Synthesis and spectral studies on mononuclear complexes of chromium(III) and manganese(II) with...

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Synthesis and spectral studies on mononuclear complexes of chromium(III) and

manganese(II) with 12-membered tetradentate N2O2, N2S2 and N4 donor

macrocyclic ligands

Sulekh Chandra* and Rajiv Kumar

Department of Chemistry, Zakir Husain College, University of Delhi, Jawaharlal Nehru Marg, New Delhi 110002,

India

Received 15 July 2003; accepted 02 September 2003

Abstract

Complexes of CrIII and MnII of general formula [Cr(L)X2] X and [Mn(L)X2] respectively were prepared from N2O2,

N2S2 and N4 donor macrocyclic ligands. The complexes have been characterized by elemental analysis, molarconductance measurements, spectral methods (i.r, mass, 1H-n.m.r, electronic spectra and e.p.r.) and magnetic

measurements. The macrocyclic ligands have three different donating atom cavities, one with two unsaturated

nitrogens and the other two have saturated nitrogen, oxygen and sulphur atoms. The effect of different donor atoms

on the spectra and ligand field parameters is discussed. All the complexes show magnetic moments corresponding to

a high-spin configuration. On the basis of spectral studies a six coordinated octahedral geometry may be assigned to

these complexes.

Introduction

Enormous progress in macrocyclic chemistry has been

made in the past decade [1, 2]. New macrocyclic ligand

molecules have been designed and prepared with en-hanced ability to encapsulate given metal ions selectively

[3, 4]. Coordinated metal ions influence the course of

many complicated reactions occurring during metabolic

activity in living organisms [5]. The coordination chem-

istry of manganese has achieved remarkable progress in

the last decade due to the increased recognition of this

metals role in biological systems [6, 7].

In this paper we report the synthesis and character-

ization of chromium(III) and manganese(II) complexes

with N2O2, N2S2 and N4 donor macrocyclic ligands

viz 2,3-diphenyl-1,4-diaza,7,10 dioxo,5,6:11,12-dibenzo

[e,k]-cyclododeca-1,3 diene[N2O2] ane (L1), (Figure 1)

2,3-diphenyl-1,4,7,10-tetraaza-5,6:11,12-dibenzo [e,k]-cyclododeca 1,3 diene [N4] ane (L2) (Figure 2) and 2,

3-diphenyl-1,4-diaza,7,10-dithia,5,6:11,12-dibenzo [e,k]-

cyclododeca-1,3 diene [N2S2] ane [L3] (Figure 3) con-

taining aromatic head, and lateral units [8, 9]. An

important aspect of the present work is the synthesis of

three novel dibenzo-substituted Schiff-base macrocycles

derived from three different diamines containing aro-

matic rings with different donating atoms.

Experimental

All starting materials used were of analar grade, were pur-chased from Sigma Aldrich, and were used as received.

Physical measurements

Magnetic susceptibility measurements were carried out

on a CAHN 2000 Faraday balance using Hg[Co(CNS)4]

(vg 16.44

10

)6

g cc

)1

at 28

C) as the calibratingagent. Molar conductance measurements were carried

out on a Leeds Northrup Conductivity Bridge 4995. I.r.

spectra were recorded on a Perkin Elmer 137 instrument

as KBr pellets. The electronic spectra of the complexes

were recorded on a Shimadzu u.v. mini-1240 spectro-

photometer in DMF solution. C and H analysis were

carried out on a Carlo-Ebra 1106 elemental analyzer.

Nitrogen was determined by Kjeldahls method. Mass

spectra were carried out on JEOL, JMX, DX-303 mass

spectrophotometers. 1H-n.m.r. spectra were recorded on

a Bruker AVANCE 300 spectrometer at 100 kHz

modulation at room temperature. E.p.r. spectra were

recorded at room temperature on a Varion E-4 EPRspectrometer at ca. 9.1 GHz and 100 kHz field modu-

lation and phase sensitive detections and DPPH was

used as marker.

The macrocyclic ligands were prepared in three steps.

Nitro compounds (Scheme 1)

(a) 1,2-Di(o-nitrophenoxy)ethane

o-NO2C6H4OH (4.78 g) in hot DMF (5.0 cm3) was

treated slowly with K2CO3 (2.39 g). The resulting solu-

tion was boiled gently and BrCH2CH2Br (1.54 cm3) was

added dropwise with constant stirring for 30 min. Themixture was then refluxed gently for 2 h and concen-

trated under reduced pressure. On pouring the solution

into cold water a granular yellow solid precipitated. It* Author for correspondence

Transition Metal Chemistry 29: 269275, 2004. 269 2004 Kluwer Academic Publishers. Printed in the Netherlands.


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was filtered, washed with dilute aqueous NaOH, dried

and recystallized from glacial MeCO2H, m.p. 169

170 C, 1H-n.m.r.: (CDCl3) d 8.1 (2H, d), d 7.3 (2H, m),

d 7.7 (2H, m), d 7.0 (H, d), d 4.0 (4H, OACH2). The

reaction is given below (Figure 4).

(b) 1,2-Di(o-nitrophenylamino)ethane (Scheme 2)

1,2-Di(o-nitrophenylamino)ethane was prepared by

heating BrC6H4NO2 (2.0 g) with 1,2,H2NCH2CH2NH2(0.26 cm3). The mixture was stirred rigorously until

complete reaction had occurred. The heating was then

reduced to keep the mass molten for a further use. The

melt was poured into EtOH (50.0 cm3), the solid so

obtained was washed with a mixture of Et2O (30.0 cm3),

C6H6 (30.0 cm3) and 1 N NaOMe solution (10 cm3). It

was recrystallized from ClCH2CH2Cl to give 1,2-di(o-nitrophenylamino)ethane (3.1 g) as bright orange needle

shaped crystals. m.p. 192194 C. 1H-n.m.r.: (CDCl3) d

8.1 (2H, d), d 7.3 (2H, m), d 7.7 (2H, m), d 7.0 (H, d), d

4.0 (4H, NHACH2). The reaction is given below

(Figure 5).

Reduction of nitro compounds (Schemes 2a and b)

The nitro products, 1,2-di(o-nitrophenoxy)ethane and

1,2,di(o-nitrophenylamino)ethane, were heated under a

N2 atmosphere with 5% PdAC (0.5 g). N2H4 H2O

(20.0 cm3) was added in (5 cm3) portions and the

mixture refluxed until the solution become colourless(30 min). After filtration to remove the precipitate (if

any), the solution was evaporated to dryness and the

solid residue recrystallized from hot EtOH under a N2atmosphere. A residue of white plates was obtained.

m.p. 130132 C. 1H-n.m.r.: (CDCl3) d 6.3 (2H, d), d 7.1

(2H, m), d 6.6 (2H, m), d 7.0 (2H, d), d 4.0 (4H, OACH2)

diamine(I) and 135136 C. 1H-n.m.r.: (CDCl3) d 6.3

(2H, d), d 7.1 (2H, m), d 6.6 (2H, d), d 6.7 (2H, d), d 3.0

(4H, m, NHACH2) diamine(II). The reactions are given

below (Figures 6 and 7).

1,2-Di(o-aminophenylthio)ethane (Scheme 3)This diamine was prepared by heating o-HSC6H4NH2(1.09 g) with absolute (99%) EtOH (3 cm3) containing

Na (0.201 g). BrCH2CH2Br (0.372 cm3) in EtOH

(1 cm3) was then added dropwise with constant stirring

to the refluxing solution. The mixture was then cooled

and poured into H2O (300 cm3). The solid mass so

obtained, was filtered washed with H2O and dried. The

product was recrystallized from EtOH, and a yellowish

residue was obtained. m.p. 75 C. 1H-n.m.r.: (CDCl3) d

6.3 (2H, d), d 7.1 (2H, m), d 6.6 (2H, m), d 7.2 (2H, d), d

2.8 (4H, m, SACH2). The reaction is given below

(Figure 8).

Fig. 1. Ligand (L1).


Fig. 4. 1,2-Di(o-introphenoxy)ethane (Scheme 1).


Structures of microcyclic ligands.

Fig. 5. 1,2-Di(o-introphenylamino)ethane (Scheme 2).

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SACH2). The mass spectrum of ligand (L3) shows a peak

449 amu.. corresponding to molecular ion (M++1).

Mass spectrum, EIMS m/z (%) 449 (M+, 52), 421 (71),

402 (15), 370 (35), 250 (25), 185 (81), 51 (38).

Preparation of complexes

A hot EtOH, solution (20 cm3) of the hydrated metal

salts, CrX3 xH2O or MnX2 xH2O (0.005 mol) (where

X Cl)

, or SCN)) was added to a hot EtOH solution

(20 cm3) of the corresponding ligand (0.005 mol). The

mixture was then refluxed on a water bath at 80 C for

57 h. On cooling a precipitate was obtained which was

filtered, washed with EtOH and dried over P4O10 under

vacuum.

Results and discussion

All the complexes have compositions CrLX3 or MnLX2(L ligands L1, L2 and L3 and X Cl

) or SCN)).

Chromium(III) complexes show molar conductances

corresponding to 1:1 electrolytes, whereas the mangan-

ese(II) complexes are non-electrolytes (Table 1). The

complexes may therefore be formulated as [CrLX2] X

and [MnLX2] respectively. Related data are listed in

Table 1.

I.r. spectra

The absence of an absorption at ca. 3400 cm)1

in the i.r.spectra of ligands shows that the free amino groups are

absent, and the absence of a strong band at ca. 1675

1755 cm)1 shows the absence of ketonic groups. It

confirms the elimination of water molecules and, as a

result, cyclization takes places with formation of a

macrocyclic ligand. In the i.r. spectra of L1 (1624 cm)1),

L2 (1620 cm)1) and L3 (1608 cm

)1) a new band appears

in all the ligands corresponding the m(C@

N) group. Thei.r. spectra of these complexes show a moderate intensity

absorption in the 15901610 cm)1 range attributed to

the imine, m(C@N). This moderate intensity absorption

band is showing a shift to the lower side in the

complexes, suggesting coordination through the nitro-

gen of the m(C@N) group.

The spectrum of ligand (L2) shows a band at

3320 cm)1 corresponding to m(NH) [10]. On complexa-

tion this band is shifted towards the lower side

3310 cm)1. This indicates diversion of the electron

cloud from the nitrogen of the imidazole or amino

group, thus resulting in a lowering of the NAH

stretching frequency. In the i.r. spectra of L1, L2 andL3 PhAOACH2, PhANHACH2 and PhASACH2 group

show bands in the 305485 cm)1 range. These bands are

also shifted to the lower side after complexation of the

macrocyclic ligands and confirm the complexation of the

macrocyclic ligands. A new band appeared in the 310

490 cm)1 range in the spectra of chromium(III) and

manganese(II) complexes. These weak bands can be

assigned to 405 cm)1 m(MAO), 485 cm)1 m(MAN) and

305 cm)1 m(MAS) coupled with other lower vibrational

modes of the ligand molecule [11, 12]. Far i.r. spectra

also confirmed the MACl band in the range 300

320 cm)1

consistent with coordination of the halogroup. Important i.r. bands of all complexes are

recorded in Table 2.

Table 1. Characterization data for the CrIII and MnII complexes

Complex Yield (%) M.p. (C) Molar

conductance

(W)1 cm2 mol)1)

Colour Found (Calcd) (%)

M C H N

[Cr(L1)Cl2] Cl 40 206 95.0 light green 8.85 57.8 2.9 4.4

Cr C28H22N2O2 Cl3 (9.0) (58.3) (3.8) (4.9)[Cr(L2)Cl2] Cl 45 200 98.0 light green 8.8 58.15 3.9 9.15

Cr C28H24N4 Cl3 (9.0) (58.5) (4.2) (9.75)

[Cr(L3)Cl2] Cl 63 190 85.0 blackish green 8.0 54.9 3.1 4.1

Cr C28H22N2 S2 Cl3 (8.5) (55.2) (3.6) (4.16)

[Mn(L1)Cl2] 60 175 12.0 pale yellow 9.8 61.6 3.9 4.8

Mn C28H22N2O2Cl2 (10.1) (61.8) (4.0) (5.15)

[Mn(L1)(SCN)2] 50 180 18.0 yellow 9.1 61.0 7.3 9.25

MnC30H22N4O2S2 (9.3) (61.1) (7.8) (9.5)

[Mn(L2)Cl2] 65 190 15.0 pale yellow 9.8 61.85 4.1 9.9

Mn C28H24N4Cl2 (10.1) (62.0) (4.5) (10.3)

[Mn(L2)(SCN)2] 61 195 11.0 yellow 8.6 61.0 4.0 14.2

MnC30H24N6S2 (8.85) (61.3) (4.1) (14.3)

[Mn(L3)Cl2] 68 180 16.0 off white 9.1 57.9 3.2 4.3

Mn C28H22N2 S2Cl2 (9.5) (58.3) (3.8) (4.9)

[Mn(L3)(SCN)2] 62 189 4.0 white 8.5 47.0 3.0 9.0MnC30H22N4S4 (8.6) (47.1) (3.2) (9.1)

2,3-Diphenyl-1,4-diaza,7,10 dioxo,5,6:11,12-dibenzo [e,k]-cyclododeca-1,3 diene[N2O2] ane(L1), 2,3-diphenyl-1,4,7,10-tetraaza-5,6:11,12-dibenzo

[e,k]-cyclododeca 1,3 diene [N4]ane (L2) and 2,3-diphenyl-1,4-diaza,7,10-dithia,5,6:11,12-dibenzo[e,k]-cyclododeca-1,3 diene[N2S2]ane [L3].

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Bands due to anions

The i.r. spectra of the thiocyanato complexes show a

single sharp band at 20892083 cm)1 [13] suggesting

that both thiocyanato groups are nitrogen-bonded, are

in a similar environment and occupy an axial position.Therefore a six coordinated structure with tetradentate

macrocyclic ligands may be suggested for these com-

plexes and related data are listed in Table 2.

Chromium(III) complexes

Chromium(III) complexes exhibit magnetic moments,

3.773.81 B.M, at room temperature corresponding to

three unpaired electrons. The moments are close to the

spin only values, suggesting an octahedral geometry

around the chromium ion [14].

The electronic spectra of the complexes recorded inDMF (hplc grade) show two bands in the 12,16515,552

and 18,62121,691 cm)1 ranges corresponding to4A2g(F) fi

4T2g(F) and4A2g(F) fi

4T1g(F) transitions

respectively. The transition 4A2g(F) fi4T1g(P) is usually

not observed in the visible region due to involvement of

the charge transfer band. The visible region of the

electronic spectra of the L1, L2 and L3 complexes show m1at 12,360, 15,552 and 12,165 cm)1, due to the presence of

different donating atoms [15]. The position of the bands

indicates that these complexes exhibit octahedral geom-

etry, consistent with D4h symmetry around the metal ion

[16]. Related data are listed in Table 3.

Ligand field parameters

Various ligand field parameters (Dt, DT, Dqy, Dqz, Ds,

Dq, Dqxy, B, C, k and b) have been calculated [17, 18]

for the chromium(III) complexes listed in Table 4. The

values of ligand field parameters are consistent withoctahedral geometry for the complexes. The first (m1)

and second transition (m2) directly give the values of

10Dq and 10Dqxy. The Racah interelectronic repulsion

parameter B is calculated from the relation.

B 2m21 3m1m2 m22=15m2 27m1. The nephlauxetic

parameter b is obtained using the relation

b B(complex)/B(free ion), where B(free ion) 918cm)1. The b values indicate that there is appreciable

covalent character in the metal ligand r bond. Related

data are listed in Table 3.

E.p.r. spectra

The e.p.r. spectra of the complexes were recorded for

polycrystalline samples at room temperature and their

values are reported in Table 3. The spectra of powdered

samples of the complexes show a broad line. The g

values are calculated from the expression: g 2:00231 4k=10Dq where k is the spin orbit couplingconstant for the metal ion. Owen [19] noted that the

reduction of spinorbit coupling constant for the free

ion value of 90 cm)1 for chromium(III) can be employed

as a measure of metal ligand covalency. The value of k

Table 2. I.r. spectral data of the ligands and their CrIII and MnII complexes

Complex m(NH) cm)1 m(C@N) cm)1 m(MAN) cm)1 m(MAO) cm)1 m(MAS) cm)1 m(SCN)

[Cr(L1)Cl2] Cl 1627 415 404

[Cr(L2)Cl2] Cl 3320 1627 469

[Cr(L3)Cl2] Cl 1607 452 309

[Mn(L1)Cl2] 1608 518 410 [Mn(L1)(SCN)2] 1607 517 401 2120

[MnCl2] 3330 1604 583

[Mn(L2)(SCN)2] 3325 1609 590 2110

[Mn(L3)Cl2] 1600 510 306

[Mn(L3)(SCN)2] 1595 525 310 2115

Table 3. E.p.r. electronic, spectral and magnetic moment data of the CrIII complexes

Complex Dq (cm)1) B (cm)1) C (cm)1) b leff B.M. g

[Cr(L1)Cl2] Cl 1686 747 2988 0.81 3.77 1.98

[Cr(L2)Cl2] Cl 1862 737 2948 0.80 3.81 1.95

[Cr(L3)Cl2] Cl 2169 605 2420 0.65 3.80 1.99

Table 4. Ligand field (cm)1) parameters of the CrIII complexes

Complex Dq (cm)1) B (cm)1) C (cm)1) b LFSE

kJ/mol)1DT/Dq Dt Dq

y

(cm)1)

Dqz

(cm)1)

Ds(cm)1)

DS k

[Cr(L1)Cl2] Cl 1686 747 2988 0.81 241.7 0.114 743.7 2537 585.0 5901 8901 44.04

[Cr(L2)Cl2] Cl 1862 737 2948 0.80 267.0 0.091 737.8 2507 571.0 5806 5806 45.53

[Cr(L3)Cl2] Cl 2169 605 2420 0.65 311.0 0.970 701.6 2783 951.0 7513 7513 53.87

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indicates that the complexes under study have sub-

stantial covalent character.

It is possible to define the covalency parameter

analogous to the nephelauxetic parameter which is the

ratio of the spin orbit coupling constant for the

complex and free ion [20].

Manganese(II) complexes

These complexes show magnetic moments in the 5.90

5.96 B.M. range at room temperature [21]. In the

complexes the intensities of electronic transitions from

the ground state 6S to states of fourfold multiplicity are

very weak, since manganese(II) has a d5 electronic

configuration. The electronic spectra of complexes show

bands at 17,10017,850 cm)1 (m1) 24,15024,240 cm)1

(m2), 28,54028,800 cm)1 (m3) and 31,000 cm

)1 (m4) [22].

These bands may be assigned as 6A1g fi4T1g(

4G) (m1),6A1g fi 4Eg (4G) (m2), 6A1g fi 4Eg (4D) m3 and6A1g fi

4T1g (4P) (m4) transitions respectively. The ligand

field parameter, values Dq, B, C, b, F4, F2 and Hx are

calculated and given in Table 5.

6A1g !4Eg; 4A1g

4G 10B 5C

6A1g !4T1g

4P 17B 5C

The energies of these transitions are independent of the

crystal field splitting energy and depend [23] only on the

parameters B and C. Dq can be evaluated with the help

of the energy level due [24] to the

6

A1gfi

4

T1g (

4

G)transition. Slater Condon parameters F2 and F4 are

related to the Racah parameters B and C as follows

B F2 5F4; C 35F4.The electronelectron repulsion in the complexes is

less than that in the free ion, resulting in an increased

distance between electrons and thus an effective increase

in the size of the orbitals. On increasing delocalization

the value of b decreases and is less than one in the

complexes. The numerical value 786 cm)1 for the B of

the free manganese(II) ion has been used to [25]

calculate the value of b. The calculated values of b

(0.790.83) and Hx indicate that the complexes under

study have appreciable covalent character.

E.p.r. spectra

The e.p.r. spectra of the complexes have been recorded

using polycrystalline samples at room temperature; their

g values are given in Table 5. The polycrystalline

samples give one broad isotropic signal centered at ca.

the free electron g-value (g0 2.0023). In DMF solutionthe e.p.r. spectra of the complexes clearly show that, in

this solvent, the complexes existed as monomeric units.

The nuclear magnetic quantum numbers MI corre-sponding to these lines are )5/2, )3/2, )1/2, 1/2, 3/2,5/2 from low to the high field [2628].

Acknowledgements

One of the authors (Kumar) gratefully thanks my

younger brother Bitto for motivation. Thanks are also

due to the Principal, Zakir Husain College, for provid-

ing laboratory facilities, the UGC New Delhi for

financial assistance, and the USIC Delhi University for

recording i.r. spectra. Thanks are also due to the SSPL

solid state physics lab for recording magnetic momentsand the IIT Bombay for recording e.p.r. spectra.

Table 5. Ligand field (cm)1) parameters of the MnII complexes

Complex Dq (cm)1) B (cm)1) C (cm)1) b F4 Hx F2 leff B.M. g

[Mn(L1)Cl2] 1785 627 3576 0.79 102 3.00 1137 5.91 1.99

[Mn(L1)(SCN)2] 1765 481 3984 0.81 113 2.70 1046 5.98 1.97

[Mn(L2)Cl2] 1750 651 3546 0.82 101 2.57 1156 5.85 1.96[Mn(L2)(SCN)2] 1745 588 2665 0.83 76.0 2.40 968 5.91 1.94

[Mn(L3)Cl2] 1710 614 3614 0.78 103 4.00 1229 6.00 1.93

[Mn(L3)(SCN)2] 1735 735 2307 0.81 65.0 2.70 1060 6.96 1.95

Proposed structure of the CrIII and MnII complexes.

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References

1. L.F. Lindoy, Pure Appl. Chem, 2179 (1997).

2. H. Okawa, H. Furutachi and D.E. Fenton, Coord. Chem. Rev, 174,

51 (1998).

3. Y. Nakamura, M. Yonemura, K. Arimura, N. Usuki, M. Ohba

and H. Okawa, Inorg. Chem, 40, 2739 (2001).4. P. Guerriero, S. Tamburini and P.A. Vigato, Chem. Rev, 95, 273

(1995).

5. D.M. Rudkevich, J.D. Mercer-Chlmer, W. Verboom, R. Ungaro,

F. Dejong and D.N. Reinhoudt, J. Am. Chem. Soc., 117, 6124

(1995).

6. K.O.A. Chin, J.R. Morrow, C.H. Lake and M.R. Churchill, Inorg.

Chem, 33, 656 (1994).

7. H. Adams, R. Bastida, A. de Blas, M. Carnota, D.E. Fenton, A.

Macias, A. Rodriguez and T. Rodriguez-Blas, Polyhedron, 16, 567

(1997).

8. C. Lodeiro, R. Bastida, A. de Blas, D.E. Fenton, A. Macias, A.

Rodriguez and T. Rodriguez-Blas, Inorg. Chim. Acta, 276, 55

(1998).

9. L. Valeneia, R. Bastida, A. deBlas, D.E. Fenton, A. Macias, A.

Rodriguez and T. Rodriguez-Blas, Inorg. Chim. Acta, 282, 42(1998).

10. P.K. Singh, J.K. Koacher and J.P. Tondan, J. Inorg. Nucl. Chem,

43, 1755 (1981).

11. K. Nakamoto, Infrared and Raman Spectra of Inorganic and

Coordination Compounds, Wiley, New York, 1978.

12. E.M. Jouad, A. Riou, M. Allain, M.A. Khan and G. M. Bouet,

Polyhedron, 20, 67 (2001).

13. K. Nakamoto, Infrared and Raman spectra of Inorganic and

Coordination Compounds, Wiley, New York, 1977, p. 270.

14. B.N. Figgis, Introduction to Ligand Field Theory, Wiley, New

York, 1978.

15. R. Ortiz, J. Barras and Jimenez, Synth. React. Inorg, Met.-Org.

Chem, 15(8), 1999 (1985).

16. J.R. Perumaredic, Coord. Chem. Rev, 4, 73 (1969).

17. F.A. Cotton, L.M. Daniels, P. Huang and C.A. Murillo, Inorg.

Chem, 41, 317 (2002).

18. J.A. Weil, R.J. Bolton and J.E. Wertz, Electron Paramagnetic

Resonances, Wiley and Sons, New York, 1994, p. 223.

19. J. Owen. Proc. Roy. Soc. London, A, 227, 183 (1955).

20. S. Chandra and K.K. Sharma, Synth. React. Inorg. Met.-Org.

Chem, 12, 647 (1982).

21. B.N. Figgis, Introduction to Ligand Field Theory, Wiley, New

York, 1978.

22. C.J. Heidt, G.F. Kostre and A.N. Johnson, J. Am. Chem. Soc, 80,

6471 (1958).

23. J.E. Huheey (ed.), Principles of Structure and Reactivity, Harper

and Row, Inst, New York, 1972, p. 363.

24. I.F. Orgel, J. Chem. Phys, 23, 1004 (1955).

25. G.M. Ehrenfield, N. Murugesan and S.H. Hecht, Inorg. Chem, 23,

1498 (1984)

26. R. Rajan, R. Rajaram, B.U. Nair, T. Ramsami and S.K. Mandal,

J. Chem. Soc. Dalton Trans., 2321 (1996).

27. M. Mc Cann, R.M.T. Casey, M. Deverewx, M. Curran and V.

Mckee, Polyhedron 5, 2321 (1996).

28. R.S. Draggo, Physical Methods in Chemistry, WB Saunders Co.,

l997, p. 530.

TMCH 5755

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