891 (sh) dp 897 ( 24)

880 ( 17)

873 (40) 876 (12) P 874 ( 7)

797 (35) 797 ( 1) 802 (10)

774 (2) ïï5 (27) "" 775 (19) 1::

726 (70) 729 ( 2) 733 ( 2)

710 (1)

- 90 -

665 (60) 667 (4)

541 (6 ) 542 (8) dp 543 (50)

501 (30)

444 ( 8) dp 446 ( 31)

421 (20) 423 (10) P 430 ( 42)

101 ( 60)

74 (26)

58 (10)

42 ( Il)

* In this and the following Taoles, "p Il denotes a totally

polarized Raman band \vhile "p" signifies a polarized band wi th

a depolarization ratio (p) of 0<p<3j4.

that a number of the fundamentals are too Vleak to be observed.

The assignments that can be made wi th any confidence are

given in Table xx.

2. Vibrational Assignments of Norbornadiene Complexes

The i.r. and Raman spectra of the (NBD)M(CO)4 (M = Cr,Mo,W)

complexes are shown in Figures 21-26. The vibrational frequencies

of the compounds in the various phases are listed in Tables XXI

and XXII. For the purposes of easier comparison, the spectra

of the complexes and of the free ligand are presented in bar

·graph form in Figures 27 and 28.

- 91 -

(A) Figure 21. Infrared spectrum of (NBD)Cr(CO)4 (CS 2 and

C2C1 4 solutions) .

(B) Figure 22. Raman spectrum of (NBD)Cr(CO)4 (solid state).

Instrument Controls 2100-20 3150-2830

Exc. 647.1 647.1

Power 40 40

Slit 4 4

Sens. 2 x 10 3 10 2

T.C. .5 10

Scan 50 10

Chart 48 48

i 1

!

._~ .. ~ C7"_ ~ -- _ .

i ,;---~~~~7-

C (~-'---

;--r:::..

~::.: --:.~ .,.-- .~_ ..

j:. i .. ,

(

f~-< 1

1 1

\ ~-

3JNVllIVIISNV<i1

(A)

-==

{

---J

------------~

-"==-=-------~ '-,

-', ? .:.

1. }

-"'->------------.-:- ---._-=:;. -------~

-,.-._~-- ---~-------"?~

(

A1ISN3.LNI

o o o C\J

o o al C\J

o o M

(B)

.. -..:........:.-:.-:.:.::::.'?:'-~.- ---~~.s.-_ ..... ;:=-._:;.:~----::- .. -:-::.-=::'- ------sa

-------~.:.-=..:..:::...--

-==-=====-~-: - ----

"E u

o o ..

g CO

- 92 ..

(A) Figure 23. Infrared spectrum of (NBD)Mo(Cù)4 (CS 2 anà

C2C1 4 solutions) •

(B) Figure 24. Raman spectrum of (NBD) Mo(CO) 4 '(solid state) .

Instrument Contro1s 760-20 1480-760 2200-1840 3160-2830

Exc. 520.8 520.8 520.8 520.8

Power 40 40 40 40

Slit 4 4 4 4

Sens. 2 x 10 3 5 x 10 2 2 x 10 3 10 2

T.C. 2 2 2 10

Scan 20 20 50 10

Chart 48 48 48 24

\

~

1

·1 1

i 1

l._:::~

c--------·-~..::--=-~ -----

(A)

o o Cl)

--" - ---_. __ ._--

-~»

. \ 1

._-----._. -----'

U IStJ:31 NI

(B)

. ....

. '~

.. i

\[1 ~ ,~

'" .' i '- . i

1

1

1 1

1

1

. --'---. -

.......

(B)

- 93 -

(A) Figure 25. Infrared spectrum of (NBD)H(CO)4 (Nujo1 and

HCBD mu11s) •

(B) Figure 26. Raman spectrum of (NBD) ~q(CO) 4 (solid sta·te) .

Instrument 2080·-1830 Contro1s 1380-20 1480-1380 3180-2930

Exc. 647.1 647.1 647.1

Power 30 30 30

Slit 4 4 6

Sens. 10 2 5 x 10 5 x 10

T.C. 10 10 40

Scan 10 10 5

Chart 24 24 12

~--_._----~~-=-~

3:)N'~ 1.1.IV'lJSNV'è::Il

(A)

o o <r

o o co

o L.O

C\I ..-

o o o «)

~"

':"liSN31NI

:.C.

o 8 C\I

o

I~

1

~

(B)

•

-.:.> -----

'.

;-.~

i

< "

:i

.. }

" " -.::. , . ~ .~

i " " 1

~ , 1

,,' 1

~

} ....

-< ;·f ~ . . ~

"

). ~ .: ..

:" ~.)

'/ . -1 "}

} .~ J { , l'

~ ~.

t 1 1

!

I§

1

1

i , ___ , __________ .-J

~11SN31NI

~::' ::..

"~

~ .......

;r

A11S"'431NI

(Bj

-. ) l 'c ~ .. ~

'.

~ )

1 / , (

~ ~

t (

~

','

') , ,

) , -......

' . . , .. ~ .

.' " -'1 .. Y i "-

ID t , LO

i '" ) 1

{

1 " S ? 1

t 1 1 .. 1 ~

! ~j

<:~ "'=' ~ j' l .... > 1 ( 1

___ ._.J

_. 94 -

(A) Figure 27. Bar-graph representations of the {NBD)M(CO)4

infrared spectra. (M = Cr,Mo,N)

(B) Figure 28. Bar-graph representations of the (NBD) M(CO) 4

Raman spcctra. (M = Cr,Mo,W)

j

J 1

---.. ----1 1

J

@"Q i z :::l 1

g i

i 1

i 1

---{ _----1 _--"l ---1

-=f --1 1

1

--1 1

.l:

1

-- --1 1

...{.;

-----J 1

1

! i-

l

cr ~ C 1 o 0 .

~ +.

Ô -6 dl CIl '

~

-_._----' 1 --; L

--' 1 1

i

--J -1 ._.J

-i -,

. _ ... _ 0 o N

.. -

___ ___ --j=1 ,-

-L Ig I~ 1

r

1

-,,- .. ·---rl .. ---. -. - -'1

.) ~

1

__ 1

(!-\) __ ~ _________ J

1 -Ï

(B)

(NBD) Cr (CO) 4

solutiona

3958 (4)

3928 (2)

3884 (1)

3844 (2)

3797 (1)

3094 (1)

3078 Cl)

3004 (15)

2963 (11)

2927 (5)

2906 (sh)

2849 (9)

2034 s

2006 w (13 CO)

1959 m

1944 vs

- 95 -

Tf.BLE XXI.

INFRARED FREQUENCIES

-1 OF 'l'HE (NBD)H(CO)4 COHPLEXES (cm ).

(NBD) Ho (CO) 4

, . a SO.Lutlon

3978 (8)

3939 (3)

3896 (2)

3835 (5)

3790 (3)

3091 (3)

3074 (sh)

3002 (27)

2965 (17)

2940 (1)

2924 (15)

2884 (2)

2847 (7)

2044 s

2031 w (13 CO)

1958 s

1925 \ol (13 CO)

(NBD)1tl (CO) 4

solidb

3093 (14)

3080 (8).

3015 (15)

3003 (24)

2970 (14)

2932 (13)

2889 (2)

2845 (3)

2044 s

2031 w (13 CO)

1957 s

19 2 4 w (13 CO )

Assignment

l v (C-OJ

1 :::=:::::ons

v{C-H)

- 96 -

1915 vs 1911 s 1910 s v (C-Q)

1885 \'1 (13 CO) 1882 \'1 (13 CO) 1881 w ( 13 CO )

1455 (4 ) 1456 ( 17) 1446 (6 ) o (CH 2 )

1433 (10) 1435 (37) 1428 ( Il) } V (C~C)

1426 (sh) 1429 (sh) 1418 ( 3)

1309 ( 17) 1304 ( 35) 1306 (19)

1251 (2)

1237 (2) 1233 (4) 1237 (4)

1225 ( 1) 1219 ( 3)

1184 (34) 1182 (35) 1181 (12)

1158 ( 7) 1150 ( 15) 1160 (10)

1124 ( 1) 1121 (1)

1103 ( 1) 1102 ( 1) 1108 ( 7)

1087 ( 8) 1082 ( 15) 1080 ( 15)

1042 (5) 1036 (16) 1039 ( Il)

1007 ( 3) 1007 (5) 1008 ( 2)

946 ( 5) 960 (10) 980 ( 4)

930 ( 3) 940 ( 13) 946 ( 4)

920 ( 8) 926 ( 8)

911 ( 7)

899 (2) 895 (9) 897 ( 8)

867 ( 3) 869 ( 1) 860 ( 3)

797 (2 ) 791 (3 ) 799 (4 )

785 (6) 779 (15) 783 (9)

759 (9 ) 724 (10) 749 ( 2)

.. 97 -

667 ( 35) 655 ( 4)

643 (sh)

635 ( 22)

621 ( 22) 616 (39) 616 (2 )

602 (25) 592 (2) 606 (22) cS (r·l-C-O)

570 (35) 570 ( 21)

549 ( 34) 547 (19)

515 (17) 503 ( 25) 511 ( 18)

496 (sh) 492 ( 7)

482 (6 )

494 (20)

466 ( 15) 462 ( 14)

448 (6) 437 ( 24) 446 (20) v (M-C)

433 ( 3) 39 J. (2) 391 ( 22)

326 ( 3)

a Obtained for CS2

and C2

C14

solutions. '"

b Recorded for Nujo1 and hexachlorobutadiene rou11s.

c v(C-Q) region was obtained for cyc~ohexane solution.

(NBD) Cr (CO) 4

solid

3102 (60 )

3097 (sh)

3083 (48)

3013 ( 45)

3003 (65)

2968 (20 )

2938 ( 20)

2924 (sh)

2849 ( 8)

2019 ( 22)

1961 (6)

1938 ( 60)

1922 (5)

1903 (3 )

1879 (37)

1456 ( 15)

- 98 -

Tli.BLE XXII.

RA1>11'.N FREQUENCIES

-1 OF THE (NBD)M(CO)4 COHPLEXES (cm ).

(NBD) Mo(CO) 4

solid

3100 (75)

3084 (58)

3014 (48)

3003 (67)

2969 (22)

2942 (10)

2928 (12)

2851 ( 10)

2033 (100)

1967 (20)

1943 (sh)

1932 ( 140)

1900 (5)

1876 (100)

1458 (40)

(NBD) W (CO) 4

solid

3097 ( 45)

3092 (sh)

3097 (34)

3013 (35)

3003 ( 35)

2968 (12)

2936 ( 12)

2926 ( 12)

2846 (6)

2030 (40)

1966 ( 8)

1938 (sh)

1929 (50 )

1895 (5)

1869 (43)

1447 (9)

. ta Ass~gnmen

1

v (C-H)

J

l 1

r v (C-O)

j ë (CH;2)

-- 99 .-

- 100 _.

469 ( 8) 464 (5 ) l 454 (46) 433 (200 ) 444 (80)

431 (sh) v (M-C)

411 (55) 405 (100 ) 414 (sh)

387 (10) 394 ( 3)

251 (42) 241 (28) 237 ( 18) } V (M-Ll

239 (35) 220 (100) 217 (45 )

142 (10) 136 (200) 137 (60 )

120 (110)

105 (170) 104 (sh) 99 (400 )

95 (1000) o (C-r.1-C)

82 (12) 77 (sh) 77 (30) o (C-Ivl-L)

52 (30) 63 (10) o (L-M-L)

41 ( 8) 48 (180 ) 49 (sh) 1attice

43 (40) modes

31 (25) 28 (100) 25 (sh)

a Specifie assignments for both the i.r. and Raman spectra are

presented in Table xxv.

- 101 -

o 1

C

0" 1 t: c,"'-t----~~ 1 M~" 1 1

~ 1" :1~ O.,.C'--------::-:::...I '~~

C 1 o

Figure 29. Probable structure of. the (NBD)fJl(CO) 4 complexes.

X-ray studies have not becn perfo:crned on these cornpounds.

However, the rnolecular geornetry can be little else than

octahedral C2v ' with two of the ais positions being occupied

by the two olefinic groups (Figure 29). Based on this ffiolecular

configuration, the calculated number and symmetry of the

fundament.al modes are tabulated in Table XXIII.

The spectra will be considered in t.~ree distinct regic!ls:

\) (C-Q) , \) (C=C) and 10\'1 frequ.ency vibrations.

- 102 -

TABLE XXIII.

SYHBETRIES OF' THE FUNDl'..MENTAL MODES

OF THE (NBD) M(CO)'1 C0i-1PLEXES a

Fundamenta1 Symmetry No. IR/R bands

\) (C-O) 2a1 + b l + b 2 4/4

\) (M-C) 2a 1 + b l + b 2 4/4

\) (M-L) al + b l 2/2

\) (C=C) al + b l 2/2

o (M-C-O) 2a 1 + 2a 2 + 2b 1 + 2b 2 6/8

o (C-H-C) 2a1 + 0. 2 + b l + b 2 4/5

o (C-M-L) a 2 + b 1 + b 2 2/3

o (L-M-L) 0.1 1/1

a <Ming to the comp1exity of the ligand, the various bending,

stretching and deformation modes associated with NBD, except for

\) (C=C) and \) (~1-L) , ,vere not considered.

a. C-O Stretching Vibrations

From Table XXIII, one predicts four IR/R active CO

-1 fundamentals (2a

1 -1- b

l + b

2) in the 2050-1850 cm region. Only

three bands are observed in the solid state Raman and solution

i.r. spectra (execpt for the i.r. spectrum of the chromium

- 103 -

complex) which can be attributed to these fundamentals. Since

a molecular geometry having a symmetry higher than C2v is

di fficult to imagine, ei "ther there is an accident al degeneracy

between two of the modes or one of the fundamentals is too weak

to be observed. The first suggestion is supported by several

arguments. The observed stretching frequencies for (NBD) vi (CO) 4

in benzene solution are 2040 (S/P), 1943 (s,dp) and 1891 (m,dp)cm- l .

As expected77 , the 2040 cm- l band is one of the al modes. The

middle bands in the Raman spectra of the three complexes are

always more :intense than the highest frequency al peaks. This

observation supports the assumption - deouced by inspection of

the i.r. spectra of the three compounds - that the middle two

bands in the i.r. spectrum of the chromium complex coalesce to

give one band in the spectra of the molybdenum and tungsten

complexes. It seems likely that the intensity of the central

Raman band for each of the three complexes is enhanced by the al

component of this accidentally degenerate pair of lines. ~1is

postulated degeneracy is clearly supported by measurements of the

* absolute integrated i.r. intensities of these bands.

As a consequence of these arguments, the c-o regions of the

~he absolute integrated i.r. intensities of the v(C-Q) bands

of these complexes, in order of decreasing frequency, are

tabulated on the next page (designated, for the sake of simplici ty , ·-1 -2

as vI to \)4). The units are H cm ,the values quoted are fOI"

10 -4 E, where E is the absolute in tegrated in tensi ty obf;ained by

W;lson and Wells method78 . 1~1' D J 1 -.... _ \1' lSS • • 0 1ansson, persor~a.!.

conununication) •

- 104 -

vibrational spectra have been assigned. The highest frequcncy

band has been shmln to be a polaLized al mode. In addition,

the middle bands are due to overlapping of the other al mode

with either b l or b 2 • From the Ra..'11an depolarization measure

ments for the tungs ten complex, the lo\vest frequency CO funda

mentaIs at ~1870 cm- l must be attributed to either the b l or b 2

modes. No further distinction can be made in the absence of

polarized single crystal measurements. In partial support of aIl

these assignments, a similar situation exists 79 ,80 for the

structurally related isoelectronic tetracarbonyl complex,

ais-Fe (CO) 4I2.

The three v.'eak peaks in the solid s tab.:: :Raman spectra are

due either to factor group splitting of the CO fundamentals or

to combination vibrations.

b. C=C Stretching Vibrations

The C=C vibrations of the NBD ligand, shift to lower

" .. h th f l' 61 frequency upon coord~nat~on. In Ilne w~t e orma lsm

discussed in the Review (vide supra, p. 77 ), "Band I" in the

(NBD)M(CO)4 complexes can be considered to be tl1e bands near

* Footnote continued from previous page.

(NBD)M(CO)4 10-4 E

M "1 "2 "., "4 .;)

Cr 3.54 ± 0.42 2.26 ± 0.52 9.57 ± 1. 24 7.99 ± 0.28

Mo 2.57 ± 0.25 13.8 ± 0.50 9.90 ± 0.52

W 2.79 ± 0.08 14.4 ± 1.0 8.37 i 0.43

1420 -1

cm

.- 105 _.

The shift in these bands, from 1574 and 1544 cm- l

in the free ligand, is in the order of 10%. Considering "Band III!

as the strong Raman bands a·t '\.01220 cm-l, the maximum shift in

these bands upon coordination is 0.4%. Thus, in accordance wi th

Powell et al' s formalism, the fra.ctional v (C=C) character is

much greater in Band 1. Therefore, the v (C=C) fundamentals can

be assigned to peaks in the 1450-1400 cm- l region. However,

there are three bands in this spectral region for each of the

complexes. Presumably, two of these are due to the v(C=C)

fundamentals of the complexed olefin, while the third is due to

the 0 (CH2

) methylene bending Ip.ode, also present in this region

in the spectrum of the free ligand. These bands can be assigned

unequivocally by considering carefully the modes in the v(C-H)

region.

Baglin found tvlO extra polarized lines in the Raman spectrt.lli1

of liquid NBD in the v (C-H) region. He at tributed these bands

to Fermi resonance between the C-H and 10\ver-lying fundamentals.

A Fermi doublet vias assigned to the peaks observed in ·the

-1 present work at 3103 and 3065 cm . This results from the

interac·tion of the firs t overtone of the b 1 v (C=C) mode at

-1 1544 cm wi th the al component of -the vinyl stretch ealeulated

to be near 3080 cm -1. In ·the NBD complexes, both C=C funda-

ment.als are shi fted to lovler frequencies upon coordination.

Consequen·tly, this Fermi resonance is expect.ed to disappear.

This is indeed found to be the case. -1 The 3065 cm Raman band

of the free ligand, as weIl as the i.r. bands at 3105 and 3070 cm- l

- 106 -

disappear in the solid state spectra of the complexes. Also,

a new strong band appears in the Raman spectra of the complexed

species in the 3085-3079 cm- l region. This band is not due to

solid state splitting in the Raman spectra (cf. solution and

solid state i.r.). These bands, together with the corresponding

weak bands in the i.r., are assigned to the vinyl al stretching

modes. Their freqllencies are in good agreement with the

ealaulated value of the undisturbed vinyl al stretching mode in

the free ligand at 3080 cm- l (The relative intensities of these

bands in the i. r. and Raman are also in accord wi th the assign-

ment. Such symmetric fundamentals are expected to be strong in

Raman and weak in i.r.) -1 'The hand near 3100 cm ,strong in Raman

and weak in i.r., is considered to be the 3125 cm- l band of the

free ligand that has shifted to lower frequency upon coordination.

A second Fermi doublet \17as assigned by Baglin to the pair

-1 of lines at 2939 and 2871 cm • They ,,,ere postulated to result

from the inte~action of the first overtone of the methylene al

bending mode at 1451 cm-l and the al methylene C-H stretching

fundamental. This undisturbed methylene stretching mode can be

caZaulated to be near 2908 cm- l in the free ligand.

The sa~e Fermi resonance is also assumed to be present in

the spectra of the complexes. -1 The low frequency band 'Ù2850 cm

is assigned as one component of the Fermi doublet involving the

al methy lene bending and stretching fundamenotals. Since the

atoms of the methylene group are the farthest from the coor~ination

si tes in the ligand, i t is reasonable to assume tha"i::o the -v·ibrati.ons

- 107 -

of this group will be lit tle affected by coordination of the

ligand. Thus, considering the Fermi doublet in the complex to

be centered at about the same frcquency as in the free ligand,

the other component of the doublet can be taken as the peak at

-1 2968 cm . Fermi resonance can be expected to occur if, in

-1 conjunction with the 2968 and 2850 cm doublets, the highest

frequency band in the 1450-1400 cm- l region is assigned to the

hl mechylene bending mode. The result of these calculations

using the frequencies obtained from the Raman spectra and the

following equation

o (CH 2 ) cale = F.R.l + F.R.2 - 2 [05 (CH 2 ) obs]

(F.R. referring. to one peak of the Fermi doublets) 1 are shown in

Table XXIV. These values indicate that there is a high

probabili ty of Fermi resonance bet~-Jeen the firs t overtone of

the methylenic cS (CH 2 ) vibration and the v (CH2 ) fundamental.

In the case of the chromium complex, for exan~le, 2 x o(CH2 ) = -1 2 x 1456 = 2912 cm ,which is close enough to the ealculated

fundamental at 2905 cm- l for interaction to occur. These

caZcuZated values are in good agreement with the caZcuZated value

-1 of the s ame mode in the free ligand at 2908 cm • It should be

emphasized that assignment of the peak around 2940 cm- l as the

second component of the Fermi doublet, as in the case of the

free ligand t gives rise to an improbable situation. No matter

which of the bands in the vicinity of 1430 cm- l is assigned to

the cS (CH 2 ) mode, Fe::-mi resonance would have to occur behleen

bands si tuated at least 60 cm-- l apart.

F.R.l (obs)

F. R.2 (obs)

2 X ô(CII 2 ) (obs)

V(CH 2 ) ( cale)

- 108 -

TABLE XXIV.

FPEQUENCIES RELEVANT TG THE

FEPJH RESONANCE CALCULATIONS (cm -1) .

(NBD) Cr (CO) 4 (NBD) Ho (CO) 4

2849 2851

2968 2959

2 x1456=2912 2x1458=2916

2905 2904

(NBD) W (CO) 4

2846

2968

2x1447=2894

2920

On the basis of the arguments given above, the highest

frequency band in the 1450-1400 cm- l range of the spectra of the

three (NBD)H(CO) 4 complexes is assigned to t.~e ô (CH 2 ) fundamental.

This leaves the other two bands to be attributed to the al and

hl v(C=C) fundamental vibrations. From intensity arguments, the

middle band, strong in i.r. and weak in Raman, is assigned to

the hl m,ode; the 10'\vest band, strong in Raman and weak in i.r.,

is assigned to the al mode. These assignments were later con

firmed by a Raman spectrum of the tungsten complex in benzene

solution. -1 Of the three bands nt 1451, 1431 and 1407 cm ,only

the lowest one is totally polarized.

The proposed assignments are in accord with observed spectra

of other NBD complexes. For instance, in the i.r. spectra of the

- 109 -

cornpounds (NBD)PtX 2 and (NBD)PdX 2 , three bands were reported in

-1 68 the 1450-1390 cm region The pattern is the sarne as in the

carbonyl complexes v'i z. a high frequency mode in the region of

1449-1437 cm-1 and a pair of lines in the 1410-1390 cm-1 region.

In view of the arguments presented abOVê, these bands are assigned

* to the o(CH 2 ) and the two v(C=C) modes, respectively. The

position of the ô (CH 2 ) mode in the complexes, compared to that in

the free ligand (1451 -1 cm ), again il1ustrates that this mode is

little affected by coordination of the ligand. As expected, this'

is not the case for the olefinic stretching vibrations.

The 150 cm-1 ('\,10%) decrease in frequency of the v(C=C) modes

upon coordination is in agreement with that observed for similar

metal-olefin complexes. Accepting the fact that these C=C funda-

mentaIs must be coupled considerably with lower-lying funda-

51 52 mentaIs ' ,no attempt will be made to correlate the metal-

ligand bond strength with the frequency decrease of the v(C=C)

modes.

c. Lm-, Frequency Vibrations

In the spectra of the (NBD)M(CO)4 complexes, two v(M-L)

fundamentals (al + bl) are expected. In similar complexes, such

modes generally lie in the 500-300 cm- l region. In the present

case, however, these funda.mentals are assigned to the two Raman

* In an independe!1t study concurrent. with this onc.:: D.M. Adams and

W.S. Fernando have reached the same assignment for ti::ese complexes.

(Personal communication) .

- 110 -

bands in the 250-215 -1

CHl region. For these compounds, no other

fundamental mode could possibly appear in this range. The

func.:1amental rE:gions for metal-carbonyl mOÎt:ties have been

clearly delineated through assignments of a legion of carbonyl

cornplexes 9,10 . In particular, the v (M-C) modes do not fall below

360 cm-l, while the lattice vibrations and the C-M-C deformation

-1 modes do not come higher than about 150 cm . Furthermore, in

the solid state Raman spectrum of the free ligand, there are no

-1 bands in the 430-100 cm region. It follows, therefore, that

-1 the two strong Raman bands in the 250-215 cm region can be

assigned to the al and b l v(M-L) modes. On the basis of relative

intensit.ies, the stronger band is assigned to the al mode, the

weaker to the b l mode. These assignments are supported by

depolarization measurements for the tungsten complex in a benzene

solution; the 218 cm- l band is totally polarized, while the 234 cm- l

band is depolarized. These observations are in line with the

assignment of the stronger band to the al mode. Only in the case

of the chromium complex is the stronger al mode at a higher

* frequency than the hl mode. This assignment of the v(M-L)

vibrati~ns for these (NBD)M(CO)4 complexes is of particular

interest because this is one of the few times that they have been

assigned definitively without resorting to such exotic techniques

* D.M. Adams anà vl.S. Fernando, who have also studied the vibra

tional spectra of the (NBD)Cr(CO)4 complex, agrE:E: with the assign

ment of the biO low frequency bands as v (M-r.). Moreover, they

found the stronger band at 249 cm- l to be polarized. (Persol1al

communication)

- III -

as metal-isotope studies 99 .

'l'he bands due to the a (N-C-Q) and \i (M-C) fundamentals are

expected to appear in the '100-400 cm- l region. The bending

fundamentals should be observed at higher frequency than the

t t h · 9 ,10 s re c.lng ones . In addition, the bending modes should be

more intense in the i.r. and the stretching modes stronger in 65 81 the Raman ' • These expectations are fulfilled for the NBD

complexes. The four lowest frequency bands in this region,

strong in Raman and relativcly weak in i.r., are assigned to the

four. M-C stretching fundarnentals. Specifically, these are the

bands in the region of 497-411, 464-387 and 446-391 cm- l in the spectra of the chromiurn, molybdenum and tungsten complexes,

respecti vely. The two s trong Raman bands in each of these regions

are assigned to the ·two al M-C vibrational modes" The six or so bands falling above the prcviously mentioned regions and below 680 cm -1 are assigned to the r1-C-O bending fundamentals. E!ach

of these complexes exhibits a weak Raman band at ~55S cm- l

which is assigned tentatively to an a2

c(M-C-O) mode, owing to

its absence in the i.r. spectra.

The spectra below 150 cm- l should display altogether nine

C-M-C, C-M-L and L-M-L deformation modes, as weIl as various

lattice modes. About seven bands are observed but it is

impossible at this stageto gi ve ass ignments for these.

The vibrational assignments proposed above fer the three

NBD complexes are collected together .in Table XXV.

Fundamen·ta1

\) (C-H) viny 1 b~. .c..

\) (C-H) vinyl al

** \) ( CH 2) al·

\)(CH 2 ) *'k

al

\)(C-O) al

- 112 -

TABLE xxv.

l'..8SIGNMENT OF Fffi\!DA11EN'J'A.L r-mDES

-1 * OF THE (NBD)H(CO)4 CONPLEXES (cm).

(NBD) Cr (CO) 4 (NBD) Ho (CO) 4

IR R IR R

3102 3100

3078 3083 3074 3084

2963 2968 2965 2969

2849 2849 2847 2851

2034 2019 2044 2033

\) (C-O) a 1+b 1 or b~. 1959 1938 1958 1932 ,t..

1944

\) (C-O) b 1 or b 2 1915 1879 1911 1876

o(CH 2) b 1 1455 1456 1456 1458

\) (C=C} b 1 1433 1430 1435

\) (C=C) al 1426 1425 1429 1431

o (H-C-O) a2 552 554

\) (M-C) al 448 454 437 433

\) (M-C) al 433 411 405

\) (M-L) al 251 220

\) (M-L) b l 239 241

* The values used are from Tables XXI and XXII.

** Fermi doublet

(NBD)W(CO) 4

IR R

3097

3080 3079

2970 2968

2845 2846

2044 2030

1957 1929

1910 1869

1446 1447

1428 1426

1418 1412

556

446 444

431

217

237

- J.13 -

3. Geometry of Free and Complexed Ligand

Since the crystal structures of the (NBD)M(CO)4 complexes

have not been investigated, it is of interest to consider

whether or not there is any spectroscopically observable change

in the configuration of the ligand upon coordination. 'Th.ro

vapour phase electron diffraction studies have been carried out

on the uncomplexed ligand75 ,76. Both of these studies indicate

that the molecular syrnrnetry is approximately C2v . There have

also been X-ray studies on the complexed ligand. In [(NBD)CuCI]4'

the functional unit is a tetramer82 with the copper and chlorine

atoms forming én eight-ffiembered tub shape ring and only one of

the olefinic double bonds of NBD being coordinated to the copper.

In (NBD)PdCl 2 , both of the double bonds are coordinated to the

83 palladium atom • The NBD ligand retains it C2 symmetry in both _v

of these crystal structures. The relevant crystallographic data

are presented in Table XXVI.

rf,he apparent differences in the molecular parameters of the

free and éomplexed NBD Inolecule are Ilot really significant ..

Using a 3a criterion, meaningful differences exist only in the

C6 -CI -C2 angle (Figure 30) - this angle decreases upon coordination

of the ligand.

7

3

Figure 30. Vapour phase structure of l1orbornadiene.

- 1.14 -

TABLE XXVI.

MOLECULAR PARl>-,~1ETERS FOR BONDED N-ID NONBONDED NBD.

NBD75 [ (NBD) CuCl1 4 82 (NBD) PdC12

83

(C=C) (A) 1.356(2) 1.345(11) 1.366(1)

1.317(11) a

C1-C2 (A) 1.549 (5) 1.537 (10) 1.554(56)

c1 -c7 (A) 1.567(12) 1.526(12) 1.547(59)

C6

-C1-C

2 106.4(6)° 102.7(7) ° 100.3(3)°

C1-C7

-C4 96.4° 93.3(6)° 94.5 ob

1vl- (C=C) ° 1.971(8) 2.159 (37) (A)

2.166(36)

v (C=C) 1574,1544 -1 1560

_la 142 8 , 1410 cm

_lc

cm cm

1460 cm -1

a Free C=C.

b Ca1cu1ated by Dr. IJ. Lerbscher using pub1ished data (persona1

corrununication)

c From reference 68.

- 115 -

Taking the C-H and C=C regions as monitors for the stereo-

chemistry of the ligand, it is concluded that in the (NBD)f.1(CO)4

complexes there is no significant change in the geometry of the

ligand upon coordination, as is the case for the (NBD)PdC1 2

compound. This conclusion can be substantiated in two ways.

First, the v(C=C) modes of the carbonyl complexes are in the same

region as the analogous modes of the palladium compound. This

implies that the metal-ligand bonding is similar in the two

species. Since there is no significant change between the

geometry of the free and complexed ligand for the palladium

compound, this can also be assumed to be true for the carbonyl

complexes. Second, a careful comparison of the spectra in the

C-H region of the free NBD and of the complexed NBD in

(NBD) l-1 (CO) 4' shows them to be very much alike. The apparent

changes in the Raman spectra in the 3100-3060 cm- l region become

less significant if the disappearance of the Fermi resonance is

taken into account .. The shift of the 3125 cm- l band in the free

lig.and to around 3100 cm -1 in the complexes is also explainable

on grounds other than a change in geometry. The effect of

coordination should be most prevalent on the vinyl group.

Therefore, this shift in the vin~ll C-H fundamental is a

consequence of complexation and not of a change in geometry.

-1 The changes in the spectra in the 3000-2900 cm region, have

already been accounted for in terms of changes in Fermi

resonance.

- 116 -

D. CONCLUSION

Partial vibrational assignments have been proposed for NBD

and the three (NBD) H (CO) 4 (M = Cr ,No ,m complexes. For the free

ligand, the two v (C=C) fundamentals, as weIl as blO of the ring

modes have been assigned. In the case of the complexes, assign

ments have been proposed for the modes of particular interest

for compounds of this type.

The apparent difference in the v(C-O) fundamental regions of

the three complexes has been accounted for, and assignments are

made for the modes of each of these complexes. 'l'he Fermi

resonances proposed previously for free NED have been sub

stantiated experimentally. On the basis of Fermi resonance

arguments, the coordinated v(C=C) modes have been assigned

unequivocally to bands in the range of 1430-1410 cm- l i.e. ,

approximately 10% lower than for t~e free ligand. The two M-L

fundamentals have ceen assigned definitively to the 250-210 cm-1

region. This range is the lowest yet observed for vibratIons of

this type. The cS (M-C-O) and v (N-C) modes have been assigned to '

the expected regions, with the al stretching modes being clearly

identified.

From the spectroscopie data obtained, it is concluded that

NBD undergoes little change in stereochemistry upon coordination.

- 117 -

CHAPTER 4. 1,5-CYCLOOCrrADIENE COMPLEXES

A. INTRODUCTION

1,5-Cyclooctadiene (CSH12 ) complexes of transition metals

have been little investigated from the standpoint of vibrational

spectroscopy. A.part from the recently published i.r. and Raman

data of Pm.,ell et aZ. 54 for sorne palladium, platinum and rhodium

complexes, rnost of the earlier ~vork has been preparati ve in

nat.ure. For example, the syntheses of (COD) PdCJ.2 84, [( COD) R.hCl] 2 85

86 and (COD) Fe (CO) 3 ' were reported about twel ve years ago. More

recently, several papers have been published on the far-infrared

spectra of the [(COD)RhCl]2 dimer 87 - 89 • These studies were

concerned with the vibrational modes of the bridging halogen

groups. The reaetions 9 0 of this rhodium dimer \.,i th tertiary

* phosphine and phosphite ligands have also been investigated.

There have been other preparative papcrs dealing with the . 91 92 chernistry of rhodlurn COD complexes ' , as weIl as sorne on the

kinetics and mechanism of the reactions of complexes of the type (COD) Rh(ASPh

3)C1 93 ,94.

The work described in this Chapter, together with the work

* It should be mentioned in passing that an a·ttempt was made to study the kinetics of the briège-breaking reaction of [(COD) R~Cl] 2 and its iodo-ana.logue with organophosphorus ligands. It was hoped that the results would yield kinetic data suitable for comparison with those of similar halogen-bridge breaking reactions. Preliminary studies showed that th8se rea.ctions \vere complete in less than 10 seconds. Consequently, they are too fast to be monitored by conventional. spectroscopie methods.

- 118 -

on the l'lBD complexes, \-las underta.1(en \'li th a view 'to\-lards

obtaining reliable assignments for ole fin complexes of the

transition metals. In particular, the vibrational spectra of

the free COD ligand and three of its complexes are considered.

In the case of the first two complexes, [( COD) RhCl] 2 and

[(COD)CuCl]2' the molecular structures have been determined by

X-ray Cl.ystallography95,96. For these complexes, vibrational

assignments are proposed. For the third complex, (COD)2CuCI04'

the molecular structure is unknown. Using the spectra of the

first two compounds as internal references, vibrational and

structural assignments are made for this complexe

The vibrational spectrum of l,5-cyclooctadiene has been

published twice97 , 54 i in nei ther case were detailed vibrational

assignments proposed. In the first case, the liquid state i.r.

and Raman spectra, and the solic1 state i.r., \Vere recorded in

the 1700-450 cm- l region. In the second, the complete i.r.,

but only a partial Raman spectrum (without depolarization data)

were published. In this thesis, these data are supplemented by

a complete solution Raman spectrum (including depolarization

measurements), and a solid state Raman spectrum.

B. EXPERIMENTAL

Di -'Il-oh Zorobis [ 1~ 5 -ay aZooetadiene rhodi um (I) ], [( COD) RhCI] 2'

was prepared by the method of Chatt and Venarlzi 85 . The iodo··

analogue '\Tas also prepared by the same published method. The

purity of these compounds was confirmed bl' t.l.c.

- 119 -

Vi -"fJ.-ah lOl'obi s [1.,5 - aNa looa tadiene covne r (I) ], [( COD) CuCl] 2'

was prepared under nitrogen by rnethod lb of reference 96. The

whi te crystals obtained \vere \vashed thoroughly to rernove any

rernaining reactants.

Bis(l,5-ayclooatadiene)aopper(I) perchlorate, (COD)2CUCI04'

was synthesized electrochernically by ï-lr. R.J. Gale, using the

method of Manahan98 . The identity (and purity) of the compound

was established by elernental analysis. (Calcd: C, 50.7; HI 6.4.

Found: C, 50.4; H, 6.6.)

To prevent polyrnerization, the COD was vacuum distilled

before i ts spectra were ~-ecorded. The fraction distilling at

21 mm Hg/33° was collected. The spectra were in good agreement

with the published results 54 . The solid state (-196°) Raman

spectrum of COD was obtained in the sarne manner as that of NBD,

described previously. The Raman spectra of the complexes were

obtained for the powdered solids in Pyrex capillaries using the

647.1 nm Kr+ line. The i.r. spectra of the copper complexes were

obtained for KBr pellets; the rhodium dimer was run as a mull in

Nujol and hexachlorobutadiene (HCBD).


1. 1,5-Cyclooctadiene

The i.r. and solid state Raman (-196°) spectra of COD are

shown in Figures 31 and 32; the observed frequencies are given

in Table XXVII. The calculated vibrational modes and their

spectral activities for the C2v "tub" and Ci "chair" configur

ations of the free ligand are listed in Table XXVIII.

- 120 -

(A) Figure 31. Infrared spectrum of 1,5'-cyclooctadie~e (neat

liquid) •

(B) Figure' 32. Raman spectrum of 1, 5-cyclooctadiene (-196 OC) .

Instrument 3050-2780 Controls 1700-20

Exc. 647.1

Power 60

Slit 4.5

Sens. 2 x 10 2

T.C. 2

Scan 50

Chart 48

\

~

3JN'111IV\lSN'1~1

(A)

l<ïg

[8 -~

o o (l)

~

~~

i .J.

(B)

- 121 -

TABLE XXVII.

VIBRl"\TIONAL FP..EQUENCIES

OF 1,5-CYCLOOCTADIENE (cm-1 ).

IR Raman

liquid liquid

3075 (5)

3009 ( 65) 3012 (60 ) P 3019 (6)

2989 (sh) 2996 (sh) P 2997 (30)

2978 (6)

2956 (sh) 2957 (10) dp 2948 ( 8)

2938 (40 )

2919 (sh) 2919 (70) P 2916 (15)

2892 (sh)

2883 (67) 2884 (95) P 2884 (50)

2838} (25)

2826 2829 (30) P 2827 (6)

* ** 1657 (20) 1661 (150) P 1658 (38)

1487 (40) 1487 (20) dp 1495 ( 14)

1447 (15) 1451 (sh) dp 1442 ( 3)

1425 ( 35) 1430 (60 ) p 1430 (50)

1407 (shj dp 1411 (6)

1356 (6 ) 1351 ( 13) P 1~51 (6 )

1321 ( 1) 1317 (16) dp 1319 (23)

- 122 -

1266 (6 ) 1275 (65) P 1276 ( 55)

1235 (10) 1239 (5)

1208 (16) 1210 (12) P 1215 (9)

1190 (sh)

1151 ( 4)

1084 (14) 1085 (22) P 1087 (10)

1015 (30) dp 1014 ( 21)

1003 (16) 1000 (sh) dp 997 ( 8)

966 ( 3) 970 ( 14) dp 976 ( 18)

905 ( 3) 904 (5 br) dp 909 ( 5)

840 (sh)

822 ( 12)

798 ( 25) 800 (110) P 804 (42)

753 (sh)

718 (sh)

708 ( 32) 708 (90) P 711 (20)

697 ( 5)

649 (35) 657 (7) dp 655 ( 12)

497 ( 10) 496 ( 12) P 501 ( 12)

466 ( 8) 467 (15) P 472 ( 10)

351 (22) P 352 (25)

332 ( 20) dp

266 (90) dp 270 (75)

237 (95) dp 249 (GO)

111 ( 10)

*

**

- 123 -

Assigned to the h v (C=C) mode. l

Assigned to the al v(C=C) mode.

88 (50)

56 (ï5)

42 (50)

Molecular Symmetry

C2v

& C. ~

~

- 124 -

TABLE XXVIII.

DISTRIBUTION OF NORr1AL 1'1ODES OF COD.

Fundamental Modes

l4a l + l4a2 +

l3b l + l3b 2

v(C-H)

3al + 3a 2 +

3b l + 3b 2

v (C=C)

al + b l

27ag + 27a u

v (C-H)

6a g + 6a u

v (C=C)

ag + a u

No. IR bands

40

9

2

27

6

1

No. Raman bands (pol.)

54 (14)

12 (3)

2 ( 1)

27 (27)

6 (6)

1 (1)

No. Coincidences

40

9

2

0

0

0

Considering the experimental data, there are two pertinent

observations that can be made. Firstly, in the Raman spectrum

of liquid COD there are 16 polarized bands; 5 in the v(C-H)

region and Il in the region below 1700 cm-1 Second 1 there are

a large nurnber of coincidences between the i. r. and Raman bands

- 125 -

throughout the whole vibra tional range. In conjunction ~'li th the

calculations outlined in Table XXVIII, these data indicate that

the ligand adapts the C2v "tub" configuration. A similar

conclusion was reached previously on the basis of limited data97 .

Pourteen polarized Raman bands are expected for the C2 v

speciesi 3 in the C-H stretching region, and Il in the lower

frcquency range. The blO extra polarized bands in the v (C-H)

s t.retching region, as in the case of NBD, are probab ly due to

Fermi resonance between the C-H stretching modes and the over-

tones of the C-H bending fundamentals in the neighbourhood of

1430 cm-1 . In particular, it seems likely that there is a Fermi

interaction between the 2884 and 2829 cm- 1 bands and the over-

-1 tone of the 1430 cm bending fundamental.

-1 The two v(C=C) fundamentals are expected in the 1700-1500 cm

region. Therefore: the very strong 1661 -1 cm polarized Raman band

is assigned to the al v(C=C}

is attributed to the hl mode.

mode, while -1 the 1657 cm i.r. peak

These values are somewhat higher

than the similar fundamentals of other olefinic sys te ms ; C2H4

(1623 cm-1}100, HBD (1574, 1544 cm-1), COT (1653,1635 cm-1)*,

butadiene (1638,1599 cm-1} 65, cyclooctene (1648 cm-1} 101.

2. Vibrational Assignments for [(COD}RhCl]2 and [(COD}CuCl]2

For the rhodium complex, an X-ray investig'.ltion has

established a square-planar coordination around the rhodium atom

* The spectrum of this compound was run incidentally in the

preliminary stages of the work described in this thesis.

- 126 -

with a coplanar arrangement of the four C=C centers, ·the two

rhodium, and the two c;hlorine atoms95 . The space group is C~h

with four molecules per unit celli the molecular symmetry is

D2h and the COD rings are in a tub configuration. In the case

of the copper complex, the Cu(I) is quasi-tetrahedrally co-

ordinated to the two chlorine atoms and the cent6rs of the two

double bonds of COD 96 . The COD is again in the tub configuration~

There are two molecules, of D211 symmetry, per unit cell (space

group Pl). The molecular confiCJurations of these two species

are shown in Figure 33.

Figure 33. Molecular structures for [(COD)RhCl]2 and [(COD)CuCIJ 2 •

Owing to the complexi ty introduced by the large liga.nd, vibra-

tional assignments will be made only for the fundamentals

involved directly in the olefin-metal-halogen bonding. The

symmetrj and activity of these fundamentals are described in

Table XXIX.

l

- 127 -

TABLE XXIX.

SYNMETRY AND ACTIVI'l'Y OF THE

[(COD) RhCl] 2 and [(COD) CuCl] 2 FUNDANENTALS.

Fundamental [ (COD) RhCl] 2 [(COD) CuCl] 2

\l (M-L) a g + bIg + b 2u + b 3u a g + b 2g + b lu + b 3u

\l (C=C) a g + bIg + b 2u + b 3u a + bIg + b 2u + b 3u g

\l (M-X) a + b, + b 2u + b 3u a + b 2g + b + b 3u g log g lu

Activity: a g' b -19

Raman active

b 2u ' b 3u - infrared active

OWing to the center of symmetry, each of the above types of mode

should exhibi t two bands in the i. r. and two in the Raman wi th

no coincidences between them (Hutual Exclusion principle) .

The solid state i.r. and Raman spectra of the two complexes

are shown in Figures 34-37. For the purpose of easier comparison

between the three COD complexes and the free ligand, these spectra

are also shown in bar-graph from in Figures 38 and 39. The

frequencies are listed in Table XXX. The spectra \vill be

considered in the distinct regions of the three fundamentals

mentioned in Table XXIX.

- 128 -

(A) Figure 34. Infrared spectrum of [(COD)RhCl]2 (Nujol and

HCBD mul1s) .

(B) Figure 35. Raman spectrum of [(COD)RhCl]2 (solid state).

Instrument Controls 200 -60 1630-160 3080 -2 830

Exc. 647.1 647.1 647.1

Power 80 80 80

Slit 5 7 6

Sens. 5 x' 10 2 2 x 10 2 102

T.C. 10 10 40

Scan 10 10 5

Chart 12 12 6

\ \ \ '\

\

---'---l" ~. o o ~

::>:)N';'l.lI:r-JSN\>'H.l

(A)

o o ru

o o C\l

o o ~Q

)"1ISN3.!NI

(E)

-_ ... _----_._----- ---- ---- ------ ._------ "!::-

--------.- <:- -----... '-------,.

~ -----_ . .---':li._. _~ _.-

-------~

-~ .. --------._------_. --- --=-_._---~~

-t-~:.~ ...

À1ISt~31tJ:

(B)

o o N

o o 1.0

- 129 -

(A) Figure 36. Infrared spectrum of [(COD)CuC1]2 (KBr pellet).

(B) Figure 37. Raman spectrum of [(COD)CuCl]2 (solid state).

Instrument 3130-2780 ContraIs 1670-160 200-30

Exc. 647.1 647.1

Power 90 90

Slit 5.5 5.5

Sens. 5 x 10 2 x 10 2

T.C. 40 10

Scan' 5 10

Chart 6 12

,,--:>

( \

\ '---- --

~-=- --.: :---:::::=----~,

~~

~

\. 3::lN, 0' WlllV~('"N"'ë.1

(A)

- ----l"E u

a a oq

a f6

o o ~

a a a C\J

----

;"1 1 SI\! 3 lN 1

(B)

-~:-~..:.-.......

AlISN::iHJ!

(B)

l,-lE u

o

o o 10

o -16

- 130 -

(A) Figure 38. Bar-graph representations of the infrared spectra


(B) Figure 39. Bar-graph representations of the Raman spectra


J ~-~ --=1- 1

'" l <f ""...:'1 :J '0 U U = .c"Q 0Sl 0: ëi 0 8 <Il .Y.. Q

(A)

OV o -. '0 (1 .= C\J 0

Ô <Il

o ~J

1'7 .. _ 't:

u

o o <;f

o o CO

.----~------- 1 ~ --- ---. ---------- --- ._ ___ -- - - -1. _____ - __ - --

- ---.---- --._----

U "0 î) ~ () If)

------------ -1---- __ -----_.--

(B)

=C';I u " -g u '0 8 ." Q

'ïE u

o o ~

o ~-- ------------- 0

:0

-t~ ------------t ----

- 0 o

jg

IR

3030

3006

2993

2981

2944

2916

2879

2834

1477

1469

1446

1430

1424

1372

1330

1324

1300

- 131 -

Ti\BLE xxx.

VIBRATIONAL FREQUENCIES OF

-1 * [(COD)RhCl]2 ~BD [(COD)CuCIJ 2 (cm ).

[ (COD) RhCl] 2 [(COD)CuCl]2

Raman IR Raman

(5 ) 3026 (sh) 3085 (6)

(sh) 3006} 3066 (6)

(30) ( 22) 2990 3011 ( 17) 3008 ( 18)

(sh) 2971 (sh) 2983 ( 22) 2978 (5)

( 30) 2936 (sh) 2954 ( 27) 2955 (5)

(sh) 2911 ( 20) 2926 (30) 2924 (30)

(32) 2877 (75) 2885 (40) 2881 ( 52)

(28) 2831 ( 40) 2832 (27) 2829 (12)

(sh) 1478} 1611 (12

( 20) ( 22) 1467 1550 ( 3) 1563 (12

(6) 1446 (sh) 1474 ( 32) 1486 ( 12)

(sh) 1432 (20 ) 1450 ( 15) 1446 (sh)

( 15) 1428 ( 51) 1428 (50)

(2) 1372 (10) 1393 ( 1)

(sh) 1385 (7 )

(25) 1325 (10) 1344 ( 13) 1341 ( 10)

( 17) 1299 {l2} 1316 ( 4) 1318 (10)

br)

br)

- 132 ..

1226 ( 5) 1236 ( 40) 1311 ( 10)

1210 ( 10) 1212 ( 8) 1260 (53)

1189 ( 22) 1237 (29)

1169 (24) 1175 (19) 1200 (12)

1149 (16) 1185 ( 18)

1076 ( 10) 1076 (6) 1161 ( 3)

1004 ( 25) 1082 ( 13) 1082 (6)

993 ( 52) 994 (sh) 1101 ( 20)

960 ( 100) 961 ( 25) 993 ( 23) 980 (sh)

879 ( 15) 880 ( 45) 956 (25) 959 ( 50)

866 (16) 901 (5)

831 ( 12) 864 ( 10)

816 (50) 844 (l8)

795 (5) 817 ( 29)

773 ( 28) 776 ( 70) 806 (sh) 811 (85)

695 (5) 742 (63)

583 (2) 58'2 (27) '129 (2'5)

514 (2) 513 ( 55) 714 ( 45)

488 (9) 671 ( 7)

477 (6) 477 ( 120) 647 (27)

393 (60) 515 (20)

387 (11) 385 ( 50) 480 (5) 481 ( 20)

351 (37) 455 ( 2)

** 278 266 (32) 411 (5) 409 (50)

** 260 249 ( 30) 348 (4) 350 ( 15)

, 165 {sh)

*

**

***

- 133 -

*** 137 (25) 349 (w)

126 (la) 291 (95)

102 (15 0) 223 (sh)

89 (20) 177 (s)

82 (l5) 151 (100)

115 (sh)

102 (80)

73 ( 100)

AlI data refer to solid state spectra.

From reference 88.

Far-infrared spectrum run for Nujol mull (reproduced be1ow) .

w u z ~ 1-~ lfl Z <l: 0:: 1-

'--"--~I ~ 100 cm-1 300

- 134 -

a. C=C Stretching Vibrations

The v(C=C) frequencies of bonded polyolefins such as NBD,

-1 COD, and COT seem to fall in the 1500-1400 cm region (cf.

Review). In the (NBD) 1-1 (CO) 4 series presented earlier in this

thesis, the coordinated C=C modes were assigned quite unambiguously

-1 to the two bands in the 1430-1410 cm region.

-1 In the case of [(COD) RhCl] 2' assignrnents in the 1500-1400 cm

region are hindered by the obvious interference of the C-H bending

fundamentals of the free ligand (Figures 38 and 39). ~vi th sorne

uncertain·ty as to which of thesc fundamentals are transmi tted

into the spectrum of the comp1ex, only tentative assignments can

be made. In this way, the Raman doublet at 1478 and 1467 cm-1

-1 and the i. r. peaks at 1469 and 1424 cm are assigned to the biO

gerade and the two ungerade coordinated v(C=C) fundamentals,

* respective1y.

For the copper dimer, a more complex situation exists, In

* It is of interest to note the influence of the electronic

interaction around the ring on the position of the coordinated

v(C=C) mode.

v (C=C) -1 Ref. cm

C2H4 1623 100

[ (C2H 4) 2RhC1 ] 2 1520 102

[ (COD) RhCl] 2 1480-1420 this work

[(COT) RhCl] 2 1410 64

~vi th an increasing degree of conjugation, th.e C=C double bond

loses i ts strict double bon(l character.

- 135 -

the paper dea1ing \vith its X-ray structure, an i.r. band at

1612 cm- l was assigned to a v (C=C) mode96 . In this work 1 tvlO

unusua11y broad bands are found in the Raman at 1611 and 1563 -1 cm ,

but there is no i.r. peak corresponding to the published one.

From the nature and position of the Raman bands, it is concluà.ed

L~at they are not fundamentals. Since the i.r. spectrum of the

complex is featureless in the 3600--3400 cm-1 region, these bands

are not due to water in the sample. Possibly, they are

combinations and/or overtones of lower frequency vibrations. The

-1 1428 cm' IR/R bands correspond closely with strong bands found

for the free ligand. Assigning these bands to ligand vibrations,

-1 -1 the 1474 and 1450 cm i.r. peaks and the 1486 and 1446 cm

Raman bands are assigned to the four v (C=C) fundamentals. As

expected, these i.r. and Raman bands do not coincide.

b. M-C1 Stretching Fundamentals

The four fundamental vibrations due to the bridging CI-M-Cl

-1 group (a + b l + b

2 + b 3 ) are expected in the 300-200 cm g g u u

region - two should be Raman active and two i.r. active.

-1 Consequently, it is reasonable for the bands at 278 and 260 cm -

in the far-infrared spectrurn of the rhodium species to have been

, d th" t' - ~ 1 88 assJ.gne 0 t. e ewo 1. r. aC_l ve tunaalf.enta s • In the present

-1 work, the b.ro strong Raman bands at 266 and 249 cm were

assigned to the t\vO expected Raman active modes. This is supported

by the disappearance of these two pea~s in the Raman spectrum of

the iodo-complex. The noncoincidence of these i.r. and Raman

- 136 -

fundamentals further domonst:cates that t.~e D2h molecl.l1ar symmetry

of the dimer is indeed reflected by the vibr.J.tional spectra.

In a series of bridged Cu(II)-Cl complexes, the v(Cu-Cl)

fundamentals have been identified in the 328-222 cm- l range l03

It is generally accepted that such metal-halogen stretching

fundamentals should decrease in frequency as the oxidation state

of the metal is loweredl04 • As an outgrO'\.olth of this, the strong

Ra~an bands at 291 and 151 cm- l and the i.r. bands at 223 and

177 cm -1 for the Cu (1) dimer are assigned ·to the bridging v (Cu-Cl)'

modes. Again there is a noncoincidence in these fundamentals in

line with the D2h molecular syw~etry.

c. M-L Stretching Vibrations

From the fe\ol assigned M- (C=C) frequencies, these vibrations

are expected to fall in the 500-300 cm-l region. The bands in

the neighbourhood of 350 cm- l in the Raman (present in aIl the

three complexes and the free ligand) are assigned to a ligand

vibration. For t.he rhodium complex, the strong Raman band at

513 cm -1 (wi th a coincident \oleak i. r. line at 514 cm -1) is also

attributed to a ligand mode. This leaves only three bands in

this 500-300 cm- l region, in both the i.r. and Raman! two of which

are necr::;ssarily the metal-olefin stretching vibrations. The very

-1 -1 strong 477 cm Raman band (472 cm in CS 2 , totally polarized)

is assigned to the symmetric a v (M-L) vibration, \vhile either 9 -,

the 393 or 385 cm ... band must be due to the other Raman active

mode. This 393/385 -1

Gffi doublet is not a solid state effect

-- 137 -

because both bands appear in solution. In addition, the i.r.

-1 peaks at 488 and 387 cm are assigned to the v (M-L) lib " modes. u

In the case of the copper dimer, the range of V(M-L)

frequencies is quite clearly defined. -1 Ignoring tl1e 350 cm

ligand IR/R peaks, there ure on1y three other bands in the

-1 520-400 cm region. ~vo of thesc, in boti1 the i.r. and Raman,

must be due to the H-L vibrations, there being no oilier

unaccounted bands in the 600-150 cm-1 region. On the basis of

i ts intensi ty, the 409 cm -1 Raman band is assigned ta ilie a mode. g

The other Raman active fundamental (b 2g) must ilierefore be the

-1 1 band at 515 cm . Sirni1ar1y, the 455 and 411 cm- ·i.r. peaks are

attributed to the two lib U" fundalllentals.

3. Vibrational Assignments for (COD)2CuCI04

In the paper desc~·ibing the electrochemical preparation of

98 this compound , blO characteristic i.r. bands were cited at

1638 and 1595 cm-1 • Ass~ming that these were due to v(C=C) modes,

it was conclnded that there is a non-equiva1ent coordination of

the two COD groups. This author fee1s that these data do not

prove the existence of symmetrica11y non-equiva1ent groups, at

best on1y that the dienes do not coordinate in a tetrahedra1

fashion with the Cu(I). For examp1e, in a C2v configuration,

four IR/R active v (C=C) modes are expect.ed, despi te the fact tha1:

the C=C groups would be equiva1ent1y bonded. Moreover f during

the CO'..lrse of an extremely câ!.-eful spectroscopie investigation,

the 1595 cm-1 band was found to be real, while the 1638 cm-1

- 138 -

peak \Vas ne va r reproduced. HO\vever, in one case 1 for a vlet KBr

disk, an additional band \'las found at '\"1630 cm- l - bands in this

neighbourhood are typical1y attributed to ,vater.

The solid state i.r. and Raman spectra are reproduced in

Figures 40 and 41, the spectral data are listed in Table XXXI.

The most striking feature in the i.r. and Raman spectra of

(COD) 2CuC10 4 is the very strong Raman band at 1591 cm -l, coinciden·t

with a medium intensity i.r. band at 1590 cm- l • Such a frequency

is too high for a coordinated double bond. However, it is

precisely in the region that a non-cool'dinated double bond of

a complexed polyene is anticipated (vide supra, p. 81 ). This

observation is further supported by the appearance of a strong

i.r. band

cis- (C=C)

-1 at 763 cm ,

105 group

which is i.ndicative of an uncomplexed

Accepting that there is a non-bonded C=C group and tllat

there are two COD groups per copper atom (from elemental analysis

data), five reasonable structures can be postulated for the

complex in the solid state. These are shown in Figure 42. The

spectra, as in the case of the other COD complexes, will be

conside!:ed in the \.l (C=C) and \.l (H-L) regions.

As mentioned above, one band characteristic of an uncornplexed

double bond is observed, [1591 (R) /1590 cm- l (IR)]. The vibra-

tions of the complexed dow)le bonds are again anticipated to be

in the 1500-1400 -1 cm region. The 8(Or 2 ) vibrations of the free

olefin rnask this regioll, alloKing only tentative assj gnment.s to

be made. -1

Thus 1 the three Harou.n bands at 1485, 1455 and 1403 cm

- 139 -

(A) Figure 40. Infrared spectrum of (COD)2cuCI04 (KBr pellet).

(13) Figure 41. Raman spectrœn of (COD) 2CuC104 (solid state).

Instrument 3100-2730 Contro1s 1720-40

Exc.

Power

Slit

647.1

Sens.

T.C.

Scan

Chart

5 x

70

4

10

10

5

6

L __ _

f

t '< ~~---~=:=.~=--'--::.:."-~-~

-------~-~~-::=:::;~~=~~-

(

\

\ \,

'-.. -. . ~-:.:. .. ~-

<jE u

o o o (Il

1

,l.liSN31NI

(B)

o o N ~

o o ~q

) - :-.. -.~ .. - -----::::,.

... _.~ -.

~ ~ --y

)

o () o

IR

3032

3013

2951

2937

2894

2845

1590

1483

1450

1430

1387

1348

1323

1257

1234

118R

1165

- 140 -

TABLE XXXI.

VIBRATIONAL FREQUENCIES AND ASSIGNMENT

-1 a OF (COD)2CUC104 (cm ).

Raman Assignment

(sh) 3020 (15)

(5)

( 17) 2963 (sh) v (C-H)

(3) 2932 (15)

( 32) 2898 ( 42)

(20) 2847 ( 12)

( 10) 1591 (90) v(C=C)free

( 32) 1485 ( 8) v (C=C) coord.

(10) 1455 ( sh) v (C=C) coord.

( 33) 1440 (23) ô (CH 2)

(5) 1403 (5 ) v(c=C)coord.

( Il) 1350 ( 4)

( 18) 1325 ( 4)

1309 (3)

(sh) 1260 (50)

( 15)

1203 ( 15)

(6) 1192 (sh)

( 8)

-- 141 -

10901 1090 (6) l

} b J(65 br) · .... '0 v 4

1080 1080 (6) "'-- 4

1015 ( 17)

9 86 ( 15) 995 (16) ClO4 vI

938 (2) 932 ( 65) CI04 v 2

907 ( 17) 910 ( 10)

868 ( 3)

852 (20)

823 ( 35) 832 (55)

763 (46) 750 ( 13)

734 ( 35)

680 ( 3)

663 ( 17) CI04 \i 3

653 (sh)

638 (sh)

625 (57) 624 ( 10) C104 v 5

520 (3) 520 ( 14) v (Cu-L)

498} 498 (h\ v{Cu-L) ,- , (3)

488 ligand

453 (2 ) 458 ( 12) C104 v6

413 ( 10) 415 ( 22) \i (Cu-L)

355 ( 22) ligand

289 ( 37) v (Cu-Q)

141 ( 32)

._---_.

a Solid state values.

b Fundamenta1s of C104 described in Table XXXIII.

- J.42 -

-1 with corresponding i.r. bands at 1483 and 1450 cm are assigned

to the fundamentals of the coordinated C=C bonds.

In the low frequency region (600-300 cm- l ) , there are two

easily eliminated interfering vibrations. The Raman peak at

-1 350 cm is assigned to a ligand mode, as in aIl the previous

cases. -1 . The very weak 488 cm l.r. band, absent in Raman; is

also attribu·ted to a ligand mode. In addition, the i.r. and

Raman absorptions at 453 and 458 cm-l, respectively, are due ta

the v 6 fundamental of the perchlorate ion (vide infra, Table

XXXIII). This leaves three sets of IR/R bands: 520/520, 498/498

and 413/415 cm-l, to be attributed ta the v(M-L) vibrations.

The calculated nuIiÙJer of v(C=C) and v(M-L) modes for each

of the possible structures (shown in Figure 42) and the nurnber

actually observed are cornpared in Table XXXII. The data indicate .J_

that structure III ls the most reasonable one for (COD) 2cu' ion

in the solid state.

The structure proposed thus far is based on a three-coordinate

Cu(I). Although Cu(I) is generally tetrahedrally coèrdinated,

there are specifie examples of trigonally bonded species. For

instru1ce, the X-ray structures of both [(NBD)CUCIJ 482 ~nd

[(COT) CuCl] 106 indicate a CI-Cu-Cl chain \"ith only one C==C group n

of the ole fin being coordinated ta the copper atom. Despite

these examples, i t still remains questionable \Olhy the fourth

double bond [in (COD)2CuCI04] does not coordir-ate to the

potEmtially available bonding si te on the copper atom. One

possible explanat2.oTI is that ·the oxygen atom of the C104 group

- 143 -

Figure 42. Five possible structures for the (COD)2cu+ ion.

0f1----CU--U &--cu---ç;f~ l II

"

III

IV

v

- 144 -

TABLE XXXII.

NU~1BER OF VIBRI\TIONAL MODES

FOR THE POSSIBLE STRUCTURES OF (COD)2CU(I) ION.

Structure Syrcunetry \1 (C=C) free v(C=C)coord. \) (M-L)

l C2v 2 IR/R 2 IR/R 2 IR/R

II C2h l IR, l R l IR, l R l IR, l R

III C l IR/R s 3 IR/R 3 IR/R

IV C2v 2 IR/R 6 IR/R 6 IR/R

V C2h l IR, l R 3 IR, 3 R 3 IR, 3 R

No. observed l IR/R 2 IR/R, 1 R 3 IR/R

liE~s close ene·ugh to' the copper atom to satisfy this fourth

coordination site. A closer examination of the spectra does

indeed support this hypothesis.

Although Cl04 is generally considered as a non-coordinating

ligand, there are instances where the oxygen atoms are coordinated.

coorc1inated octahedrally by four sulfur ane t\"c oxygen 107 atoms .

'l'he Co-O distance is 2. 341L o Since this distance is O.l-O.3A

longer than other Co(II)_o bonds, it supports ~1e argument that

the anion is only vleakly bonded ~ nevertneless, i t is bO!:1deà.

A coordinated perchlorate group shou1.d give rise to a l'ilet.al-

- 145 -

oxygen stret.ching vibration. In a series of M-(acac) complexes,

including Cu (II), one of the hlO \) (M-O) frequencies has been

assigned in the 300-290 cm- l regionl08 In view of this, the

t b d f ( ) 1 2 89 -l, 'd s rong Raman an or COD 2CuC_04 at cm lS asslgne to

the \.' (Cu-O) mode. l'li th one of the oxygen a-toms bonded, the

tetrahedral perchlorate group undergoes a C3v

perturbation.

8uch a perturbation of the CI04 group has been considered

109 previously for a Cu(II) compound, Cu(CI04)2.2H2o . The cor-

relation between tl1e free (T~) and coordinated (C3 ) ion is Q v

shown in Table XXXIII. This perturbation should be, and is,

manifested in the vibrational spectrum of (COD)2CUCI04. As

seen in 'l'able XXXI, i t is possible to assign bands to aIl of

the expected modes of the perturbed perchlorate grou.p. Based

solely on the spectroscopie evidenee presented above, the final

postulated structure for (COD)2CuCI04 i5 shown in Figure 43.

AlI the proposed vibrational assignments for the three

COD complexes ean be found in 'l'a'Jles XXXI and XXXIV.

Figure 43. Pcstu1ated structure for (COD)2cuCI04.

KCI04 -·1 IR( cm )

932 VVl

460

1110 vs

626 vs

TABLE XXXIII.

CORRELATION DIAGRi\H FOR

THE Td m~D C3v PERCHLORATE IONS. a

CI04-(T

d) * M-O -CI0 3 (C3v)

* VI al (R) sym. str. ) v 2 al (IR/R) CIO str.

\)2 e (R) sym. bend. ) \) 6 e (I R/ R) rock

~ \)1 al (IR/R) CI03

str. \)3 t 2 (IR/R) asym. str.

* ~ \)4 e(IR/R) CIO asym. bend.

~ \)3 al (IR/R) CI03 sym. bend. \)4 t 2 (IR/R) asym. bend.

~\)5 e(IR/R) CI03 asym. bend.

a From reference 109.

CU(CI04 )2· 2H 20

-1 IR( cm )

920 vs

480 m

1030 vs

1158 vs

648 s

62O} 605 s

1-' ,!:.

~

- 147 -

TABLE XXXIV.

ASSIGNED FUNDM1ENTAL I-10DES (cm- 1 )

* OF [(COD)RhCl]2 AND [(COD)CuCl]2.

[ (COD) RhCl] 2 [(COD) CUC1] 2

IR Raman IR Raman

v (C=C) sym. 1478 1486

v (C=C) sym. 1467 1446

v (C=C) asym. 1469 1474

v (C=C) asym. 1424 1450

ligand 514 513 480 418

v (M-L) asym. 488 455

v (M-L) a g 477 409

v (M-L) bIg 393 515 (b2g

) 385

v (I-1-L) asym. 387 411

ligand 351 348 350

v (M-C1) asym. 278 223

v (M-Cl) sym. 266 291

v (M-C1) asyrn. 260 177

v (M-C1) sym. 249 151

* Frequencies from 'rab1e xxx.

- 148 -

D. CONCLUSION

Vibrational assignments have been proposed for the i.r.

and Raman spectra of COD, [(COD)RhCl]2' [(COD)CuCl]2 and

(COD) 2CuC104. The data for liquid COD verify that othe ligand

exists in a IItub ll configuration. Due to interference by ligand

modes, the v(C=C) fllndamentals of the bonded COD can be only

tentatively assigned to the 1480-1400 cm- l region - a range

proposed previously for modes of this type. The H-L stretching

frequencies have also been designated, in sorne cases quite

specifically, to bands in the 520-380 cm- l region. This range,

in contrast tothat for the M- (NBD) stretching frequencies, falls

within the previously established range for such fundamentals.

Assignments have also been made for the v(M-Cl) stretching modes

of the rhodium and copper dimers. In the case of the copper

-1

complex, one of these modes occurs at a lower frequency (151 cm -)

than usual.

On the basis of spectroscopie evidence, a structure !las

been proposed for the complex, (COD)2cuC104. The main points

of the argument are as follovlS. Firstly 1 there certainly exists

a non-bonded ethylenic group. Second, a low frequency Raman

band can be attributed to a Cu-O vibration. Further evidence

points to the reduction of symmetry of the C10 4 group. Since

there are also ~~10 COD groups per copper atom, the postulated

structure is the only one t.hat agrees wi th the available data.

PART III

7r-CYCLOPENTADIENYLMANGANESE (I) THIOCARBONYLS,

CpMn(CO)2CS AND CpMn(CO) (CS)2

- 149 -

CHAPTER 1. IN'rRODUCTION

In the literatnre, untold numbers of carbonyl complexes

have been documenteà for essentially aIl ·the transition metals.

In contrast to this, the analogous ·thiocarbonyl complexes

containing the terminal CS grouping are known for only a limited

number of metals; in fact, only abou·\: 25 such complexes have

been identified. Moreover, most of these thiocarbonyl complexes

contain Group VIII metals such as ruthenium, rhodium and iridiumllO •

As yet, to the best of the author's knowledge, a detailed

vibrational assignment for a Uliocarbonyl complex has not been

reported. To date, the approach to the spectra of thiocarbcnyls

has been ra"ther·limited. In every case, only the i.r. active

(C S) f d t 1 · b t dlll-118 d th ~ v - un amen a s nave een repor e ,an even .en on.Ly

frcr!:l the viewpoint of characterization of the complexes. These

fundamentals oocur in the 1380-1250 cm-l regionl19 •

This vlOrk was u!lder'caken follovling the serendipi tous

c1isc:V'3.r:y in t.his lél. .. ~oratory of the complex, CpHn(CO) 2CS. This

compound is obviously similar to the analogous tricarbonyl

complex, for which the vibrational spectra have been thoroughly

.... '" dl20-l23 s\.-ua~e . rrhus, it vias deemed of interest to investigat.e

the vibrational spectrum Qf this thiocarbonyl complex. It ".tlas

hoped that the fundameni:.als associated wi th the Mn-C-S moiety,

-1 particularly in the low frequency (700-300 cm ) region, could

be located and assigned. Such assignrnents \"10uld establish a

precedent for the subsequent interpretation of t.~e spectra of

other thiocarbonyl complexes.

,

- 150 -

Before the resul ts are discussed in Chapt.er 3 , the

experimental procedure will be described briefly in Chapter 2.

- 151 -

CHAPTER 2. EXPEfUHENT1\L

!n-CycZopentadienyZ)dicarbonyZ(thiocarbonyZ)manganese(I),

CpMn(CO)2CS and (TI-cyqZopentadienyZ)carbonylbi~(thiocapbonyZ)-

124 manganese(I) , CpMn(CO) (CS)2' were prepared by Mr. A.E. Fenster •

The first compound was purified by vacuum sublimation at room

temperature, before the spectra were obtained. In contrast to

this, successive sublimations of the latter compound did not

eliminate aIl of the mono-Qliocarbonyl complex. The amount of

this remaining impurity, however~ is estimated to be in the

order of 1%. The iron complexes, [CpFe(CO)3]BPh4 and

[CpFe(CO)2CS]BPh4, were prepared by the author through pLilllished

methods 125,126 .'

The Raman spectrum of the powdered CpMn (CO) 2CS ',vas obtained

in a capillary, using the 647.1 nm ex ci ting line at 45 mlv pm'ler.

The solid state spectra, at room temperature and at -78°C, did

not show any significant difference. Solution Raman spectra

were attempted several times, however, under aIl the varied

conditions, the solutions decomposed rapidly.. The Raman spectrum

of CpNn(CO) (CS) 2 was run for the solid s·tate sample (647.1 nm/

60 mW). The iron complexes yielded only very low quali ty Raman

spectrai the majority of the bands were those resulting from

the BPh4 anion.

The i.r. spectra of Cp!-1n(CO) 2CS \olere obtained in a host of

solvent.s and in the solid state (KBr disk). The solid state

i . r. spectra of Cpr.1n (CO) (CS) 2 and the tvlO iron complexes ~vere

recorded for the sarnples pressed in KBr disks. The vapour

- 152 -

phase i.r. spectrum of the mono-thiocarbonyl complex was obtained

for the sample heated to lOQoe in an evacuated Beckman heated

gas celle The far-infrared spectrum was cbtained for the

compound dispersed in a Nujol mUll, and dissolved in benzene.

- 153 -

CHAPTER 3. RESULTS k~D DISCUSSION

In discussing the vibrationa1 modes of CpMn(CO)2CS and

CpHn (CO) (CS) 2' the now \ve11-established concept of "local

symmetry", as proposed by Cotton et aZ. 127 , will be employed.

As a consequence of this theory, to a first approximation,

Cp~1n (CO) 2CS can be considered as two distinct non-interacting

parts: the Cp-Mn group of CSv symmetry, and the Mn(CO)2CS group

of Cs sy~~etry. The same approach is taken for the groupings

of CpMn(CO) (CS)2. (It will be determined later to what extent

this assumption of non-interaction between the two parts of L~e

molecules is justified.)

In keeping with this approach, the vibrational spectra of

these complexes will be considered in the two distinct parts:

the vibrations of the Cp-Mn moiety, and those of the Mn(CO) (CS)L

group. The symmetries of the fundamental modes of these groups

[for CpMn(CO)2CS] are listed in Table XXXV.

A. RING VIBRATIONS

The common point of comparison of the vibrational spectra

* of the three similar compounds, CpMn(CO) 3' CpMn(CO)2CS, and

CpMn(CO) (CS)2' is the assessment of the ring vibrations of

* The isoelectronic analogues, (CpFe(CO)3]BPh 4 and [CpFe(CO)2CS]BPh4,

of the first two compounds, have also been synthesized. The

observed frequencies, minus those definitely attributable to BPh4 are listed in Table XXXVI. Assignments can be proposed for these

compounds, or.ly in the regions where t.he BPh 4 vibrations ào not

interfere.

- 154 -

TABLE xxxv.

* SPECTHAL PREDICTIONS FOR Cpt'ln (CO) 2CS.

** Mn(CO)2 CS

Fundarnental 122 Syrnrnetry Fundarnental Syrnmetry

C-H str. al + el + e 2 c-o str. a' + ail

C-H bend. (1) al + el + e 2 c-s str. a' ·0 *** ring breath. al Mn-C str. a' + ail

C-H bend. (II) a2 + el + e 2 l' CS 'ln- str. a'

C=C str. al + e 2 Mn-C-O bend. 2a ' + 2a"

C=C benè.. Cl) e 2 rtill-C-S bend. a' + ail

c=c bend. (li) e 2 C-Mn-C dei. a'

Cp-Hn str. al C-Mn-C ' def. a' + ail

Avtivitics fOl:' CSv: al (IR/R) , a" (inact.) ... , el(IR/R) , e 2 (R)

C : s a' (IR/R) , ail (IR!R)

* The ring-to-I'h1 (CO) 2 CS skeletal modes are: Cp-~1n s tr. (a ') ,

ring tilt (al), ring twist (ail).

** ***

For the modes of the r.ln(CO) (CS)2 moiety, interchange o and S.

In this Parc the Mn-C stretching modes will be differentiated

as being either a Mn-carbonyl or Mn-thiocarbonyl type, by the

a.ppropriate superscript on the C atome

- 155 -

TABLE XXXVI.

* INFRARED FREQUENCIES AND ASSIGN~ŒNTS

-1 FOR [CpFe(CO) 3]BPh4 AND [CpFe(CO)2CS].BPh4 (cm ).

+ [CpFe(CO)2 CS ]

solid

3117 w

3097 m

2092 vs < a')

2058 vs (ail)

2027 w,sh

1416 m,sh

1347 vs

833 w

764 w,sh

+ [CpFe(CO) 3]

solid

3107 sh

3099 s

2121 vs (al)

2076} vs (e)

2068

2040 w,sh

2025 w,sh

1705 vw

1440 w

1419 sh

1361 vw

1342 vw

1114 m

1015 w

907 w

764 w,sh

Assignment

C-H stretch. al

C-H stretch. el

C-O stretch.

C=C stretch. el

C-S stretch. a'

ring breath. ~1

C-H bend. <n) el

C-H bend. (1) al

- 156 -

730 s 732 m,sh

720 m,sh

597 s

1 572 s 578 s Fe-C-O bend.

565 sh

480w

463 w

439 w

401 vw Fe-C stretch.

387 w Fe-ring stretch.

375 vw Fe-ring tilt

** 364 vw

345 \'1 349 w

310 w

* Bands directly attributable to the BPh4 anion, are not recorded

in this Table.

** The Raman spectra of both complexes have been rune The only

significant peaks obtained are those for the tricarbonyl cornplex

at 365 (w) and 315 (w) cm-l.

- lS7 -

these complexes. The vibrations of the TI-cyclopentadienyl ring

have been studied extensively for various complexes by Parker

and Stiddard122 • Their approach will be employed here.

The vibrational spectra of CpI'in (CO) 2 CS are reproduced in

Figures 44 (vapour phase i.r.), 4S (soluti.on i.r.), 46 (far-

infrared), and 47 (solid state Raman). The solid state i. r. and

Raman spectra of Cp~m(CO) (CS)2 are shown in Figures 48 and 49.

The observed frequencies are collected together in Tables XXXVII

and XXXVIII. Fer comparative purposes, the solid state i.r. and

Raman spectra are also represented in bar-graph form in Figures

50 and 51.

Not surprisingly, there is good agreement between the

frequencies observed for the relateü modes of the three complexes

(Table XXXIX). The only exception is the appearance of the e 2

Raman band (v 9) at ~2970 cm-l in the spectra of the thiocarbonyl

complexes. Previously, this mode had not been observed for any

TI-cyclopentadiellylmetal carbonyl complex, and consequently had

been assumed to be accidentally degenerate with VSo In the

present work, it is possible that the v9 mode has been shifted

('\1120 cm -1) by a weak hydrogen bonding effect in the crystal

bet\veen adj acent TI-CSH5

rings 12 B

From Table XXXIX, it is immediately evident that the ring

modes of the CS deri.vati ves of Cp~..n (CO) 3 conform much more

closely to the predicted activities, based on CSv geometry, than

dû those of CpHl'1 (CO) 3' In particular, the IR/R inactive v 4 mode

which is masked by 'J (C-S) in the case of CpM...'1. (CO) 2CS is defini tely

not observed in the spectrum of the CpMn{CO) (CS)2 complexo Of aIl

- 158 -

(A) Figure 44. Infrared spectrum of CpMn(CO)2 CS (vapour phase) •

(B) Figure 45. Infrared spectrum of CpIVm (CO) 2 CS (CS 2 solution) •

( C) Figure 46. Far-infrared spectrum of CpMn(CO)ZCS (benzene

solution) •

(D) Figure 47. Raman spectrum of CPMn(CO)2CS (solid state).

Instrument Contro1s 3200-3050 2100-520 520-100

Exc. 647.1 647.1 647.1

Power 45 45 45

Slit 4.5 5 4

Sens. 2 x 10 2 x 10 2 5 x 102

T.C. 40 10 10

Scan 5 20 20

Chart 6 24 24

3:JN'9' llli'\lSN'9'èll

(A)

o o <:

0 0 co

0 0 ~

0 0 '!2

0 0 0 C\j

o o ll1 N

o o o CO)

,-------'.,5 - <::::...-

~ ---- --

==--c----- -- -r---~=-

ç r~

.. --=---

(---~

)

! ?

c!-<; f:'~

'<-- _. - ---~-~-=----)

'f C-.--

~~ a 0 co

[§

0 a

~"

0 0 a N

a a ,g

l,__ 1 '---~:: .-.,-- J

--_._-

(B)

:3:)N'\11 l 1 V'-l SN "lèi l ( C)

1'1 E u

o o ~

o o C")

Al1SN31.NI

(0)

o o <0 ....

o o o C\I

o o .... fi')

------- ~~

LL-_~===-=::::::: ~

AliSN31NI

(D)

o o '<f

o o a:J

o o

l" 1

- 159 -

(A) Figure 48. Infrared spectrum of Cp!.1n(CO) (CS) 2 (solid state) •

(B) Figure 49 • Raman spectrum of CpHn(CO) (CS)2 (solid state) •

Instrument Controls 3160-2900 2100-150 150-20

Exc. 647.1 647.1 647.1

Power 60 60 60

Slit 5 4 4

Sens. 5 x 10 10 2 10 3

T.C. 40 10 2

Scan 10 20 50

Chart 12 24 48

,.--_._._~----_.~

.~-.-

3:JNXflJ.'iI'ISN"'~1

(A)

o o CO

o o (\j

o o ~

o o o M

-

(B)

Al.l9Gl.NI

.. ------ .. - '---".,

} }

..-'" ~

o ~

§ c.'

8 ...

- 160 -

(A) Figure 50. Bar-graph representations of the infrared spectra

of CpMn(CO)3 and its CS derivatives.

(B) Figure 51. Bar-graph representations of the Raman spectra

of CpMn(CO)3 and its CS derivatives.

1 :E ~

u

0 0

~ "'"

~ ~

~ 0 0 CO

1

j ~=t l

1 !

N ~

l 1

N ;j') 1 f§ ~ l' 1 ~ - & ~

B B 1 B t CCI C 2 2 2 a a a U U U

1 .

--l

1 2

1 1 J ,1.

1 f~ ~ -=t

(A)

9-' ~ --- -

1

,

----~ --~ ---

--

1

- ~

,.sJ I..f' Ul U ~ 1 Â" Ô 0 !d .!::I c c ::E ::E a a U U

1

l + j 1

1

(B)

-. -

~I o o .;r

~ 1

o o

'0 C\:

TABLE XXXVII.

SOLID STATE INFRARED AND RAMAN DATA (cm -1)

AND ASSIGNMENTS FOR CpMn(CO)2CS AND CpMn(CO) (CS)2.

CpMn (CO) (CS) 2 CpMn(CO)2 CS

IRa Ramanb IRa Ramanb Assignment

3110 vw 3115 3120 w 3124 C-H stretch. al

2972 2971 C-H stretch. e 2 1--'

'" 1-' 1997} 2009 vs 1986 (50) C-O stretch. a' 1989 vs 1980 1981 (15)

1933 vs 1953 (90 ) C-O stretch. ail

1914 w,sh

1424 m 1422 m 1427 (8) C-C stretch. el

1338 (18)

1298 vs 1260 vs C-S stretch. a'

1289 sh

1235 sh 1213 sh

1220 vs C-S stretch. ail

1113 (60) 1115 w 1116 (130) ring breath. al

1060 "vVl 1064 m 1068 (9) C-H bend. (1) e 2

1011 vw 1005 w C-H bend. (II) el

923 vw

865 vw

845 vw,sh 845 (10) C-H bend. (1) el

832 s 834 (12) 835 s C-H bend. (1) al '\

625 m 645 s 646 (8)

590 s 607 s 609 ( 4) 1-'

570 s 0\ IV

, Mn-C-O and 499 m 500}(10) 516 s 511 (15)

494 Mn-C-S bend.

479 rn 478 (30) 473 vw

448 vw 437 sh ~

429 V'il 428 (85) 458 vw 460 (140) Mn-Co stretch. al

437 vw 437 (43) 0 . i'ln-C stretch. ail

419 '\'1 (360 + 60)

404 (43) Mn-Cs stretch.

382 w 383 (w,sh) ring tilt al

364 w

359 (55)

350 (vw,sh)

321 (500) 339 w

135 s c

115 (55) 110 m,br

92 (vs) 92 w,sh

72 (vvs) 60 m,br

39 (vvs)

a Spectrum run for pressed KBr disk.

b Recorded for the powdered sample in a capillary.

c Far-infrared data for Nujol mull.

367 (55)

338 (150)

136 (50)

120 (180)

83 (800)

s Mn-C stretch. al

Mn-Cs stretch.

ring tilt al

ring-Mn stretch. al

def. and

lattice modes

....... 0'\ W

- 164 -

TABLE XXXVIII.

INFRARED DATA AND COMPLETE VIBRATIONAL ASSIGNMENT

-1 CS

2 (cm )

4005 s

3940 vvs

3900 s

3121 s

2719 w

2656 ID

2613 s

2562 rn

2521 s

2477 s

2438 w,sh

2424 m

2389 m

2365 VVi ,sh

401.2 s

* FOR CpMn (CO) 2 CS IN SOI,UTION.

4016 ID (2007 + 2007)

3942 vs 3946 s (2007 + 1956)

3904 s 3910 ID (1956 + 1956)

3117 s 3125 ID C-H stretch.

2719 w (3121 - 399)

2670 w 2660 w (2007 + 645)

2617 ID 2615 ID (2007 + 612) ,

2562 ID 2564 w (1956 + 612) ,

2523 s 2527 ID (2007 + 519) ,

(1266 ;. 1266)

2476 s 2485 ID (1956 ;. 528) ,

2442 ID 2446 w,sh (2007 + 430)

2432 ID 2430 w (2007 + 409)

2391 w 2393 w (1956 + 430)

2365 w (2007 + 360) ,

2334 ID 2340 m (1962 + 379)

2273 ID 2279 w (1270 + 1005)

2135 \"l (2007 + 122)

al

(2007 + 605)

( 1956 + 605)

(2007 + 513) ,

(1956 + 519)

(1956 + 409)

i'

2007 vs 2016 s

1996 vw 1999 w

1956 vs 1962 s

1946 vw,sh

* 1924 w ( CO) 1930 w

1879 m,sh 1888 Ir.

1836 s 1835 s

1757 m,sh 1760 w,sh

1724 vs 1734 vs

1699 vs 1706 vs

1663 s 1656 s

1602 vvs

1520 m

1266 vs 1272 s,br

1226 w

1156 w 1154 vs

1113 w 1113 s

1074 m

1061 m 1060 ln

- 165 -

2017 s

1959 vs

1931 sh

1885 w

1840 m

1759 w,sh

1729 m

1704 m

1667 w

1598 s

1425 vvs

1394 w,sh

1359 w,sh

1270 vs

1228 w,sh

1157 m

1114 w

1074 w

1061 m

C-O stretch. al

13c_o stretch. a'

c-o stretch. ail

(1113 + 824)

13C_O stretch. ail

(1266 + 612)

(917 + 917)

(1266 + 513)

(917 + 825)

(1266 + 430)

(1266 +,399)

(1266 + 330)

C-C stretch. e 2

C-C stret~h . el

{1266 + 122)

(1266 + 103)

C-s stretch. a' 13 c-s stretch. a'

C-H bend. (II) e 2

ring breath. al

(645 + 430)

C-H bend. (1) e 2

'\

- 166 -

1039 vw 1035 w,sh 1040 w (612 + 430)

1006 s lOlO w,sh 1005 s C-H bend. ( Il ) el

998 vs (645 + 360) , (605 + 399)

978 w 979 m (645 + 330)

947 m (612 + 330)

917 m 914 vs 917 m C-C bend. (II) e 2

825 vs 824 s 825 w/br C-H bend. (1) al

645 vs 646 s 645 s

612} 613 vs 613 s vs

605 605 sh 607 sh Mn-C-Q and

528 w,sh Mn-C-S bend.

519} S20}m vs 513 512 s 514

430 w 432 w 431 w Mn-Co stretch. ail

409 m (330 + 78)

399 sh 379 vw 383 vw ring tilt

360 w 361 w 364 w r.m-cs stretch. al

C6

H6

377 w ring tilt

360 s Mn-Cs stretch. al

330 w Mn-ring stretch. al

122 w ~ C-M-C and

103 C-M-C I def. w J 78 vw ring twist ail

- 167 -

Footnote to Table XXXVIII.

* The lists of frequencies have been divided into several

sections; the intensities are quoted relative to the most

intense peak within each section.

** '!he frequencies used for assignment of the cOIT~ination bands

are from the CS 2 solution data, except i.n the regions where

these are not available.

*** The frequencies observed in the vapour phase i.r. spectrum are:

3119 vw, 2973 w, 2025 vs, 1979 vvs, 1947 w, 1279 vs, 10B4 m,

1025 s, 818 s, 643 w, 610 m, 515/509 vw, 423/417 vvw, 397 w.

3125 IR/R

837 IR/R

1114 IR/R

1266 IR

3096 IR/R

lOl4} IR 1007

- 168 -

TABLE XXXIX.

COHPARISON OF THE RING VIBRZi.TIONS (cm -1)

OF CpMn (CO) 3 AND ITS THIOCARBONYL DERIVA'l'IVES.

CpMn ( CO) (CS) 2

IR Raman IR Ré".rnan

3120 w 3124 (15) 3110 3115

835 s 832 s 834

1115 w 1116 (130) 1113

masked

1005 w 1011 vw

( 12)

( 60)

Mode

(\) . } ~

1

2

3

4

5

6

Symmetry

al (IR/R)

a2

848 IR/R 845 ( 10) 845 vw 7 el (IR/R)

l424} a] IR/R 1422 m 1427 ( 8) 1424 m 1420

3096 IR/R 2971 (12) 2972 9

1154 IR 10

lO64} IR/R 1064 m 1068 (9) 1060 vw Il

1059 e2

(R)

1520 IR 12

941 IR 923 'i'W 13

611 masked masked masked 14

a The i.r. frequencies quoted are from reference 122, the solid

state Raman activities from the author's work.

- 169 -

the modes v9-v13 , which are strictly i.r. inactive, only vII is

observed in the i.r. spectrum of CpMn(CO)2CS. In addition, none

of the degenerate e modes are split in the i.r. or Raman spectra.

These observations can be interpreted to mean that there is

little intramolecular interaction in the thiocarbonyl complexes.

Thus, the tendency to lmqer the local CSv syrnmetry of the ring

to the molecular Cs symmetry, is much less in the CS compounds

than in Cp~~(CC)3. In the series constructed by Parker and

Stiddard (p. 488 of reference 122), for the order of decreasing

local symmetrj for the Cp-M moiety, CPMn(CO)2CS would fit in the

same place as CpV( CO) 4. In view of this, the possibili t l" that

the 610 crci- l ban.d in the spectra of the thiocarbonyl complexes

is due to the v14 ring mode, is considered remote, since this

mode only becomes i.r. active much farther down the series.

This means that the G10 cm- l band can then be attributed to a

Ô (Mn-C-O) fundamental. The impor.tance of this conclusion will

become evident shortly.

The fa ct that vII is the first and only e 2 mode to become

i.r. active is rationalized on the basis that this C-H (1)

bending vibration is the one that interacts most strongly with

the metal atome Such an interaction is not unreasonable when

one notes the trends observed for the frequencies of the v(C-C)

and the two other ô(C-H) (1) modes (v 2 and v7 ) for a series of

n-cyclopentadienyl complexes including the CS compounds. There

is an apparent correspondence between the charge density on the

metal atom and the position of these bending modes (Table XL) •

Complex

CpM.'1 (CO) 2NO +

CpMn(CO) 3

CpMn(CO)2 CS

CpMn(CO) (CS)2

CpMn(CO)2PPh3

- liO -

TABLE XL.

CŒ-1PARISON OF \) (C-O)

1j7ITH \)2 AND \17 (cm -1) • a

\) (C-O)

2096, 2049 885

2027, 1944 847

2009, 1933 845

'\11990 845

1934, 1864 842

852

837

835

834

829

a The data, except for the thiocarbonyls, are from Table 11

of reference 122.

- 171 -

In contrast to CPMn(CO)3' aIl the ring modes observed in

the solid state i.r. spectrum of CpMn(CO)~CS are also present ... in the solution spectrum. The relative intensities of the bands

under the two conditions are approximately the same, including

those of VIl. This indicates that there is no increase in the

symmetry of the Cp-~m moiety in CpMn(CO)2CS in going from the

solid to the solution state. In addition, v IO ' v12 and v 13

appear in the solution i.r. spectr.um, although they are not

present in the solid state i.r. spectrum. Since these are all

e 2 modes that should be i.r. inactive, it seems that in fact the

Cp-Mn moiety has a Zo~er local symmetry in solution than in the

solid state. Since gross intermolecular effects are generally

considered to be negligible in solution, it must be intra-

molecular interaction between the Cp-Mn part and the rest of the

molecule that is responsible for the lowering of the ~yrnmetry.

One possible explanation for this phenomenon is the slow (longer

than the vibration al time scale) rotation of the Cp ring around

the Cp-I411 axis [of. (COT) Fe (CO) 3 reference 63]. Such a motion

is more likely to occur in solution than in the condensed solid

state. This "TOuld result in a lcwering of the overall symmetry

of the molecule. This hypothesis is further justified by the

splitting of several of the low frequency modes in solution and

in the vapour phase (the vapour phase data are given in the

footnotes to Table XXXVIII) •

- 172 -

B. Hn-C-O AND Mn-C-S VIBRATIONS

When one contemplates the complete vibrational spectra of

the thiocarbonyl complexes, the most striking observation is the

total absence of the v(C-S) fundamental in the Rfu~an spectra.

This is even more surprising since sulfur is generally con-

sidered to be a readily polarizable atomi and thus, CS might

be expected to give rise to a strong Raman effect. The reason

for this apparent anomaly is not yet understood.

Since CS is nmv believed to be a better TI-accepting ligand

than C0129-131, it is expected that in the thiocarbonyls the

v(C-O) frequencies will be higher, and the v(Mn-C) and ô(~m-C-O)

frequencies lower, than the corresponding modes in Cp~m(CO)3.

These predictions can be seen to be validated in the bar-graph

xepresentations of the spectra (Figures 50 and 51) •

Such generalized bonding arg~ments can also be utilized in

+ the comparison of the Mn with the isoelectronic Fe' complexes.

The decrease in electron density around the central metal atom,

+ in going from ~m to Fe , is manifested by the observed shifts

in certain of the vibrational modes. Thus, the v(C-O} and

v(C-S) frequencies are found to be higher, and the ô(M-C-O) and

the V(M-C) frequencies lower in the Fe+ than the Mn complexes

(Tables XXXVI and XXXVII). This is attributable to the decrease

in backbonding to the CO and CS groups.

Since it has been established that the Cp-Mn moiety can be

treated successfully by the method of "local symmetryll, the

remainder of the mole cule will aIse be considered as an

- 173 -

independent unit. The C3v symmetry of the Mn(CO)3 moiety is,

of course, lowered by the substitution of the CS groups. This

change is shown in the correlation diagram between Mn{CO)3 and

its CS derivatives (Table XLI). The fundamental modes will be

discussed in order of decreasing frequency. The values quoted

are from the solid state i.r. spectra, unless otherwise noted.

The 2009 and 1933 cm- l bands are assigned to the a 1 and ail

v(C-O) modes of CPMn(CO)2CS respectively. These assignments are

proposed in view of the fact that the highest frequency mode of

a metal carbonyl complex is invariably the in-phase totally

t . 77 symme r1.C one • However, in the absence of depolarization

measurements, it is possible that these assignments may be

reversed, particularly since the 1933 cm- l Raman band is the more

intense one. For the bis-thiocarbonyl derivative, the triplet

-1 . peak at ~1990 cm 1.S attributed to the al v(C-O) mode; the

splitting must be due to solid state effects. The 1260 cm- l band

in the i.r. spectrum of the mono-thiocarbonyl and the 1298 and

1220 cm- l bands in the i.r. spectrum of the bis-thiocarbonyl are

assigned to the v(C-S) fundamenta1s of these compounds.

The lower frequency modes will be considered next. As it

was shown before, the bands in this region shift to lower

frequency upon increasing replacement of CO by CS groups in

CpMn(CO) 3. These shifts are of importance in correlating the

fundamentals ·of CpMn(CO)3' CpMn(CO)2CS and CpMn(CO) (CS)2.·The

proposed assignments are based on those120-l23 of CPMn(CO)3.

It should be noted that L~e solid state Raman data presented

Fundamental

v (C-O)

v(C-S)

ô (M-C-O)

v (M-C)

ô (C-M-C)

- 174 -

TABLE XLI.

CORRELATION BETWEEN

Mn (CO) 3 AND ITS CS DERIVATIVES

Mn(CO) 3

C3v

al + e

al + a2 +

a'

a'

2a ' 2e"""""" ~a'

.",a ' al + e ---~a'

"a 1

al + e----~a'

+ an

+ 2a"

+ ail

+ ail

+ ail

Mn (CO) (CS)2

Cs

a'

a' + ail

a' + a"

2a ' + 2a"

a'

a' + ail

a'

a' + a"

Fundamental

'J (C-O)

v (C-S)

ô (M-C-O)

6 (M-C-S)

v (M-Co)

v (M-Cs )

ô (C-M-C)

ê (C-M-C ')

here for the tricarbonyl (Table XLII) are the first complete data

to be reported.. Al though ,the Raman spectrum of the CO s tretching

region has been studied before, no solid state data were recorded

f th ~h ob tO 1 ° 123 or e o~ er V1 ra 10na reg10ns

In the tricarbonyl, the very strong Raman band at 354 cm-l

has been assigned to the al v(Cp-Mn} rncde. Consequently ~~e ve~'

high intensity lowest frequency Raman bands at 338 and 321 cm-l

are assigned to the a'\) (Cp-Mn) modes of the 'two CS complexes.

* IR

3126 m

3098 w

2022} vs

2018

1954 s

1937} vs

1922

1914 sh

142S}s 1420

1359 m

lO62}S 1057 m

1008

849 s

834 s

668} vs

663

- 175 -

TABLE XLII.

VIBRATIONAL FREQUENCIES A~D ASSIGNMENTS -1 FOR SOLID CpHn(CO} 3 (cm ).

Raman

3131

3093

2015 (20)

1944 (40)

1921 (53)

1914 (w,sh)

1429 (7)

1361 (6)

1114 (67)

1062 (12)

846 } (7)

836

668 (4)

** Assignment

C-H stretch.

C-H stretch.

C-O stretch.

c-o stretch.

c-o stretch.

c-o stretch.

c=c stretch.

al

el

el

ring breath. al

C-H bend. <1> e 2

C-H bend. el

C-H bend. <1> el

C-H bend. <1> al Mn-C-O bend. e

· )

* IR

3126 rn

3098 w

2022} vs

2018

1954 s

1937} vs

1922

1914 sh

142S}s 1420

1359 rn

lO62}S 1057 m

1008

B49 s

834 s

66B} vs

663

- 175 -

TABLE XLII.

VIBRATIONAL FREQUENCIES .AI.~D ASSIGN~.ENTS

-1 FOR SOLID Cp.Hn (CO) 3 (cm ).

Raman

3131

3093

2015 (20)

1944 ( 40)

1921 (53)

1914 (w,sh)

1429 ( 7)

1361 (6)

1114 (67)

1062 (12)

846} 7)

836

668 (4)

** Assignment

C-H stretch.

C-H stretch.

C-O stretch.

c-o stretch.

c-o stretch.

c-o stretch.

c=c stretch.

al

el

el

ring breath. al

C-H bend. ' l , '-LI e 2

C-H bend. el

C-H bend. <1> el

C-H bend. (1) al

Mn-C-O bend. e

- 176 _.

643 vs,br Mn-C-O bend. e

609 m 607 ( 3) C-C bend. (1) e 2

541 s 545 (7) Mn-C-O bend. al

499 w 500 (58) r.1n-C stretch • al

487 w 489 (sh) Mn-C stretch. e

373 w 385 (20) } ring tilt e 367 (sh)

357 w 354. (350) ring-Mn stretch. al

140r ,br 120

107 w 113 (240) def. and

97 (sh) 1attice modes

55 (sh)

46 (sh)

39 (sh)

* Infrared data from reference 120.

** . 120-123 Based upon various previous ass1.gnments

.- 177 -

-1 Similarly, the weak Raman bands at 383 and 350 cm are assigned

to the al ring tilt modes of CpMn(CO)2CS and CpMn(CO) (CS)2'

respecti vely.

-1 In the region below 500 cm and above the Cp-Mn stretching

frequencies assigned previously, three strong bands appear in the

Raman spectra of the thiocarbonyl complexes. Since only two and

one v(Mn-Co ) modes are expected for CpMn(CO)2CS and CpMn(CO} (CS)2

respecti vely, the remaining bands mus t be due to the v (Mn-Cs)

fundamentals. Thus, the two Raman bands for Cp~m(CO)2CS at 460

and 437 cm- l are assigned to the al and ail V(Mn-Co ) modes -

syrnrnetries assigned on the basis of relative intensities - whi1e

the 10wer frequ~ncy band (due to the mass effect expected for

sulfur) at 367 cm-1 is assigned to the v(Mn-Cs ) fundarnenta1. In

o the vapour phase i.r. spectrum ç the lower frequency v(Mn-C ) mode

-1 is split into a doublet at 423/417 cm • For CpMn(CO) (CS)2' the

assignments are as fo1lows: al V (Mn-Co) at 428 cm-l, the two

v (Mn-Cs) modes at 40'4 and 359 cm- l

In the solid state i.r. spectrurn of CP!~(CO)2CS, there are

four bands in the region usua1ly associated wi th the 0 (M-C··O)

modes (650-470 cm-l ) i while there are six for cprvln(CO) (CS) ..... ~

However, for these compounds there shou1d be four and two

o (Mn-C-O) modes, respective1y, in this region. The only other

-1 type of fundamental expected in the 700-300 cm region is the

o (Mn-C-S) • Consequently, the extra bands in the case of the

bis-thiocarbony1 complex must be due to the o(X4n-C-S) modes.

Moreover, since the predictions based on the "local sym .. netryll

- 178 -

arguments for the Cp-Mn and Hn(CO)2CS moieties have been shown

to be valid, it must be accidentaI degeneracies that are the

cause of the apparently too few bands in this region of the

spectra of the mono-thiocarbonyl complexe This reasoning is

supported by the splitting of two of these bands into doublets,

in the solution i.r. spectra. A similar observation was found

earlier for the ring modes i.e. the appearance of extra bands in

solution indicates an apparently lower molecular symmetry in

solution than in the solid state.

Thus, for CpMn(CO)2CS and CpMn(CO) (CS)2 the bands in the

645-473 and 625-448 cm- l regions, respectively, are assigned to

the 0 (Mn-C-O) and ô (r.lln-C-S) fundamental vibrations. Conclusive

assignments for these modes cannot be made at this time. Hcwever,

it is deemed significant that at least the regions for the

ô (M-C-S) and V(M-Cs ) fundamentals can be assigned unequivocally.

Also, it is interesting to note that the relative intensities of

these sulfur containing modes are the same in i.r. and Raman as

those of the carbonyls i.e. ô (Mn-C-S) is strong in i.r. and weak

in Raman, while V(Mn-Cs ) is strong in Raman and weak in i.r.

The bands below 150 cm- l are assigned to the three C-Mn-C

modes, the ring twisting mode and. the lattice vibrations. lUI

the assignments proposed above~ for these complexes in the solid

state, are collected in Table XXXVII.

The solution i.r. data for CpMn(CO)2CS, and a complete

vibrational assignment (in the 4000-60 cm-l region) are presented

in Table XXXVIII. It should be noted that aIl the cornbination

- 179 -

and overtone bands of CpMn(CO)2CS have been assigned vlithout

requiring combinations between modes associated with the Cp and

Mn(CO) 2CS moieties. This further substantia·tes the initial

assumption that the vibrations of these two fragments can be

assigned on the basis of "local syrnrnetry Il •

Sorne of the cornbination bands, which are considered to be

important to the arguments presented in this Chapter, will nOtIl

be discussed.

The 2273 cm- l band cannot be explained on the basis of any

cornbination other than that between the inactive a2 ring mode

-1 (v 4 ) and the el ring mode (v 6 ) nea.r 1000 cm . This would place

v 4 at 1270' cm-l, in good agreement with the frequency of this

mode, observed in other complexes in the 1266-1259 cm- l

region122 The other alternative, that v(C-S) combines with v6

,

is considered unlikely, since no other ring modes are found to

co~bine with either v(C-O) or v(C-S). This same type of reasoning

-1 substantiates the previous assignment of the 612 cm band (CS 2

solution) to a 8 (Mn-C-O) mode, rather than the \1 14 ring mode.

The co~bination of this band with both the v(C-O) and v(C-S)

vibrations designates this fundamental to the r.1n(CO)2CS moiety.

A close examination of the cornbinations between the low frequency

(benzene solu,tion) fundamentals and the other assigned modes,

-1 indicates that the 122 and 103 cm bands can be assigned

tentatively to the c-r-1n-C and C-Hn-C 1 deformation modes, while

the 78 cm-l peak °b-'..L.t ob t d t th Il ° can poss~_iy oe a~ r~ u e 0 e a r~ng

t\'listing mode.

- 180 -

In contrast to all ·the other fundament.als, the 399 cm -1

(CS2

solution) and 330 cm -1 bands combine \.,ri th both the Cp and

~m(CO)2CS fundarnentals. The latter mode has been clearly

identified as the al Cp-Mn vibration. Since this mode involves

stretching of the bond connecting the two fragments of the

molecule, it could have been anticipated that it would combine

with the fundamentals of both the ring and the Mn(CO)2CS

fragments.

A corollary to the previous argument is the assignment of

the 399 cm- l band (in CS2

) to the al ring tilt vibration of

CpMn (CO) 2CS. This assignment leads to another note\vorthy point.

In a solvent shift study (Table XLIII) perforrned on CpMn(CO)2CS,

it is this 399 cm- l band that is the most significantly solvent

dependent. Since solvent shifts are generally correlated with

bond polarities, it can be concluded that this Cp-Mn bond is

the most polar one in this molecule, in particular, more polar

than the c-o and C-S·bonds. (The al Cp-Mn fundarnental in solution

is just out of the practical range of the available instrumentation).

CS 2

V (C-O) al 2007

v (C-O) ail 1956

v(C-S) al 1266

Ô (C-H) el 1006

Ô (C-H) al 825 r

645

612 ô (M-C-O)

605 Ô (M-C-S)

519

513

0 \.1 (l4-C ) ail 430

ring tilt al 399

s v(r4n-C ) al 360

TABLE XLIII.

EFFECT OF SOLVENTS ON SOME OF THE FUNDAMENTAL

MODES OF CpMn(CO)2 CS (cm- l ).

C6H12 CC1 4 C6H6 CH 2C1 2 CHC13 CH 3I

2016 2017 2003 2011 2015 2011

1962 1959 1954 1956 1954

1272 1270 1269 1269

998 1005 1007 1005

824 825 824 632

646 645 645 646

613 613 614 613 613

605 607 602 607 608 607

520 517 517 517

512 514

432 431 435 436 435

379 383 382 383 381

361 364 364 365 361 363

CH 3CN CH 3N02 bv

2014 2009 13

1952 1951 11

1264 8

1005 8 1-' co

842 841 17 ......

646 1

613 2

6 '1

518 515 l 8

J 434 429 7

395 20

350 367 17

- 182 -

CHAPTER 4. CONCLUSION

The first vibrational assignment for a thiocarbonyl complex

has been achieved for CpMn(CO)2CS in both the solid and solution

states. Sorne of the fundarnental modes of CpMn(CO) (CS)2 have

also been assigned. The.' ô (.Mn-C-S) and \.\ (Mn-Cs) modes occur

in the sarne regions (with the sarne relative i.r. and Raman

intensities) as the corresponding carbonyl fundamentals. In a

solvent shift study, the frequency of the Cp-Mn ring tilt mode

is the most solvent sensitive.

The method of "local symmetry" has been found to be much

more meaningful for the thiocarbonyls than for CpMn (CO) 3. In

the solid state'especially, the thiocarbonyls exhibit little

intrarnolecular interaction. The "slow" rotation of the ring

in solution causes an apparent decrease in the syrnmetry of both

the Cp-Mn and Mn(CO)2CS moieties.

- 183 -

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- 185 -

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CONTRIBUTIONS 'ro Ki.'W'iVLEDGE

PART l

1. The molecular geometry of Mn(CO)4NO, in the vapour phase

and in solution, has been determined to be a C3v trigonal

bipyramidal one.

2. The infrared spectrum of ~~(CO)4NO has been assigned in

-1 the 5250-33 cm region.

3. The ionization potential of Hn(CO)4NO has been determined

by mass spectrometry.

4. A ne\V' route has been developed for the synt.hesis of

Fe (CO) 2 (NO).2·

5. The solution i.r., far-infrared and Raman spectra of

Fe(CO)2(NO}2 have been assigned.

6. Low frequency assignments h.ave been put forward for the

complexes Fe(NO)2(CO}PPh 3 and Fe(NO)2(Co)p(OMe}3.

PART. II

1. For the (NBD)M(CO)4 complexes, the coordinated C=C and the

metal-olefin stretching fundamentals have been assigned.

2. Vibrational assignments have been proposed for the olefin-

metal-halogen linkages of [(COD}RhCl]2 and [(COD)CuCl]2.

3. A vibrational assignment, and a novel geometry, have been

suggested for the species (COD)2CUCl04.

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Pl--RT III

1. The firs"t vibrational assignrnents for thiocarbonyl complexes

have been achieved for CpMn(CO)2CS and CpMn(CO) (CS)2'

resulting in the identification of the low·-frequency !-ln-C-S

fundamental vibrations.

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EHRA'rZ\

l. p. 35, l. 3 : o (M- ~\!-O) should be 6 (M-C-O) •

2. p. 35, l. 9 : preceding.

3. p. 58, 1- 3 : predictions.

4. p. 60, footnote a: omitted.

5. p. 87, l. 9 : The compound discussed in refs. 73, 74 is

cyclopentadiene, CS

H6 , not cyclopentene.

6. p. 102, last line: excepte

7. p. 136, l. 1: demonstrates.

8. p. 154, Table XXXV heading: This should be CSHSMn.

vibrational spectra of some organometallic complexes

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