PHYSICO-CHEMICAL STUDIES ON METAL CHELATES OF SULPHUR AND

NITROGEN CONTAINING LIGANDS

DISSERTATION Submitted in partial fulfilment of the requiremtiw

for the Award of the Degree of

illafittr of $l)iio$op!)j> IN

CHEMISTRY

BY

IttftFQAT UUiSAItt RAF1EJ1

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA)

1995

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i CKECEED-2002 W A 3

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Department of Chemistry Division of Inorganic & Bioinorganic Chemistry Aligarh Muslim University, Aligarh, U. P., 202 002, India TELEX

Dr. Sartaj Tabassum

C E R T I F I C A T E

Certified that the work embodied in this

dissertation is the result of the original

researches of the candidate carried out under

my supervision.

Sarta jJ Tabassum " Lecturer

edicated

ACKNOWLEDGEMENT

Behind every success there is, certainly, an

unseen power, power of Almighty God, but an aim is the

paramount condition of success which is attainable at

perfection in everything by those who preserve with the

association of their predecessors, Teachers, family,

friends and colleagues.

It is a good fortune and a matter of privilage for

me to have the brilliant supervision of Dr.Sartaj

Tabassum, Lecturer, Department of Chemistry, AMU,

Aligarh. I gratefully acknowledge my deep indebtedness

to him for his able guidance and cordial cooperation. It

is unforgettable that whenever I faced any problem he

encouraged me angelically to move ahead through his

valuable suggestions & benevolent behaviour. I owe him

once more for all that I learnt & gained.

My indebtedness is also due to Dr. Farukh Arjmand

who gave me several key insights on many occassions during

the course of discussion with her. I owe her for the

scientific support and constructive criticism which I

received during the course of work.

I am thankful to Dr.Nurul Islam, Chairman, Deptt.

of Chemistry for providing necessary laboratory facilties.

I am extremely beholden to my parents, family

members particularly to my brother Mr.Ashiq H. Rafiqi for

their affectionate encouragement and sacrificed support.

To all my colleagues and friends I express my

warmest thanks for their cooperation. My special thanks

to Dr.Nahid Nishat, Prof.S.A.Qazi and Mr.N.P. Singh for

their generous help. In the end I would like to pay my

thanks to M/S MEC TYPEWRITING for typing this manuscript.

SHAFQAT H. RAFIQI

C O N T E N T S

CHAPTER - I

INTRODUCTION 1-8

CHAPTER -II

EXPERIMENTAL 10 -15

CHAPTER -III

RESULTS AND DISCUSSION 16-21

REFERENCES 22-26

CHAPTER - I

I N T R O D U C T I O N

INTRODUCTION

Coordination chemistry has so diversified that

with the advent of time new interesting fields of

research have emerged. Thus came to the picture new

frontior area of research the Bio-inorganic chemistry.

The emerging field gained momentum with the discovery of

cis-platin. A variety of transition and non-transition

elements are found in biological system and it is an

established fact that without these metal ions, the

activity of organic portions with which they complex is

completely vanished. Again it emphasises the importance

of the metal ions in the living system, suggests that

the organic groups act simply as chelating agents and

provide the basic infrastructure. Importance of metal

ions is however well understood nowadays. Many

researches have focussed their attention to the

1-5 synthesis of bx-tri and poly metallic complexes. In

fact metal complexes of desired nuclearity can be

synthesised and have been well characterized by

Gianfranco et al. These studies have a number of

objectives including finding structural analogues of

metalloproteins, studying the cooperative physical

behaviour of contigous metals and in general exploring

the metal complexes of new ligand types. By use of

2

different metal combinations distinct reactivity

patterns might be expected. In other words, chemistry

of such complexes can be described as assembling

molecular components, exhibiting suitable properties in

appropriate patterns or tethering of two or more

different binding subunits or versatile ligands capable

of providing distinct environment to the metal atom

leading to the formation of di, tri and polynuclear

compounds.

The area of binucleating ligands capable of

forming homo and heterodinuclear complexes is of great

7—8 interst because of a variety of reasons. First they

serve as models for metalloproteins such as superoxide

dismutase, oxidases and peptidases. Second, the

dinuclear copper containing complexes are biologically

important as two copper centers in the active site of

copper proteins like hemocyanine transport oxygen and

the monooxygenase tyrosinase and dopamine B-hydroxylase

incorporates oxygen into organic substrates. Third,

dinuclear complexes can be exploited as bifunctional g

catalysts as shown by McKenzie for dipalladium

complexes in the catalytic hydration of acetonitrile.

They have suggested a bimetallic pathway involving

concerted action by the two metals in LPd-(MeCONH)

and L Pd2(MeCONH) where L and L are the binucleating

ligands (Fig. 1).

3

o z ov C \ / \ / Q-

N S N \ / \ / Pd W

N Z N ^

^ >

Fig. 1

Recently heterobimetallic asymmetric catalyst has

also been synthesised in which two different metals play

different roles to enhance the reactivity of both

reaction partners . Bimetallic compounds have now been

recognised for the design of molecular based Magnets

also

The condenstion of primary amines with carbonyl

compounds was first reported by Schiff and since then

the condensation products are referred to as Schiff

12 bases . Their metal complexes have been studied from

different angles. Di Copper(II) complexes of unsymme-

trical dinucleating Schiff base ligands bearing

chemically distinct sites derived from 4-bromo-2-formyl-

6-(4-methyl-piperazin-l-yl-methyl) phenol and 4-bromo-2

[(2-diethyl aminoethyl) ethyl amino methyl]-6-formyl

phenol with 2-(aminomethyl) pyridine, 2-(2-aminoethyl)

4

pyridine and (2-aminoethyl)-4-nitro phenol have been

13 prepared by Crane et al (Fig. 2).

Donor Set I

Donor Set 2

Fig. 2

Such dinucleating ligands have stimulated much

interest in their potential as models for dinuclear

14-15 metallobiosites where the metal ions may be found

in chemically or geometrically distinct environment.

Singh et al reported the reaction of Cobalt(II),

Nickel(II) and Copper(II) oximate with antimony

trichloride in DMSO yielding bimetallic complexes, with

the liberation of HC1. Also the reaction of Cobalt(II)

and Nickel(II) Schiff base complexes with antimony

trichloride gave bimetallic adducts in which geometrical

transformation from square planar to octahedral occurred

(Fig. 3).

Fig. 3

Chromones used in photoxidative cyclisation of

1 7 — 1 R some conjugated trienes, react with primary amines

under reflux yielding Schiff base. Its Schiff base

provides several coordination sites and therefore has

been used as a chelating agent. Many copper complexes

containing Schiff base type ligands. have shown antitumor

activity. Neutral complex transbis(Salicylaldoximato)

19 Copper(II) and Copper(II) complex salt of macrocyclic /

ligand (Fig. 4) tetrabenzo [b,f,j,n] 1,5,9,13-tetraaza-

20 cyclohexadecane were found to show efficacy against

experimental animal tumor.

A little work has been done on heterobimetallic

complexes of Group(IV) metal tetrachlorides and

21-22 organotins. Cunningham et al have synthesised

transition metal Schiff base complexes of SnCl3(OEt).EtOH to

L

2+

2 CI"

Fig. 4

give SnCl3(OEt)ML and SnR2[NiL(NCS )2]. Malisch and Kiefer

et al have synthesised a variety of (hydrosilyl)

tungsten complexes of the type [(C-Me-)(OC)_(Me_P)-

23 W-SiR_] and studied comprehensive vibrational analysis •

These reactions prove that the tungsten silanes are

attractive materials to modify the ligand combination

concerning the Silicon.

In another set of reactions, hetero bridged

iridium complexes with SnCl- were synthesised to give

24 trihalogentin derivatives [Ir2 (/l-pz) tyi-SBu) (SnCl2x)2

(CO)2 {P(OMe)3)2] where pz=pyrazolate, x=Cl, I, and SBu=

ligand (Fig. 5).

7

Fig. 5

However, Group(IV) metal compounds exhibit anti-

proliferative properties for instance, germanium and tin

compounds have also been shown to act as antitumor

agents. The octahedral organotin halide complexes

(Fig. 6) with mono and bidentate ligands have been

reported to possess antiproliferatic activity and it is

worth considering that antitumor tin complexes

structurally resemble cis-platin or other cytostatic

Platinum metal complexes with respect to the presence of

cis-dihalo metal moiety

Observations on structure activity relationship of

the complexes has led to propose that in tin compounds

. . . 27 the activity is related to Sn-N bond length

R

/ Sn

/l\ R

Fig. 6 Extensive application of these Schiff bases and

their complexes have been made in diverse fields such as 28—30

medicine/pharmacology and analysis. It is further

well known that when sulphadrug is ingested it forms

Schiff base in the body system before being assimilated.

Possibly the formation of Schiff base facilitates the

absorption of the drug. The metallated Schiff base

can further act as an electron donor species which

easily binds metal ions affording bimetallic complexes.

In the present work Cu(II) Schiff base complex has been

further allowed to react with Group(IV) tetrachlorides

and bis(trimethylsilyl) amine to achieve heterobi-

metallic complexes.

9

Present Work

In this work Copper Schiff base complex was

synthesised and used as a ligand. Copper Schiff base

complex was then treated with Si(IV), Ge(IV), Sn(IV),

Ti(IV), Zr(IV) metal tetrachlorides and N,N,bis

(trimethylsilyl) amine to achieve novel heterobimetallic

complexes of type [Cu(SB)2M'CI -]C12 and [Cu(SB)2bis

(tmsa)-].

These complexes were characterized by IR, UV/Vis

EPR spectroscopy, magnetic moment, elemental analysis

and molar conductance measurements. The Group(IV) metal

achieve octahedral coordination in each case.

CHAPTER - I I

E X P E R I M E N T A L

10

EXPERIMENTAL

Si(IV), Ge(IV), Sn(IV), Ti(IV) and Zr(IV) tetra-

chlorides, bis(trimethylsilyl) amine (Fluka), 0-hydroxy

benzaldehyde (E. Merck), CuCl2.2H20 (BDH) and sulpha-

pyridine (Sigma) were used as such. The IR spectra

(4000-200 cm" ) were recorded on Perkin Elmer 621

spectrophotometer in KBr and nujol. UV/Vis spectra were

run on Pye UNICAM PU800 spectrophotometer in DMSO. The

EPR spectra were recorded on Bruker ESP-300X band

spectrometer. The conductivity measurements were made

in DMF on an Elico conductivity bridge type CM-82T.

Elemental analysis were done on Perkin Elmer 240B-

Microanalyser. Estimation of chloride were done by

41 standard gravimetric method

Synthesis of Complex (A) [CulSp^lCl^

Sulphapyridine (0.02 mol) in EthanoKlOO mL) and

hydrated CuCl2(0.01 mol) in Ethanol (20 mL) were

refluxed for two h and the solution kept overnight at

room temperature. Fine green crystals of complex(A),

were formed. The crystal that appeared were filtered,

washed with ether and dired in vacuo(Fig. 7).

Yield 70%, M.P. 185°C, % C 44.77(44.90), % H 3.68

(3.71), % N 14.00 (14.12) and % S 5.33 (5.48).

11

H ^ H^l

o r N*o Fig. 7

Synthesis of Complex(B) [Cu(SB)2]Cl2

Complex (A) was dissolved in DMF (10 mL) and then

refluxed with O-hydroxy benzaldehyde for three h. The

resulting mixture was allowed to cool for one h at room

temperature. 5 ml of Hexane was added to this mixture

and left overnight at low temperature in refrigerator.

The complex (B) appears in the form of a yellowish green

amorphous powder. This compound was washed with

ethanol, flushed with ether and finally dried in vacuo

(Fig. 8).

Yield 60%, M.P. 200°C, % C 51.61 (51.89), % H

3.58 (3.62) % N 10.03 (10.15).

12

NH NH

oAo Fig. 8

Heterobimetallic complexes of Group(IV) Metal

Tetrachlorides

Synthesis of [(SB)2Cu.SiCl.]C12

Si(IV) metal tetrachloride (0.01 mol) in 1:1 rtio

was added to the solution o£ complex(B), dissolved in

hot methyl alcohol/DMF (20 mL). The mixture was then

allowed to reflux for three h and left at room tempera-

ture for six h. On cooling amorphous yellow coloured

compound was obtained. The yellow coloured bimetallic

compound was filtered washed with ether and dried in

vacuo. Yield 55% M.P. 215°C, %C 42.85 (43.02), % H 2.97

(3.03), % N 8.33 (8.44), % $ 6.34 (6.45), % CI 20.83

(21.60).

13

Synthesis of [(SB)2Cu.GeCl4]Cl2

Ge(IV) metal tetrachloride in 1:1 ratio was added

to the solution of complex(B) dissolved in hot Methyl

alcohol/DMF(20 mL) . The mixture was refluxed for seven

h and kept at room temperature for four h, light orange

amorphous product appeared. This compound was filtered,

washed with ether and dried in vacuo.

Yield 60% M.P. 220-222°C, % C 40.04 (40.44), % H

2.85 (2.99), % N 7.98(8.10), % S 6.08 (6.28).

Synthesis of [(SB)2Cu.SnCl.]Cl2

Sn(IV) Metal Tetrachlorides in 1:1 ratio was

added to the solution of complex (B) in hot methyl

alcohol/DMF (20 mL) . The mixture was refluxed for nine

h. On standing for six h at room temperature yellow

coloured amorphous compound was formed. This compound

was filtered , washed with ether and dried in vacuo.

Yield 45%, M.P. 227-230°C % C 39.34 (39.60), % H

2.73 (2.84), % N 7.65 (7.73), % S 5.82 (5.92).

Synthesis of [(SB) Cu.ZrCl ]C12

Zr(IV) Metal Tetrachloride in 1:1 ratio was added

to the solution of complex(B), in hot methyl alcohol/

DMF (20 mL) . The mixture was refluxed for three h and

14

cooled at room temperature for six h. Orange coloured

amorphous compound was formed. This orange coloured

compound was filtered, washed with ether and dried in

vacuo.

Yield 60% M.P. 238-240c, % C 40.32(40.55), % H

2.80 (2.90), % N 7.84 (7.98), % S 5.97 (6.10).

Synthesis of [(SB)2Cu.TiCl4]Cl2

Ti(IV) Metal Tetrachloride in 1:1 ratio was added

to the solution of complex(B) dissolved in hot methyl

alcohol/DMF (20 mL) . The mixture was allowed to reflux

for eight h and then kept at room temperature for seven

h. Orange coloured amorphous compound was formed. This

compound was filtered, washed with ether and dried in

vacuo(Fig. 9).

Yield 50%, M.P. 238-241°^% C 42.02(42.30), % H

2.91(2.97), % N 8.17(8.28), % S 6.22(6.34).

s-ia Q N-»-Sn-«-N

02S 2C IW /SOg

XNH NH

Cu

15

Heterobimetallic complexes of bis(trimethylsilyl) amine

Synthesis of [Cu(SB)2(tmsa)2]Cl2

Complex(B) dissolved in hot methylalcohol/DMF was

treated with bis(trimethylsilyl) amine. The mixture was

refluxed for six h and allowed to stand overnight.

Yellow coloured compound was obtained. It was filtered,

washed with hexane and dried in vacuo.

Yield 40%, M-.P. 289-291°C, % C 52.84(53.10), % H

6.25(6.36), % N 10.27(10.30).

CHAPTER - III

RESULTS AND DISCUSSION

16

RESULTS AND DISCOSSION

The analytical data of the ligands and their

complexes are listed in Table 1. On the basis of

elemental analysis the complexes may be formulated as

[Cu(SB)2]Cl2, [Cu(SB)2M'Cl43Cl2 and [Cu(SB)2bis(tmsa)2],

where M'=Si(IV), Ge(IV), Sn(IV), Ti(IV) and Zr(IV).

These complexes are thermally stable and insoluble in

common organic solvents. The molar conductance of the

[Cu(SB) ]C12 and [Cu(SB) M'Cl^C^ in DMF lies in the

-1 2 -1 range (95-112 ohm cm mol ) reveals their 1:2 electro-

42 lytic nature . The molar conductance of [Cu(SB)_

-1 2 -1 bis(tmsa),,] measured in DMF (45-55 ohm cm mol )

indicated that it is non electrolyte.

DMF [Cu(SP)2]Cl2 + 2 o-hydroxy > [Cu(SB)2]Cl2

benzaldehyde"2H2° (A) (B)

[Cu(SB).]Cl, + M'Cl. MeOH/DMF > [ C u ( S B ) M.cl ]cl 2 ^ 4 110°C *

[Cu(SB) ]C19 + bis(trimethyl —MeOH/DMF—> [Cu(SB) b i s 1 l silyl)amine -2HC1 (tmsa)2]

bis(tmsa)

17

Infrared Spectra

The important IR frequencies and their tentative

assignments are given in Table-2.

Two peaks of medium intensity at 3380 & 3490 cm

assigned to "̂ NH have been observed for sulphapyridine.

The copper complex of sulphapyridine (A) exhibit two

distinct absorption bands at 3250 cm and 3100 cm

corresponding to "̂ NH. The band appearing at 1630 cm

and 1610 cm~ respectively have been assigned to C=N

stretching vibrations. As a consequence of the reaction

of complex (A) with o-hydroxy benzaldehyde the schiff

base complex has been formed. From a study of

43 tetradentate dioxime Schiff base , it has been known

that C=N stretching frequency appears in 1627-1679 cm

44 \ range while in Schiff base of sulphadrug the ~\ C=N

appears at 16 50 cm & 1670 cm . In the present work,

we observed C=N stretching frequency at 1630 cm . It is

difficult to distinguish between C=N stretching

frequencies of complex (A) & (B). In complex (B) on

formation of Schiff base the two stretching frequencies

are coupled together and single band of \)C=N appears.

Sharp bands appearing at 1610, 1630 and 1635 cm

respectively imply that both the pyridyl nitrogen and

45-48 azomethine nitrogens are involved in coordination

In the bimetallic complexes with group IV metals, these

18

bands undergo slight negative shift due to the reduction

in C = N double bond character. The free Schiff base

containing OH have absorption bands in the range 3450-

3570 cm" . In this case a broad band appears at 2830

cm" due to intramolecular hydrogen bonding. In addition,

a band at 2730 cm has also been observed. These

absorptions remain unaltered showing non involvement of

OH in coordination. Two sharp bands in the spectra of

complex(B) at 1280 cm ascribed to "V C-0 remain almost

unchanged which indicate that it does not participate in

49-50 -1

coordination . The band at 1390 cm is due to C-H

absorption. The medium intensity bands of v C-N + 8 NH

and C-N in complex(A) have been found to observe at 1570,

1500, 1470, 1410 and 1357 cm" which are shifted towards

lower wave number region in the complex(B) and further

shifted towards negative side in the heterobimetallic

complexes. The M-N stretching vibrations are of

particular interest because they give direct information

about the coordinate bond. The complexes exhibit new

bands in the far i.r. spectral region. The complex (A)

and (B) show vibrational mode at 285 cm which is

assigned to M-N stretching. In the heterobimetallic

complexes an additional band has been found to observe in

405-415 cm region, which are assigned to M'-N stretchig

mode (M'=Si(IV), Ge(IV), Ti(IV) & Zr(IV). The silicon

19

(IV) complex of Schiff base exhibited two metal chlorine

bands at 310 cm" and 343 cm" . In other heterobi-

metallic complexes these two bands are observed at 315

and 340 cm region. In [Cu(SB)2 bis(tmsa)23 only metal-

nitrogen stretching frequencies are observed at 285 cm

& 405 cm" .

Electronic Spectra

Intense Charge Transfer bands appearing at 245-275

mm region in all the cases have been observed. The

weeker bands in the visible region have -been used to

indicate the geometries of these complexes.

A broad weak band at 820 nm in the case of copper

2 2 9

(II) has been assgined to T2 < E transition for d

system which approximately corresponds to lODq value and

is influenced by Jahn Teller effect. The Magnetic moment

value (1.55 BM) and electronic spectrum are consistent 51 with a distorted octahedral geometry for Cu(II) ion in

case of bis(trimethylsilyl). It has also been supported

by gi (2.263) and g„ (2.046) values in the EPR spectra of

complex bis(tmsa) which correspond to a distorted

octahedral geometry for Cu(II) ion.

20

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22

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