DONOR ACCEPTOR COMPLEXES

OF GROUP IV ELEMENTS TIN AND GERMANIUM

A THESIS

SUBMITTED TO THE ALIGARH MUSLIM UNIVERSITY, ALIGARH FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN CHEMISTRY

Department of Chemistry Aligarh Muslim University, Aligarb, India

TAHIR ALI KHAN M. Sc. , M . Phil. (Alig.)

February, 1977

T1671

0 HCV11T?

ABSTRACT

^Uany new donor acceptor type of complexes of t e t r a h a l i d e s

of group(lV) elements with t h i o u r e a s and d i a z i n e s have been

syn thes ized and c h a r a c t e r i z e d . The s i t e of c o o r d i n a t i o n i n

t h i o u r e a s has been a c o n t r o v e r s i a l s u b j e c t , both su lphur and

n i t r o g e n having been claimed as the donor atom. Diaz ines have

been found t o ac t as u n i d e n t a t e or b i d e n t a t e l i gands forming

o c t a h e d r a l , monomeric or po lymer ic , complexes i nvo lv ing azine or

halogen br idged s t r u e t a r e s . ^ I n some complexes the t h i o u r e a s have

a l s o been found t o ac t as c h e l a t i n g b i d e n t a t e l i g a n d s , i nvo lv ing

both the n i t r o g e n atoms. I t was, t h e r e f o r e , of i n t e r e s t t o s tudy

the n a t u r e of bonding and s t r u c t u r e s of newly syn thes ized complexes.

The composi t ion of the s o l i d complexes has been e s t a b l i s h e d on the

b a s i s of e lemental a n a l y s i s . Infreired s p e c t r a l s t u d i e s have been

made t o e l u c i d a t e the s t r u c t u r e s of the complexes. Changes i n the

IR f requenc ies of d i f f e r e n t groups upon c o o r d i n a t i o n have been

s t u d i e d and the c o o r d i n a t i o n s i t e s proposed . The f a r i n f r a r e d

s p e c t r a of the conqjlexes i n the r eg ion 650-200 cm"" have been

recorded to a s s ign the meta l -halogen s t r e t c h i n g v i b r a t i o n s and

t o e s t a b l i s h , theref rom, the s t e r eochemis t ry of the complexes.

The moleir conductances of the so lub l e complexes have been measured

i i -

to exanilne I f they were i o n i c . The r e s u l t s Indicate that they

are bas ica l ly non->ionic in na ture .

Complexes of various N,N»-dlsubstituted thioureas of

the type SnX^.2L(X=Cl, Br, I ; I«N,N'-dial ly 1 th iourea , N,N'-

d le thyl th iourea , N,N'-dibutyl thiourea, N,N'~diisopropylthiourea

and N,N'-diphenylthiourea) have been studied mainly with a view

to resolving the controversy about the s i t e of bonding in th ioureas .

The sh i f t s in the N-H s t re tch ing and various other mixed v ibra t ion

bands of thioureas upon complexation are in favour of ni trogen

coordination* However, discrepancy ar i ses in t i n ( i v ) iodide

complexes of N,N'-die thyl thiourea and N,N'-di isopropyl thiourea,

where a negative sh i f t in the low frequency 0=3 band may be c i ted

as an evidence for coordination through sulphur, but a marked

negative sh i f t in the N-fl s t re tch ing frequency i s in clecu: support

of coordination through n i t rogen . Actual ly, i t i s d i f f i c u l t to

base any conclusion on the sh i f t s of the v ib ra t ion bands of the

l igand, where the observed bands of the ligand a r i se from mixed

v ib r a t i ons . The far IR spectra ind ica te a t rans-octahedral

configuration for a l l the complexes involving one of the ni trogen

atom of the thiourea l igand. The IR spectra of thioureas ind ica te

intermoleculcu* hydrogen bonding between hydrogen of the NH group

and sulphur of the C^S group, both in the so l id phase and in

concentrated so lu t ion . The IR spectrum of N,N'-diphenylthiourea

shows evidence of the existence of rotamers, with N-H bonds e i s

- l i i -

and t rans with respect to the thlocarbonyl sulphur, however,

the spectra of N,N'-die thyl thlourea , N,N»-dibutylthiourea and

N,N'-di lsopropylthiourea correspond to only t rans rotamers.

Complexes of pyrimidine ( l , 3 -d i az ine ) and some of i t s

der ivat ives were studied in view of t h e i r b io logica l importance

and lack of information on the s t ruc tu res of such complexes.

Tin(lV) ha l ides and germanium(lV) chlor ide complexes of pyrimidine,

2,4,6-triaminopyrimidine, 4-pyrimidinol, 4,6-diamino-2-mercapto>

pyrimidine and 4-amino-l,3-dimethyl-2,6-dioxopyrimidine have been

studied to explore the p o s s i b i l i t y of the formation of polymeric

species , since they have more than one coordination s i t e s . The

IR spectrum of 4,6-diamino-2-mercaptopyrimidine reveal i t s

existence in the thioamide form. Pyrimidine and 2 ,4 ,6- t r iamino-

pyrimidlne have been found to coordinate through r ing n i t rogen ,

however, in 4-pyrlmidinol and 4,6-diamino-2-mercaptopyrimidine

complexes coordination through carbonyl oxygen and thlocarbonyl

sulphur, r espec t ive ly , have been proposed. 4-Amino-l,3-dimethyl-

2,6-dloxopyrimidlne has been found to coordinate through the r ing

nitrogen atom. However, in I s l complexes of SnCl^ and SnBr^ i t

acts as a b identa te l igand, also involving the amino n i t rogen .

The far IR spectra of 1:1 and I j 2 complexes ind ica te a t r a n s -

octahedral geometry involving unidentate or b identa te l igands .

A polymeric s t ruc ture i s proposed for the l 5 l complexes.

- iv -

Pyridazine (1 ,2-diazine) complexes of the type MX.(pyridazine)

/~M=Sn; X=Cl,Br,I; n=l ,2 aJid M=Ge,Si,Tl; JfcCl; n=2_7 have been

studied with a view to determining t h e i r s t ruc tures and the den t lc i ty

of pyridazine. The far IR spectra ind ica te a t rans-octahedral

environment of the metal ion with both bidentate (n=l) and

unidentate (n=:2) pyridazine. A polymeric s t ruc ture involving

azine bridging i s proposed for the i s l complexes.

I t appears from the general consideration of the far IR data

that a l l complexes are t rans-oc tahedra l , and in any case there i s

no evidence for c is -octahedra l or pentacordinated t r igonal

bipyrimidal s t r u c t u r e s . They are a l l monomeric, excepting the

t in( lV) hal ide complexes of 4-amino-l,3-dimethyl-2,6-dioxopyrimidine

and pyr idazine , which have polymeric octahedral s t ruc ture involving

ligand b r idges .

Department of Cbenlstry Aligarh Muslim University

Aligarh

Certified that the work embodied in this thesis

ent i t led "Donor Acceptor Complexes of Group (IV) Elements,

Tin and Germanlttra" i s the result of the original researches

carried out under my supervision by Mr. Tahir All Khan

and i s suitable for submission for the award of the Ph.D.

degree of Aligarh Muslim University.

• ^'0^^.^^^^ (S.A.A. Zaidi)

Reader in Chemistry

it J' Ace Xo,

ACKNOWLEDGEMENT

I wish to express ay deep sense of gratitude towards

Dr. S.A.A, ISaidl, M.Sc.(Alig. )f M.A., Ph.D.(Toronto), A.R.I.C.

(London) for bis keen interest and help in this work and in the

interpretation of the resul t s . I em particularly grateful to

him for his encouragement and unending sympathetic behaviour

throughout the course of this work.

Thanks are also due to professor, W. Rahman, Head,

Department of Chemistry, Alig€U*h Muslim University, Aligarh,for

providing the research f a c i l i t i e s and to Professor P.T. Manoharan,

Indian Inst i tute of Technology, Madras, for help in getting the

IR spectra in his laboratory.

The author i s grateful to Mr. A.H. Siddiqi, Mr. M. Agha

and Mr. S. Salahuddin for doing analysis and to Mr. M.Ismaeel

for running the IR spectra. In the end I must thank my colleagues

for their cooperation and useful discussion during the course of

this work.

Financial assistance from UGC, New Delhi, i s gratefully

acknowledged.

(Tahir All Khan)

C O N T E N T S

Page

1. LIST OP PUBLICATIONS

2. LIST OP TABLES

3. ABSTRACT

4. CHAPTER - !•

Introduction 1

5 . CHAPTER - I I .

Eorperimental methods 10

6 . CHAPTER - I I I .

Complexes of t i n ( l V ) ha l ide s with N,N' -d i subst i tuted thioureas 35

7. CHAPTER - IV,

Complexes of t i n ( l V ) aad germanium(lV) ha l ides with pyrimidines 54

8 . CHAPTER - V.

Complexes of t i n ( l V ) , germanium(iy), s i l i c o n ( l V ) and t i tan ium( iv ) h a l i d e s with pyridazine 69

9 . REFERENCES 79

LIST OF PUBUCATXONS

1. Ident i ty of donor atom In N,N*-disubst i tuted thiourea complexes of t in(IV) h a l i d e s ,

S.A»A. 2 a i d i , T.A. iChan and K.S. Siddiqi , Acrta Chimica (In p r e s s ) .

2. Complexes of Sn(lV) & Ge(l7) ha l ides with pyrimidines , S.A.A. Zaidi and T.A. Kban, Indian Journal of Chemistry ( i n p r e s s ) .

3 . Complexes of Sn(lV), Ge(lV), S i ( lV) & Ti( lV) ha l ide s with pyridazlne ,

S.A.A. Zaidi and T.A. KhaSf Indian Journal of Chemistry ( i n p r e s s ) .

LIST OP TABLES

Page

1. Colour, melting point and ana ly t i ca l data of

thlottrea complexes. 42

2* Molar conductance of thiourea con^lexes . 43

3 . Assignments of IR spectra (4000-200 cm ) of thioureas and the ir complexes. 47

4 . Colour, melting, point and a n a l y t i c a l data of pyrimidine complexes. 58

5 . Molar conductance of pyrimidine c o i ^ l e x e s . 59

6. Assignments of IR spectra (4000-200 cm*" ) of pyrimidines and the i r con^lexes . 61

7. Colour, melting point and ana ly t i ca l data of pyridazine e o i ^ l e x e s . 72

8 . Molar conductance of pyridazine complexes. 73

9 . Assignments of IR spectra (4000-200 cm" ) of pyridazine and i t s coBi{>lexes. 75

C H A P T E R - I

INTRODUCTION

INTRODUCTION

The atoms of the group (IV) e lements resemble those of 2 2 carhon and s i l i con in having the ns np e lectron configuration

3 and P ground s t a t e , and In forming the te t rahedra l bonds asso-

g

elated with sp hybr idizat ion. However, downwards in th i s group

there i s an increasing tendency to form an ' i n e r t p a i r ' ion , and,

in most s table s a l t s , lead preserves an ns ' c o r e ' , appearing as 2+ Pb , Transient covalent species of the type MX for carbon and

s i l icon also have been described. The s and p sub-group t rends ,

such as an increase , with increasing atomic weight, in metal l ic

character of the elements and the s t a b i l i t y of compounds of the

lower oxidation s t a t e , are marked in the group. The difference

between carbon and other elements in t h i s family i s that the

l a t t e r , possess low-lylng unf i l l ed d o r b i t a l s through which they

can increase t h e i r coordination numbers to five or s ix , or some­

times even up to e i g h t ( i ) .

There are three poss ible ways in which an element in the

4+ s ta te could form der iva t ives : (a) by loss of a l l four valence

electrons to form the M "** Ion, (b) by hybridizat ion of the a v a i l ­

able atomic o rb i t a l s in a sui table environment to form four

equivalent covalent bonds, and (c) by complex formation, i . e . ,

making use of the empty d o r b i t a l s , which are of s imilar energy

- 2 -

to the valence electron o r b i t a l s . This i s represented formally

as overlap of empty hybrid o r b i t a l s on the metal with f i l l e d

o rb i t a l s on a su i t ab le ligand to form dative covalent bonds.

In the case of t in( lV) conq)Ounds one could predic t a spherical

ion of radius 0.74A° for ionic bonding, t e t rahedra l coordination

of the t i n atom in covalent bonding, and an octahedral coordina­

tion in most of the complex ions .

I t w i l l be appropriate to give a b r i e f account of some

of the important compounds of t i n and germanium and the follow­

ing paragraphs wi l l be devoted to th i s descr ip t ion .

Organotin compounds have s igni f icant use as s t a b i l i s e r s

and ca t a ly s t s in the p l a s t i c indust ry , as biocides for a n t i -

fouling paints and timber preserva t ion , and as crop pro tec tan ts

in ag r i cu l tu re . Tr iphenyl t in-acetate and hydroxide are now well

establ ished as agr icu l tu ra l fungicides, especia l ly for the control

of phytophthora infes tans on potatoes and cercospora on sugar

bee t . These t r iphenyl t in compounds also exhib i t i n sec t i c i da l

a c t i v i t y , mainly through the i r antifeedant function i . e . rendering

leaves of crops unpalatable to the insec t pes t , which therefore

starves to death. Triphenyltin compounds have found sa t i s fac tory

use for t r ea t ing fungal diseases in cocoa, coffee, onions,bananas

and pecan nu t s . Complexes of t r iphenyl t in chloride with dimethyl-

sulphoxide and quinoline N-oxide have been reported to be effect ive

for protec t ing tomatoes, celery and sugar beet and to be low in

- 3 -

mammalian t o x i c i t y . Rubber p e l l e t s containing t r i b u t y l t i n oxide

are used for eradicat ing the sna i l c a r r i e r s of Bi lharz ia . T r i -

organotin compounds are found to be ef fec t ive against mosquitoes.

The r a r i t y and high cost of germanium r e l a t i v e to s i l i c o n , t i n ,

and lead have probably retarded development of i t s chemistry and

no s igni f icant chemical ^ p l i c a t i o n has appeared for organo-

germanium compounds, although i n t e r e s t in organogermanium research

i s increasing g rea t ly .

Much of the recent work on t i n and germanium chemistry

concerns the synthesis and charac te r i sa t ion of t he i r organo-

meta l l lc compounds(2-6). A good deal of work has also been done

on the reac t ion of t in and germanium(lV) ha l ldes with various

Lewis bases forming donor acceptor type of complexes often des ­

cribed as adducts(7 ,8) . Anhydrous t i n ( i v ) and germanium(lV)

hal ldes act as Lewis acids by accepting a lone pa i r of e lectrons

from a Lewis base. Studies on such addit ion compounds of group(IV)

ha l ldes , pa r t i cu l a r l y on t in( lV) ch lor ide , are quite extensive .

In the present work a study of the formation and charac te r i sa t ion

of the adducts of a few ha l ldes of group(iv) elements, germanium

and t i n , has been undertaken with a view to determining the i r

s t ruc tu re , stereochemistry and comparative Lewis ac id i ty of the

hal ldes used v i z . , germanlum(lV) chloride and t ln( lV) ha l ides

(excepting the f luo r ide ) . Si l lcon(lV) and tltanium(lV) chloride

complexes of pyrldazine have also been inves t iga ted .

4 -

Complexes of t r ans i t i on metal ions with various ni trogen

containing ligands have been the subject of act ive research in

the past few y e a r s ( 9 , l 0 ) , Adduct formation by the react ion of

t in( lV) ha l ldes with donor molecules l ike pyridines,amines,

ammonia, a n i l i n e s , u reas , amides, aminobenzoic acid and an thrani l ic

acid have also been inves t iga ted . The corresponding GeCl. adducts

a re , in general less s tab le at room temperature, hence have not

been well charac ter i sed . The formation of a 1:2 adduct of SnCl. 4

with amine and aminobenzoic acid and of a Ijl adduct with anthra­

nilic acid has been confirmed by indicator titration and analytical

results(ll). Infrared spectra of all these adducts confirmed

nitrogen to metal bonding. The analogous GeCl. adducts have

received little attention, however, its adducts with bipyridyl

and terpyridyl have been shown to have a trans configuration in

the solid state, and ionic nature( 12,13) in nitrobenzene. Trost(l4)

has studied a trimethyl amine adduct ot GeCl. and from the thermal

decomposition of this adduct has shown it to be a molecular addi­

tion compound. Poller and Toley(l5) have studied 4,4'-bipyridyl

adducts of stannic chloride and organotin halides of the type

Rn SnX jj where n = 1,2 or 3, Tin(iv) chloride adduct of 4,4'-

blpyridyl (is2) was found to have a trans octahedral geometry. A

polymeric structure was suggested for the is 1 adducts of organo-

tindihalides and trihalides with 4,4'-bipyridyl. However, a

monomerlc structure was assigned to 4,4'-bipyridyl triphenyltin-

chloride adduct. A Isl adduct of pyrazine (1,4-diazine) with

- 5 -

d ipheny l t l nd lCh lo r ide was a l s o r e p o r t e d bu t i t s s t r u c t u r e could

not be e s t a b l i s h e d with c e r t a i n t y .

Germanium t e t r a h a l i d e s as wel l as organohalogermanes r e a c t

wi th amines t o form adduc t s . Most of t h e s e , however, a re s t a b l e

only a t temperatures below 0*^C. By i n t e r a c t i o n between GeCl ^ and

a n i l i n e or between GeCl. and cyclohexylamine, Davidson prepared

the compounds ClGe (NH C Q H - ) ^ , C I , GeCNHR)^ (a=phenyl or c y c l o ­

hexyl ) and Ge(NH CgH. ) ^ ( 1 6 ) . However, g e n e r a l l y the d e r i v a t i v e s

con ta in ing two or more NHg or -NHR groups bonded with a germanium

atom are u n s t a b l e . This has been i l l u s t r a t e d by the formation of

the R-GeNH and RGeN type d e r i v a t i v e s i n ammonolysis of organo-

germanium d i - and t r i h a l i d e s , as well as by the formation of GeCNH)^

i n GeCl^ and Gel^ ammonolysis(17,18). The (RHN)^Ge type d e r i v a t i v e

l ead to d e r i v a t i v e s of the GeCNR)^ type . Thomas and Southwood( 19)

r e p o r t e d the formation of germanium diphenyldi imide d ihyd ro -

c h l o r i d e Ge(N CgHg, HCl)^ , In the ac t i on of GeCl^ on a n i l i n e . The

a c t i o n of e thylamine on GeCl. r e s u l t s i n an u n s t a b l e adduct and

f i n a l l y i n the formation of germanium d i e t h y l d i i m i d e GeCNCgHg)^.

The ac t i on of d ie thylamine leads t o the formation of germanium

d i e t h y l d i i m i d e hydroch lo r ide Ge(NC2H5)2» HCl. P i p e r i d i n e ,

however, y i e l d s t e t r a s u b s t i t u t e d d e r i v a t i v e s . The r e a c t i o n of

GeCl. with monomethylamine r e s u l t s i n the formation of a t r i m e r i c

c y c l i c molecule , (ClgGeNMe),, having a s ix-a tom backbone of

a l t e r n a t i n g Ge and N a toms(20) . Germanium t e t r a c h l o r i d e r e a c t s

wi th a number of N , N ^ - d l s u b s t i t u t e d e thylenediamines to give s p i r o -

- 6 -

imldazolidines with germanium as the cen t r a l sp i ro atom(2l).

Either nitrogen or oxygen can act as the donor atom in

u reas , and s imi lar ly e i the r nitrogen or sulphur can act as the

donor atom in thioureas* I t i s evident, however, from the cons i -

derahle number of s t ruc tu ra l and chemical s tudies( 22-28), on urea

and thiourea complexes of t r a n s i t i o n metals that oxygen or sulphur

i s the preferred donor atom. There are occasional exceptions, for

example, the urea complexes of P t ( l l ) and P d ( l l ) appear to he N-

coordinated(29), and ce r t a in unidentate and chelat ing hidenta te

complexes of subs t i tu ted thiourea with t i tanium te t rachlor ide(30)

are also N-eoordinated. Very few adducts with main group elements

have been studied comprehensively but the majority again seem to

be oxygen or sulphur coordinated(3l ) , Thioureas coordinate through

sulphur atom not only with t r ans i t i on metals , but a lso with Sn(lV),

Sn( l l ) and Pb( l l ) (32-34) . Attack v ia ni trogen was observed in the

react ion of phosphorus pentaohloride with 1 ,3-disubst i tuted ureas

(35) . Some other possible N-coordinated systems include the u rea -

BP„ adduct, compounds from the react ion of t r i (n -p ropy l ) borate

with a urea or thiourea, and a few phosphorus der iva t ives of N-

subs t l tu ted N'-dimethyl th ioureas(36) .

Considerable study has been made of the coordination

a b i l i t y of the amides and thioamides, mainly with i n t e r e s t to

discover the s i t e of bonding. An amide to metal linkage generally

involves coordination through the oxygen atom(37-45). Recent

studies on the complexes of metal hal ides with a number of t h i o -

- 7 -

amides show on the bas i s of infrared spect ra l evidence that the

s i t e of bonding i s presumably the sulphur atom(46-48). On the

other hand several workers have also reported coordination through

nitrogen in thioamides and thioureas(49-57). However, there i s

much l e s s l i t e r a t u r e on thioamide complexes than on those of

th iourea. Thioureas have been reported to coordinate with the

t e t r aha l ides of group(lV) elements through ni t rogen(30,58,59) .

Tin(iv) hal ide complexes of various N,N'-subst i tu ted thioureas

v i z . N ,N ' -d ia l ly l th iourea , N,N«-diethylthiourea, N,N' -dibutyl -

th iourea , N,N'-di isopropylthiourea and N,N'-diphenylthiourea have

present ly been studied with a view to inves t iga t ing the s i t e of

bonding in order to understand the nature of bonding of these

complexes.

The t r an s i t i o n metal complexes of pyrazines ( l , 4 -d i az ines )

(60-78) have been more extensively studied in the past few years ,

however, there have been very limited s tudies on the complexes of

pyrimidines ( i , 3 -d iaz ines ) (7 i -80) and pyridazines ( l , 2 -d i az ines )

(74-78), Copper(l) ha l ides (3C=Cl,Br,l) formed complexes with

pyrazine(8l) in which there are two cuprous hal ide groups for each

pyrazine molecule. These represent the f i r s t complexes where each

nitrogen i s bonded to metal atom. For acceptor elements other

than t in i t has been shown e a r l i e r that pyrazine and i t s homologues

form coordination polymers(73-75,81-88) with copper, n icke l , cobal t ,

molybdenum, zinc, cadmium, mercury e t c . Recently Goldstein and

Unsworth(89) have studied the t i n ( i v ) hal ide complexes of pyrazine.

- 8 -

The low frequency infrared and Raman spect ra of the complexes

SnX^ (pyrazine)jj(}fcCl, Br, I; n=l and X=C1, Br; n=2) indica te

s t ruc tures containing t rans-octahedral MX N (Nspyrazine)

skeletons with b identa te (n:al) or unidentate (n=2) pyrazine

l igands, A polymeric s t ruc tu re was assigned to 1:1 complexes. 1 iQ *

The f i r s t reported examples of quadrupole s p l i t t i n g in the Sn

Mossbauer spectra of SnX^ N groups are the complexes SnX^-

(pyrazine) (X = CI, Br, l ) ,

Pyrimldines are of much i n t e r e s t owing to t h e i r b io logica l

importance as compounds of nucleic ac ids . Weiss and Venner(80)

have studied the formation of complexes between pyrimidine bases

that occur in nucleic acids and Co(ll) and N i ( l l ) . These metal

ions show closely s imilar behaviour towards pyrimidine bases and

became linked to the r ing N of the pyrimidine nucleus. Some

ligands often produced both te t rahedra l and octahedral aurrange-

ments, which appeared as d i f fe rent ly coloured spec ies . Cytosine

was exceptional among the pyrimidine der iva t ives which acted as

a monodentate llgand with N i ( l l ) in which the octahedral arreuige-

ment was predominant, while i t s Co(l l) complexes have a t e t r a ­

hedral s t ruc tu re , Weiss and Venner(80) have also studied the

complexes of Cu(ll) and Cu(l) ions with various pyrimidine d e r i ­

vat ives subs t i tu ted in pos i t ions 2,4, or 6 in which SH groups

were found to be act ive as complexing groups. Perraro et a l .

(74-76) have studied the complexes of the a n ( l l ) , C d ( l l ) , Hg( l l ) ,

Mn(l l ) , P e ( l l ) , C o ( l l ) , N i (H) and Cu(ll) hal ides with pyrazine

- 9 -

pyrimldine and pyr idazine . Reflectance spect ra , I .R. spectra

from 4000 to 80 cm" , and magnetic moments were determined. An

octahedral environment was suggested involving hal lde and azlne

bridging in the I s l complexes, and an octahedral environment

involving hallde bridging and terminal azlnes in 1:2 complexes.

No pyrimldine complex of t i n and germanium hal ides has

so far been repor ted . I t was, therefore , of I n t e r e s t to syn­

thesize and charac ter i se the complexes of such b io logica l ly

important pyrimidines with t in and germanium ha l lde s . The

present study of SnX^ and GeCl^ adducts of pyrimldine, 2 ,4 ,6 -

triamlnopyrimidlne, 4-pyrimidinol, 4,6-diamine-2-mereaptopyri-

mldlne and 4-amlno-l,3-dimethyl-2,6-dloxopyrimldlne was under­

taken to explore the p o s s i b i l i t y of the formation of polymeric

or polynuclear species since they have more than one coordination

s i t e . In case they acted as unidentate ligand i t was worthwhile

inves t iga t ing which of the donor s i t e s was more suscept ible to

coordination. Fur ther , i t was of i n t e r e s t to study the r e l a t i v e

bas i c i t y of the l igands .

Pyridazine i s known to form polymeric complexes with

t r ans i t i on metals involving azlne bridged s t rue tu res (74 ,75) ,

Tln(lV), germanlum(lV), sHlcon(lV) and titanlum(IV) hal lde

complexes of pyridazine have present ly been studied with a

view to inves t iga t ing i f i t acted as a bridging l igand.

C H A P T E R - I I

EXPERIMENTAL METHODS

EXPERIMENTAL METHODS

Several phys ico-chemical methods are now-a-days a v a i l a b l e

for s t r u c t u r e e l u c i d a t i o n of c o o r d i n a t i o n compounds* The

techniques used for the i n v e s t i g a t i o n of the s t r u c t u r e of newly

syn thes ized compounds desc r ibed i n the p r e s e n t work a re i n f r a r e d

spectroscopy and molar conductance measurements. While in forma­

t i o n s about t he se techniques a re found i n most of the modern

t e x t - b o o k s , a b r i e f d e s c r i p t i o n of these methods seems appro­

p r i a t e .

INFRARED SPECTROSCOPY

I n f r a r e d spectrum a r i s e s from the d i f f e r e n t modes of

v i b r a t i o n s and r o t a t i o n of a molecule . The pure r o t a t i o n a l

spectrum of molecules occurs a t very long wave-length i n the

microwave reg ion wel l beyond the wave-length l i m i t of about 25y^.

At wave-length below 25 ji the r a d i a t i o n has s u f f i c i e n t energy to

cause changes i n the v i b r a t i o n and of course a l s o the r o t a t i o n a l

l e v e l s of the molecule .

According to the quantum theory the re €ire d i s c r e t e energy

s t a t e s , both r o t a t i o n a l and v i b r a t i o n a l i n which each molecule

u

can ex is t* For diatomic, l inear polyatomic, and spherical top

molecules the energy ot ro ta t iona l l e v e l s i s given by the equation

iriiere J i s the ro ta t iona l quantum number irtiich can have any

in tegra l va lue , 0 , 1 , 2 , 3 , . . . . , and I i s the moment of i n e r t i a

of the molecule about the curls of r o t a t i o n . For symmetrical and

asymmetrical molecules the formula i s someirtiat more con^lex.

Transitions between the d i f f erent ro ta t iona l l e v e l s in the

microwave and infrared regions are governed by the s e l e c t i o n rule

A J S 4 > 1 « I f a molecule i s ra ised from an energy s t a t e with a

quantum number J to that with quantum number J>1, the energy

Involved w i l l be

h)} « A E = Ej^^ - Ej Eqn. (2)

from which the frequency of energy absorbed in wave numbers can be

obtained by substitution of Eqn.(l) in Bqn.(2) as follows;

O ,.hii±il « 2B (J^l) Eqn. (3)

where B, the rotational constant, is equal to h/8 ff IC. The

pure rotational spectrum then would consist of equally spaced lines.

The constant frequency separation between successive lines being

equal to 2B, i.e., to h/4 tT IC cm" . It will be observed that

as the moment of inertia I increases, so the frequency of the

rotational lines, for a given J value, decreases. For relatively

12

heavy or large molecules, the pure ro t a t ion spectrum wi l l thus

appear In the very far inf rared .

In the infrared region below 25y(J , changes in the v i b r a ­

t ional s t a t e s of the molecule occur during absorption of rad ia t ion

for small amplitude of v ib ra t ion , the v ib ra t ion may be considered

harmonic and the energy of the v ib ra t iona l quantum level i s given

by Eqn.(4) ,

E^ « hCO(v + 1 ) Eqn. (4)

where OO Is the fundamental vibrational frequency of the harmonic

oscillator, and v is the vibrational quantum number which can have

any integral value, 0,1,2,3 , , . The difference in energy between

successive energy levels of the harmonic oscillator is thus always

hCO.

In order that a vibrating molecule should interact with the

fluctuating electrical field of electromagnetic radiation the

molecular electrical dipole moment must change its magnitude or

orientation with respect to a fixed coordinate system during the

motion. It is the magnitude of this change of dipole moment which

determines the intensity of a transition. There are 3N-6 normal

vibrations of a non-linear molecule of N atoms and hence the 3N-6

frequencies associated with them are called fundamental frequencies

of the molecule. From the symmetry that a molecule possesses one

can determine how many of the 3N-6 vibrations will be observed in

13

Its Infrared spectrum, and conversely, from the infrared spectrum

the molecular symmetry may be deduced. A vibration will be infrared

active if its symmetry species is the same as that of .at least one

of the dipole moment components. For harmonic oscillators, transi­

tions between the various energy levels are governed by the selec­

tion rule A V = + i. In actual fact, the purely harmonic condi-

tions do not prevail for real molecules* The frequent observation

of overtones and combination tones of these vibrations corresponding

to changes A v s 2,3, etc. is a consequence of the anharmonio

nature of the normal modes. These additional bauds are usually

very much weaker than the parent fundamentals.

For harmonic oscillation the frequency (X) is related to the

force, f, binding the vibrating groups together and the reduced

mass i^ , by the relationship

where m. and BL are the mewses attached to either of the vibrating

system. In terms of the frequency \)ytin wave numbers, Eqn.(6)

becomes

Thus the frequencies of vibration of a molecule cure related

to the masses and binding forces. In many of the normal modes of

vibrations of a molecule the main participants in the vibration are

two atoms held together by a chemical bond. The frequencies are

14

only s l i g h t l y af fected by another atoms, attached to the atoms

concerned, and thus these v ibrat iona l modes are c h a r a c t e r i s t i c of

the group In the molecule and are very usefu l in Ident i fy ing a

compound, e s p e c i a l l y in deducing the structure of an unknown

substance. In t h i s work, only those frequencies which «u:e p e r t i ­

nent to the d i scuss ion of the newly synthesized complexes w i l l be

discussed.

y-H Stretching Vibrations - The N-H s tre tch ing v ibrat ions occur

in the region 3500-3300 cm"^ in d i l u t e s o l u t l o n s ( 9 0 ) , Frlaary

amines in d i l u t e so lut ions of non-polar so lvent s g ive two absorp­

t ion bands in t h i s region. The f i r s t which i s due to symmetric

s t re tch i s usua l ly found near 3500 cm and the second which a r i s e s

from the corresponding asymmetrical mode i s found near 3400 cm~ .

The p o s i t i o n and In tens i ty of both these bands are s e n s i t i v e to

s u b s t i t u t i o n . Secondary amines show only a s i n g l e SSL s t re tch ing

absorption in d i l u t e so lu t ion i n the above mentioned region. The

i n t e n s i t y and frequency of N-H s tre tch ing v ibrat ions of secondary

amines are very s e n s i t i v e to s tructural changes. The band i s found

in the range 3350-3310 cm" (low I n t e n s i t y ) i n a l i p h a t i c secondary

amines, and near 3490 cm" (much higher i n t e n s i t y ) i n he terocyc l i c

secondary amines such as pyrrole and i n d o l e . Fluorine subs t i tu t ion

general ly seems to enhance the i n t e n s i t y of the band. Ring s t r a i n

seems to have l i t t l e e f f e c t on N-S. s t re tch ing v ibrat ion as can be

seen by the values of ethylenelmlne (3367-3341 cm" ) and dlmethyl-

amlne (3384 cm" ) .

15

The N-H stretching absorption s h i f t s to lower va lues In the

s o l i d s t a t e due to extens ive hydrogen bonding. At very low con­

centrat ion pyrrol idine shows a band at 3367 cm due to the monomerlc

N-H s tre tch ing frequency(9l ) . As the concentration Increases , a

new band appears at 3268 cm due to intermolecular a s s o c i a t i o n

(N-H • . « . N bonding). The I n t e n s i t y of the low-frequency band

increases with Increasing concentration u n t i l complete a s s o c i a t i o n

occurs in the l iquid s t a t e . Hydrogen bonding i s very common in

ureas and thioureas(92)* In concentrated so lu t ions of thioureas

in CCl^ and CHClg two to four bands i n the 3500-3000 cm~^ region

are present . The highest frequency band i s much sharper than any

Of the others , the broadness of which can reach 200 cm . Further,

the molar e x t i n c t i o n of the h ighest frequency band increases with

decreasing concentrat ion, the trend being opposi te for the other

bands. In very d i l u t e so lu t ions only the h ighest energy band i s

v i s i b l e . There i s always i n the s o l i d spectra , however, a s trong,

broad band together with weaker and narrower bands on the lower

frequency s i d e . This suggests a strongly assoc ia ted condit ion for

thioureas in the s o l i d s t a t e .

Valuable information has been obtained on the structure and

tantomerism of many he terocyc l i c molecules and the ir subs t i tu ted

der iva t ives from a study of the N-H s t re tch ing absorption. The

(5(- and y HBiercaptopyri ml dines and other mercapto-aza-aromatic

compounds e x i s t i s the thione form, both' i n the s o l i d s t a t e and in

so lvents of low p o l a r l t y ( 9 3 ) . In the s o l i d s t a t e a weak band i n

l 6

the range 3160-3190 cm" I s regarded as evidence for the presence

of N-fl groups. In so lut ion a broad band i s shown in the range

3350-3420 era" , due to H-B. s t re tch ing i n unassociated molecules

(weaker bands a l so appear at lower frequencies , due to as soc ia ted

molecules) . The IR spectra of 2 - and 4-hydrojcypyrlmldines in the

s o l i d . s ta te and in CHClo so lu t ion g ive absorption bands due to

N-H bond s tre tch ing v i b r a t i o n s , ind ica t ing the ir ex i s t ence in the

tautomeric keto form(94). However, aminopyrimidines, genera l ly ,

e x i s t In the non-tautomerio form, and in so lut ion (CHC1«, CCl.)

g ive two bands c h a r a c t e r i s t i c of amino group(95,96)«

N-H Deformation Vibrations - For the deformation frequencies of

the NHn group in primary amines four c h a r a c t e r i s t i c peaks should

appear. But the only d e f i n i t e assignment has been done i n the case - 1 of s c i s sor ing v ibra t ion , genera l ly observed in region 1650-1590 cm

( 9 7 ) , The lower frequency deformation v ibrat ions of the NHg group

have not been inves t iga ted in d e t a i l . The NH. t w i s t i n g , wagging

and tors ional v ibrat ions i n methylamine have, however, been assigned

to 1455, 780 and 264 cm , respec t ive ly* Secondary a l i p h a t i c amines

show an extremely weak band in the range 1650-1550 cm" due to N-^

deformation v ibrat ion and i t i s d i f f i c u l t to detect t h i s band

r e a d i l y . The assignment of t h i s v ibrat ion i s very d i f f i c u l t in

the case of aromatic amines because of the presence of aromatic

r ing v ibrat ions in t h i s reg ion .

I 7

C-g Stretching Vibrations - These v ibra t ions are usual ly

observed In the 3100--3000 cm In carbocycllc and heterocycl ic

systeni|i(9l). Some aromatic compounds give r i s e to three bands near

3038 cm"" . pyridine shows C-fl absorption in the range 3070-3020 cm~^,

which appear as a se r i es of imiltlple absorptions under high r e s o l u -

t ion(98) . In pyrimldines t h i s band i s observed near 3050 cm .

A weak band i s observed in the case of t r i s u b s t i t u t e d pyrimldines,

since only one free r ing hydrogen atom i s present and t h i s band i s

absent in t e t r a subs t i t u t ed pyrimldines*

C-H In-Plane And Out-Of-Plane Deformation Vibrations} A number —1 of c h a r a c t e r i s t i c absorption bauds in the region 1250-iOOO cm ,

exhibited by most of the he terocycl ic compounds are a t t r i bu t ed to

C-H in plane deformation and the r ing breathing modes(91). In

diazines these bands are observed in the range 1239-1021 cm (99)»

Bands appearing in the region 900-700 cm" have been a t t r i b u t e d to

the C-H out of plane deformation v i b r a t i o n s , and the pos i t ion of

these bands depend on the number of free hydrogen atoms adjacent

to one another.

S-H Stretching Vibrations - The S-H v ib ra t ions in mercapt€Uis

are usual ly observed in the range 2600-2550 cm (100). The S-H

absorption I s not inherent ly s t rong , and i s often d i f f i c u l t to

detect in d i l u t e solut ions or in samples examined in very thin

c e l l s . I t i s also obscured in compounds containing COOH groups

]8

nHiiich exftlblt general absorption in th i s region* However, i f

allowance i s made for these factors the presence or absence of a band

in t h i s region can afford deciss ive evidence for the occurrence of

a mereapto group.

Simple mercaptans such as propyl , butyl and isoamyl mercaptans

gave a well defined but r a the r weak absorption at 2650-2550 cm ,

Randall e t a l . ( l O l ) proposed the range 2688-2560 cm for the S-H

band, but t h i s i s c lear ly designed to include hydrogen sulphide

which has i t s asymmetric S-H mode at 2688 cm" . This i s an excep­

t iona l case, and aromatic mercaptans do not appear to absorb at

higher frequencies than 2600 cm , Sweeney et a l . ( l 0 2 ) have shown

that ls2-dimercaptoethane absorbs a t 2350 cm in the l iquid s t a t e ,

but t h i s appe«urs to be wholly except ional . Thus even th ioace t lc

acid (2550 cm ) and d i th ioace t l c acid (2481 em" ) absorb at higher

frequencies, indica t ing that polymerisation does not occur to any

ex ten t , and Indeed the S-H l ink i s not appeu'ently capable of the

extensive degree of hydrogen bonding which occurs with OH and NH

groupings. There i s very l i t t l e change in the frequency of S-4i

absorptions on passing from the l iqu id s t a t e to d i lu te so lu t ions ,

so that any Intermoleculeor bonding effects must be very small . On

the other hand, small sh i f t s suggestive of hydrogen bonding have

been observed in solut ion in ce r t a in bases and other compounds,

ind ica t ing the formation of weak SHS - - - N bonds. Thiophenol i s

capable of hydrogen bonding to sulphoxldes, to give a frequency

sh i f t of the S-fl v ibra t ion of 100 cm"^, however, with aryl sulphoxldes

19

the s h i f t i s somewhat smaller.

Studies in th i s region have been used to determine urtiether

cer ta in heteroaromatic mercapto coiq)ounds e x i s t in >the mercaptan

or th io -keto form(93 , l03) . The absence of any S-H absorption from

the spectrum of mercapto-benzthiazole i s one of the s trongest p i ece s

of evidence for the ex i s tence of t h i s substance as a thio-ketone

under normal condi t ions . 3-Mercaptopyridine and 8-mercaptoquinoline

e x i s t in the mercaptan form in so lvents of low d i e l e c t r i c constant

( 9 3 ) . The broad and weak band at 2520 cm in the spectrum of

8-mercaptoqulnoline ( for which there i s no counterpart i n the

spectrum of 8-methylthioquinoline) i s a t tr ibuted to S-H s tre tch ing;

there i s probably some intermolecular hydrogen bonding between the

S-S group and the v i c i n a l nitrogen atom.

C=N Stretching Vibrations - A band of var iable I n t e n s i t y in the

region 1690-1640 cm i s a t tr ibuted to C=N s tre tch ing v ibra t ions

in open-chain systems or in non-conjugated ring systems(104) . With

conjugated c y c l i c systems the p o s i t i o n i s imich l e s s c l e a r , and the

CsN absorptions have been assigned as being within the range

1660-1480 cm , In c y c l i c compounds and c y c l i c materials without

in ternal conjugation the C N absorption i s assigned to the 1650 cm"

region. The C=N absorption band occurs near 1667 cm" in oxazines ,

oxazo l ines , oximes and Imines. However, the C=N absorption bands

are d i f f i c u l t to ident i fy for two reasons . F i r s t owing to the

considerable changes in i n t e n s i t y n^ich follow:>changes i n i t s

20

environment, and secondly because information avai lable on the

effects of conjugation in r ing systems i s often conf l ic t ing and

indecis ive .

C-N Stretching Vibrations? The C-N s t re tch ing absorptions give

r i s e to strong bands in the region 1360-1230 cm in aromatic amines

(90) , In a l ipha t i c amines the absorptions are in the 1220-1020 cm~*

range and are often of low i n t r i n s i c I n t e n s i t y , In aromatic primary

amines there i s one band in the region 1340-1250 cm but in

secondary amines two bands have been observed in the region 1350-

1280 cm~^ and 1280-1230 cm"" . The pos i t ion of C-N absorption does

not d i f fe r much from C-C absorption, but the in t ens i ty i s r e l a t i v e l y

Ifirge because ot C-N p o l a r i t y .

Ring Stre tching Vibrations - Charac te r i s t i c aromatic r ing

v ibra t ions appeeo* in the region 1600-1350 cm (9 l ) in most of the

heterocycl ic compounds. The pos i t ion and i n t ens i t y of these v i b r a ­

t ions are dependent on the nature of the r ing and type of s u b s t i t u ­

t ion . Six membered r ings show four bemds around 1605, 1575, 1480,

and 1430 cm" , nHiereas 5-membered r ings show three bands around -1 1590, 1490, and 1400 cm , The i n t e n s i t i e s of these bands give an

idea of the pa t te rn and nature of subs t i tu t ion in the r i n g . Thus,

in 4 -subs t i tu ted pyridine-1-oxides and 3-subst i tu ted pyridines the

i n t ens i t y of the band around 1605 cm"* i s high for both e l ec t ron -

withdrawing and electron-donating subs t i t uen t s , whereas in the case

21

of 2 - and 4-su1)stltuted pyridines and 3 - sabs t i tu ted p y r i d i n e - 1 -

ox ides , the i n t e n s i t y i s high with e l ec tron donor groups and low

with e l ec tron acceptor groups. The i n t e n s i t y of the band eiround

1575 cm~ a l so shows s imi lar var ia t ions with s u b s t i t u t i o n . Electron

donating subst i tuents increase the i n t e n s i t y of the band around -1 - 1

1480 cm , whereas the band necir 1430 cm i s unaffected by the

nature of the subs t i tuent s . This par t i cu lar trend in the chemge

of i n t e n s i t i e s has been explained as due to the charge disturbances

in the molecule.

The cheuracterlstic pattern of absorption of the ring

s tretching v ibrat ions r e s u l t s from the complete i n t e r a c t i o n of

the C»C, C=N and/or N=N v ibra t ions ( e . g . in i , 2 - d i a z i n e ) and i t

i s , there fore» very d i f f i c u l t to i s o l a t e the d i f f erent v ibrat ions*

This i s due to the fact that the lone pair of e l ec trons on the

nitrogen atom w i l l be able to conjugate with the r ing , the magnitude

of which depends on the poplanarity of the system. Therefore, these

v ibrat ions are s e n s i t i v e to minor a l ternat ions in molecular geometry

and are d i f f i c u l t to d i s t ingu i sh from other v i b r a t i o n s . Even though

a band of var iab le i n t e n s i t y in the region 1660-1630 cm" i s

a t tr ibuted to C=N s tretching in open-chainc<' jft-unsaturated

compounds, in c y c l i c conjugated systems the appearance of bands

in t h i s region can only be at tr ibuted to the ring s tre tch ing modes.

Subst i tuted pyrimidines, genera l ly , show four bands in the

1590-1375 cm reg ion(99 ,105-107) , The aminopyrimidines show a

band at about 1650 cm"^(98) nhich i s probably due to NH^ deformation

2 2

mode. The hydroxy pyrlmidines are also not suitable for the

development of correlations for ring vibrations of this type, as

they may exist in the tautomeric keto form, in which the double

bond absorptionscof the ring would be expected to be different from

the fully aromatic systems.

C=0 Stretching Vibratjonss The C=0 stretching vibrations of

various carbonyl groups absorb in the region 1900-1600 cm (108),

A more specific range is defined by the type of carbonyl (e.g.,

ketones, esters etc.), and the position is further affected by a

variety of effects. The frequency of the carbonyl absorption is

determined almost wholly by the nature of its Immediate environment,

and the structure of the rest of the molecule is of little importance

unless it is such as to give rise to chelation or some similar

effect. Thus the carbonyl frequency shifts away from the normal

position ±nc>(^ -unsaturated materials and in carbonyl compounds

with strongly electronegative substituents on the <?(_ -carbon atom,

ii illst in cyclic ketones the frequency shift and its direction are

related to the degree of streiin of the ring. Frequency shifts due

to chelation and to mutual interference effects can also be consi­

derable in some cases. However, in each of these oeises the extent

of the frequency shift to be expected is known, and the new range

of frequencies falls within comparatively narrow limits.

A carbonyl group situated between two methylene groups

represents the simplest case of an undisturbed 0=0 stretching

23

v i b r a t i o n . Studies by many workers have shown that in so lu t ion

the frequency of the carbonyl absorption of simple ketones of

t h i s type always l i e s within the narrow range 1725-1706 cm ,

provided that no hydrogen bonding or other in ter ference e f f e c t s

occur ( l09 ) , Carbonyl groups in unstrained saturated r ings absorb

within the same overa l l frequency range 1720-1706 cm" ,

The physical s t a t e has a d i rec t e f f e c t on the carbonyl —1 frequency. Acetone^ for example, absorbs at 1742 cm i n the

vapour phase> yfiierea.s in so lu t ion the frequency l i e s between -1 —1

1728 cm and 1718 cm , depending on the so lvent . S imi lar ly , dldecyl ketone absorb at 1740 cm** in the vapour s t a t e , and

-1 -1

between 1724 cm andjl717 cm in s o l u t i o n . I t i s probable that

some form of dipolar assoc ia t ion i s occurring in the condensed

phase, r e su l t ing in a low frequency s h i f t of the order of 20 cm" ,

Conjugation of a carbonyl group with a C=C linkage r e s u l t s

in a lowering of the frequency by an amount depending on the nature

of the double bond. An a l i p h a t i c C C bond in conjugation with a

carbonyl group reduces i t s frequency by about 40 cm and the

absorptions occur in the range 1685-1665 em* • When an aryl group

i s d i r e c t l y attached to the carbon atom of a carbonyl group, the

frequency s h i f t of the carbonyl i s l e s s than that occurring with

a fu l l double bond in conjugation, and the absorption band occurs

i n the range 1700-1680 cm , With two aryl groups d i r e c t l y

attached, however, there i s a further f a l l in the frequency to

^4

1670-1660 cm"* . The Influence oi ano( -aryl group I s addi t ive

with that of any other s tructure which i s capable of in f luenc ing

the C=0 frequency. With a s i x membered ring C=0 with anp< -aryl

group, the frequency i s found to be 1695-1686 cm , which i s

same as with s imi lar open-chain mater ia l s . With a f i v e membered

ring C=0, however, the frequency increases to 1715-1706 cm , the

s t ra in of the five-membered ring being o f f s e t to some extent by

the aromatic conjugation. Halogen subs t i tu t ion in the immediate

v i c i n i t y of a carbonyl group r e s u l t s in a high frequency s h i f t of

the carbonyl absorption. This i s par t i cu lar ly marked i n the acid

c h l o r i d e s , where a chlorine i s d i r e c t l y attached to the carbonyl

group, but there i s s t i l l an appreciable e f f e c t when the halogen

i s . s i tua ted on thec< -carbon atom, c< -Chloroproplonic ac id ,

for example, absorbs at 1730 cm" , as against 1710 cm" f or j8 -

chloroproplonic ac id .

Hhen Intramolecular hydrogen bonds are formed, the carbonyl

absorption bands may be lowered by 50 cm~ according to H-bond

s t r e n g t h ( l 0 8 ) . 1-Hydrosyanthraquinone shows two 0=0 bands at

1680-1675 cm and 1630-1622 cm" , corresponding to free and

bonded carbonyl groups. With two hydroxyl groups in each of the

| 3 -pos i t ions only one band i s shown at 1639-1623 cm" , whi l s t in

the extreme case of 1,4,5,8-tetrahydroxyanthraquinone the carbonyl

frequency has f a l l e n to 1595 cm . S imi lar ly , fumaric acid

absorbs at 1680 cm , in contrast to the normal value of 1705 cm"

of maleic ac id . Sa i l eye l i e acid absorbs at 1655 cm" , and t h i s

Z5

Is comparable with the sh i f t s experienced with thec>( -hydroxy-o<'^-

unsaturated ketones. 3-Ainino-2-naphthoic acid absorbs at 1665 cm"- ,

All amides show a strong absorption band near 1640 cm

when examined in the sol id s t a t e ( l 0 9 ) . The fact tha t the absorp­

t ion i s at an appreciably lo^er frequency than the carbonyl

absorption of normal ketones, must be due to the resonance effect

with the Ionic form. This i s enhanced by the strong associa­

t ion effects in the so l id s t a t e , and the corresponding vapours

absorb at considerably higher frequencies. The amide I absorp­

t ion i s subject to considerable a l t e r a t i o n on change of s t a t e

in which hydrogen bonding i s broken, and i s also l i a b l e to

va r i a t i ons in solut ion depending on the po la r i ty of the solvent

employed. Thus hexoamide absorbs at 1655 cm" in the so l id s t a t e , —1 —1

at 1668 cm in concentrated solut ions and at 1680 cm in d i l u t e

chloroform so lu t ion . The corresponding values of 169 2 cm

and 1672 cm given for t h i s absorption band in dioxane and in

methanol indicate the degree of frequency sh i f t s l i ke ly to be

associated with a l t e ra t ions in the type of solvent employed. The

carbonyl absorption of N-ethylacetamide ranges from 1687 cm to

1663 cm over a se r i es of so lvents , even at concentrations at

which hydrogen bonding effects are precluded. At higher concen­

t r a t i o n s the frequency var ies continuously with the concentra­

t ion due to change in s t rengths of the intermolecular hydrogen

bonds. Pormamide absorbs at 1740 cm as vapour and at 1709 cm

in d i l u t e chloroform solu t ion . Thus, the vapour carbonyl

z6

frequencies are much c l o s e r to those of ketones and suggest that

the contribution of the i o n i c form i s quite small under these

condi t ions .

N^N-Disubstituted amides are incapable of forming hydrogen

bonds, and the carbonyl absorption band i s consequently not much

inf luenced by changes in phys ica l s t a t e . In these cases the amide

I band usual ly f a l l s near 1650 cm unless a phenyl group i s

subst i tuted on the nitrogen atom, when i t i s ra i sed to 1690 cm"' .

This i s due to the competitive e f f e c t of the ring for the lone

pair e l ec trons of the nitrogen atom. In consequence the c o n t r i ­

bution of the i o n i c form of the amide i s reduced and the carbonyl

frequency i s ra i s ed . A s imi lar e f f e c t may account for the high —1 frequencies shown by N-nitrosoamides, which absorb near 1740 cm

in s o l u t i o n . The inverse e f f e c t occurs in dimethylurea, in which

the i o n i c character of the carbonyl i s reinforced by the second

nitrogen atom so that in the s o l i d s t a t e the frequency f a l l s to

1610 cm'^.

Infrared spectral work(107,110-116) has shown that a large

number of ©( - and y -hydroxy-aza-aromatic der iva t ive s are amides

both in s o l i d s t a t e and in s o l u t i o n . A very strong band in the

range 1620-1750 cm" shows the presence of a C=0 group. 2-flydro3y-

pyrimldlne and the 4-lsomer In the s o l i d s t a t e and i n so lu t ion

show absorption bands in the 1600-1700 cm region which have no

counterpart i n the spectra of the methoaiy der iva t ives and must be

due to the C=0 bond s tretching v i b r a t i o n s , so these compounds in

the s t a t e examined e x i s t predominantly in the amide form.

Z 1

CaS Stretching Vibrat ions; The iden t i f i ca t i on of the pos i t ion

of the C=S absorption has been a matter of some d i f f i c u l t y . In

carbondisulphide the C iS s t re tch ing modes have been assigned to -1 -1

1522 cm and 650 cm , i rhl ls t in carbonyl sulphide i t i s given

at 859 cm~ (lOO), These are unusual cases in indiich the carbon i s

doubly unsaturated, and they do not offer any guidance to the

l ike ly posi t ion of the CsS v ibra t ion in saturated th ioes te r s and

s imilar compounds. Freliminary ca lcu la t ions indica ted that the

r a t i o CsO/CaS would be about 1.5 and tha t the C=S frequency would -1 be found in the 1200-1050 cm region. Just as with the carbonyl

group, the C=S absorption i s found to be sens i t ive to the nature

at the surrounding s t ruc ture but the r e l a t i v e ef fec ts of various

subs t i tuents are not always the same, and the r a t i o between the

carbonyl and thiocarbonyl frequencies va r i e s over the range

1.6-1.14.

Systematic co r re la t ions of the available data on t h i o ­

carbonyl s t re tching frequency ind ica te tha t ii^en i t i s unambi­

guously i d e n t i f i a b l e , e .g . in (-CS=CH-)2C=sS and -CS.SR der iva­

t i v e s , i t i s at 1150 • 70 cm~^(117,118). However, in some

molecules, notably thioamides eind thioureas the thiocarbonyl

s t re tch ing frequency i s uncer ta in , as there i s complete mixing

(22,119) between the C=S s t re t ch ing motion and other v ibra t ions

of s imilar frequencies. This frequency i s hardly suscept ible to

polar e f f ec t s . I t has been ca lcu la ted( l20) that the C=sS s t re tching

frequency in thioformaldehyde should be 1120 + 40 cm" , while in

Zi

thiocarbonyl chloride I t I s at 1140 cra"^. By con t ras t , the

carbonyl s t re tching frequency in carbonyl chloride (1827 cm"'* )

i s considerably higher than that in formaldehyde (1744 cm"^).

Fresence of thiocarbonyl s t re tch ing frequency in mercapto

compounds, provides a d i rec t evidence for t h e i r existence in

the thioamide form. Spinner (93) observed an in tense band in

the range 1100-1190 cm"* , in several o( - and J -mercapto-

aza-aromatic compounds, a t t r i bu t ab l e to C=S s t re tch ing frequency

indica t ing them to be In the thioamide form.

There has been great izidefiniteness lidth regard to the

assignment of the 0=3 s t re tch ing frequency in ni t rogen containing

compounds and the assignments in these compounds vary in the

wide range of 850-1570 cm ( l 2 l ) . Elmore(122) has shown tha t

the band which i s generally assigned to C»S s t re tch ing v ibra t ion

in such compounds r e s u l t s from the coupling of the C-N and CaS

s t re tch ing v ib ra t ions . Normal coordinate analysis of N-methyl-

thioformamide, N-methylthloacetamlde, N,N'-dimethylthiourea and

tetramethylthiourea(52,123) shows c lear evidence for v ib ra t iona l

mixing in these compounds. In secondary thioamides the bands

with considerable contr ibut ion from the CsS s t re tch ing v ibra t ion

are found in the region 870-700 cm" (51) , considerably lower than

in simple thiocarbonyl compounds where the C=S v ib ra t ion i s

loca l ized . In thiourea, two bands in the region 1080-730 cm

are found to have appreciable contribution from the CaS s t re tching

za

v l l ) ra t ion(22) . Suzuki *s ca l cu la t i on8 ( l23 ) show that the 843 cm"^

band for HCSNHg correspond to an almost pure CaS mode and the

I n t r i n s i c frequency of the CsS v ibrat ions vary in the region

from 900 to 850 cm"" . Gosavi e t a l . ( 5 2 ) performed a normal

coordinate analys i s of N,N'-dimethylthiourea and tetramethyl-

thiourea and assigned various mixed CsS s t re tch ing frequency

bands. The mixed v ibrat ion bands of N,N'-dimethyIthiourea have

the contribution from C=S s tretching v ibrat ions ass 1504 cm"''",

10%; 1420 cm"* , 18% and 752 cm"" , 83%. Simi lar ly i n tetramethyl-

thiourea the contribution from 0=3 s tretching v ibrat ions i s ass

1408 cm"*, 25%; 1013 cm"*, 50%; 990 cm"*, 50% and 462 cm"*,

37%. Since the force constants t„^ and f _ are quite s imi lar ,

the major contributions from C-N and 0=3 v ibrat ions are found

in the bands which are quite c lo se to each other ( e . g . 850 and

752 cm in N,N'-dimethylthiourea) . The mixed v ibrat ion bands

are in the regions of s o - c a l l e d >N-C=S b a n d s ( 5 l ) .

Metal-halogen Vibrationss Metal halogen v ibrat ions which

appecp: in the low-frequency infrared region, are quite use fu l in

determining the stereochemistry of coordination complexes. In

a tetrahedral MX^ molecule (Td) there are four normal modes of

v i b r a t i o n . All the four v ibrat ions are Raman a c t i v e , whereas

only two ( 4) are infrared a c t i v e , and t h e i r p o s i t i o n

depend upon the mass of the metal and h a l i d e ( l 2 4 ) . For an

30

octahedral MIg molecule (Ojj)(e,g. GeClJ , SnClg^, e t c . ) there

are a l x pos s ib l e normal modes of v i b r a t i o n . Three ( ^ i » l ^ 2 *"***

Vg) are Raman a c t i v e , i^iiereas only two ( V g j K ^ ) are infrared

a e t i v e ( l 2 5 ) . In octahedral ions (Gei^ , SnjL , e t c . ) the M-5

v ibrat ions are found at lower frequencies than those found for

s imi lar v ibrat ions in a tetrahedral environment. 9heu metal

t e t r a h a l i d e s , MX , form octahedral complexes» MX^,2 donor, the

M-X s tretching v ibrat ions by analogy with these octahedral i o n s ,

are considerably s h i f t e d to lower frequencies (8 ,126-129)

r e l a t i v e to those of the free t e t r a h a l i d e s . In many addit ion

compounds ffletal->halogen v ibrat ions are much more in tense than

l igand v i b r a t i o n s . In group IV, t h i s i s most marked for adducts

of t i n t e t raha l ides and l e a s t marked for adducts of s i l i c o n

t e t raha l ides i^ere i n t e n s i t i e s are frequently comparable.

Ligands may occupy e i t h e r o i s - or t rans -pos i t ions in the

octahedron. The use of infrared spectroscopy i n the far IR

region to study the c i s - t r a n s isomerism of the adducts of the

type MX.Lg (iriiere M i s s i l i c o n , germanium, or t i n , X i s halogen

and L i s a monodentate l igand) has been out l ined by many workers

(129-136) . Neglecting the coupling between the M-X and the

l igand v ibra t ion , the trans-adduct i s considered to be s imi lar

to a perturbed square planar MX u n i t , so that only one infrared

ac t ive fundamental M-X s tretching v ibrat ion ( e symmetry) i s

predic ted , however, for the c i s configuration there would be at

3 1

l e a s t two ftinda]aentals(l29)« There are numerous flaws i n t h i s

simple approach. Fermi resonance may make a combination band

intense enough to be accepted as a fundamental. A l t e r n a t i v e l y ,

certa in fundamentals may be very weak, as for gaseous antimony

t r i c h l o r i d e , whose a, fundamental i s very strong r e l a t i v e to the

weak e fundamental. Accidental degeneracies may occur or bands

m6^ be unresolved. Electronic t rans i t i ons and l a t t i c e v ibrat ions

may appear. Calcium f luor ide , for ezan^le, has a broad infrared

absorption band at about 270 cm"" . C r y s t a l - f i e l d e f f e c t s may

reso lve degeneracies , thus one t r i p l y degenerate f, fundamental

of symmetrical SiPg i s resolved i n t o two peaks in the c r y s t a l l i n e

compound BaSiPg, probably owing to e longat ion of the octahedron

along the three - fo ld a x i s , causing a lowering of the symmetry

from Oj to Dg^.

Bea t t i e and coworkers(137) carried out a normal coordinate

ana lys i s of the octahedral spec ie s c i s - and trans-MX^L- by

Wilson*s P-G matrix method, and ca lcu la ted v ibrat iona l frequen­

c i e s for coordination compounds of some t e traha l ides of Group(lV).

The ca l cu la t ions show that for a c i s -adduct three high frequency

bands are to be expected, the next nearest band ly ing cons ider ­

ably below t h i s group ( a l l the bands are infrared and Raman

a c t i v e ) . In the case of the trans-adducts i f the metal- l igand

force constant i s low compared with the metal-halogen, there

w i l l be one main band in the same region as the s e t of three

32

absorptions mentioned for the c i s -adducts . However, wbere the

metal-ligand force constant I s high, the e and a~^ v ib ra t ions

(both IR act ive) wil l occur in s imi lar regions of the spectrum.

Thus, In a c rys t a l l i ne compound, c r y s t a l - f i e l d resolut ion of the

e„ v ib ra t ion to a doublet, plus the presence of an a», v ibra t ion u all

could lead to a spectrum similar to that of a c ls-adduot . The

e v ib ra t ion (antisymmetric s t r e t ch ) I s r e l a t i v e l y insens i t ive

to the value of fw * and also to the value of the bending force

constants . Thus, i den t i f i ca t ion of c i s - and trans-isomers by

infrared spectroscopic examination i s helpful in favourable

cases , par t icul tu ' ly ndien solut ion spect ra can be obtained.

Metal-lijgand Vibrations - The metal-l igand s t re tching

frequency i s of p a r t i c u l a r I n t e r e s t since i t provides d i rec t

information regarding the coordinate bond. I t appears in the

low-frequency region and depends on the following fac to r s .

1. Mass of the metal and ligand

2. Oxidation number of metal ion

3 . Coordination number of metal Ion

4 . Geometry of the complex

5 . Basici ty of the ligand molecule

6. Bridging or non-bridging anions

7. Llgand-field s t a b i l i z a t i o n energy.

33

MOLAR CONIXJCTMCE

The c o n d u c t i v i t y measurement i s one of the s i m p l e s t and

e a s i l y a v a i l a b l e techniques used i n a r e s e a r c h l a b o r a t o r y , for

the c h a r a c t e r i z a t i o n of c o o r d i n a t i o n compounds. I t g ives d i r e c t

informat ion r ega rd ing whether a given complex i s i o n i c or cova len t

i . e . whether the anions s a t i s f y the pr imary or the secondary

valency of the metal ion i n a c o o r d i n a t i o n compound. Seve ra l

s t u d i e s of molar c o n d u c t i v i t i e s ( 1 3 8 - 1 5 0 ) of d i f f e r e n t k ind of

e l e c t r o l y t e s i n d i f f e r e n t s o l v e n t s a re now a v a i l a b l e and i t i s

use fu l to compare molar conductance ( W -,) va lue of a given

complex with t h a t of the s i m i l a r e l e c t r o l y t e . Convent iona l ly

s o l u t i o n of lO""^ s t r e n g t h a re used for the conductance measure­

ment. Molar conductance va lue s for d i f f e r e n t type of e l e c t r o l y t e s

i n n i t r o - b e n z e n e at t h i s c o n c e n t r a t i o n are as I s l , 20-30; 2 :1 ,50 -60 ;

351 , 70-82; 4 : 1 , 90-100 ohm~^cm^mole"^(l46).

A good d e s c r i p t i o n of e l e c t r o l y t i c behaviour of c o o r d i n a ­

t i o n compounds i n v a r i o u s organic s o l v e n t s i s given in a r e c e n t

r e v i e w ( l 4 6 ) . Molar conductance v a l u e s for complexes of the —3 v a r i o u s e l e c t r o l y t e types a t 10 M c o n c e n t r a t i o n s i n n i t romethane

are as 1 :1 , 75-95; 2 : 1 , 150-180; 3 : 1 , 220-260; 4 : 1 , 290-330 ohm"^ 2 —1

cm mole . Reference va lue s fo r non-complex e l e c t r o l y t e s lead —1 2 —1

t o an a v e r a g e ^ va lue for 1:1 e l e c t r o l y t e s o f ' \ - ' 9 1 . 5 ohm cm mole However, t he va lues f o r the t e t r a p h e n y l b o r a t e and te t ra i soauQr lbora te

•6k

s a l t s a re very low because of the low i o n i c m o b i l i t i e s , and

i f these v a l u e s are excluded from the o v e r a l l average , a va lue

••1 2 —1 of ^^96 ohm cm mole i s ob t a ined . Average va lues for complexes

—1 2 —1 Of u n i d e n t a t e l i gands are for 1:1 e l e c t r o l y t e s 88.5 ohm cm mole

—1 2 —1 and for 2 :1 e l e c t r o l y t e s 167 ohm cm mole . For the whole range of complexes which has been s t u d i e d , va lues cledmed for

~1 2 —1 l : i e l e c t r o l y t e s range from 60-115 ohm cm mole , wi th an

—1 2 —1 average va lue of z * 83 ohm cm mole , For 2 :1 e l e c t r o l y t e s ,

- 1 2 - 1 va lues claimed cover the range 115-250 ohm cm mole , an

—1 2 —1

average va lue be ing 168 ohm cm mole • Values as low as

180 ohm"^ cm^ mole" and as h igh as 300 ohm" cm mole" have

been given for 3 :1 e l e c t r o l y t e s ; a reasonab le average va lue i s

242 ohm"'* cm mole"^. For 4 : 1 e l e c t r o l y t e s ( 147-150) , v a l u e s —1 2 —1

cover a range 244-341 ohm cm mole wi th an average va lue of —1 2 —i

307 ohm cm mole . An unusual e l e c t r o l y t e type i s t he compound /"•CrLo_72('5^4)3* ^ e r e 1*= 2 -aminoe thyIpyr id ine , for which a va lue

—1 2 —1 Of 419 Ohm cm mole i s quoted*

C H A P T E R - I I I

COMPLEXES OF T I N ( I V ) H A L I D E S WITH N,N'-DISUBSTITUTED THIOUREAS

COMPLEXES OF TIN(lV) HALIDES WITH N,N'-DISUBSTITUTED THIOUREAS

The s i t e of c o o r d i n a t i o n i n thioeunides and t h i o u r e a s has

been a sub j ec t of con t rove r sy , both su lphur (32-34 ,46-48) and

n i t rogen (49 -57 ) having been claimed as the donor atom from time

to t ime. Recent s t ud i e s of the behaviour of t h i o u r e a s i n s t rong

ac ids( 151,152) have shown t h a t p r o t o n a t i o n occurs on the su lphur

atom, however, i n super ac ids a d i p r o t o n a t i o n which invo lves the

n i t r o g e n atom a l so o c c u r s . Thioureas have been r e p o r t e d to c o ­

o rd ina t e with the t e t r a h a l i d e s of group(lV) elements through

n i t r o g e n ( 3 0 , 5 8 , 5 9 ) , I t was, t h e r e f o r e , of i n t e r e s t t o syn thes i ze

t i n ( l V ) h a l i d e complexes with v a r i o u s N , N ' - d i s u b s t i t u t e d t h i o u r e a s

v i s . N , N « - d i a l l y l t h i o u r e a ; ( d a t u ) , N , N ' - d i e t h y l t h i o u r e a ( d e t u ) ,

N , N ' - d i b u t y l t h i o u r e a ( d b t u ) , N , N ' - d i i s o p r o p y l t h i o u r e a ( d i t u ) and

N , N ' - d i p h e n y l t h i o u r e a (dp tu) having va ry ing degrees of e l e c t r o n

dens i t y on the n i t r o g e n atoms and t o examine i f n i t r o g e n could

supersede su lphur i n i t s donor a b i l i t y .

3 6

EXPERIMENTAL

Preparation and Pur i f ica t ion of Reagents;

Preparation of anhydrous t in( lV) chloride - Anhydrous stannic

chloride was prepared according to the method given in the l i t e r a -

tu re ( l53 ) . Thionyl chloride was added to SnCl^.SH 0 (May & Baker)

in a flask with ground glass Jo in t s and the mixture was refluxed

for a few hours, with a drying tube attached to the condenser.

The excess thionyl chloride and hydrogen chloride formed during

the course of the react ion were removed by d i s t i l l i n g over a

water bath . Sulphurdloxide was removed by evacuation and crude

SnCl^ was l e f t in the react ion f lask , which was then d i s t i l l e d

at ll4*'c. The f i r s t and l a s t por t ions of the d i s t i l l a t e were

re jected to ensure complete removal of thionyl chloride and

sulphurdloxide. Owing to i t s hygroscopic nature i t was s tored

in a closed vessel having t i gh t l y f i t t i n g s topper . The following

equation represents the reac t ion .

SnCl^.SHgO + 5SOCI2 = SnCl^ 4. SSOg ••• 10 HCl

Preparation of anhydrous t in( lV) bromide - Pieces of t i n

metal were taken in a long neck d i s t i l l i n g flask with a side

arm close to the body of the flask having calcium chlor ide tube(l53).

The flask was closed with a s ingle hole rubber stopper and a

3 7

dropping funnel with i t s tube drawn out to a cap i l l a ry was so

Inser ted in to i t tha t i t nearly touched the bottom. Pure bromine

was then added dropwise through the funnel. Addition of bromine

produced a vigorous react ion accompanied by heat evolution and

sometimes ign i t ion a l so . Addition of bromine was so regulated

that the temperature did not exceed the boi l ing point of bromine

l » e . 59 C and no SnBr^ or bromine was allowed to penet ra te in to

the side arm. This was conveniently achieved by cooling the

react ion flask in ice af ter each addition of bromine, fhen the

react ion was completed the dropping funnel was replaced by a

thermometer and the side arm was kept upward, and the f lask was

heated to remove the excess of bromine, whereas SnBr. condensed

in the f l ask . When the product became nearly colourless i t was

d i s t i l l e d taking care to keep atmospheric a i r out. After cooling

snow-Tirtiite c r y s t a l l i n e substance was obtained. Further p u r i f i c a ­

t ion was done by fract ional d i s t i l l a t i o n . I t i s a highly hygro­

scopic substance so i t was s tored in a g lass contedner having

t i gh t ly f i t t i n g stopper.

Sn + SBr^ = SnBr^

Preparation of t ln( lV) iodide - I t was prepared by the

action of iodine over powdered t i n in carbondisulphide(l53).

Tin powder was prepared by melting t i n and grinding i t in a

mortar when ho t . Six pa r t s by weight of pure CS^ were poured

over one par t by weight of t i n powder in a round bottom flask

3^

with a ground g l a s s s topper and four p a r t s by weight of i od ine

were g radua l ly added. This r e a c t i o n f l a s k was kept cooled with

i c e t i l l the a d d i t i o n of iod ine was complete . A red brown l i q u i d

was formed i«^ich was then t r a n s f e r r e d t o another f l a s k and eva­

po ra t ed t o dryness by an a s p i r a t o r vacuum. The a t t ached s ide

arm of the f l a s k was connected t o ca lc ium ch lo r i de tube to

p reven t m o i s t u r e . Tin( lV) i od ide thus ob ta ined was f u r t h e r

p u r i f i e d by r e c r y s t a l l i z a t i o n from chloroform. After r e c r y s t a -

l l i z a t i o n o range- red , c r y s t a l l i n e subs tance was ob t a ined .

Sn + 2I2 = Snl^

P r e p a r a t i o n and S t a n d a r d i z a t i o n of Stock S o l u t i o n of Metal

Ha l ides - jinhydrous metal h a l i d e s (SnCl. & SnBr.) were

t r a n s f e r r e d to a 100 ml vo lumet r i c f l a s k . The volume was made

up t o the mark by abso lu te e t h a a o l or chloroform, and 10 ml of

t h i s s o l u t i o n was taken in a beaker and hydrolysed by the

a d d i t i o n of hot d i s t i l l e d water wi th cont inuous s t i r r i n g ( l 5 4 ) .

The c o n t e n t s were then hea ted on a water ba th and the p r e c i p i ­

t a t e allowed to s e t t l e . I t was cooled , f i l t e r e d through a

g r a v i m e t r i c f i l t e r paper and thoroughly washed with ho t water

t o ensure complete removal of hyd roch lo r i c a c i d . The p r e c i p i ­

t a t e was d r i ed and i g n i t e d i n a p r e v i o u s l y weighed s i l i c a

c r u c i b l e , vidien a white substance was l e f t , i t was weighed as

SnOg.

SnCl^ + iHgO = Sn(OH)^ + 4HC1

Sn(OH)^ = SnOg •»• 25i^O

•di)

Prom t h i s weight of SnO^ the amount of SnCl^ or SnBr^ was

calculated in 10 ml so lu t ion . Thus s t rength of stock solut ion

was determined and further d i lu t ion was made by taking por t ions

from t h i s stock so lu t ion .

Solution of t in( lV) iodide was prepared d i r ec t ly from i t s

c rys t a l s as i t does not hydrolyse in the a i r . Germanium t e t r a ­

chloride solut ion was standardized toy determining the quantity of

germanium in a known sample by tannin procedure(155). The solut ion

of desired d i lu t ion were prepared in chloroform.

N,N'-Dial lyl thiourea (m.p. 46°C), N,N'-die thyl thiourea

(m.p. 78°C), (both Eastman Kodak reagents ) , N,N*-dibutylthiourea

(m.p. 85°C), N,N'-diphenylthiourea (m.p. 154°C) (both BDH reagents)

and N,N'-dl isopropylthiourea (m.p, 151 C) (Pluka reagent) were

r ec ry s t a l l i z ed from ethanol. All manipulations were ca r r i ed out

in a dry box.

Prepttration of the Complexes - All the complexes were prepared

by mixing the chloroform solut ions of the metal hal ides and the

ligand in a Is 2 metal to ligand r a t i o . In the case of N,N'-

d ia l ly1th iourea , N,N«-diisopropylthiourea and N,N'-diphenyl-

thiourea c r y s t a l l i n e products were obtained e i the r immediately

or af ter heating the react ing solut ions together . Tin(lV)

chloride and bromide complexes of N,N'-diethyl thiourea and

N,N'-dibutyl thiourea were obtained by shaking the reac tant solu­

t ions and the viscous layer thus formed was separated, washed with

40

chloroform and dried in vacuo, N,N'-Diethylthiourea, however,

yielded a c ry s t a l l i ne product immediately with S n I . .

Apparatus Used - The infrared spect ra were recorded on a

Beckman IR-12 spectrophotometer, in 4000-650 cm" region in KBr

disc or in CCl^, CHClg solut ion and in 650-200 cm~' region in

nujol mull. Conductivity measurements were made on a Systronix

conductivity bridge type 302.

Elemental jtoalysis - The elemental analysis for carbon,

hydrogen and nitrogen were done on a Coleman Analyzer in the

mlcroanalytical laboratory of Chemistry department, at Aligarh

Muslim Univers i ty , Aligarh and I . I . T . , Katipur.

u

RESULTS AND DISCUSSION

The analytical data (Table l) indicate all the complexes

to be of the type SnX^.2L. These are fairly stable at room

temperature. The molar conductances of 0.002i(ii solutions of

these complexes have been measured at room temperature in nitro-

methane and nitrobenzene to see if they are ionized. It has

been found that these values fall well below (Table 2) those

quoted for typical uni-univalent electrolytes in these solvents

(146). This indicates that the complexes are basically non-

ionic, the slight conductivity being due either to some solvation

of the type,

SnX^.aL + solvent ^ /~SnX3( solvent)L2_7^ X"

or to slight hydrolysis due to handling difficulties of such low

concentrations of moisture-sensitive solutes.

In thioureas both nitrogen and sulphur could act as the

donor atom. In order to ascertain the bonding site the infrared

spectra (4000-200 cm ) of the ligand and their complexes have

been recorded (Table 3). Interpretation of the infrared spectra

of these adducts is complicated due to strong intermolecular

association. An added difficulty is that the principal vibra­

tional modes are strongly coupled. The spectra of the ligand in

42

•H

I

en

»

o o

«

O

o •H •+J

•H O P<

'H

u § iH O o

Vl (3 O

• d - d

sa •© "O

5 08

Si i-^

us la

t9w O •o

o o o

DO

o o

TH O «0 O O t - <0 00

•H O t - (3> t - CD 00 eo

CM a • ^ c j •«*eo - H M (MTI* < C « O CVI jt T-l«0 >*»(? O W W W

cj eo 00 00 CO -«* O O •H TH Oil (M

)0 W •H TH

CJ N •H -H

«0 O '^ CO

o •>* CM t -

CO CO 00 O

•rt 00 CM Ti< 00 N

0> CJ 00 O 0> M CJ 1*

CO Oi O 00 CD

CI CO O t -

•H CJ

CJ CJ •H CI

ca CI lO JO t - CO

»fl in CI N d CJ

00 O « •<# 00 CO CJ CJ

-H CI CI 00 110 UO

CO W CO CO

O 00 TH CO T^ 0 0 W5 t - l > "^ 0> CO

•H t -CI 05 •H CJ

oo o» Tit » •

O t - eO'^ Tjioo cacj CIT-I OCO 0 0 0 0 0>CD c o c o 0>0> cOOO O C 3

o»o» cot- o » o oo»- co CO 0000 COcO 0>0> t-lf- UOMO t-t- COCO

O CJ V3 W

Tj< T *

0 1 • ^ CO C3

CO CJ to C I

CO CO

CJ o> • H CO

O • H T H CO

- * Tit

0 0 0 > CO 0 0

0 0 Tj*

CO 0 0

O a O O

CJ T H

O t -

CO CJ

C J O O

0> <M l O CO

CO CO

o - CO OS

CO "<* l O 0 >

W " *

0 0 T H

CO t o

• H W t o i O

m Hi

O OJ

00 d

Til Tj*

00 «5 0> -H

00 O CO • *

CO 00

00 K i O t -

o> t -CO C5

CO CO

• H l O

CO O

a> t -CJ CJ

l O 0> •«1< 0 0

00 0> CI W

CJ CJ CI d

CI CJ CI CI

t- tr CO CO CO 00 03 03

t- to CM CJ

05 00 O CI 00 l-CM CJ CJ CJ -H -H

00 00 T* Tjl 00 03

CO O CJ

O O CI

CD ••a 4J

g ^

o CO •H

o

4)

.£3 (aO

O 00

00

O

o

N CJ CJ CJ

UO 00

o

0>

•H

CJ

O 0>

o

d o d

o

0)

•p

laO

00 00

o oo

o

o ^

o

d d d

d 00 •H

o

«

-P

d

00 CO

o

d d d

3 + j

(0 <e

Tjt r H

0 5

s +» (d "O

S M ^

Tl<

u <§ to

5J +» 0) 7 3

s«<'

'* I H

w

d +> (p

•o ^»>i#'

Tjt

u CO

<n

'" 0

• P 0 )

•o N a V

"* M

m

tf +> .o •d >«

• < *

( H

w

d +» ^ T J

Sw***

T»< U

0 3

OT

3 +> • H •d

* * > ^ Tl<

i H

OT

d • p • H •d

N M ^

-* »4

S OT

. - " s

d +* • H • d

> « » ' Tjt

d OT

s +J p< <d

" S M ^

Tjt i H

o d OT

d • p

p. •d

N M ^

-rH SH

<§ OT

43

TMhE - 2

Molar conductance* of 0»002M s o l u t i o n In n i t robenzene and

n i t romethane a t room t empera tu re .

W - i In n i t robenzene ^ i n n i t romethane Complexes (ohm-1 cm^ mole-^) ^^^^-1 ^^2 ^^^i^-l)

SnCl^(detu) 1.694 6.932

SnBr^Cdetu)- 1.525 6,440

S n l ^ ( d e t u ) 2 3.389 7.587

SnCl^(dbtu)2 2.168 6.779

SnBr^Cdbtu)^ 1.119 6 .371

SnCl^Cditu)^ 1.356 3.512

SnBr^Cditu)^ 1«966 4 .612

S n l ^ ( d i t u ) 2 2.000 7.457

SnCl^Cdptu)^ 2.644 3.694

SnBr^Cdptu)^ 3.631 5 .841

• datu complexes a re not s u f f i c i e n t l y s o l u b l e i n n i t robenzene

and n i t rome thane .

4 4

sol id and in solution phase show a marked difference in the

pos i t ions of N-H and c=S s t re tching frequencies, indica t ing

intermolecular hydrogen bonding between hydrogen of the NH group

and sulphur of the C=S group. Even in concentrated solut ions a

broad N-rH frequency band i s observed together with a sharp band

or bands. This broad band disappears in very d i l u t e solut ions

and i s due to associated spec ies . On the other hand hydrogen

bonding in the cotrrplexes i s absent and only sharp N-H peaks are

obtained. To eliminate the effect ot hydrogen bonding the spectra

of the ligands in d i lu te solut ions have been compared with those

of the complexes in KBr.

In d isubs t i tu ted .thiourea de r iva t ives , d i f ferent configura­

t ions are possible where the thioamide hydrogen and the th ioca r -

bonyl sulphur take c i s and t rans posi t ions with respect to each

other (Fig . I - I I l ) . The presence of two closely spaced N-H

s t re tch ing bands i s due to such rotamers ( l 5 6 ) .

H

H —

both-

1

/ "

) " -N"^

\R

-trans

[

S

/ »

R N.

R — W^ ^ H

both-cis

I I

:S R—

H —

cis

/ "

^ R

-trans

I I I

S

4 0

The higher N-H s t re tching frequency I s assigned to the t rans

Isomer and the lower one to the c is- isomer. The infrared spect ra

of N,N«-diethylthlourea, N,N'-dlbutyl thiourea and N,N'-di isopropyl-

th iourea show only one sharp N-S s t re tching frequency band c o r r e s ­

ponding to t rans retainers, however, in N,N*-diphenylthiourea two

shairp N-H peaks correspond to c is and t rans isomers.

Rivest(30) observed marked negative sh i f t s in N-fl s t re tch ing

frequencies In TlCl^ complexes of thiourea, N,N'-die thyl thiourea

and N,N'-diphenylthiourea and suggested coordination through n i t r o ­

gen, N-Allylthiourea i s known to coordinate through nitrogen with

t in( lV) hal ides(59) and with t r ans i t i on meta l s ( l57) . The Infrared

spect ra of a l l the complexes show a marked negative sh i f t in N-fl

s t re tch ing frequency ind ica t ing coordination through ni t rogen.

Since the sh i f t in the N-H s t re tching frequency may also be due

to hydrogen bonding between the iminohydrogen and the halogen of

the metal hal ide(92,158,159), the effect of coordination on the

other sens i t ive bands have also been examined.

Unfortunately pr inc ipa l v ib ra t iona l modes in thioureas are

s t rongly coupled and the majority of observed bands a r i se from

mixed v ib r a t i ons . A wide range of 1570-850 cm ( l 2 l ) has been

a t t r i bu t ed to the C=S s t re tch ing frequency. Gosavl e t a l . (52)

performed a normal coordinate analysis of N,N*-dlmethylthiourea

employing the Urey Bradley force f ie ld and assigned various mixed

v ib ra t ion bands in i t s spectrum. In dia lkyl thioureas(52) the

4 6

^4

bands at/\/ 1560 andK'1420 cm have both high contr ibut ions from

l)(CN) and S ( N H ) , The contr ibut ion from ^ (NH) i s also high in

the case of the 1505 cm"" band. The contr ibut ion from p (CS) i s

found to be grea tes t in the band around 750 cm , Since the force

constants f„j^ and f^g are qui te s imi la r , the major contr ibut ions

from }/^(CN) and )) (CS) are found in the bands Tii*iich are quite

close to each other .

In N,N'-dlmethylthiourea the mixed C=S s t re tch ing frequency

bands were assigned at 1504, 1420, 1290 and 752 cm (52) . Recently

the C=S frequency i s assigned to absorptions at 1512-50, 1350,

1135-80 and 930-72 cm" in the infrared spectra of various

N,N' -d isubst i tu ted thioureas( l60) in CHClg so lu t ion . The t h i o -

amide I band in N-a l ly l th lourea has been assigned at 1442 cm" (59) .

By analogy of these workers a strong band observed at about 1500 cm

in thioureas described in t h i s work can be assigned to thioamlde I .

This band i s known to be pos i t i ve ly shif ted upon coordination

through nl t rogen(49,58,59) . In a l l the complexes t h i s band shows

a pos i t ive shi f t indicat ing coordination through n i t rogen . The

pos i t ive sh i f t in the thioamlde I I (except in N,N'-dibutyl th lourea

complexes) and \)(CS) + o (NCS) frequency bands also i nd i r ec t l y

support nitrogen coordlnat ion(49,59) .

The negative shi f t observed in the bands assigned to J / ( C N ) +

^ ( N C N ) in a l l cases except in N,N'-diphenylthiourea complexes i s

also in favour of coordination through ni t rogen. The thioamlde I I I

CO

0 i H P«

o o •o %

CO •d

§ bO

eo -H r«4

1 4-1

9 ° &• 1

B 5)

O o C<l 1

o o o '<J4

« u o P4 CO

4H O

00 • p

a 0) B c Q) •M n

^

«

+» a 0}

B

0

ttf

• H

CO

»

-<

25 T

? 0

' ^

J - - V

Wl o %

3o •f

^f o o

^ : : ^ ' : = S '

i « 0 * 0 ^ 1 •H t j M •a § H

+

T 6 O 55 %-«'>—>'

' ? ^ 6 0

4-

cn CO II U

o ^ N U ' S . M '

'>6o

1 0) O t3 •H •H M X] S M &4 S

M

1 « o •© •H Tl X) S e< «

? 55

O*.

as ^ 0?

(H

t O

o

a 00 00 t -

co > CO TH

o>

CO

o> o •H

« ^ Tjt CM rH

X3 CO

O * i in •H

P

t -ca eo

•d •H r-4 O OS

5J •P CD -0

fii • h

^ U3 lO

i( CO o 00 t -

00

o ^ o>

CO

o> o •rt

CO 00 N CJ •H

CO

O 00 eo •H

00

^ o «o • H

CO >

o o <4l 1-4 - * "ilt CO e o

»«~» '«J'

r-1 o o

^a t f '

a o •H ••J 0

I H

o CO

J§ ^

a 00 eo eo

A •« so

00 •<1< Mi

B it 00 e« O 00 00 t -

CO oo eo o>

CO 00 00 o •H

CO

eo e*i T^

CO to T^ Tjt •H

00

s ^ U3 • H

OS > to

CMO eo eo

N - 0 +* «

•O N i ^

rjt r-t O a to

1 o CO

00

rH ^

Xi • h

OS •* •* U5

OS ^ CVI - ^ H 00 00 t -

CO

• ^

0>

CO

o en 5 TH

00

eo w TH

00

^ 1-1 T»t • H

00 ^ h ^ to 1-1

OS > 00 (C (0 eo in ca o eo CO

ea ^ - s .

0 4 3

<0 >o

V i , ^

ll* ) H

pa fl to

00

^ (0 o 00

OS

> " t *

-* o>

00

to o 1-)

OS

^ <o ca i H

OS

^ 00 CO 1-4

00

^ 00 •«1» 1-4

p • k

09

00 00

o CO

CO

00 c» CM

,D (A

a t ^ r» CO <0 to to

* CO 09 > > > to -^ o> o l» 00

CO

a t to w CO CO a> Oi

OS OS >

to MJ

o o 1-4 i H

» OS 00 O 00 CJ CM eo i H 1-1

09 OS

^ (^ 00 00 CO eo 1 - 1 1 -4

CO CO > > > 00 <0 o> eo •^ Vi i H T H

09

^ ^ 00 > ^ ^ •<* to o i*t

t - CM i jt CO iH " f CJ TH O !<• CO O CO CO eo CO eo CO

•d •H i H

o CO

s +» « X5

yf-^

•^ i H O CM

o -^ w 3 +9

a « O t ) •H >—' +a Kt(

3 H (H O O CI CO CO

OS OS O CM •H 0) eo CM

00

CM CM

CO « ^ ^ ^ > o o CO to to to

CO > i? 00 00 O 00 00 t -

os

"* S e o CM o» o>

00

to CO

o o iH -H

B B 00 O 1-4 O CO CO 1-4 i H

" .-^ tS 00 "H CO ''J4 i H T H

00 OS u eo O to to T H 1 ^

CO OS

w to •H to eo ca eo eo

CM /—V N

S c 4S S fl) +> •C 0) w "d

"^v-^ IH -T*" CO M e e w to

CO > •* t -t -

00

1 CO <3J

s to

OS

00 ^ •H 1-1 CO e o

A A

m s > CM <0 00 t -lO to

* -09 > 00 CO CI CO t -fr- t -

QS > CO to to • * 'H* O) Oi

00 «> w > 09 > 00 ^ do <0 to 00 O CO to 00 t - to o o o o o ^ 1 - 4 1-1 i H i H

00 00 00 CM •H

00

^ 00 eo 1-1

CO

ca 00 1 * i H

fii • k

^ * 00 B CM CM 00 0> CM CM 1-4 1 - 1

OS B to to 00 00 00 CO iH ft

OS 00 > > to 00 o> *o 1 * to T H 1-4

OS

> 61 S OB ^ 5 o • * 00 '"i* <o CM •^ eo CM CM T ^ o <* eo CO eo eo eo eo

•d •H r-4 o 09

0 4* j C "d

,^ •^

r-4 O CI o ^^ ^ 5 +* fi p

o "d •H ^-^ +» ^ ^ Tt iH O o fl OS t o

a ^ CO

CM

43 CO OS >

Cft CJ CM ca CM CM

JO ««

09 > CO to to

Xi «»

B CO (0 t -

a o •«* o>

00 O t - to o o 1-1 i H

i ^ 1-4

cS 00 eo "H

OS

^ eo to i H

09

CO o eo eo

CM ••^^ d •*» p -d

> . * ' .'^ » 5 Ci to

4?

a

•a •p a o o P5'

6H

CO

+»

St

a &

laO

• H

CO

<

xi (0

M

0)

o o

CO > 00

I 00 0>

o

•H

eo •H

CO

N

00 Q fc (0 00 N O tf> O " ^ O CO CO CM • H O

«o 00 CM

(B

Cil

SB

SB > CO a 01 w O <0 <H O O H CO CO CO OJ

« «

OB

CB

o 00 lO

* OB > 00 "<* l -

i9 t-lO

OB > <o ^ »•

SB ^

O CJ CO CO

OB « N O o> o eo >* <H - H

SO CO > 00 «

CO

N 00 M ca •* eo

eo 00 CO CO eo eo

o OD

CO H

o CO

5 p f-t

o a CO e o

A OB X] OB 00 > SO O O •«*•'* 00 (O <0 to W5 W m M5

CO

eo

00 O

uo

so 00

so

CO

OB

CM

CO OB

en

so o 0> o

OB ( 0 00 CJ>

^ 00 CM o

OB

o 00 Oi

00 00 CI o

OB

o CO OJ

CM CO • H

OB > 00 0> CO •H

CO

OB t -W CO

B a O "H t - CO t - b -

SO

00 QO

O

CO

CM

* •

X] OB X] OB SO > OB >

00 O O CO CO CO OO CO t - t - t - t -

00 >

10 eo

OB ^ ^ O o

w •H

so CM

a 00

o

00 lO CM

09 > 00 t o CO

CO > in

00

a o 00

o

a 00 CM

SO

C M - ^ 0 0 CO

SB O

o 00 o -H

00 CM

03

( B X i « Jd > CO ^ so 00 W to 00 00 O t - eo W W " * CO CM e a o o 00 CO CO eo eo

CM

s +9

CM O OB

OO OB

CO 0 0

00

CM

o

^ M fl to

0 +s ^

0 I H

o 00

o

CM

•o

u PQ

SB 00 0> CO T-l

OB SO

- o C O O lO lO H <H

00 a

CM CM CO CM CO e o

> CO <j>

eo •H

OB > SO to 00 CMOS lO <^ •H t-4

SO SO > CM 00 CO N CO CM CO CO

>> u « > II

00 > •

«k

^

1 II

»

a 0

•H •0 0)

f - l

o 1 0 tn o> SB

c 0) 4 3

a 'T*

"d § "S o h

x> «

a

4 5

o u fit

u

o X! so

X3 CO

o u -p 00

I:? >

> s a II

OS o

^ g

o * U (i> -p •© OB O a

X! a • -d

ttO 0)

o u OB

so

5! o OB XI o

4 9

band shows a decreetse In frequency on complexation, however, In

some con5)lexes th i s band i s only weakened in i n t e n s i t y . Previous

workers have also observed such a change in thioamide I I I band

on nitrogen coordination (49,50,59) .

The low frequency C=S band could not be observed in the

infrared spectra of thioureas in d i lu te so lu t ion . The 806-748 cm""

region bands ^rtiich a r i se from the v ibra t ions consist ing of C=3

s t re tch ing and symmetric C-N s t r e t ch ing , a f te r complexation are

pos i t i ve ly shif ted or are v i r t u a l l y unchanged. However, in SnI.

con^lexes of N,N'-diethyl thiourea and N,N'-diisopropy1thiourea

t h i s band i s negatively sh i f ted which may be c i t ed as an evidence

for coordination through sulphur, but a marked negative sh i f t in

the N-H s t re tching frequency i s in c lear support of coordination

through ni t rogen.

In thioureas the 0=3 s t re tch ing v ibra t ion i s not local ized

and many of the major IB bands a r i se from mixed v i b r a t i o n s . The

i n t e r p r e t a t i o n of the IR spectra of metal complexes becomes

d i f f i c u l t Ti4iere the observed bands of the ligands a r i se from

mixed v ib ra t i ons . While in simple cases one can derive useful

Information on the s t ruc ture of the complexes and the nature of

the llgand-metal i n t e rac t ion on the bas i s of the s h i f t s of the

IR absorption bands in the 4000-650 cm region, i t often becomes

d i f f i c u l t to be def in i t ive regarding these aspects , p a r t i c u l a r l y

i f mixed v ibra t ions are involved. In the complexes of th ioureas .

50

irtiere the force constant of \ ) ( C N ) and )) (CS) are comparable,

mixing between these v ib ra t ions wi l l be appreciable and i t i s

d i f f i c u l t to base any conclusion on sh i f t s of the v ibra t ion bands

with contr ibut ion from C=S s t re tch ing v ib ra t ion . Thus, the v a r i a -—1 t ions in the 972 and 774 cm bands of N-methylthiourea(50) have

been found to be s imilar I r r espec t ive of iiriiether the coordination

i s through sulphur or n i t rogen. The infrared absorption bands -1

near 1550 cm assigned to N-fl deformation and C-N antisymmetric

s t re tch ing v ibra t ions in a l l complexes show a pos i t i ve s h i f t .

This i s common for both nitrogen and sulphur bonding (52,57) and

i s not useful in d is t inguishing bond type. In current discussion

of complexes of thioureas the va r i a t ions in the pos i t ions of many

of the ske le ta l v ibra t ions of the ligands on complexation cure

s t i l l d i f f i c u l t to i n t e r p r e t . In thiourea complexes the spec t ra l

evidence for the coordination through nitrogen i s not so conclu-

sive as in the case of urea complexes, due to the fact that the

C=0 s t re tch ing frequency in ureas l i e s well above the C-N

s t re tch ing frequency, whereas the C=S frequency in thioureas i s

not much dif ferent from the C-N frequency.

The NCS bending mode at about 550 cm" shows a negative

sh i f t on complexation in a l l the complexes, except in the

SnCl.Cdetu). complex in which i t i s unchanged. The negative

shi f t (54) in t h i s band i s also in support of ni trogen coordination.

c: 1

Various authors( 161-166) have reported negative sh i f t when

metal coordinates to double or t r i p l e bonds. In N , N ' - d i a l l y l -

thiourea besides nitrogen and sulphur the C=C double bond i s a lso

a po ten t ia l bonding s i t e . However, i t s C=C s t re tch ing frequency -1

band at 1656 cm remained unchanged af ter complexation rul ing

out coordination through the double bond. Thus from the preceding

discussion i t i s concluded that coordination in a l l the cases

occurs through the nitrogen atom.

Far IR Spectra (650-200 cm ) and Structure of the Complexes;

Addition compounds of the type MX L (where M i s s i l i c o n ,

germanium, or t i n , X i s halogen and L i s a monodentate ligand)

are well known although t h e i r stereochemistry has only recent ly

been extensively s tudied. Information on the stereochemistry of

coordination compounds of the non- t rans i t ion elements, where the

lack of p a r t i a l l y f i l l e d d-shel l s renders other techniques i n a p p l i ­

cable , may be obtained by studying absorption spect ra in the far

i . r . region.

I f we assume the presence of d i sc re te s i x coordinate species ,

i t i s necessary to decide between the c i s and the t rans configura­

t i o n . The trans-adduct i s considered to be s imilar to a perturbed

square planar MX u n i t , so that only one infreired act ive fundamental

M-X s t re tching vibra t ion of symmetry type e i s p red ic ted ( l29) .

For the cis-configurat ion there would be at l ea s t two fundamentals

c. 2

associated with M-X s t re tching modes, Beat t ie and coworkers(i37)

performed a normal coordinate analysis of the octahedral species

c i s - and trahs-MX.Lg. For a cis-adduct three high frequency bands

are to he expected, the next nearest band lying considerably below

th i s group. In the case of t rans adducts i f the metal ligeind

force constant i s low compared with that of the metal-halogen,

there wi l l be one main band in the same region as the set of

three absorptions mentioned for the c is -adduct . However, where

the metal-ligand force constant i s high, the e and a v ib ra t ions

wi l l occur in s imilar regions of the spectrum. Thus, in a

c r y s t a l l i n e compound, c r y s t a l - f i e l d resolut ion of the e v ibra t ion

to a doublet, plus the presence of an a ^ v ib ra t ion could lead to

a spectrum similar to that of a cis-adduct with the difference

tha t in such a t rans compound there i s one s trong band with the

remaining bands being of weaker i n t e n s i t y .

The s t ruc tures are determined primari ly by the ligand

ra the r than by the halogen. Those ligands having a po la r i sab le

IT-bond linkage behind the spearhead atom give cis-complexes with

t i n h a l i d e s ( 8 , l 6 7 ) . Thus overlap of theTT -bonding charge cloud

of the ligand with an empty d-orb i ta l of the cen t ra l atom plays

a s igni f icant par t in the linkage and stronger bonding of the

ligands develops through the use of the two d i f fe ren t d -o rb i t a l s

required for the cis-complex.

t: 3

The far infrared spectra in the 650-200 cm"^ range locate

the ]) (Sn-X) and y (Sn-N) absorptions (Table 3 ) . The bands which

are v i r t u a l l y unaffected by changing halogen are a t t r i bu t ed to

Sn-N) modes. In the spectrum of the complexes i r r e spec t ive of

Lewis acid taken new bands are observed in the 256-310 cm" region

iR iich can be assigned to ]) (Sn-N). In the N,N'-diphenylthiourea

complex of SnCl. t h i s baud i s presumably obscured by the broad

and intense ))(Sn-Cl) mode.

Since y (Sn-X) bands are usual ly more intense than \/(Sn-N)

and sh i f t to lower frequencies as X i s progressively changed in the

sequence CI —^ Br - 4 I , these can eas i ly be assigned. The l) (Sn-l)

could not be observed in the spec t ra l range s tudied. The probable

geometry for these 1:2(SnX^;ligand) complexes i s an octahedral one,

involving one of the ni trogen atom of the thiourea l igand. The

llgands should occupy e i the r the e l s or the t rans pos i t ions in the

octahedron. In these complexes presence of only one strong Sn-X

s t re tch ing band i s ind ica t ive of a t rans-octahedral geometry,

however, in N,N'-dibutyl thiourea complexes and SnCl. complex of

N,N'-di lsopropylthiourea there i s a s l i gh t s p l i t t i n g of t h i s band

and more than one hands are obtained which are of weaker i n t ens i t y

and may be due to c rys t a l f i e ld effects on D.. model.

C H A P T E R - IV

COMPLEXES OP TIN(IV) AND GERMAMIUM(IV) HALIDES WITH PYRIMIDINES

COMFLEIES OF TIN(IV) AND GERMANIUM(IV) HJiLIDES WITH PYRIMIDINES

During recent years several studies on tbe metal con^lexes

of diazines have lieen reported(60-80), but these are mainly con­

cerned with l ,4-diazine8 (pyrazines). Pyrimidines ( i ,3 -d iaz ines )

are of interest owing to their biological importance as compounds

of nucleic acids. Complexes of Co(ll) and N i ( l l ) with pyrimidine

bases occurring in nucleic acids have recently been reported(80)«

Although pyrazine complexes of t in ( iy ) halides(89) have been

reported recently, there i s no report on the con^jlexes of t in and

germanium(IV) halides with pyrimidine or substituted pyrimidines.

Thus, i t was of interest to synthesize and characterize tin(lV)

and gerraanium(lV) halide complexes of pyrimidine (pym) and some

of i t s derivatives v i z . 2,4,6-triaminopyrimidine (apy); 4 -

pyrimidinol (pyl); 4,6-diamino-2-mercaptopyrimidine (apy) and

4-.amino-l,3-dimethyl-2,6-dioxopyrimidine (opy). I t was of further

interest to examine the steric ef fects of the various substituents

in the pyrimidine ring, and also to examine i f other donor s i t e s

at different positions of the pyrimidine ring could coordinate to

the metal atoms in preference to the ring nitrogen, and to explore

the poss ib i l i ty of the formation of polymeric species .

; jo

ESPERIMENTjyL

Preparation and Pur i f i ca t ion of Reagents;

2,4,6-Trlamlnopyrliaidlne (m.p, 250**c); 4-pyriiiiidinol

(m.p, 165 C); 4,6-dlaiBlno-2-mercaptopyrlmldlne (m.p.^ 280**C)

( a l l Pluka reagents) and 4-affllno-l,3-dlmetliyl-2,6-dioxopyriBiidine

(m.p. 298°C) (Koch Light) were recrystaXllzed from ethanol .

Pyrlmldlne (m.p. 21**C) and GeCl^ ( b . p . 83®C) (both Koch Light

reagents) were used as such.

Preparation of the Complexes?

Complexes of pyrlmldlne - Pyrlmldlne complexes were prepared by

mixing chloroform so lut ions of the l igand and the metal ha l ides

i n a 1:2 (metal- l igand r a t i o ) . In each case a p r e c i p i t a t e i^peared

Immediately which was f i l t e r e d , washed with chloroform and dried

i n vacuum des iccator . Tln(lV) chloride and bromide complexes

were r e c r y s t a l i i zed from ethanol .

Complexes of subst i tuted pyrimidines - Tln( iv) ha l ide

complexes were prepared by mixing equlmolar a l coho l i c so lu t ions

ot the metal ha l ides and the l igand. 2,4,6->Triaminopyrifflldine

y i e l d e d needle shaped c r y s t a l s immediately but with other l igands

i t weus necessary to heat the reactants ^ for an hour and to leave

56

the misrture for a few days. 4,6oDiamino~2-meroaptopyrimicline

and l,3-diniethyl-2,6-dioxopyrliaidine yielded needle shaped and

granular crystal l ine products respectively. In the preparation

of 4-pyrlinidinol complexes of SnCl^ and SnBr., the yellow viscous

mass obtained in each case after a week was heated to y ie ld a

so l id product, which was washed with benzene and recrystal l ized

from ethanol to yield granular crystal l ine products. Excepting

the 4-pyrimidinol complex of GeCl which was obtained immediately

after mixing their equimolar solutions, the GeCl complexes of

a l l other ligands were obtained after keeping the equimolar

solutions of the reactants in dry alcohol chloroform mixture for

a week.

a?

RESULTS J^V DISCUSSION

The analy t ica l data ubioh agree with the proposed s t o i -

chlometries are presented along with the colour and melting points

in Table 4» All the cooiplexes cure f a i r l y s table at room tempera­

tu r e . The molar conductances ot pyrimidine complexes, which

only, are soluble in nitromethane (Table 5) ind ica te them to be

non-ionic in na tu re ( l46) . Other complexes are not soluble in

usual organic so lvents .

All of the subs t i tu ted pyrimidines used in t h i s present

work have addi t ional coordination s i t e s besides the pyrimidine

r ing n i t rogen. Infrared spect ra of the l igands , and the complexes

have been recorded to ascer ta in the mode of coordinat ion. The

l igand v ib ra t iona l frequencies upon coordination to d i f ferent

metal atoms are changed. The magnitude of these s h i f t s give

information about bonding between the ligand and the metal atom.

The assignments of various sens i t ive bands of the subs t i tu ted

pyrimidines and the i r complexes are presented in Table 6« There

have been extensive infrared spectroscopic s tud ies on pyrimidines

on account of t h e i r b io log ica l importance* However, owing to

the many tautomeric forms(93,94,107,110-116) in which i t i s

poss ible to write the s t ruc tu res of some subs t i tu ted pyrimidines,

including some in lihich the aromatic character of the r ing i s

^ 5

TABLE - 4

Colour , mel t ing po in t and a n a l y t i c a l d a t a of the comple:?es

M.F, % Q foE %N %X %U Colour / 0 - . Calcd. Calcd. Calcd. Calcd. Calcd.

^ ^' (Pound) (Pound) (Pound) (Pound) (Pound) Complexes

SnCl^(pyi!i)2

SnBr^(pym)2

Snl^(pyni)2

GeCl^(pyai)2

SnCl^(apy)2

SnBr4(apy)2

GeCl4(apy)2

SnCl^CpyDg

SnBr^(py l )2

GeCl4 (py l )2

SnCl^(nipy)2

SnBr^(iiipy)2

GeCl4(mpy)3

SnCl^.opy

SnBr-^.opy

GeCl^(opy)g

White

L ight y e l l o w

Brovm

White

Ifhite

Ye l low

Hurler Tirfiite Light y e l l o w

Ye l low

White

Dark hrown

Ye l low

Brown

White

Ye l low

Light y e l l o w

26 2d

243d

170

120

310

290

295 d

215d

208d

195

310d

354

325

>360

2 i 5 d

135

2 2 . 3 5 ( 2 2 . 4 6 )

1 6 . 0 5 ( 1 6 . 6 6 )

1 2 . 2 2 ( 1 2 . 9 9 )

25 .65 ( 2 5 . 8 9 )

1 8 . 8 0 ( 1 7 . 0 8 )

13 .96 ( 1 4 . 8 8 )

20 ,68 ( 2 0 . 5 4 )

2 1 . 2 3 ( 2 0 . 1 9 )

1 5 . 2 4 ( 1 4 . 9 9 )

2 3 . 6 4 ( 2 3 . 6 0 )

17 .64 ( 1 7 . 3 1 )

13 .29 ( 1 3 . 2 1 )

22 ,49 ( 2 2 . 3 1 )

1 7 , 3 3 ( 1 7 . 0 1 )

1 2 . 1 3 ( 1 1 . 9 1 )

3 1 . 7 9 ( 3 2 . 0 1 )

1 .91 ( 1 . 9 5 )

1 .34 ( 1 . 3 8 )

1 .02 ( 0 . 9 6 )

2 .15 ( 2 . 2 5 )

2 .76 ( 2 . 5 6 )

2 .05 ( 2 . 3 3 )

3 . 0 3 ( 2 . 9 4 )

1.78 ( 1 . 2 4 )

1.27 ( 1 . 2 5 )

1.98 ( 1 . 8 9 )

2 . 2 2 ( 2 . 0 9 )

1 .67 ( 1 . 6 1 )

2 . 3 3 ( 3 . 2 6 )

2 .16 ( 2 . 1 3 )

1 3 , 3 2 ( 1 2 . 9 8 )

9 . 3 6 ( 9 . 8 1 )

7 . 1 2 ( 7 . 3 1 )

14 ,96 ( 1 4 . 7 9 )

2 7 , 4 1 ( 2 5 . 9 8 )

2 0 , 3 3 ( 1 9 , 8 1 )

3 0 . 1 3 ( 2 9 . 4 1 )

1 2 . 3 8 ( 1 1 . 3 9 )

8 , 8 8 ( 8 . 4 7 )

13 .78 ( 1 3 . 0 1 )

20 .56 ( 2 0 , 9 8 )

1 5 . 5 0 ( 1 5 . 4 0 )

2 6 . 2 1 ( 2 6 . 8 0 )

1 0 , 1 1 ( 9 . 9 0 )

1 .52 7 . 0 8 ( 1 . 1 9 ) ( 6 . 8 1 )

4 , 0 0 ( 3 . 3 5 )

1 8 , 5 5 ( 1 7 , 8 3 )

3 3 , 7 0 ( 3 3 . 8 1 )

5 3 . 3 9 ( 5 3 . 0 1 )

6 4 . 5 5 ( 6 3 . 5 0 )

3 7 . 8 4 ( 3 6 . 9 9 )

27 .75 ( 2 7 . 5 9 )

4 6 . 4 1 ( 4 7 , 1 1 )

3 0 , 5 1 ( 3 0 , 9 1 )

3 1 , 3 2 ( 3 1 , 1 2 )

5 0 . 7 0 ( 4 9 . 1 3 )

3 4 . 8 7 ( 3 3 . 9 9 )

2 6 . 0 2 ( 2 5 . 9 9 )

4 4 . 2 3 ( 4 4 . 9 9 )

2 2 . 1 2 ( 2 1 . 3 5 )

3 4 . 1 2 ( 3 4 . 1 1 )

5 3 . 3 7 ( 5 2 . 9 8 )

20 .35 ( 1 9 . 9 1 )

2 8 . 2 1 ( 2 7 . 2 5 )

1 9 . 8 2 ( 2 0 , 2 1 )

15 .09 ( 1 5 . 1 2 )

2 3 . 2 3 ( 2 3 . 9 5 )

1 7 , 2 3 ( 1 7 . 1 4 )

2 6 , 2 1 ( 2 5 , 8 1 )

1 8 , 8 2 ( 1 7 , 9 9 )

2 1 , 7 8 ( 2 1 , 7 0 )

1 6 , 4 2 ( 1 5 , 9 8 )

28 ,58 ( 2 7 , 7 6 )

2 0 . 0 1 ( 1 9 , 4 0 )

d = decomposition temperature

i i^

TABLE - 5

Molar conductance of O.OOIM s o l u t i o n i n n i t romethane a t

room tempera tu re .

Complexes ^ (ohm cm mole )

SnCl^(pym)2 31,86

SnBr^(pym)2 34.57

Snl^Cpym)^ 38 .01

GeCl^Cpym)^ 32.96

60

completely l o s t , i t has not y e t proved poss ib l e to develop s a t i s ­

factory corre la t ions for the recogni t ion of t h i s par t i cu lar c l a s s

of compounds.

Pyrimidine ( i , 3 ~ d i a z i n e ) complexesi Character i s t i c aromatic

ring s tretching v ibrat ions appe€ur in the range 1600-1350 cm"^ in

most of the he terocyc l i c compounds(9l). The ring s tre tch ing

v ibrat ions probably r e s u l t from the complete i n t e r a c t i o n of CsC

and CaN v ibrat ions and i t i s , therefore , very d i f f i c u l t to

separately I s o l a t e the d i f f erent v i b r a t i o n s . Coordination through

the nitrogen atom causes an increase in the CsC and C=N s t re t ch ing

fre( |uencie8(i63,169) in donor molecules s imi lar to pyrimidine v i z .

i n pyridine and in quinol ine . In pyrimidine complexes the ring

s tre tch ing v ibrat ions appear in the higher frequency region

(1638-1408 cm ) as con^ared to those of the free l igand at 1570,

1467 and 1402 cm . Similar p o s i t i v e s h i f t s have a l so been

reported for pyrimidine complexes of t r a n s i t i o n meta l s (74 ) . The

region of 4000-650 cm i s only concerned with the l igand v i b r a -

t i ons modified by complexation. The region below 650 cm" i s more

informative regarding the nature of the binding of the metal to

the l igand.

2,4,6-Triaminopyrimidine complexes - 2,4,6-Triaminopyrimidine

may coordinate e i ther through the pyrimidine ring nitrogen or

through the nitrogen of the amino group. The IR spectra of these

6 to QO a> M

» > > -^ CO <n

m (M t -03

00 >

00 eo CO

m

00

OQ

M

n to • H

CO MS

09

0)

o o

01

O

fk

<0 T H

. 'a

« o

o o o

o

IB

0}

a CI

bO

• H

CO

09

m II o

09

o 11

o

o • r l

09

> tO "^

n

09 > >• 00

09

o

09 > 00 00 10 •H

09

>

CO

09

10

* 09 •% OD » V^ 4K ^

n > 09 n CO ^ <o O to 00 •^ O CO 00 t - w CO ca to lo "^ to lo TH ^ TH -H -H T^ KH

OB 09 > > K 09 > > IH >

o> o po to lO •^ to •«}• rH ^ T-l ^

(«

O

a • p S 07 S a bO

• H so CO

SB O l O

CO

CO

o l O

CO 00 CO JO

09

B •rH

«k

09 00 • « *

10

ca 00 lO TH

• h

^ • *

CO (0 •rt

09 t -M •* •n-i

CO lO <o TH

«« ^ SB

CJlO •H TH fc- l O •H yi

> Vi •»1<

•» ^

s t -•H

09

<^

•« »

<J> 00 to •H

» 00 to CJ CO

•» CO

00 t-eo eo

CO

^ vn o CO

09 lO eo >H CO

• k

09 o o CO CO

09 l«-• ^

C3 CO

•• SO o to rl< CO

09 00 CO ca CO

«> CO CM t-< CO

09 « X a>

o o

>» A

ca S >>

O c 03

ca

Is > . P .

>—'

CO

ca ca

e >> ex.

•<i M fl

OT

>» Pk

• I

»-t O

a> OJ

w W«N»,

{^

&

" ^ t H

o a OT

ca rf^^

>, §-

> M ^

- l" U

? OT

C3 , ^~S

• . &

N a ^

Tj" f - t

ti>

n ^ •^ CO

to

^ • ^

N

w ^ ^ CM O •«#

$ ^ ^

S OB O ;0

Tjt eo

62

a

CO

CO

eo ea

a 09

•H 0 • * • < *

n o

o

1-^

O

o

I

OB

d

o

s a

n

o II u

O II

O

1 ^

00

8 • H

09

> m 00 <M to <o •H - H

oa CO • H

<0 t -W - ^ •H rH

SB •H CO (O •H

OB 0 <M •TI* "H

• k

OB •H CO 10 r4

^ CM <* to ^

« t -w •«1« T4

• k

^ •H »-5j« ft

OB

CO 1 0 • H

•k n

t -o» 10

CO 00 QO Mi eo

^ tr­io •H

^ 0 00 M5 TH

0 0 (0 •H

CO 1 0

CO > 00 t -

• (O '•HI to

SB > 10 t-

OB

OB SB 1 0 W t - 00 to 10 •H ^

• k Vk

CO CO ^ > > ^

CO w eo ;0 <D •^

TH TH

xi 06

t -(0 «D

^ t -«o CO

«Q t -(0 tf>

OB

CO to • H

o t-10

> ^ (O GO ca o 50 ^

SB

to

tO

eo <o • H

n t-eo •TH CO

" • ^ 00 a>

<o 00 0 0 CO ^ T>l • H

a o t -10

o to

00 to O -H CO to

09

eo

to

to

00 eo to

(0 t-<o (O

09 to t-00 •H

«k

SB 00

o

09

• H to •H

to

CO

10

00

a «0 w CO

09 OB to (O TH O

eo eo

09 >

CO • k

a

eo OB

00

- * CO

O vi

eo -r* CO e o

•% ^ OB a ^ t -

eo eo

OB

to

CO

t-<o eo eo 00 o to ^ eo

09 to 0» •H CO

<0 CO eo OS o (O

eo

09 d esj eo eo

•> 09 o o 10 00

OB > to •H CO

OB

CM CO

OB to

to eo

u

Si

a o o to

09

fH

I-o o

M N CI CM W CO

P* Pi Px

• < * •*!• ^

>-l O CQ U >> >> d C3 V P. p< w 10 c5 a

o a xn CO

p^ o o to

• » §-

eo

o

U IH

o

6^

complexes reveal no s i g n i f i c a n t decrease in the N-fi s tre tch ing

frequencies rul ing out the involvement of the amino ni trogen in

coordinat ion. For NHg coordination there should be em extens ive

change in the N-H s tre tch ing frequencies . However, the C=C and

CaN s tretching frequency bands show a p o s i t i v e s h i f t ind ica t ing

coordination through the ring nitrogen atom.

4~Pyrimidinol (4"hydroxypyrimidine) complexes - 4-Pyrimidinol

i s capable of tautomerism because the l a b i l e hydrogen atom may

be attached e i ther to a ni trogen or an, oxygen atom. Infrared

spectroscopic S t u d i e s ( l 0 7 , l l 0 - l i 6 ) of 4-pyrimidinol in s o l i d s t a t e

as wel l as in d i f f erent so lvent s show that i t occurs predominantly

in the ketonic form(lV). Thompson and coworkers( l l4) e s tab l i shed

that i t e x i s t s f u l l y in the ketonic form. In chloroform so lu t ion

i t mainly assumes(l l5) the ortho-quinonoidamide form(lVa)y the

amount of para-quinonoid-isomer(lVb) and ^he enol form(V) being

undetectable . Infrared spectroscopic s tudies of S p i n n e r ( l l l ) i n

aqueous so lut ion show the presence of zwlt ter ions (Vl ) and ( V I l ) .

OH

(IV) (V)

o4

(VI) (VII)

4-Pyrlmidinol has three potential sites available for

coordination and may act as a multidentate llgand. Its complexes

do not show any significant decrease in the N-H stretching

frequency and the ring stretching frequencies also do not show

any positive shift ruling out coordination through the N-fl group

and the ring nitrogen. Now the carbonyl oxygen is the only

remaining coordination site. The C=0 freqpiencies of ketones are

negatively shifted(l70) upon coordination to metal ions. The

complex formation due to the withdrawal of the electron cloud

from the carbonyl oxygen decreases the force constant and also

the carbonyl stretching frequency. This frequency has been found

to be negatively shifted by 60, 50 and 39 cm"''' for SnCl^, SnBr^

and GeCl. complexes, respectively, indicating coordination through

the carbonyl group. The carbonyl stretching frequencies shift to

the lower spectral region on complex formation and this can be

used to compare the strength of Iiewis<-acids. Thus, SnCl> has

been found to be a stronger Lewis acid than GeCl ^ which might be

ascribed to the increasing size of the central atom. For tin(lV)

complexes the order of Lewis acidity has been found to be SnCl^^

SnBr., which is in agreement with the decreasing electronegativity

and increasing steric hindrance on going from chlorine to bromine.

00

4,6-Dlainino~2-mercaptopyrlmldlne complexes - Infrared s p e c t r o ­

scopic s tudies of Spinner(93) show that theo<^ - a n d / -mercapto-

aza-aromatic compounds are C€5>able of tautomerism i , e . they e x i s t

i n the thioamide form, A strong band in the v i c i n i t y of i l 4 0 cm

was assigned to the thiocarbonyl s t re tch ing v i b r a t i o n . There i s

no evidence for the zwit ter ion structure for mercaptopyrimidines

l i k e hydroxy pyrimldines, thus thiocarbonyl s t re tch ing frequency

i s i n s e n s i t i v e to polar e f f e c t s *

The presence of an in tense band at 1200 cm at tr ibutable

to c=S s tretching frequency and the absence of S-^ band in the

2550-2600 cm region(lOO) in the infrared spectrum of the free

l igand suggest i t s ex i s tence in the thiotunide form(VIIl) rather

than in mercaptoform(lX). The N-H s tre tch ing frequency bands are

observed at 3448, 3289 and 3125 cm •

NH2 NH2

(VIII) (IX)

This molecule has several s i t e s avai lable for coordination

which could occur through sulphur or nitrogen atoms. The p o s s i ­

b i l i t y that i t may act as a multldentate l igand has been considered,

The Infrared spectra of i t s complexes are not very d i f f eren t from

that of the l igand except in the C=S absorption region (1200-

66

1175 cm' ) , The NHEl s t re tch ing frequencies observed in the

3145-3484 cm"" region in the adducts are not much d i f f erent from

i t s p o s i t i o n in the l igand. The ring s t re tch ing frequencies

observed in the 1408-1639 cm" region i n the complexes a l so remain

almost unchanged. I t i s , therefore , i n d i c a t i v e of non-involvement

of any of the nitrogen atom i n the coordination with the metal

atom. The thlocarbonyl s tre tch ing frequency has been found to be

negat ive ly s h i f t e d by 22,25 and 19 cm for SnCl^, SnBr. and GeCl>

complexes, r e s p e c t i v e l y , ind ica t ing coordination through thlocarbonyl

sulphur atom. This negat ive s h i f t in the C=S s t re tch ing frequency

a f t e r complexation i s due to the wecOcening of the bond, and can

be expected as r e s u l t i n g from the e lec tron drainage from the sulphur

atom due to i t s coordination toothelmetal iatom.

4-JUBlno-l,3-dimethyl-2«6-dioxopyrimidine complexes - The —1 carbonyl s tre tching frequency observed at 1667 cm in the l igand

m

remain unchanged in the complexes rul ing out coordination through

the oxygen atom. In the IH spectrum of the l igand there are two —1 —1

strong bands at 3322 cm andr3500wdi!ii: ^orireaponding to the

symmetric and antisymmetric N-B s tre tch ing v i b r a t i o n s , r e s p e c t i v e l y .

These bands in the complexes are not well reso lved but in SnCl^

and SnBr^ complexes there i s a lowering of t h i s frequency i n d i c a t ­

ing coordination through amino group. In a l l the complexes there

i s a decrease in the ring s tre tch ing frequencies which i s due to

coordination through the r ing n i t rogen(76 ) .

67

Low Frequency Infrared Spectra

The M-X s tre tch ing frequency bands usua l ly appear as strong

• bands irtiich have been i d e n t i f i e d by re ferr ing to previous data

on other re la ted systems(89,129-136) , The Sn-I s t re tch ing frequency

band could not be observed in the spec tra l range . s tudied , Pyrimi-

dine does not have fundamentals below 346 cm to o f f er any

interference in the region of metal-halogen and metal-nitrogen

s tretching v i b r a t i o n s . The bands which are v i r t u a l l y unaffected

by changing halogen are at tr ibuted to \ (M-N) and y (M-O), In

complexes of 2,4,6-triaminopyrimidlne and 4,6-diamino-2-mercapto-

pyrimidine the )) (M-N) and y (M-S) bands, r e s p e c t i v e l y , could not

be d i s t inguished unambiguously from the l igand in terna l modes. In v

4-pyrimidinol complexes the 552-574 cm region bands have been

assigned to p (M-O) modes ( l7 l ) .

I t i s known that with smaller donor spec i e s t i n and germanium

form adducts having the two l igands i n a c i s p o s i t i o n whereas with

bulky l igands they form trans-octahedral spec ie s due to s t e r i c

r e a s o n s ( l 6 7 ) . A. trans-octahedral s p e c i e s should exhib i t one

infrared ac t ive \) (M-X) mode (e symmetry), however, the c i s -

isomer i s expected to have four such modes {2a^ • b . + b ) ( 1 3 7 ) .

In Is2 (MX.;ligand) complexes the presence of only one M-X band

i s i n d i c a t i v e of a trans-octahedral conf igurat ion. The l igand

must be monodentate in a l l the I t 2 complexes. In pyrimidine and

2,4,6-triaminopyrimidine coordination should be occurring through

any one of the two equivalent nitrogen atoms. Tin(lV) chloride

bd

and bromide complexes of 4-aralno-l,3-dlmethjrl-2,6-dioxj»pyrimidlne

obtained In a I j l r a t i o also have only one M-X s t re tch ing frequency

band at 3l4 cm" and 230 cm respec t ive ly . This i s very close to

t h e i r pos i t ion in other hexacoordlnated complexes of the present

s e r i e s and a lso in previoui^ly recorded pyrazlne cofflplexes(89).

The close s imi l a r i t y between the spect ra of 1:2 and I s l complexes

ind ica te tha t the complexes SnCl^.opy and SnBr.,opy also have a

polymeric 6-coordlnated t rans-octahedral geometry with ligand

bridging involving the amino group and one of the r ing nitrogen

atoms. The nitrogen atom should presumably be the one at pos i t ion

i i f a l inea r polymer i s being formed, however, the p o s s i b i l i t y

of the formation of a non-l inear polymer involving ni t rogen a t

pos i t ion 3 can not be ruled out. The 1:3 complexes of GeCl>

presumably have a s ix coordinated ca t i on l c s t ruc tu re (GeCloI'3)Cl ,

however, in view of the absence of conductivi ty data due to

i n s o l u b i l i t y of these complexes I t i s only a t en t a t i ve suggestion.

I t appears from the considerat ion of the far infrared

spect ra that the frequency of M-X band depends upon the nature

of X(X=C1, B r , I ) and have been found to decrease with increasing

s ize of halogens showing the order Snr:Cl)>^ Sn-Br^ Sn- I . The

s t re tching frequency Ge-Cl i s higher than Sn-Cl for corresponding

adducts of t i n and germanium, thus with increasing size of the

cen t ra l atom the M-X s t re tching v ibra t ion frequency decreases .

C H A P T E R - V

COMPLEXES OP TIN(IV) , GERMANIUM( I V ) , SILICON(IV) AND

TITANIUM(IV) HALIDES WITH PYRIDA3INE

CQMPliEJffiS OF TlWdV), GEmiANI0M(lV). SlLICON(lV) AND TITANIUM(IV) HALIDES WITH PYRIDAZINE

Biazines have been found to act as unidentate or bidentate

ligands forming octahedral, monomeric or polymeric, coisplexes

involving azine and/or halogen bridged structures(73-75,81-88),

Pyrazlne ( l ,4 -d iaz ine) complexes of tin(lV) halides of the type

SnX^(pyrazine) and SnX4(pyrazine)„ have recently been reported

and a trans-octahedral structure involving azine bridging in the

1:1 compleares and a terminal coordination of the ligand in the

i ;2 complexes have been proposed(d9). Pyridazine ( l , 2 -d iaz ine ,

pyd) complexes of the general formula MX^(pyridazine)j^MaSn;

XsCl, Br, 1} n s l , 2 and MsGe, S i , Tij XsCl; n=2_y have presently

been studied with a view to determining their structures and the

denticity ot pyridazine*

EIPERIMENTAL

Preparation and Purification of Reagents:

Pyridazine (b,p. 206°C), 8i l icon(lV) chloride (b.p. 58®C)

(both Koch-Light reagents) and titanium(IV) chloride (b.p. 137 c)

(B.O.H. reagent) were used as such.

70

Preparation of the Compleyejg;

All the coiqilexes were prepared by mixing the ohloroforn

solutions of the metal halldes and the ligand in definite molar

rat ios . In each case a sol id product was obtained immediatelyt

which was washed with the solvent and dried in vacuo*

MX^Cpyd) complexes - These were prepared by the addition

of metal solution to ligand solution in a 1:2 (metal-ligand)

molar ratio so that the ligand was always in excess .

Ml.(pyd) complexes - In this case metal and ligand solutions

were taken in a 2:1 (metal-ligand) molar ratio and the mode of

addition of reactants was reversed so that the metal was always

in excess.

PJ 1

RESULTS AND DISCUSSION

All the actducts except those of SnCl^ and SnBr. are

highly a ir and moisture s e n s i t i v e . The ana ly t i ca l data along

with the colour and melting point of the complexes have been

presented in Table 7. The comparison ot the molar conductance

va lues (ca . 40-60 ohm" cm mole at lO" molar concentration)

(Table 8) with those of typica l uni -univalent e l e c t r o l y t e s in

nitromethane (ca« 75-95 ohm cm mole' ) ind icate that these

complexes are b a s i c a l l y non- ionic In nature*

The complexes formed have the composition MX^(pyd) or

Mi:>,(pyd)2, The MX.(pyd) complexes could be formulated as:

( a ) a f i v e coordinated monomer with moaodentate pyridazine»

(b) a c i s -octahedral monomer with bldentate pyridazine»

( c ) a chain polymer with octahedrally coordinated metal atoms,

bridged by pyridazine molecules arranged c i s or trans to each

other , or (d) an octahedral s tructure with monodentate pyridazine

involv ing halogen br idges .

The infrared spectra of pyridazine and i t s coiqplexes and

the various assignments have been presented in Table 9 . The ring

s t re tch ing v i b r a t i o n s , vvhioh r e s u l t from the complete i n t e r a c t i o n

of the C=C, CsN and N=:N v i b r a t i o n s , after complexation show a

p o s i t i v e s h i f t , however, in some complexes these v ibrat ions

C I « »

/4

TJfflLE - 7

Colour , mel t ing po in t and a n a l y t i c a l d a t a of the complexes

Complexes

SnCl^Cpyd)^

SnCl^(pyd)

SnBr^Cpyd)^

SnBr^(pyd)

Snl^Cpyd)^

Snl^(pyd)

GeCl^Cpyd)^

S l C l 4 ( p y d ) 2

TiCl^Cpyd)^

Colour

White

White

I fh i te

Ye l low

Dark brown

Dark green

Murky ^ i t e

Ifhite

Murlqr whi te

M.P •

295d

26 Od

195d

170d

110

125

154

198 d

230d

% C Calcd .

(pound)

22 .85 ( 2 2 , 4 6 )

1 4 . 1 1 ( 1 4 . 9 8 )

16 .05 ( 1 5 . 5 6 )

9 . 2 7 ( 9 . 9 8 )

1 2 . 2 2 ( 1 2 . 6 1 )

6 . 8 0 ( 7 . 5 6 )

25 .65 ( 2 5 . 6 2 )

2 9 . 1 2 ( 2 8 . 9 1 )

27 .48 ( 2 8 , 0 0 )

% H Calcd .

(Pound)

1 .91 ( 2 . 3 7 )

1.18 ( 0 . 9 0 )

1 .34 ( 1 . 3 2 )

0 , 7 8 ( l . l O )

1 .02 ( 1 . 2 9 )

0 , 5 7 ( 0 , 8 7 )

2 ,15 ( 2 , 8 3 )

2 .44 ( 2 . 5 4 )

2 . 3 0 ( 2 . 6 1 )

% N C a l c d .

(Pound)

1 3 , 3 2 ( 1 3 . 4 0 )

8 . 2 3 ' ( 9 . 0 1 )

9 , 3 6 ( 8 , 8 4 )

5 , 4 1 ( 5 , 8 9 )

7 . 1 2 ( 7 . 4 1 )

3 , 9 7 ( 3 , 9 8 )

14 .96 ( 1 5 , 3 1 )

1 6 . 9 7 ( 1 7 . 8 8 )

1 6 , 0 2 ( 1 6 , 9 8 )

Ca lcd . (Pound)

3 3 . 7 0 ( 3 4 . 5 6 )

4 1 . 6 3 ( 4 0 , 8 2 )

5 3 . 3 9 ( 5 2 . 4 2 )

6 1 . 6 6 ( 6 0 , 1 2 )

6 4 . 5 5 ( 6 5 . 6 1 )

71 ,86 ( 7 0 , 1 1 )

3 7 . 8 4 ( 3 8 , 0 1 )

4 2 . 9 5 ( 4 2 . 4 0 )

4 0 , 5 2 ( 4 1 . 8 3 )

3

T^LE - 8

Molar conductance* of O.OOlM solut ion in nltromethane at room temperature.

Con^lexes <J\f (ohm cm mole )

SnCl^Cpyd) 47.25

SnCl^Cpyd)^ 42.95

SnBr^(pyd) 46.03

SnBr^(pyd)2 41.74

Snl^(pyd) 45,01

Snl4(pyd)2 40.38

* Other complexes are not su f f i c ien t ly soluble in nltromethane

<k

remain almost uncbanged. The region of 4000-630 cm"^ is a poor

region to get any conclusive evidence regarding the structure of

complexes, since in this region one is dealing only with ligand.

vibrations, modified by complexation. The region below 650 cm""*

is very important for structure elucidation. This region contains

the metal->halogen and metal-ligand vibrations, and thus, may be

quite useful in determining the stereochemistry of the complexes*

Observation of the position of the low-frequency infrared vibra­

tions could possibly give an insight into the nature of the

bridging, occurring in these complexes.

Pyridazlne has three absorptions in the far IR region

at 634, 540 and 368 em' , which have been assigned as ring

vibrations* As expected, the ring vibrations upon complexation

are positively shlfted(lT2), due to the fact that complexation

places certain rigidity on the ligand molecule, and the vibrations

require more energy to occur* In all the complexes a new band

—1 appears at about 400 cm which may be due to the change of

symmetry of the ligand molecule*

The \) (M-JC) bands are Identified on the basis of previous

IR data on pyrazine(89) and other related systems( 129-136).

These show the usual shift to lower frequencies with Increasing

size of the halogen* The \/ (M-Cl) vibrations because of atomic

mass difference of the metal involved, also shift to lower

frequencies in the sequence Si—^ Ti—^ Ge -^ Sn. Since pyridazlne

Va I (Nl

o >,, EH >»^

I CM

o >, •H P<

® ft

I . - V

n Pt CO N - '

I

U tJ

^

<3 >» B P.

I

f-t "d

o >. Ml > - '

p .

to •p 9 B a to 09

4g

»f ^ 09 a O • * rj< O ca a> • w <o »o w • ^ •H TH T<

^ o CX) N •H

> o t -•H •H

^ « a e <o <o w o 00 " * lO O »o i n -«* -"d* t-l •H -H T-l

IB OD m « • j> O 00 W N CJ 00 ># lO <o w « • * YH TH -r* ^H

^ a n n a t - 00 W t - OO CO lA ^ 00 O to K3 U3 -*H ^

CO 09 n o t- o t o CO T^ W ««Jt - jt r^ H TH

Si „ t» a CM TH t -0> t~ "H to CO W K5 W Tli • j4

Rt ^ n t - CJ w

Ss > OB > > O O t - T^ 00 O t - N " * O CO i n U3 TH rj) •H -H TH -H t- l

* OJ a > tn a MS b- -H <0 t - T-l «0 O W M5 •* •* •H T-t TH -H

a « SB

09 •H t -W M5 "H ^

QQ ^ Ol

CO 09 n « ca w ^ rjt t - to • * "H m U3 "'i* Tjt

I ,, 1

ir It H o osz;

> ^ 00 o>

JS5 ^ NQO 00 (0 t» t-

> 09 » to OQ •>*

to to to

^ to t-eo

0)

> to •ri

00

IK

§8 CM

00 CM

OB

Tjt CO t - M5 CM -H

a a to CO b- »0

i? CJ CO

o>

a > to •<* t - 00 O Q> •H

A a to

-«* O t o t -O 0 )

0) tjt 00

OB

t 00 00 t -

09 > a> CO t -

> 00 CM to

OB

» CM to to

^ OQ CM to

X> • k

^ to to m

a j ^ 00 <D CO t -CO CO

it 09 W lO

o> r-CO CO

15 CM

o> CO

> W5 U3 •<*

OB

00 CO

o o .w.

^ 00 •H CO

^ o t -CM

1 t -CJ

Hi O to t -O <3>

«

to l < ^ t - 10 lO 10

o o CM ^v

IS to lO

^ a ^ TH ^ CO

t - to s 09

to

^ > a CM CM 00 00 to to lO lO CO

00 CO CM

^fHf

09

a »

^ ^ ^ ^ •^ CD t o 00 TH C^ to 00 to to lO CO

* *

o 00 CM • H

00 CM

OB CO 00 CM

to

a CO

a o to

> 09 o o t - l -O OJ • H

OB

b- t -

o o>

OB 09 CM T H

OB CM

> lO

^

^ 09 8B 00 to o CO CM to to to lo

I* • !?

09

a ^ oa >• jK •«# '^ CM «* CI 05 00 CO CM "* 00 CO 00 CO CM

n t - 00

to to UO CO ^ s s * ^

n < ^ CO CO

00 CM

^<0 (O 0>

CM to

o lO

(0 00 to CO

ta fi •H U

a a tt) t)0 C O -H U X} •O 0 >> V W,e

ttO a •H h

V I • O *H

0) +><e 0 o « ^ § o e.

CI V s

1=

•d at o

Xi

u o -d 3 o SB

IB

(SO

u • M 09

>

890

o u CD

0)

09 >

^

•d 2 ^ a -H ri-H

» a a

o t o o Si lO

St +»o 03 O

o II rH

"> o.

•d o

a

u

to

>. p

to

I TH -d t - <» -^ u

d • o

%^ CO 0) P *H O

* ** *

Vt)

does not have fundamentals below 368 cm"'* the new bands below

this frequency are attributed to ^ (U-n) modes. The assignment

of \) (Sn-N) in SnBr^ complexes i s d i f f i cu l t because \) (Sn-Br)

absorptions also occur in the same region. The \) (Sn-N)band in

these complexes i s presumably obscured by the strong 0(Sn-Br)

mode (cf . SnBr^.pyrazine and SnBr^,pyridine2)(89,13l), In the

far IR region the l iguid modes do not interfere with the \) (M-X)

and \) (M-N) vibrations, except in germanium and titanium complexes

in irtiich the strong bands are tentatively assigned to y) (M-Cl)

vibrations. Furthermore, the ligand modes in a l l cases are sharp

n^ile ]^ (M-Cl) i s a broad one.

The presence of only one \) (U-K) band in the infrared

spectra of the MX4(pyd)2 type of complexes i s in accord with the

predictions(89) for these molecules with a trans-octahedral

geometry (Pig.X) (point group J>^^)i

^mol == 2a^g(«) * ^lg(^> • ^2g^^> * V ^ ^ * ^a^^^^^)

* 3e^(IR) * bgjjCinactive);

The vibrations of the polymeric species .SnX^(pyd) are

more correctly treated in terms of their l ine group symmetry(i73).

Neglecting orientation of the pyrldazlne groups, the l ine group

'ii

I s isomorphous with point group D.. . A fac tor group ana lys i s

leads to the fol lowing pred ic t i ons ;

"^01 - « lg («) * *>lg(«> * \gW * eg(R)

+ 2a^j(lR) 4. 3e^j(lR) • b2jj(Inactive);

^ n X ' ^lg<»)^ * ^ g < « ) * «u(^»>5

'snN * ^au^I"*^*

Thus the Infrared spectra of SnX.(pyd) complexes should be

essentially the same as those of corresponding SnX.(pyd)2

complexes.

The Identical position of | (Sn>X) in Isl and ls2 complexes

of tln(iv) Indicates a similar environment In both the complexes,

thereby ruling out the possibility of 5>coordlnated tin In the

case of MX.(pyd) complexes. Thus the latter complexes may also

be six coordinated. The slight splitting of \} (Sn~Cl) band In

the spectrum of SnCl^(pyd) is attributed to crystal field effects

on D - model (cf. SnCl-.pyrazine^ and SnBr.,pyrldlne2)(89,13l).

To account for the stolchlometry required for an octahedral

structure for SnX.pyd, the sixth site must be satisfied by a

bridging halogen or a ligand molecule. A bridged halide would

be expected to be found at lower frequency(l72»lT4). The shift

of a \ (M-X) vibration to lower frequency upon bridging is well

understood, since each halogen atom bridges two different metal

/5

atoas. In contrast to t h i s , the )) (M-N) vibration would not be

expected to shif t s ignif icantly upon bridging, since for the

azines the bridging i s through the molecule rather than an atom.

As there i s no evidence for halogen bridging, the SnX.(pyd)

complexes are, therefore, postulated as polymeric trans-octahedral

confounds (Pig.XI) involving azine bridging. A similar structure

has been proposed for the pyrazine coo^lexes of tin(lV) halide8(89).

O X X

\ / Sn

. / ^ .

N ^ ^

\ - ^

^—N I I

Sn

\ / Sn

XI X I

! X

I t i s , therefore, concluded that pyridazine in the 1:1

complexes prefers to act as bridging ligand (bidentate) , whereas,

in the Is2 complexes i t acts as a terminal ligand (unidentate).

I t i s quite expected that trtien one of the ring nitrogen atom

coordinates to the metal atom the electron demand from another

nitrogen makes i t less basic and a MX.(pyd)2 type of complex

i s formed.

7'J

REFERENCES

1. K* Ramaiah and D.F. Martin, Chem. Commun.» 2* ^^^ (1965).

2. R.K, Ingham, S.D, Rosenberg and H. GilBian, Chem. Rev., 60, 459 (1960),

3. D. Quane and R.S. Bottei, Chem. Rev., 6^, 403 (1963).

4. A.6. Davies, Chem. Britain, 4, 403 (1968).

5. P. Glockling, Quart. Rev., , 45 (l966).

6. O.H. Johnson, Chem. Rev., 48, 259 (l95l).

T. D.F.N. Satchell and R.S. Satchell, Chem. Rev., 69, 251 (l969).

B. I.R. Seattle, Quart. Rev., IJ, 382 (1963).

9. S.E. Livingstone, Quart. Rev., , 386 (1965).

10. M. ^bar All and S.E. Livingstone, Coord. Chem. Rev., 13, 101 (1974).

11. R.C. Aggarwal and F.P. Singh, J. Inorg. Nucl. Chem., ^ , 1651 (1966).

12. J.E. Fergusson, V.R. Roper and C.J. Wilkins, J. Chem. Soc., 3T16 (1965).

13. O.A. Osipov, U.L. Shelepina and O.E. Shelepin, 2h. Obshch. Khim,, 36, 264 (l966).

14. TI.R. Trost, Can. J. Chem., 30, 835 (1952).

15. R.C. roller and D.L.B, Toley, J. Chem. SOC,(A), 1578 (1967).

16. M. LesbPe, P. Mazerolles, J. Satge, **The Organic Compounds of Germmlum'*, Interscience Publishers, London, 539 (1971).

17. R. Sehwarz and P.W. Schenk, Chem. Ber., 63, 296 (1930).

18. J.S. Thomas and Th. Pugh, J. Chem. Soc., 60 (l93l).

so

19. J*S. Thomas and W.W. Southwood, J. Chem. Soc., 2083 (l93l),

20, W. Eisenbuth and J.R. van Wazer, Inorg. Nucl. Chem. Letters, 3, 359 (1967).

21* C.H. Yoder and J.J. 2uckermann, Inorg. Chem., , 1329(1964).

22. A. Yamaguchi, R.B. Fenland, S. Mlzushima, T.J. Lane, C. Curran and J.V. Quagliano, J. .Amer. Chem. Soc, 80, 527 (1958).

23. M. Nardelll, L. Coghl and G. Azzonl, Gazzetta, , 235 (1953).

24. R.L, Carlin and S.L. Holt,Jr., Inorg. Chem., 2, 849 (l963).

25. M. Schafer and C. Curran, Inorg. Chem., , 265 (1966).

26. M. Nardelll and L. Pave, Acta Cryst., jL2, 727 (1959),

27. A.L, Castro and M.H. Truter, J. Chem. Soc, 1309 (1963).

28. N.R. Xynchur and M.R. Tniter, J. Chem. Soc, 3478 (l958).

29. R.B. Penland, S. Mlzushima, C. Curran, and J.V. Quagllano, J. Amer. Chem. Soc, 79, 1575 (1957).

30. R. Rlvest, Can. J. Chem., 40, 2234 (l962).

3 1 . I . L fndqv l s t , ' •Inorganic Adduct Molecules of Oxo-compounds*, Spr inge r Ve r l ag , B e r l i n ( l 9 6 3 ) .

32 . J . E . Cass ldy, W. Moser, J . D . Donaldson. A. J e l e n and D.G. Nicholson, J . Chem. S o c . ( A ) , 173 (1970) ,

3 3 . D.S. Bys t rov , T.N. Sumarokova and V.N. Pl l imonov, Opt ika 1 Spekt roskoplya , 9 , 460 ( i 9 6 0 ) .

34. M. Neu-delli , L. Cavaloa and A. Br«i ibant i , Gazze t t a , 8 6 , 867, 1037 (1956) .

3 5 . H. U l r l c h and A.A.R. Sayigh , J . Org. Chem., 30, 2779 (1965) .

36. H . J . Beeher, Chem. B e r . , 8 9 , 1691 (1956) .

37 . W, Ger ra rd , M,P. Lapper t , H. Fyszora and J.W. W a l l l s , J , Chem. S o c , 2144 ( I 9 6 0 ) . _

38 . II.E. B u l l , S.K. Madan and J . E . W i l l i s , I n o r g . Chem., 2f 303 (1963) ,

81

3 9 . HiC. Aggarwal and P . P . S i n g h , a . Anorg. A l l g . Chem., 3 3 2 , 103 ( 1 9 6 4 ) .

4 0 . C.S, Kralhanze l and S .C . Grenda, I n o r g . Chem., 4 , 1 0 3 7 ( 1 9 6 5 ) .

4 1 . Archambault and R. R i v e s t , Can. J . Chem., 38 ( i 9 6 0 ) ,

4 2 . R . J , B e r n ! , R.R. B e n e r i t o , W.M. 4 y r e s and H,B. J o n a s s e n , J . I n o r g . Nuc l . Chem., _25, 807 ( l 9 6 3 ) .

4 3 . J ,A . Costamagava and R. L e v i t u s , J . I n o r g . N u c l . Chem., 2 8 , 2685 ( 1 9 6 6 ) .

4 4 . S.K. Madan and J . A . S t u r r , J . I n o r g , Nuc l , Chem., 2 9 , 1669 ( 1 9 6 7 ) .

4 5 . P . P . S ingh and R. R i v e s t , Can. J . Chem,, 4 6 , 1773 ( 1 9 6 8 ) ,

4 6 . S.K. Madan and M. S u l i c h , I n o r g . Chem., 5 , 1662 ( 1 9 6 6 ) .

4 7 . S.K. Madan and 0 . M u e l l e r , J . I n o r g . Nuc l . Chem., 2 8 , 177 ( 1 9 6 6 ) .

4 8 . SiK, Madan and C. G o l d s t e i n , J . I n o r g . Nuc l . Chem., 2 8 , 1251 ( 1 9 6 6 ) .

4 9 . P . P . Singh and R. R i v e s t , Can. J . Chem,, 4 6 , 2361 ( l 9 6 8 ) .

5 0 . T .J . Lane, A. Yamaguchi, J . V , Quagl iano, J . A . Rayan and S. Miznshima, J . Am. Chem. S o c . , ^ , 3824 ( 1 9 5 9 ) .

5 1 . C.N.R. Rao and R. Venkataraghavana, Spectrochim, A c t a , J[8, 541 ( 1 9 6 2 ) .

5 2 . R.K. Gosav i , U. Agarawala and C.N.R. Rao, J . Am. Chem. S o c , 8 9 , 235 ( 1 9 6 7 ) .

5 3 . N.N. Greenwood and B.H. Robinson, J . Chem, S O C , ( A ) , 5 l l ( l 9 6 7 ) .

5 4 . R.A. B a i l e y and T.R. P e t e r s o n , Can. J . Chem., 4 6 , 3119 ( 1 9 6 8 ) .

5 5 . M. Genchev, M. A l e k s i e v and N. A l e k s l e v a , Nature ( P l o v d l v ) , 3 , 41 ( 1 9 7 0 ) .

5 6 . V.M, Shulkan, Z.A. S a r e l ' e v a , J,M. Cheremis ina , Y a . V . V a s i l ' e v and V . F . Anufrienko, I z v . S i b . Otd. Akad. Nauk SSSR, S e r . Khim. Nauk, 1 , 77 ( 1 9 7 2 ) .

s^

57. R.K, Gosavi and C.N.R, Rao, J, Inorg. Nucl. Chem., 29, 1937 (1967). "~

58. S.C. Jain and R. Rivest, J. Inorg. Nucl. Chem., 29, 2787 (1967). ~~

59. P.P. Singh and I.M. Pande, J. Inorg. Nucl. Chem., 34, 591, 1131 (1972).

60. J. Zaremhowitch and L. Sebagh, J. Inorg. Nucl. Chem., 35, 4113 (1973).

61. A.H. Goodtrin and R.N. Sylva, Inorg. Chlm, Acta, 4, 197 (1970).

62. L. Sacconl, M. Ciampollni and G.P. Speroni, J. Amer. Chem. Soc, 8J, 3102 (1965).

63. M. Ciampolini, N. Nardl and G.P. Speroni, Coord. Chem. Rev., 1, 222 (1966).

64. E.L. Muettertles and R.A. Schunn, Quart. Rev., , 245 (1966).

65. P. Lions, I.G. Dance and J. Lewis, J. Chem. Soc.(A), 565(1967).

66. P. Bamfield, R. Price and R.G.J. Miller, J. Chem, Soc.(A), 1447 (1969),

67. B. Mayoh, P, Day, J. Amer. Chem, Soc., 94, 2885 (1972),

68. J.M, Malln and R.E, Shepherd, J. Inorg. Nucl. Chem., 34, 3203 (1972),

69. J,E, House.Jr. and R. Parran, J. Inorg. Nucl. Chem., 34, 1466 (1972).

70. J.£. House,Jr. and M-iJ. Adams, J, Inorg, Nucl, Chem,, 32, 345 (1970),

71. G, Beech and C,T. Mortimer, J, Chem, Soc,(A), 1115 (l967).

72. J,P. Gibson and S.A, Cotton, J, Chem, SOC.(A), 1696 (l97l),

73. A, Teuersteln, B.A, Felt and G, Navon, J, Inorg, Nucl, Chem,, 36, 1055 (1974).

74. J.R. Perraro, J. Zipper and W. Vozniak, pl, Spectrosc, 23, 160 (1969).

b'^

75 . J .R. F e r r a r o , W. Wozniak and G. Roch, R i c . S c i . , 3 8 , 433 ( 1 9 6 8 ) *

7 6 . J .R . F e r r a r o . C. C r i s t a l l l n i and G. Roch, R l c , S c i . , r r , 435 ( 1 9 6 7 ) .

7 7 . C. Relmann and G, Gordon, N a t u r e , 205 , 902 ( l 9 6 5 ) ,

7 8 . E .E . l y n s l e y and If.A, Csunpbell, J . Chem, S o c , 832 ( 1 9 5 7 ) .

7 9 . M,M. Taqui Khan and C,R, Krishnamoorthy, J , I n o r g , Nuc l , Chem,, 3 6 , 711 ( l 9 7 4 ) .

8 0 . R. Weiss and H. Venner, H o p p e - S e y l e r ' s , 2 . F h y s l o l . Chem,, 3 1 7 , 82 ( 1 9 5 9 ) ; 345 , 122 ( 1 9 6 6 ) ; 350 , 396 ( 1 9 6 9 ) ,

8 1 . A.B.P. Lever , J . Lewis and R.S . Nyholm, Nature , 189 , 58 ( l 9 6 l )

8 2 . H.D. Stidham and J .A, Chandler, J . I n o r g . N u c l . Chem., 27 , 397 ( 1 9 6 5 ) ,

8 3 . W.M. Carmichael and D.A. Edwards, J . I n o r g . N u c l . Chem., 3 2 , 1199 ( 1 9 7 0 ) ; 3 4 , 1181 ( l 9 7 2 ) .

8 4 . A .B .P . Lever , J . Lewis and R . S . Nyholm, J . Chem. S o c , 1235 ( 1 9 6 2 ) ; 3156 , 5042 ( l 9 6 3 ) .

8 5 . G.TT. Inman, J r . and W.E. H a t f i e l d , I n o r g . Chem., J ^ , 3085 ( 1 9 7 2 ) .

8 6 . R.F. Eckherg and W.E. H a t f i e l d , J . Chem, Soc , Dal ton T r a n s . , 616 ( 1 9 7 5 ) .

8 7 . M. Sek izak l and K. Yamasaki, Rev. Chim. M i n e r . , 6 , 225 ( 1 9 6 9 ) ,

8 8 . M. S e k i z a k l , Acta C r y S t . . B 2 9 , 327 ( l 9 7 3 ) .

8 9 . M. G o l d s t e i n and W.D, Unsworth, Spectrochim. A c t a , 27A, 1055 ( 1 9 7 1 ) .

9 0 . L . J . Be l lamy , *The I n f r a - r e d S p e c t r a of Contplea: M o l e c u l e s * , Methuen, London, 249, 257 ( 1 9 5 8 ) .

9 1 . C.N.R. Rao, "Chemical A p p l i c a t i o n s o f I n f r a r e d S p e c t r o s c o p y " , Academic P r e s s , New York, 3 1 8 , 327 ( 1 9 6 3 ) .

9 2 . 0 . P i o v e s a n a and C. P u r l a n i , J . I n o r g . N u c l . Chem., 3 ^ , 879 ( 1 9 7 0 ) .

S4

9 3 . E. Sp inner , J . Chem. S o c , 1237 ( i 9 6 0 ) ,

9 4 . D.J . Brown, S .P, Mason, "The Py r imld ine s " , I n t e r s c i e n c e F u b l l s h e r s , London, 494 (1962) .

9 5 . D . J . Brown. E. Hoerger , and S.P. Mason, J* Chem. S o c . , 4035 (1955) .

96 . S.P, Mason, J . Chem. S o c , 3619 (1958); 1281 (1959) ,

9 7 . C.N.R. Rao, "Chemical j ^ p l l c a t i o n s of Infreured Spec t roscopy" , Academic P r e s s , New York, 250 (1963) .

9 8 . L . J . Bellamy, "The I n f r a r e d S p e c t r a of Complex Molecules" , Methuen, London, 278, 282 (1958) .

9 9 . R.C, Lord, A.L. Martson and P.A. M i l l e r , Spectrochim. Acta , 9 , 113 (1957) .

100. L . J . Bellamy, "The I n f r a r e d S p e c t r a of Complex Molecu les" , Methuen, London, 351 , 355 (1958) .

1 0 1 . Randa l l , Powler , Puson and Dangl, " I n f r a r e d Determinat ion of Organic S t r u c t u r e s " , Van Nostrand (1949) ,

102. D.M. Sweeny, S. Mizushima and J .V. Quagliano, J . Amer. Chem. S o c , I J , 6521 ( l 9 5 5 ) .

103 . R.B. H a n n a n , J r . , J . H . L i e h l l c h and A.6. Renfrew, J . Amer. Chem. S o c , 71» 3733 (1949) ,

104. L , J . Bellamy, "The I n f r a r e d Spec t r a of Complex Molecules" , Methuen, London, 268 (1958 ) .

105 . R.H. Wiley and S.C. Slaymaker, J . Am. Chem. S o c . , 79 , 2233 (1957 ) .

106. I . A . Brownlie , J . Chem. S o c , 3062 (1950) .

107. L,N, Shor t and H.W. Thonqpson, J . Chem. S o c , 168 ( l 9 5 2 ) ,

108. K. Nakan l sh i , " I n f r a r e d Absorpt ion Spec t roscopy" , Nankodo Company Limi ted , Tokyo, 42,> 48 (1962) .

109. L . J , Bellamy, "The I n f r a r e d S p e c t r a of Complex Molecules" , Methuen, London, 134, 209 (1958) .

110. A. Alber t and E. Sp inner , J . Chem. S o c , 1221 ( i 9 6 0 ) .

SJ

111. E, Sp inner , J . Chem. S o c . , 1226, 1232 ( i 9 6 0 ) ,

112. R*A. Katrl tzkjr and R.A. J o n e s , J . Chem. S o c . , 2949 ( i 9 6 0 ) .

113. D.J . Brown and L.N. S h o r t , J . Chem. S o c , 331 (1953) .

114. H.W. Thompson, D.L. Nicholson and L.N. S h o r t , Discuss ions Faraday S o c , 9_, 222 ( l 9 5 0 ) .

115. S.P. Mason, J . Chem. S o c , 4874 ( l 9 5 7 ) ,

116. Tanner, Spectrochlm. Acta , 8 , 9 ( l 9 5 6 ) ,

117. J . I . J o n e s , W. Kynaston and J . L . H a l e s , J . Chem. S o c , 614 (1957 ) .

118. E. Spinner , J . Org, Chem., 23, 2037 ( l 9 5 8 ) .

119. M. Davies and W.J. J o n e s , J . Chem. S o c , 955 (1958) .

120. E. Sp inne r , Spectrochlm. Jkcta, 95 (1959) .

121. C.N.R. RaO, **Chemical .(implications of I n f r a r e d Spectroscopy**, Academic P r e s s , New York, 300 ( l 9 6 3 ) .

122. D.T. Elmore, J . Chem. S o c , 3489 (1958) .

123. I . Suzuki , B u l l . Chem. S o c Japan, 35 , 1286, 1456 (1962) .

124. K. Nakamoto, ' • Infrared S p e c t r a of I n o r g a n i c and Coordinat ion Compounds'*, John Wiley & Sons, I n c . , New York, 103, 106 (1963) .

125. K. Nakamoto, " I n f r a r e d Spec t r a of Ino rgan ic and Coordinat ion Confounds", John Tfiley & Sons, I n c . , New York, 118 (1963) .

126. T.L. Brown and M. Kubota, J . Am. Chem, S o c , 8 3 , 4175 ( l 9 6 l ) .

127. I . R . S e a t t l e and M. Webster , J . Chem. S o c , 3672 (1965) .

128. R.C. Aggarwal and P . P . Singh, J . I n o r g . Nucl . Chem., ^ , 1651 (1966) ,

129. I . R . S e a t t l e , G.P. McQuillan, L. Rule and M. Webster, J . Chem. S o c , 1514 (1963) .

130. I . R . S e a t t l e , G. Gibson, M. Webster and G.P. McQuillan, J . Chem. S o c , 238 (1964) .

5>d

1 3 1 . I . a . S e a t t l e , M. M i l n e , M. Webster , H.E. B l a y d e n , P . J . J o n e s , R.C.G. K l l l e a n and J . L . Lawrence, J . Chem* S o c . ( A ) , 482 ( 1 9 6 9 ) .

132 . I . H . S e a t t l e , T.R. G l l s o n and G.A. Ozlm, J . Chem. S O C . ( A ) , 2772 ( 1 9 6 8 ) .

1 3 3 . I . R . S e a t t l e , R. Ilulme and L. R u l e , J . Chem. S o c . , 1581(1965)

134 . I . Douek, M.J. P r a z e r , 3 . G o f f e r , M. G o l d s t e i n , B. Rimmer and H.A. W i l l i s , Spec troch lm. Acta , 23At 373 ( l 9 6 7 ) .

1 3 5 . T. Tanaka, Y. Matsumura, R. Okawara, Y. Musya and S, Kinumaki, B u l l . Chem. S o c . Japan, 4 1 , 1497 ( 1 9 6 8 ) .

136 . J . P . Clark, V.M, Langford and C.J . W l l k i n s , J . Chem. S O C . ( A ) , 792 ( 1 9 6 7 ) .

137 . I . R . S e a t t l e , M. Webster and G.W. Chantry, J . Chem. . S o c , 6172 ( 1 9 6 4 ) .

138 . N.N. Greenwood, B . F . Staughan and A.B. W i l s o n , J . Chem. S o e ( A ) , 2209 ( 1 9 6 8 ) ,

139 . A.D. A l l e n , P . B o t t o m l e y , R.O. H a r r i s , V . F , R e i n s a l u and C.V. Senof f , J . Amer. Chem. S o c , 8 9 , 5595 ( 1 9 6 7 ) ,

140 . D.P. Anes and P.G. S e a r s , J . P h y s . Chem., 5 9 , 16 ( l 9 6 5 ) .

1 4 1 . CM. H a r r i s and A.D. Meckenz ie , J . Chem. S O C . ( A ) , 746 ( l 9 6 9 ) .

1 4 2 . N. Katsaros and J.W. George, J* I n o r g . N u c l . Chem., ^ , 3503 ( 1 9 6 9 ) ,

143 . G.J. S u t t a n , A a s t r a l i a n J , Chem., 2 0 , 1859 ( 1 9 6 7 ) .

144 . W. Rosen and D.H. Busch , I n o r g . Chem., £ , 262 ( 1 9 7 0 ) .

145 . K.W. B a g n a l l , D. Brown, P . J . Jones and J .G.H. du P r e e z , J . Chem, S O C , 3594 ( 1 9 6 5 ) .

146 . W.J. Geary, Coord. Chem. R e v . , 2» 81 ( 1 9 7 l ) ,

147 . S.K, Madan and A.M, Donohue, J , I n o r g . N u c l . Chem., 2 8 , 1303 ( 1 9 6 8 ) ,

148 . M.D. J o e s t e e n , I n o r g . Chem., 6 , 1598 ( l 9 6 7 ) .

! » ;

149 . H.A. Mackay and R.P. S c h n e i d e r , I n o r g . Chem., 6 , 549 ( 1 9 6 7 ) .

150 . K.P. Lanrest and M.D. J o e s l e n , I n o r g . Chem., 2» 2048 ( 1 9 6 8 ) ,

151 . T. B i r c h a l l and R ,J . G i l l e s p i e , Can. J . Chem., 4 1 , 2643(1963) ,

152 . S.A.A. Za id l and 2 . A . S l d d i q i , J . I n o r g . Nuc l . Chem., 3 7 , 1806 ( 1 9 7 5 ) ,

153 . G. Brauer , *Handboo!c of P r e p a r a t i v e I n o r g a n i c Chemistry", Academic P r e s s , New York, 730 , 733 , 735 ( 1 9 6 3 ) .

154 . N . a . Furman, "Standard Methods of Chemical A n a l y s i s " , Van Nostrand C o . , I n c . , New York, 1091 ( 1 9 6 2 ) .

155. C.J . Rodden, " A n a l y t i c a l Chemistry of the Maahattan P r o j e c t " , M c G r a w ^ i l l Book C o . , I n c . , 374 ( l 9 5 0 ) .

156 . R.A. Russe l l and H.W. Thonqsson, Spectroch lm. A c t a , 8 , 138 ( 1 9 5 6 ) .

157 . A.U. Mal ik , J . Ind ian Chem. S o c . , 4 5 , 163 ( l 9 6 8 ) .

158 . J . Chat t , L.A. Duncaiison and L.M. Venanz i , J . Chem. S o c . , 2712 ( 1 9 5 6 ) .

159 . A. Nakahara, Y. S a i t o and H. Kuroya, B u l l . Chem. S o c , Japan, 25 , 331 ( 1 9 5 2 ) ,

160 . A. Mohsen, M.E. Omar and S.A. Osman, Pharmazie , 2 8 . 30 ( 1 9 7 3 ) .

161 . H.B, Jonassen and W.B. K i r i s h , J . Am. Chem. S o c . , 7 9 , 1279 ( 1 9 5 7 ) .

162 . P . E . S lad and H.B. J o n a s s e n , J . Am. Chem. S o c , , 7 9 , 1277 ( 1 9 5 7 ) .

163 . H.B. Jonassen and J . E . F i e l d , J . Am. Chem. S o c , 2^» 1275 ( 1 9 5 7 ) .

164 . H.B. Jonassen and J .R. D o y l e , J . Am. Chem. S o c , 7 8 , 3965 ( 1 9 5 6 ) .

165. J . Chatt and L.A. Duacanson, J . iMn* Chem. S o c , 2939 ( 1 9 5 3 ) .

166. K. Nakamoto, "Infrared S p e c t r a of I n o r g a n i c and Coordinat ion Compounds", John Wiley & S o n s , I n c . , New York, 143 ( 1 9 6 3 ) .

b3

167. I . E . S e a t t l e and L. Rule , J . Chem. S o c , 3267 ( l 9 6 4 ) .

168. N.N. Greenwood and K. Wade, J . Chem. S o c , 1130 ( i 9 6 0 ) .

169. N.S . G i n , R.H. N u t t a l l , D.E. Soai fe and D.W.A. Sharp , J . I n o r g . Nucl . Chem., 1 8 , 79 ( l 9 6 l ) .

170. R.D. Hancoch, H.W. Socles, R. Thornton and D.A. Thornton, I n o r g . Nucl . Chem. L e t t e r s , 3 , 51 (1967) .

171 . R.C. P o l l e r , J . I n o r g . Nucl . Chem., J 4 , 593 (1962 ) .

172. R . J .H, Clark , C.S, Wi l l i ams , I n o r g . Chem,, 4 , 350 (1965) ,

173. M. Golds te in and W.D. Unsworth, I n o r g . Chim, Acta , 4 , 342 (1970) .

174. G.E. Coates and D. R id l ey , J . Chem. S o c , 166 (1964) .