chapter-4 heterobimetal ion-pair complexes of tin(ii) and...

CHAPTER-4

Heterobimetal Ion-Pair Complexes Of Tin(II) And Lignocaine With

Cd(II), Fe(III) And Ni(II)

Heterobimetallic complexes of Tin

INTRODUCTION

Tin is a group IVA metal and has a valence shell configuration Ss Sp . Earth's

crust constitute about 6x10'* % of tin. It is found in cassiterite, stannite, and tealite.

Several studies have been focused on the increasing amount of both organic and

inorganic tin in ecosystem. It has been evaluated as y^ most important pollutant

element in the ecosystem. This has raised some concern in that tin may enter the

human food chain^. Some organometallic tin compounds are known to be toxic^

but some of them are found to be active against leukemia^ very likely, those

different behavior are possibly be correlated to the nature and number of covalentiy

linked organic groups which yield species with different structural co-ordination

numbers. Owing to this environmental and biological relevance, many studies have

been devoted to its chemical'* and biological characterization^.

Oragnotin complexes may interact with biological systems in many different

ways, as bactericides^, fungicides^ acaricides, industrial biocides and in recent years,

several investigations to test their antitumor activity have also been carried out^. Tin

(II) chlorides have played a central role in the non-instrumental analytical chemistry

of platinum group metals^ and SnF2 is commonly used as source of fluorides in

protective tooth pastes^^. Tin complex containing radio therapeutic agents are used

for treatment of bone cancer^^. Antitumor activity of tin complexes are reviewed by

J. Cox Michael et al ^ and Gielen *3. S.Thayer John et al '*. have reported the role of

tin compounds in medicine and nutrition. Armitage^^, i6,i7 ^nd Horrison^^ have

reviewed in detail the chemistry of tin compounds and Lappert^^ has reviewed on

the advances of chemistry of tin (II) compounds. Yoshida et al o. have reviewed on

the redox selective reactions of organotin compounds.

The bimetallic complexes, Sn[Co(CO)4]4 and Sn2[Co(CO)4]x were used in several

homogeneous catalytic reactions, such as hydro-formylation of olefins, acetal

formation from aldehydes, hydrolysis of cyclic carbonates, double carbonylation of

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Heierobimetallic complexes of Tin

alkylbromides followed by aldol condensation, isomerization of terminal epoxides to

aldehydes and ring opening of epoxides with alcohols^'. Tin complexes are also

used as catalysts for the dehydrogenation of long chain alkanes22. It is used as active

and selective catalyst for the Baeyer-Villiger (B-V) oxidation of cyclic and acyclic

ketones23. Potential symptoms of over exposure to metallic tin are irritation of eyes,

skin, and respiratory system and to organic tin compounds are irritation of eyes,

skin, respiratory system, headache, vertigo, psychoneurologic disturbances, sore

throat, cough, abdominal pain, vomiting, urine retention, paresis, focal anesthesia,

skin burns, pruritis '*. 25_

Literature survey

Tin is known to form octahedral and tetrahedral complexes in both of its

oxidation state +2 and +4. Rodolfo Graziani et al . have reported the synthesis of

hetero binuclear complexes of formulae C5Hi5FeC5H4COOSn(CH=CH2)3 (I), C5H5

FeC5H4COOSnPh3(II) and Ph3GeCOOSnPh3(III). Complexes are characterized by

IR spectra. The polymeric structure of solid C5H5FeC5H4COOSn (CH=CH2)3 has

been established by X-ray crystallography. In this compound, the tin atoms are five-

coordinate trigonal bipiramidal, with the vinyl groups equatorial and two apical

oxygen atoms from bridging carboxylato groups. The resulting structure is a linear

polymer with Sn—O bonds.

T. M. Aminabhavi et al . have reported the synthesis of biologically active hetero

bimetallic complexes of either copper, cobalt or nickel acetylacetonates with silicon,

tin, selenium and tellurium chloride. Complexes are characterized by elemental

analyses, conductivity measurements, magnetic and spectral data. The binuclear

complexes are 1:1 adducts and non-electrolytes in solution. The complexes are

biologically active as demonstrated by bacteriostatic, mammalian acute toxicity, and

antialgal activity tests. Kenji Shindo et al . have reported the synthesis of hetero

binuclear M(II)-Sn(IV)(CH3)2 (M=Cu,Co) complexes of N,N-bis(3-carboxy salicylic

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dene) ethylenediamine(H4fsaen) where the copper(II) or cobalt(II) ion is bound at

the N2O2 site and the tin(IV) ion at the O4 site with two methyl groups at the axial

positions. Both complexes are fairly stable towards atmospheric moisture in the

solid state but decomposed into a mononuclear complex [M (H2fsaen)] by a trace

amount of water when dissolved in solution. Spectroscopic investigations on the

Cu-Sn complex in pyridine revealed that the coordination of pyridine to the copper

(II) is sterically hindered by the methyl groups attached to the neighbouring tin (IV).

In case of the Co-Sn complex such a steric effect of the methyl groups is not

pronounced enough to binder the coordination of pyridine to the axial site of the

cobalt (II). ESR spectra at liquid nitrogen temperature revealed that the cobalt (II)

ion adopts a pentacoordinate structure at room temperature and a hexa coordinate

structure near liquid nitrogen temperature with pyridine molecule(s) at the axial

site(s).

Jorg Lorberth et al^ . have reported crystal structure of a binuclear complex

formed by dimethyltin dichloride and the potentially tridentate ligand

Me2NCH[OEt)2P=0]2. Complex crystallizes in the space group as dimers

{Me2NCH[(OEt)2P=0]2 •Me2SnCl2}2 in which the oxygen atoms of one phosphoryl

ligand are bridging two tin atoms each having a distorted octahedral coordination

sphere. Francesco Caruso et al o. have reported the synthesis, spectroscopic

(Mossbauer, IR and NMR) and X-ray structural studies of tin complex formed by

reaction of 2,2'-bipyrimidine (bipym) with diorganotins R2SnCl2 (R = methyl, ethyl).

Complexes of the types R2SnCl2 bipym, R2SnCl2 bipym • bipym and (KiSnCli)!

bipym were studied by 'H and '^C NMR spectroscopy in solution, and by IR and

Mossbauer spectroscopy in the solid state and frozen solutions. The complexes

Et2SnCl2bipym -bipym and (Et2SnCl2)2bipym were characterized by X-ray diffraction

methods. In both complexes the tin environment is octahedral with chloro atoms in

a cis disposition, the ethyl groups in a trans disposition and two N atoms from the

ligand bipym. These complexes may have a potential antitumour activity.

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Montserrat Ferrer et aP^ have reported the reaction of NEu"^ and PPN+

(bis(triphenylphosphine)nitrogen(+)) salts of [HFe(CO)4]" with several tin halides.

Reaction of (NEt4)[HFe(CO)4] with ClSnRa (R = CeHs, p-C6H4(CH3)) and

Cl2Sn(C6H5)2 gives the bimetallic species (NEu)[R3SnFe(CO)4] and (PPN)

[Cl(C6H5)2SnFe(CO)4], respectively. Reaction of SnCU with (PPN)[HFe(CO)4] gives

the orange tri metallic complex (PPN)2[Cl2Sn{Fe(CO)4}2]. Reaction of [NEu] [Hfe

(CO)4] with SnCU in toluene gives the SnCU solvate of the corresponding NEt4"'"

salt, an X-ray diffraction study of which has enabled approximate location of the Sn,

Fe, and CI atoms. The tin atom in the anion is tetrahedrally surrounded by two

chlorides and two Fe(CO)4 units with an average Sn—Fe bond distance of 2.58(3)

A. Addition of an excess of the NEU" salt to SnCU gives the red

(NEu)3[ClSn{Fe(CO)4}3], which reverts to (NEt4)2[Cl2Sn{Fe(CO)4}2] upon

treatment with 1 equivalent of SnCU- The use of (PPN)2[Cl2Sn{Fe(CO)4}2] as a

possible precursor for larger nuclearity clusters has also been examined.

A. Bacchi et al ^ have reported the synthesis of mono and bimetallic organotin

complexes with pyrrole-2,5-dicarboxaldehyde bis(2-hydroxybenzoylhydra2one)

(HSdfps) and pyrrole-2,5-dicarboxaldehyde bis(2-picolinoylhydrazone) (H3dfpp)

.The complexes were characterized by IR, ^H and "^Sn NMR spectroscopy. X-ray

analysis of the complex [Sn(H3dfps)(C6H5)2] •(CH3)2SO revealed a penta

coordination around tin through a N,N,0 terdentate ligand behaviour of the

hydrazone. Wagner M. Teles et al ^^. have reported the synthesis of a polymetallic

Pt, Sn complex containing square planar and trigonal bipyramidal platinum

centers.Crystal and molecular structure of bisjchlorotriethyl phosphino platinum

(II)} [ji-2,3,5,6-tetrakis(a-pyridyl)pyra2inetetrakis(trichlorostannyl)triethyl phosphino

platinate(II) [{Pt(PEt3)Cl}2[x-(TPP)][Pt(SnCl3)4(PEt3)] where Pt is at the centre of a

trigonal bipyramid, in addition to two other square planar Pt atoms in the cationic

moiety.

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Corrado Pelizzi et al ^'^. have reported the synthesis, crystal and molecular

structure of a silver tin complex salt, [Ag(PPh3)4][SnPh2(N03)2(Cl,N03)] .The

crystal and molecular structure of the complex have been determined by X-ray

diffraction. The structure is composed of discrete [Ag(PPh3)4]+ cations and

[SnPh2(N03)2(Cl,N03)]- anions, with the latter showing a disordered distribution

involving CI" and one NO3" group. The Ag atom is bonded to four

triphenylphosphine molecules in a slightly distorted tetrahedral environment. Taken

account of the disorder, the coordination about tin can be described as distorted

pentagonal or hexagonal bipyramidal with the equatorial positions occupied by the

disordered Ugand and two NO3- groups, the phenyl rings being at the apices. Daniel

Miguel et al^ . have reported the synthesis of substituted seven-coordinate

molybdenum-tin and tungsten-tin complexes by reacting BuSnCb with [M(CO)3

(NCR)3] (M = Mo, R = Me; M = W, R = Et). These [M(CO)3(NCR)2(SnCl2Bu)Cl]

complexes react further with three molar equivalents of P(OR')3 (R' = Me, Et) at

room temperature giving dicarbonyl tris-phosphite complexes

[M(CO)2{P(OR')3}3(SnCl2Bu)Cl] through displacement of the two nitrile ligands

and one CO group.

Georgina Barrado et al ^^. have reported the synthesis of seven-coordinate

molybdenum-tin complexes [Mo (CO)2(S2PX2)(S2CPR'3)-(SnRCl2)] (2; R = Ph or

Bu; X = OEt or Ph; R' = Cy or iPr) by reactions of [Mo(CO)3(NCMe) (S2PX2)

(SnRCb)] (1) with an excess of S2CPR3 .An X-ray structure analysis of [Mo(CO)2S2P

(OEt)2(S2CPCy3)-(SnPhCl2)] (3a) showed that both sulphur ligands chelate

molybdenum. Additionally, one sulphur atom of the S2CPR3 gtoup is within

bonding distance of the tin atom, and thus bridges molybdenum and tin. Beatriz

Moreno et al^ . have reported the synthesis and some reactivity of

pentamethylcyclopentadienyl-ruthenium complexes with an SnCb ligand. The

complex [(C5Me5)Ru(SnCl3)(COD)] (COD = 1,5-cyclooctadiene) was characterized

by an X-ray crystal structure. The reaction of [{CpRuCl}4] (2) with hex-1-ene in the

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presence of SnCk yields [Cp Ru(SnCl3)(l,3-hexadiene)](5), which was fully

characterized by 'H and ^ C NMR spectroscopies.

Lian Ee Khoo et al ^^. have reported the preparation of three new dinuclear tin

complexes, [Me2Sn(2-OC6H4CH-NCH[Pri]COO)]SnMe2Cl2 (1), [Me2Sn(2-OCioH6

CH-NCH2COO)SnMe2Cl2 (2) and [Ph2Sn(2-OCioH6CH-NCH2COO)]SnPh2Cl2 (3),

and are characterized by spectroscopic studies and elemental analyses as a 1 : 1

adduct between diorganotin dichloride (acceptor) and bicycloazastannoxide (donor).

A full X-ray crystal structure analysis was performed on 3 and the results confirmed

that the donor and the acceptor moieties of 3 are bonded with an Sn-O bond. R.

Alan Howie et al . have reported the synthesis and crystal structure of bis{di-|jL-

hydroxobis[fac-tribromoaquotin(IV)]}heptahydrate 2[Br3(H20)Sn([ji-OH)2 Sn(02H)

Bra] • 7H2O, 2[fac-(l: X = Br)] • 7H2O from a reaction mixture of Br2 and Phs

Sn(CH2)i3CH3 (3:1 mole ratio) in CHCI3 solution in air. The solid-state structure

consists of a central rhomboidal planar Sn202 ring. The tin centres have distorted

octahedral geometries, with each Br ligand trans to an O atom.

Matthias Seibert et al o. have reported the synthesis of [(COD)M+(Cl)

(PPh2CH2CH2SnCl4)] (1: M=Pd; 2: M=Pt) and trans-[(Et2S)2M+(CI) (PPh2CH2CH2

SnCU)] (3: M=Pd; 4: M=Pt)by the reaction of P-functional organotin chloride

Ph2PCH2CH2SnCl3 with [(COD)MCl2] and trans-[(Et2S)2MCl2] (M=Pd, Pt) in molar

ratio 1:1. The same reaction with [(COD)Pd(Cl)Me] yields under transfer of the

methyl group from palladium to tin complex [(COD)M+(Cl) (PPh2 CH2CH2 Sn

MeCb)] (5) which changes in acetone into the dimeric adduct [CbPd (PPh2CH2

CH2SnMeCl2 •2Me2CO)]2 (6). In molar ratio 2:1 ,Ph2PCH2CH2SnCl3 reacts with

[(COD)MCl2] to from the complexes [Cl2Pd(PPh2CH2CH2SnCl3)2] (7: M=Pd,

mixture of cis/trans isomer; 8: M=Pt, cis isomer). In a subsequent reaction 8 is

transformed in acetone into the 16-membered heterocyclic complex cis-

[Cl2Pt(PPh2CH2CH2)2SnCl2]2 (9). trans-[(Et2S)2PtCl2] and Ph2PCH2CH2SnCl3 in

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molar ratio 1:2 yields the zwitterionic complex [(Et2S)M+(Cl) (PPh2CH2CH2

SnCl3)(PPh2CH2CH2SnCl4)] (10).

Synthesis and crystal structure of complexes, [Rh2([J.-pz)([jL-SBut) (SnCl2l)2 (CO)2

{P(OMe)3}2][pz =pyrazolate]4i,[(y]5-C5H4CH3)(CO)3MoSnPh3]42, cis-bis(triphenyl

phosphine)hydro(triphenylstannyl)platinum(II) and cis-bis(triphenyl phosphine)

hydro(triphenylsilyl) platinum(II) ' ^have been reported. Synthesis, characterization

and electrochemistry of [(P)SnRe(CO)5]BF4 and [{(P)Sn}2 Re(CO)4]BF4 derivatives,

where P = tetra-p-tolyporphyrin or tetra-m-tolylporphyrin have been reported ^ .

Synthesis and characterization of osmium nitrosyl complexes with osmium-tin

bonds having crystal structure of Os[Sn(p-tolyl)3](NO)(CO)2(PPh3) have been

reported ^s. Synthesis of hexametallic complex^^ CH2{(r]5-C5H4)Fe(CO)2SnPh2(r]5-

C5H5)Fe(CO)2}2 and new hexacyclic binuclear tin complexes derived from bis-(3,5-

di-tert-butyl-2-phenol)oxamide'*^ have been reported.

Iron was probably the first metal used nearly 6000 years ago' ^. Iron is the fourth

most abundant element in the earth's crust occurring to the extent of about 50%. It

is also believed that the earth's core consists mainly of iron'^^. Iron exhibits

oxidation states varying from +2 to +6 in its compounds. The highest oxidation

state known is +6 and it is rare^o. It also exhibits lower oxidation states, notably in

the iron carbonyls and their derivatives. Among the oxidation states of iron, +2 and

+3 are important in the ordinary aqueous and related chemistry of iron. Large

numbers of iron (III) and iron (II) complexes with different coordination numbers

are known. The ligands involved in the complexation are neutral, ionic,

monodentate, bidentate, chelate and macrocycUc^^.

Nickel discovered52 by Cronstedt in 1754. Occurs free in meteorites. Found in

many ores as sulfides, arsenides, antimonides and oxides or silicates, chief sources

include chalcopyrite, pyrrhotite, pendandite, garnierite, niccoMte and millerite^^.

Metallic nickel is reasonably anticipated to be a human carcinogen. Nickel

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compounds are listed as known human carcinogens54. 55,56 Nickel (II) forms a large

number of complexes with coordination number 4, 5 and 6 having tetrahedral,

square planar, trigonalbipyramidal, squarepyramidal and octahedral geometries^'^-î.

An LCAO-MO study of static distortions of (NiC^în the complex [(Ce H3)3

CH3As]2(NiCl4)2" has been reported and assigned tetrahedral geometry^^

Friedrich Stromeyer discovered53 the element cadmium in 1817. In nature, two

oxidation states are possible (0 and +2), however, the zero or metallic state is rare^^.

It has the valance configuration 4dô Ss^. It has a stable oxidation state' ' of +2.

Cadmium is considered as a non-essential and highly toxic element with a serious

cumulative effect^^. It has no biological function and is highly toxic to plants and

animals^^. However cadmium compounds with some oral glysemic agents exhibits

antidiabetic activity^''.

Though tin is well known to form complexes, which are diamagnetic, and

spectrally un interesting, but the literature survey on the compounds of tin are

found to be extremely interesting, possessing various physico-chemical behavior

account for their applications^2,i3,20-23 g Subramanya Raj Urs^^ has reported the

isolation and characterization of octahedral monometallic tin (II) complexes

associated with Ugnocaine cation. Complexes were characterized by elemental

analysis, IR, NMR, molar conductance, magnetic susceptibility, phase stabilization

using X-ray profile analysis and thermal studies, kinetic parameter has been

calculated using thermal data. Considering these aspects, also use of bimetallic tin

complexes in various homogenous catalytic reaction2i-23 and potential cationic and

possible diverse nature of lignocaine'î- ''^^ an attempt in the present work is made to

synthesize and characterize tin complexes, [SnCleJpeCUJILHJs, [SnCl6][CdCl4][LH]4

and [SnCle] [NiCU] [LH] 4 where LH= lignocaine hydrochloride and a moderate

attempt being made to understand the structural features of the complexes through

various physico-chemical techniques.

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EXPERIMENTAL

Preparation of complexes

1. [NiCl4][SnCl6][LH]4

The complex was prepared by mixing 25ml ethanolic solutions of tin metal

(0.3262g, 0.1099M) and nickel chloride hexa hydrate (0.6207g 0.1045M). About 3 to

4 ml of concentrated hydrochloric acid was added. To this, 25 ml alcoholic solution

of lignocaine hydrochloride (3.3755 g, 0.4985M) was added. The resulting solution

was mixed well and the pH of the solution was adjusted to about 4 with 2 M

hydrochloric acid. The solution was evaporated to a small volume on a steam bath.

The resulting pale yellow colored solution was kept at room temperature. After 3-4

days pale yellow colored crystals were separated out. Crystals were filtered off,

washed with diethyl ether and were dried in a desiccator over anhydrous silica and

the yield was about 55%.

2. [CdCl4][SnCl6][LH]4

The complex was prepared by mixing 25ml ethanolic solutions of tin metal

(0.3345g, 0.1127M) and CdCl2.2.5H20 (0.6347 g, 0.1112M). About 3 to 4 ml of

concentrated hydrochloric acid was added. To this, 25 ml alcoholic solution of

lignocaine hydrochloride (3.3865 g, 0.5001 M) was added. The resulting solution was

mixed well and the pH of the solution was adjusted to about 4 with 2M


The resulting colorless solution was kept at room temperature. After 3-4 days

colorless crystals were separated out. Crystals were filtered off, washed with diethyl

ether and were dried in a desiccator over anhydrous silica and the yield was about

48%.

3. [FeCl4][SnCl6][LH]3

The complex was prepared by mixing 25 ml ethanolic solutions of tin metal

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(0.3279g, 0.1105M) and ferric chloride hexa hydrate (0.7437g O.llOlM). About 3 to

4 ml of concentrated hydrochloric acid was added. To this, 25 ml ethanoUc solution

of lignocaine hydrochloride (3.3952 g 0.5014 M) was added. The resulting solution

was mixed well and the pH of the solution was adjusted to about 4 with 2 M


The resulting pale yellow colored solution was kept at room temperature. After 3-4

days pale yellow colored crystals were separated out. Crystals were filtered off,

washed with diethyl ether and were dried in a desiccator over anhydrous silica and

the yield was about 52%.

RESULTS AND DISCUSSION

Elemental analysis

Tin content of the complexes was brought into solution by repeated

decomposition of the complexes with concentrated hydrochloric acid. Later tin

content was determined with cupferron and weighed as tin(IV) oxide, SnOa^ . The

solution containing cadmium was neutralized with sodium carbonate and metal was

precipitated with sodium anthranilite solution. The precipitate was washed with

alcohol, dried and weighed as Cd[C7H602N]2^^. Iron(III) was estimated

gravimetrically as FezOs^^, and nickel was estimated by dimethylgloximate method^^.

Chloride content of the complexes was estimated by gravimetric method using

AgNOa as a precipitating agent - ^ .The nitrogen content of the complexes was

estimated by Kjeldahl's method^^. The complexes were also analyzed for C, H and

N by micro analj^cal methods. The elemental analysis data of the prepared

complexes are presented in Table 1 suggest that, in all the complexes except Fe (III)

complex, Sn: LH: M were found to be in 1:4:1 ratio, whereas that for Fe (III)

complex it was found to be in 1:3:1 ratio. Therefore, they may be represented by the

formulae [SnCl6][FeCl4][LH]3, [SnCl6][CdCl4][LH]4 and [SnCk] [NiCU] [LH] 4.

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Conductance measurements

Molar conductance values of lignocaine complexes measured in acetonitrile are in

the range 196.2 to 206.5 Ohm-i cm^ moli, suggests that the complexes are ionic in

nature and the values are slightly more in comparison with earlier reported values

for mono metallic tin complexes with amide group ligands' -' ^ The molar

conductance values are given in Table 1 and are found to be greater than 1:1

electrolytes'"'' '' . Higher molar conductance values for these complexes suggest that

the complex ion dissociate in solution and this could be account for 1:2 electrolyte

nature.

Electronic absorption spectra

The absorption bands of transition metal complexes are commonly of two kinds.

Those due to charge-transfer transitions and those arising from transitions that are

considered to be taking place within the d-shell of the metal ion' '*. It is usually

possible to decide to which class an observed band belongs, although, in certain

complexes where the interaction between two metal ions and the ligand is

particularly strong, the two types of transitions are no longer approximately distinct

and the theoretical treatment involved is normally be complicated. The degeneracy

of the orbital of a transition metal ion is removed more or less completely, when the

metal ion becomes part of the crystal''' . The ions or molecules, which are important

in determining the energy level scheme of the ion, thus bear the common features

of the spectrum as solution and solid. The electrostatic field set up by the Ugands

removes the degeneracy of the d-orbital. UV-Visible spectra of the complexes were

recorded in acetonitrile and important spectral bands are given in Table 2.

The electronic absorption spectrum of the complex [SnCl6][CdCl4][LH]4

recorded in acetonitrile solution is given Fig.lc. which shows the characteristic

bands at 292nm, 247nm, 232nm, and 216nm. Since there is no ligand field

stabilization effect in Cd2+ ion because of their completed d shells, their

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stereochemistry is determined solely by consideration of size, electrostatic forces

and covalent bonding forces. Further ions having d^ and d o configuration have no

characteristic absorption spectra'''^. The standard absorption spectra of [CdCU]^-,

[SnCle]^" and Ugnocaine hydrochloride show the absorption bands in the region 220-

247nm. The absorption bands of [CdCU]^-, [SnCU]^- and lignocaine hydrochloride in

the prepared complexes appear almost at the same wavelength region. Therefore the

absorption band appear in the region 200-240nm is an envelope band of [CdCU]^-

[SnCle]^' and lignocaine hydrochloride; hence it is difficult to assign these bands

either to Cd (II) or to Sn(IV) or to lignocaine hydrochloride. On the basis of

literature survey 71,77,78,79 tetrahedral geometry may be assigned to complex anion

[CdCU]^". G. Engelô have reported the existence of octahedral [SnCle] îon, on the

basis of the literature survey''^- ^ ' ^ octahedral geometry may be assigned to complex

anion [SnCl6]2'.

The electronic absorption spectrum of the complex [SnCl6][FeCl4][LH]3 recorded

in acetonitrile solution is given Fig.la. which shows the characteristic bands at

357nm, 312nm, 247nm,225nm and 214nm. The absorption band appear in the

region 214nm-247nm is an envelope band of [SnCleJ^' and lignocaine

hydrochloride^!. Qn the basis of literature survey^^' 80,8i,82 octahedral geometry may

be assigned to complex anion [SnCle]^'. The bands at 242nm, 315 nm and 363 nm

have been used for the detection and estimation of complex anion83,84 [FeCU]" The

commonly observed high intensity band in the UV region at 242 nm is missing,

whereas the remaining two bands at 312 nm and 363 nm are at the expected region.

Except high intensity charge transfer band it is similar to the observation made by

Gill 85 and visible spectra are also similar to observation of Lindenbaum^^ând

Costant et al^^^ which un equivocally support tetrahedral geometry for [FeCU]"

complex anion. This supports the tetrahedral geometry for the [FeCU]" in the

complex [SnCle] [FeCU] [LH] 3-

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The electronic absorption spectrum of the complex [SnCl6][NiCl4][LH]4 recorded

in acetonitrile solution is given Fig.lb. which shows the characteristic bands at

361 nm, 308nm, and 234nm. The absorption band at 234nm is an envelope band of

[SnCle] 2" and lignocaine hydrochloride'^'. On the basis of literature survey' '- 80.8i,82

octahedral geometry may be assigned to complex anion [SnCU] ". The characteristic

bands for tetrahedral Ni(II) complex should be in the region 300-421 nm " . So the

prepared complex is having the bands at 361 and 308nm suggesting the tetrahedral

geometry to complex anion [NiCU] ".

IR spectra

The IR spectroscopy can provide valuable information as to whether or not the

reaction has occurred. IR spectral data of lignocaine complexes of tin with other

metal ions are given in Table 3.

IR spectrum of lignocaine hydrochloride regenerated from the complexes is

having broad multiple absorption bands in the region 3500-3200 cm-1,

corresponding to vNH frequency, a medium absorption band at about 1670-1650

cm-1 may be assigned to >C=0 stretching frequency of amide group weak

absorption bands appear in the region 2710-1660 cm-1 are due to stretching

frequency of tertiary nitrogen group^^ indicate that lone pair of electrons on

nitrogen atom have taken part in salt formation and weak band at 2455 cm-1

correspond to v+NH. IR spectra of the complexes [SnCle] [MCU] [LH] 4 where M is

Ni or Cd and [SnCle] [FeCU] [LH] 3 show broad absorption bands in the region 3446-

3441cm-l which are characteristic stretching frequencies of NH in the complexes

(Fig. 2a, 2b and 2c). The absorption bands at 1668-1667 cm-1 are due to stretching

frequency of C = 0 of amide group. The weak absorption bands in the region 2977-

2976 cm-1 indicate v C-H of N-C2H5, which is almost unaltered, compared to the

vCH of N-C2H5 of lignocaine hydrochloride. This is in agreement with the

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observation made by Patel and Patel ^ and weak band at about 2445 cm-1

correspond to v+NH.

In the lignocaine complexes, the vNH of amide group shifts towards higher

region, compared to its position in the spectrum of lignocaine indicating non-

participation of amide nitrogen atom in coordination bond formation. This

behavior of nitrogen atom was accorded by the presence of bulky phenyl group

attached to it, which hinders the coordination of nitrogen.

Magnetic susceptibility

These were made with Gouy balance using mercury tetra thiocyanato cobaltate

(II) as a calibrant. The measured molar susceptibility value in each case was

corrected for diamagnetic contribution using Pascal constants^O' ^^ The magnetic

moment of tetravalent tin octahedral complexes having ionic nature is generally

diamagnetic in nature. According to valance bond theor}' octahedral coordination is

having sp^d^ hybrid orbital. Tin atom in the complex involved in the formation of

sigma bonds with six ligands. As a consequence of it, the 4d level is undistorted and

ten 4d electrons of Sn(IV) are distributed among all the five 'd' orbital. Therefore

octahedral complexes of tin (IV) in ground state have completely filled d-orbital and

have no unpaired electrons. Hence octahedral tin (TV) complexes are diamagnetic in

nature.

The magnetic moment values calculated for the heterobimetal complexes of

Sn(IV) with Cd(II), Ni([I) and Fe(III) are given in Table 2. According to valance

bond theory tetrahedral coordination is having sp^ hybrid orbital. The sp^ hybrid

orbital of the cadmium atom is involved in the formation of sigma bonds with four

ligands. As a consequence of it, the 4d level is undistorted and ten 4d electrons of

Cd(II) are distributed among all the five 'd' orbital. Therefore tetrahedral complexes

of cadmium (II) have completely filled 4d shell. Hence, the cadmium (II) complexes

are diamagnetic. In the prepared complex Sn-Cd both Sn(IV) and Cd(II) has no

96


unpaired electrons and d-orbital are completely filled, hence the complex Sn-Cd is

expected diamagnetic in nature; indeed experimentally it is found to be diamagnetic.

The effective magnetic moment value was calculated^^ fQ Fe(III) at room

temperature falls in the range of 5.91-6.05 BM and are in agreement with the

previously reported^3,94,95 values for tetrahedral and octahedral complexes of

iron(III). The measured magnetic moment value of complex Sn -Fe is found to be

5.56 BM which is sUghdy less than the expected spin only value 5.91BM of d

system there by indicating that there is spin-spin interaction leading to

antiferromagnetic coupling at normal temperature itself " 3,84 Therefore complex is

high spin complex with five unpaired electrons. High spin octahedral and

tetrahedral complexes of Fe(III) are having same ground state term ^Ai(g) and

moments are expected to be close to spin only value. As a result it is difficult to

assign geometry to complex based on magnetic moment alone, however, magnetic

data coupled with the data on elemental analysis and conductometric measurements

support tetrahedral geometry for complex anion [FeCU] '. The magnetic moment

([JLB) value of Sn -Ni complex is found to be 2.60 BM. This experimental value is

less than those calculated from the spin only formula there by indicating that there

is spin-spin interaction between the metal ions leading to antiferromagnetic

coupling at normal temperature itself ''^' '*.This measured magnetic moment value is

in agreement with tetrahedral structure^^- - ^ and supports tetrahedral geometry for

complex anion pSIiCU] ".

The prepared complexes Sn-Ni and Sn-Fe contain Sn(rV), since Sn(iy) ion is

expected to be having octahedral geometry in the complexes is diamagnetic '*'' ', the

observed magnetic moment value will depend on other metal ions, Ni(II) or

Fe(III)ions and the values obtained correspond to 2 or 5 unpaired electron with

antiferromagnetic coupling respectively. Hence the paramagnetism of the complexes

is arising either from Ni (II) or Fe(III)ion.

97


Electron spin resonance spectra

The ESR spectrum of the complex was recorded using poly crystalline 1,1-

diphenyl-2-picrylhydrazyl, DPPH is used as a 'g' value standard. The magnetic field

strength (Ho) at which the resonance line of the DPPH appears was measured.

The ESR spectrum of the hetero bimetal tin cry^staUine complex [SnCk] [FeCU]

[LH]3 is as shown in Fig 3. Since second ion in the complex, Sn(IV) is diamagnetic,

it is ESR in active. Hence, the ESR spectrum of the complex [SnCle] [FeCU] [LH] 3 is

mainly due to Fe (III) ion. The calculated g| | and g -'- values for complex

[SnCleJpFeCUJpLITJBis found to be 2.0729and 1.8871 respectively, which account for

the anisotropic nature of the complex and it arises from the coupling of the orbital

angular moment to the spin angular moment of the metal ion through spin orbit

interaction. This is also in agreement with the reduced magnetic moment values

obtained from the magnetic susceptibility measurements compare to spin only value

for the idealized tetrahedral environment around Fe (III) ion in the complex^^.

NMR spectra

^H NMR spectrum of lignocaine complex shows signals at 6.5-7.2ppm for (Ar.H

singlet), 3.26ppm for (-CO-CH2-N, singlet), 2.4ppm for (-CH2-CH3, singlet) and

l . lppm for (Ar-CH3, singlet). ^ C NMR of lignocaine hydrochloride regenerated

from the complex exhibit signals at 171.8ppm for (-CO) 125-140ppm for (phenyl C-

atom), 13ppm for (-CH2-CH3-), 49ppm (-CH2-CH3-) and 58ppm (-CO-CH2N-). ^H

and ^^C NMR spectra of lignocaine and its complex confirm the presence of

carbonyl, amide and phenyl group and also account for the un involvement of

carbonyl group in coordinating with Sn([V). The spectral data are shown in Table 4.

Mass spectra

The mass spectrum of lignocaine complex [SnCleJjFeCUjfLHJs is shown in the

figure 4. It is difficult to assign completely, fragmentation of the molecule, which is

98


having high molecular weight'^^. However some fragmentation of the molecule is

made and is given in Table 5. Mass spectrum of the complex shows the m/z value

1340 corresponds to the molecular weight of complex having formula

[SnClc] [FeC14] [LH] 3. Spectrum shows the base peak at m/z value 235 corresponds

to molecular mass of the Ugnocaine base. The peak at m/z value 469 corresponds to

molecular mass of [Lb] 2 radical, where Lb is lignocaine base. The peak at m/z value

86 corresponds to molecular mass of {C4H9NO}+ion.

99

i t V

C

u G

OJ C

•a u o G bJO

G

<u "a, o

O (U

<u

-M

13 u

•a G

H

<u u G

^0

^ y.

^ y.

Z13 iS y .

y 13 iS y .

y

G ig^

V4

'o y

X

a o y

(N r~; o

IT)

o (N

00 OS o t o

o

C^

0 0

o

SO

so CO

0 0

IT) (N

IT)

s6

C7N

o

<N

<N

00 to

00

00

en

GO

as o

00 r—t

(N

ON in

<N

r en K

in

en r-

T—1

c- .

in

00 00 00

(N in

^ o =3 (U ^ u 13 CIH

• " ^ ^

y

' so'

y G CA),

tL

vo in

-M

[^

^

' 't'

y y

0 G CO

d.

t^ ^

^ 0 =3 y > V

13 Ci

' "1-'

y

y G CO,

o o


<

5.723

4.000 -

2.000

0.000 -

•1.736

190.00 400.00 600.00 nm.

800.00 1100.00

vt

<

2.500

2.000

1.000 -

-0.100 l—^ 190.00 300.00 400.00 460.00

nm.

Fig.la. UV-visible spectra of [SnCle] [FeCU] [LH] 3


2.000 r

1.SOO -

w 1 .000 -

O.SOO -

0.000 -

1100.00

^ J ) S ' ^ ^ ^ ^ Fig.lb. UV-visible spectra of [SnCU] [NiCU] [LH] 4


5.000

4.000 -

£1 <

2.000

•0.100 190.00 300.00 400.00 460.00

nm.

3.000

2.000 -

1.000 -

-0.100 190.00 400.00 600.00

nm. 800.00 1100.00

Fig.lc. UV-visible spectra of [SnCl6][LH]4[CdCl4]

i

^ a u

0 c

X V

"a, 6 o (J

a a U <u a,

I

ti 0

u c C/D,

"0,

o (J

o

(J

a,


Table 2. Electron spectral bands and magnetic moment values of Sn (IV) hetero bimetal complexes with Lignocaine and cd(ll), Ni (11) and Fe (III).

Complex Absorption bands (nm) Hcff(BM)

[SnCl6][NiCl4] [LH]4

[SnCl6][CdCl4] [LH]4

[SnCl6][FeCl4] [LH]3

361,308,234

292,247,232,216

357, 312, 247,225, 214

2.60

Diamagnetic

5.56

Table 3. IR spectral bands of Sn (IV) hetero bimetal complexes with Lignocaine and Cd (II), Ni (II) and Fe^II)

Lignocaine hydrochloride (Cm-i)

3259

1660

1498

2450

2969

764

Complexes of Tin and LH with

[NiCU] (Cm-i)

3291

1669

1471

2455

2988

786

[CdCU] (Cm-i)

3293

1669

1470

2448

2988

785

[FeCU] (Cm-1)

3292

1670

1473

2452

2988

786

Assignment (Tentative)

vNH or vN+H Stretch

vC=0 Amide

vC=C Aromatic

vNH

vC-HofCaHs

V C-H aromatic

101

s

I f

V

u

C V tuO V

<u G

•3 u O

go C

X U

"a, o

U

'O •c o

(J

o u

T3 > j : : !> G

•a u O

go O

Pi

I

u -a c

H

G O

u

C

G O *-t

O u OH

G

u

s a,

13

u U

a, 3 o u

o

u flj

m •a 0 0

a •;i

V-l

G

u ^

3 O u

o

Pi

z I

u ^ u G

G •a ^

o u

u G V

U")

I CO

^ 1

ui 1 0

u

m

E u 1

UI 1

X UI

1

u -^

0 0

^ t--' — 1

0

^ T—1

i n CM

00 LO

O N

•<t IT)

_ K 1

^

tN

K U 1

0 r 1

n: u 1

u

X u I

CM

o

rn

0

(N

0 r-

CN C<S

0 (N

<N <N


Table 5. Mass spectral fragments of heterobimetal complexes of Sn(iy) with Lignocaine and Fe(III).

Fragments

(Tentative)

{[SnCy[LH]3[FeC]J}*

{[SnCy[Lb]3[FeCy}-

{[SnClJ[Lb]3[FeCl3]}^

{[SnCy[Lb]3[FeCy}^

{[SnClJ[Lb]3[FeCy}^

{[SnCl3][Lb],[FeCI]}^

{[SnCy(Lb][FeCy}^

{[SnCy[Lb][FeCy}*

{[SnCl][Lb],}"

{[Lb]J-

{Lig-HCl}

{Lig. Base}'

{C,,H,,NP}^

{CgH^N}-

{C4H9NO}^

Molecular mass of complex [SnCy[FeCy[LH]3

Observed

1340

1231

1196.9

1090.43

856.09

785.09

692.75

625.71

622.88

469

269

235

205

120

86

Cal

1341.93

1232.43

1195

1093

859

780

691

626

626

468.68

270.84

234.34

205

121

87

103

I

I

rsi \ e

CD

irti

i n en

en OJ

- # * •

i n

^

CO

• ^

CSD

LO M cn ^

• _ • 1 . . a ^

N --^^1 ^ J • " ^ '-^9

• ^ s

•9g n ' ^^ cn Ji J ' ^ v ^

- (S

- (S _ S)

ru r *""* ' . *'' .'-teas) p i n

—* fo

E t i ' Tf '

u

•;,•

• : V •

1 J •1

PVi? ; GX m.' .'*•_= '' <T»,1- -l£f ru ^l^-' J •

W 1

' — -. -

—

-" r>, ~

(S t n m

C3 K3 rt

Q in

i n

CD

A)

i n

CSD

S) CD c n .

s m 0 1

cs 4-

X

i n

in cn

cn

in CD

oo

cs CD c\j r ^ CSD

S) CD in

CO: rvj "s i n

^ a u

<u EL ' o '

u G

X

s o u G

•CJ

o

<u

<u Si

o

u u ex.

CO


CONCLUSION

The data based on elemental analyses and conductance measurements of the

complexes indicate that the tin: lignocainium:M, where M= Cd(II) and Ni(II) is

found to be in the ratio 1:4:1 whereas for the other metal ion Fe(III) the ratio is

found to be 1:3:1. From the elemental analyses data obtained for the complexes

[SnClc] [MCI4] [LH]4 and [SnCleJjPeCUJpLHJs, indicate the presence of heterometal

ions in each one of the complexes and also account for the general formulae

indicated as above. The conductivity measurements made for the complexes in their

acetonitrile solutions account for the ionic nature of the complexes and suggest that

the complexes are 2: 4 electrolytes. The mass spectral analyses of the complex

[SnCU] [FeCU] [LH] 3 is atlso accounting for the general formula molar mass of the

complex. Absorption and ESR spectral studies of the complexes coupled with their

magnetic susceptibility measurements would also account for octahedral geometry

for the anion [SnCle]^- whereas tetrahedral geometries for [FeCU]^", [CdCU]^- and

[NiCU]^" anions and hence the general formulae of the complexes suggested. The

NMR and IR studies show that lignocaine is present in the complex as lignocainium

ions, which are interacting with the two complex anions per complex through

coulombic force of attraction.

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chapter-4 heterobimetal ion-pair complexes of tin(ii) and...

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