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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
I
.N.e> A?. 5 0 < M , 0 ...
KX
>v. -"'•'•••.• ^su t -H-
1 " FEB 1Q97
fed 'vcv Coi«^u * * »
u.
i CKECEED-2002 W A 3
DS2812
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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R E F E R E N C E S
22
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