\ FLUORIDE COMPLEXES OF THE PLATINUM METALS

A thesis presented for the

Degree of Doctor of Philosophy

in the

Faculty of Science

by

JOHN STOCKS

University of Leicester

September I969.

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STATEMENT

The experimental work described in this thesis has been carried out by the author, in the Department ofChemistry of the University of Leicester, between October 1966 and September I9 6 9 , under the supervision of Professor R .D.Peacock and Dr.R.D.W.Kemmitt. The work has not been, and is not concurrently being, presented for any other degree.

September I9 6 9

: • a c k n o w l e d g e m e n t s

I would like to express my sincere thanks to my

Supervisors, Professor R.D.Peacock and Dr.R.D .W ,Kemmitt,

for their help and encouragement throughout the course of

this work.

I would also like to thank; DréJ .Burgess, for

guidance and assistance in the work described in the

final chapter, the many other colleagues in this

department who have assisted me, and Miss A.R.Hayes for

typing this thesis.

The a If a r d. of a maintenance grant from the Science

Research Council is also gratefully acknowledged.

SUMMARY

The reactions of compounds containing sulphur-fluorine

bonds with tertiary phospbine complexes of the platinum

metals in low oxidation state, have been investigated. The

preparation and properties of a novel metal-pentafluoro-

sulphur complex and new chlorofluoro complexes of platinum

rhodium and iridium, are reported.

Novel metal containing sulphur-nitrogen-fluorine

complexes have been prepared, and their chemical

properties have been investigated^

The properties of new tertiary phosphine transition

metal fluoride complexes, prepared by a variety of

fluorination techniques, are also reported.

The chemical properties of low oxidation state,

transition metal complexes, that have been extensively

used in' this work, are discussed briefly in the

introduction.' ' ■

The interaction of various transition metal complexes,

with various organic acceptors and donors, has been

studied, using visible absorption and electron spin '

resonance spectroscopic methods.

CONTENTSPage

Introduction 1

Chapter 1 . ,

Part 1. The reactions of sulphur chloride

peritafluoride with some transition metal

complexes.

Introduction

Results ■ 6Discussion 12

Experimental ■ 20

Part 2. The reactions of sulphur hexafluoride with

some transition metal complexes.

Introduction 27

Results , 28Experimental , 2 9

Part 3 . The reactions of some sulphur-nitrogen-

fluorine compounds with some transition

metal complexes.

Introduction ' 31

Results and Discussion .32

Experimental • ■ : 48

Chapter 2 . The preparation and properties of tertiary

phosphine metal fluoride complexes.

Introduction 5#Part 1 . . .

S eçtion A. The reactions of platinum (II),

palladium(II), and nickel(II) complexes

with liquid hydrogen fluoride.-

Results and Discussion 62

Section B . The reactions of other complexes with

liquid hydrogen fluoride.

Results and Discussion . . 69Section C. Other attempted methods of preparation

of tertiary phosphine metal fluoride

complexes.

Results and Discussion. 71

Experimental . . 75

Part 2

Section A . The reactions of aerovalent metal tertiary

. phosphine complexes with liquid hydrogen

fluoride.Results and Discussion 84

Experimental 94

Section B. The reactions of the complex fluorotris- .

(tripbenylphosphine)platinum(II),

hydrogen diflnoride.

Results and Discussion 99

Experimental 11]

Chapter 3 . Reactions of organic acceptor and donor

compounds with transition metal complexes

Introduction 119

■Part 1 . The interaction between transition metal

dithiolene complexes and organic acceptors, .,

Results and Discussion 120

Part 2. The interaction betwepn transition metal

phosphine complexes and organic acceptors.

Results and Discussion 139

Experimental 134

References 155

INTRODUCTION

INTRODUCTION

The reactions of olefins, acetylenes, alkyl halides,

and other organic compounds with transition metal

complexes have received much attention. These studies are

important because the complexes isolated from these

reactions sometimes yield valuable information on

intermediates, which may be involved in inetal catalysed

reactions, e.g. polymerisation reactions of olefins and

acetylenes.

Many sulphur-fluorine compounds have similar

characteristics to organic compounds. Thus, trifluoro-

methyl iodide has similar chemical properties to sulphurpchloride pentafluoride, and sulphur-nitrogen-fluorine

compounds, containing double or triple bonds between

sulphur and nitrogen, show some similarities to olefins and 2acetylenes. These similarities suggest that the sulphur-

fluorine compounds might also co-ordinate to transition

metals. It is also possible that a study of these reactions

may lead to the formation of novel polymeric sulphur-*nitrogen-fluorine compounds.

Recently; new complexes have been prepared, with

which small molecules readily co-ordinate. In particular,

the tertiary phosphine complexes of the platinum metals,

readily undergo co-ordination reactions with small.10mo lecules. Thus, the d zerovalent tertiary phosphine

•1-

- 3complex## of palladium and platinum, e.g.Pt(PPh_)^, f t (PPh^Me)]|^^ and Pd(PPh_)^^ undergo both, co-ordinativedissociation reactions involving oxidation of the metal

atom, (d^^----> d^),

M(PR_) + (XY^-------->M(PR_).(X) (Y) +(n-2)PR_3 n 3 <; 3

and co-ordinative addition reactions, the formal oxidation state of the metal being unchanged.

M(PR^)^ + (XY) ----> M(PR_)2(X— $Y) 4(n-2)PR^(n= 2,3,4. M=Pt or P d , PR_= tertiary phosphine).

Examples' of co-ordinative dissociation reactions of4these complexes include XY = trifluorotnethyl iodide, and

hydrogen cyanide^ and of co-ordinative addition reactions,7 8XY=tetrafluoroethylene and hexafluorobut-2-yne. Similarly,

the neutral square planar d^ complexes of rhodium andiridium, of general formula trans M^X(CO)(R_P)g , also

undergo analagous co-ordinative dissociation reactions,involving oxidation of the metal atom, (d^^— -> d^)

trans MX(CO) (R_P)g MX(A)(B)(CO)(R_P)g

and co-ordinative addition reactions.

- 2-

trans MX(CO)(R.P)g— > MX(CO)(AB)(R_P)g(N.Rh or Ir)

Examples of co-ordinative dissociation reactions9 10 include AB = perfluoroaIky1 halides and hydrogen.

Examples of co-ordinative addition reactions include,AB = tetrafluoroethylene and acetylenes.

8Another d rhodium(l) complex, RhCl(PPh^)_, recentlyprepared, also readily undergoes similar co-ordinative

13dissociation and addition reactions.In view of the ability of these complexes to

co-ordinate small molecules, the reactions of sulphur- fluorine compounds and also hydrogen fluoride with low oxidation state tertiary phosphine metal complexes, have been studied.

^ 3^

CHAPTER 1

PART 1 .THE REACTIONS OP SULPHUR CHLORIDE PENTAPLUORIDE WITH SOME TRANSITION METAL COMPLEXES

INTRODUCTIONCompounds in which a pentafluorosulphur group is

14bonded to a variety of non-metal atoms, e.g. chlorine,15 16 17 18 bromine, nxtrogen, carbon and oxygen, have been known

for some years. However, compounds in which the pentafluorosulphur group is bonded to a metal, are not known. Compounds containing metal-pentafluorosulphur bonds could be useful intermediates in synthesis of new compounds,containing the pentafluorosulphur group, just as Grignard reagents and organo-1ithio reagents may be used in chemical synthesis.

Roberts has compared the properties of sulphur chloride pentafluoride with those of trifluoromethyl iodide. Thus, both add across double bonds of olefins,

1) P SCI + CgH^ ------ > PgS'CHg'CHg.ClR) P_CI + CgH^ ------ » CF^'CHg'CHg'I

reactions occurring readily,under the influence of ultra­violet light or, alternatively, in the case of reaction 1) in an autoclave at 90*. This similarity in propertiesis due to the presence of a positive halogen atom in the

i” /V 7- /+compounds. e.g. CP^ I ,F^S Cl.Although perfluoroaIky1-lithium and perfluoroaIky1

■"4 —

Grignard reagents exist, vigorous reactions occur between

sulphur chloride pentafluoride and organo-lithio compounds

or Grignard reagents, reducing sulphur chloride1 19pentafluoride to sulphur tetrafluoride. Massey and Packer

attempted to prepare metal-pentafluorosulphur compounds

by the reaction of pentafluorosulphur chloride, with first

row transition metal carbonyls.Reaction between sulphurchloride pentafluoride and nickel carbonyl, at room

temperature, resulted in release of carbon monoxide, but

no sulphur containing species was retained. The compound

obtained was formulated as nickel chlorofluoride and the

other main product was sulphur tetrafluoride.SF Cl •

Ni (CO), --- 2---> NiClF + 4C0 + SF.25°

Reaction between iron pentacarbonyl and excess^o 'sulphur chloride pentafluoride at -23 caused steady

evolution of carbon monoxide. However, on warming to

room temperature, a vigorous reaction took place in

which all carbonyl groups of the iron pentacarbonyl were

evolved as carbon monoxide,and the remaining volatile

material contained carbonyl fluoride, chloride, chloride

fluoride and sulphide. The final residue contained only

ferric fluoride and ferric chloride.

Reaction between excess iron pentacarbonyl and

sulphur chloride pentafluoride gave a compound containing

terminal carbonyl groups, but no sulphur-fluorine bonds.

In both cases V(excess of either reagent), if the reaction

was stopped after five minutes^ at room temperature, an

infrared spectrum of the solid product showed the presence

of bridging carbonyl groups. The reaction of sulphur

chloride pentafluoride(or sulphur tetrafluoride) with

this compound gave rise to the carbonyl halides noted

amongst the products. ^

Trifluoromethyl iodide has been shown^to react with 10the d zerovalent tertiary phosphine complexes of

palladium and platinum'in a typical co-ordinative

dissociation reaction.

Pt(Ph_P)^ -f- CF^I Pt(CF^)l(PlyP)g 2Ph^P

■ Collman et al.^ have also shown that trifluoromethyl' ' 8 iodide also reacts with the d neutral square planar

complex trans chlorocarbonylbis(dipheriylmethylphosphine),

iridium(I) in a typical oxidative-addition reaction

IrCl(CO)(PhgMeP)g + CF I — >IrClI(GE^)(CO)(Ph^MeP)^

/It was hoped, therefore, to synthesise complexes

containing metal-pentafluorosulphur bonds by reaction

between sulphur chloride pentafluoride and suitable rhodium,

iridium and platinum complexes.

RESULTS

PLATINUM COMPLEXES

Reaction between trans stilbene bis(triphenylphosphine)

platinum(O) in benzene, in a sealed tube at 70 , with

excess sulphur chloride pentafluoride, gave a good yield of

cis chloropentafiuorosulphurbis(triphenylphospbine)20platinum(II)(A) as a benzene insoluble,orange solid.

: ' , , : ' '^6^ 1 ''

This complex shows characteristic sulphur-fluorine

stretching modes in it's infrared spectrum, in particular

a strong hand at 891cm,is characteristic of a pentafluoro- sulphur group.

The complex,(A), cis PtCl(SF^)(Ph^P)^ may also'be

prepared by reaction of excess.SF^Cl with diphenylacetyl-

enebis(triphenylphosphine)platinum(0 ) or tetrakis(triphenyl

phosphine)platinum(0). Triphenylphosphine displaced from

the reaction between Pt(Ph^P)^ and SF^Cl reacts further

with SF^Cl to give difluorotriphenylphosphorane Ph^PFg,

The complex,(a ), cis PtCl(SF^)(Ph^P)p is an orange

solid stable in dry air^ and insoluble in benzene, ether

and alcohols. It dissolves readily, however, in

dichloromethane and acetone, to give a yellow solution,

from which yellow crystals of dichlorodifluorobis(tri-

X)henylphospbine )platinumCCV) (B) may be isolated. The far-

infrared spectrurn(400-200cm ^ ) of this complex(B) shows

two strong bands. ,

The ready decomposition of cis PtCl(SF^)(Ph^P)2 ,in these solvents,precludes ^^F nuclear magnetic resonance

studies or molecular weight determination the complex

being formulated as a monomer.

The reaction of some trans hydridochlorobis(lertiary-

pbosphine) platinum(II) complexes with SF^Cl has also been

investigated.

Trans Hydridochiorohis(triphenylphosphine)platinum(II)

reacted at 40°, with excess SF^Cl to give a pale yellow

solid, containing no sulphur, and exhibiting^ no bands,in

the infrared spectrum, attributable to sulphur-fluorine

stretching modes. This complex was identified as,

dichlorodifluorobis(triphenylphosphine)platinum(lV)(C), an

Isomer of(B), which shows only one strong band in an“1infrared spectrum,(400-200cm '). This complex has also

been obtained by reaction of tetrakis(triphenylphosphine)-

platinum(O) with 1,1,1-trifluoro 2,3,3-trichloroprop-

2-ene^^However,, trans hydridochlorobis ( trie thy Iphosph ine )

platinum(ll) did not react in the same way with excess

sulphur chloride pentafluoride. The products of this

reaction were an intractable red-brown oil, and the known 22complex trans tetrachlorobis ( trie thylphosphine ) pla tinum (IV)

All attempts to isolate the red-brown oil as a solid

proved unsuccessful. An infrared spectrum of the oil,

however, showed the absence of sulphur-fluorine bonds in

the complex.

RHODIUM COMPLEXES

Trans chlorocarbonylbis(triphenylphosphine)rhodium(I)

reacted with excess SF^Cl to give an orange solid which

contained no sulphur. The infrared spectrum of the conpilex

showed Y CO characteristic of a rhodium(ÏII)complex.

The complex was identified as dichlorofluorocarbonylbis™

(triphenylphosphine)rhodium(III),which, on recrystall­

isation from benzene, contained one mole of benzene

RhCl2P(C0 )(Ph P)gC^Hg.Trane chlorocarbonylbis ( dimethylphenyiphos|5hine )

rhodiumd ), RhCl (CO ) (PMe^Ph ) 2 reacted in a similar way to

give dichlorofluorocarbonylbis(dimethylphenylphospbine)

rhodium(III),which also exhibited vCO above 2000cm in it's

infrared spectrum, which is typical of a rhodium(lil)complex.

The reaction between chlorotris(triphenylphosphine)

rhodium(l) and SF^Cl has also been briefly studied.

The red-purple RhCl(Ph^P)^reacted with excess

SF^Cl to give an orange solid which exhibited novS-F in

it's infrared spectrum, and contained no sulphur. The

complex is probably a chloridefluoride of rhodium(III)

IRIDIUM COMPLEXES

Trans chlorocarbonylbis(triphenylphosphine)iridium(I)

reacted with excess SF^Cl to give a pale yellow solid,

• which contained no sulphur, and exhibited norS-F in it's

infrared spectrum, although the complex showedYCO, typical

of an iridium(IIl) complex. The complex was identified as

dichlorofluorocarbonylbis(trijjhenylphosphine)iridium(lll)•

SPECTRA

i)lWFRARED

The characteristic infrared absorptions of the new

complexes are shown in table 2.

- 9- ' '

The complex cis PtCl(SP_)(Ph„)_,(A), exhibits a— , .7 7 & 'strong band at 89I cm .^assigned to the pentafluorosulphur

group^^and another T S-F at780cm*"^. Other YS-F bands may

overlap with other bands, due to tertiary phosphine

ligands. The complex cis PtCl (SF „ ) (Ph„.P ) „ also exhibits

one strong band in the region ( 400~ 200cm" .) which has been

assigned toyPt-Cl, by comparison with vPt-Cl in other, , 24 -Pt(II) complexes.

In the case of the two isomers of PtCl2Fg(Ph^P)^(B),and(C), the far infrared spectra(400-200cm ^ ) give

information about the stereochemistry of the complexes.

No absorptions have been assigned to metal-fluorine

stretching modes, as these probably occur in regions

corresponding with bands due to the tertiary phosphine

ligands. • ' „

For complexes of the type MXY(PEt» )^,Goggin and25. . ..:Goodfellow have shown that, although the symmetric P-Pt-P

stretching mode is formally infrared active in both cis

and trans configurations, it is of very low intensity in

the trans case, and a distinction between them becomes

possible. .

However, in the case for complexes of triphenyl­

phosphine, a distinction is more difficult. It is not

possible to obtain* information from H nuclear magnetic

resonance, and solubilities are generally too low for 31P, nuclear magnetic resonance studies. Triphenylphosphine

■10-

itself, has a very, weak band at which makes.the•=•1interpretation of the V'Pt-P stretching region,(450-400cm )

I, t 26of the spectrum difficult. However, Pt(C_F. ) (Ph P)„,26 ^ ^

Ft(CpCl^)(Ph^P)2 , and cis PtCl^(Ph^P)^ , all of which have

the cis configuration, show two absorptions in this region,27 _ 26

whereas, a), PtC l( CF = CF ) ( Ph^P ) 2 , b ) , PtCl (C.^Cl ) ( Ph^P ) 2 ,and c), jptCl(CO)(Ph^P)gj^ ion^ all show one absorption, and

the triethylphosphine analogues of a), and c), have been

shown to have the trans configuration. In the case of

PtCI(SF_)(Ph„P)„, two bands have been assigned to 7 7platinum-phosphorus stretching frequencies, suggesting

that the complex has a cis configuration.

The far infrared spectra of the complexes

MClgF(CO)(R^P)2 also gave information upon the stereo­chemistry of addition to the square planar d^ complexes

trans MCI(CO )(Ph^P)2 i(see discussion). Once again, no

metal-fluorine stretching modes could be assigned, because

the bands due to the tertiary phosphine ligands obscure

this region.

ii ) NUCLEAR MAGNETIC RESONANCE

The ready decomposition of c is PtCl(SF^)(Ph^P)2 in 19solution, meant that no F n. rn.r.spectra could be

obtained. The fact that complexes containing triphenyl­

phosphine are not very soluble,meant that in many cases no19 • . ' 'F n.m.r.spectra could be obtained. Also, in m_any complexes

the percentage of fluorine was low, contributing to the19difficulty in obtaining F n .m .r .da ta(results in Expt'l)

- 11-

DISCUSSION

The complex cis PtCl(SF^)(Ph^P)2 is prepared by atypical cp-ordinative dissociation reaction,(see -1.Introduction) in which the co-ordinating molecule SF^Cl

displaces triphenylphosphine(two moles.), trans stilbene

(one mole.), and diphenylacetylene(one mole.) from the

complexes Pt(PPh^)^, P t (t-CgHgPhg)(PPh^ 2'Pt(PhC„Ph)(PPh„)„, respectively.

28It has been recently shown for the complex .

bis(triphenylphosphine)(ethylene)platinum(O), in benzene

solution, that the reactive intermediate,in certain

substitution reactions, is the bis(triphenylphosphine)-

platinum(O) species. In benzene solutibn the complex

Pt(Ph^P)2(C2H^) is extensively dissociated,

- H -Pt (Ph^P) 2 (C2H^ ) Pt(Ph^P.)2 CgH^ (rapid equilibrium)

and reaction of the Pt(Ph^P)2 species with molecule X, gives rise, to the products.

K i .

e.g. Pt(Ph_P)g+ CH^I --^ ^ Ptl(CH^) (Ph^P)2 '

A similar mechanism may be postulated for reaction of

trans stilbenebis(triphenylphosphine)platinum(0 ) with sulphur chloride pentafluoride.

Similarly, the complex tetrakis(triphenylphosphine)28 ' 'platinum(O), in benzene solution, has been shown to be

extensively dissociated into tris(triphenylphosphine)~

platinum(0 ).

Pt(PPh^)^ Pt(.PPh-)^ 4- PPhg

The co-ordinatively unsaturated species Pt(PPh^)^has

been shown to be the reactive intermediate in certain

substitution and oxidative addition reactions» Presumably

the reaction of sulphur chloride pentafluoride with

tetrakis(triphenylphosphine)piatinum(0 ), in benzene

solution, goes via this intermediate.29

Allen and Cook have shown that substitution reactions

of complexes of type Pt(Ph^P)^ (acetylene),in cyclohexane,

involve formation of the relatively stable intermediate

bis(triphenylphosphine)pi atinum(0 ) ,

. . . . ^1 .Pt (Ph^P ) g( acetylene ^--- — Pt(PPh^)g 4- acetylene,

Probably reaction of sulphur chloride pentafluoride with bis(triphenylphosphine)(diphenylacetylene)platinum-(0) also goes via the bis(triphenylphosphine)platinum(0) intermediate.

The complex, cis PtCl(SF^)(Ph^P)2 » although stable in the solid in dry air, decomposes readily in

; - - 1 3 - \

methylene chloride solution. This decomposition in

solution is unusual, and suggests that another species

may be present, which has not yet been isolated, the

yields of PtCl^Fp(Ph^P)2 s(B), being low in this reaction.

The far infrared spectrum of (B), shows two strong bands

in the region(400-200cm ^ ), and suggests that there is a

cis arrangement of the chloride ligands in the coinplex.

By reaction of SF^Cl with trans PtHCl(Ph^P)^, an

isomer,(C), of (B), is obtained, which has only one strong

band in the region,(400-200cm ^ ), suggesting a trans

arrangement of chloride ligands. This complex has also

been prepared by reaction of 1 ,1 ,1-trifluoro—2 ,3,32 %

t±ich.loroprop-2-ene , and Pt(Ph^P)^. A complex

chlorofluorobis(triethylphosphine)platinum(ll) has30previously been isolated by Clark and Tsang, in low

yield, from the reaction of trans hydridochlorobis-

triethylphosphine)platinum(II) with trifluoroethylene.

trans PtHCl(PEt )^ + CF^ = CFH ----- ftrans PtClF(PEt^)2

Metal-fluorine bonds are presumably formed by

cleavage of carbon~fluorine bonds, and, in the formation

of PtClgF^tPh^P)^ from cis PtCl(SF_)(Ph^P)^, in methylene chloride, cleavage of sulphui— fluorine bonds, and

formation of pla tinum-fluorine bonds, presumably occurs.

14-

In the reaction between trans bydridoch1erobis~(triethylphoAphine)platinnm(II) and SF_C1, premumablycomplexes of the type PtClgF2 (PEt_)g, are formed, and,upon further reaction, trans PtCl^(PEt^)g, and a fluorinecontaining platinum complex are formed.

Reactions between SF_C1 and the neutral d® squareplanar complexes of type trans MCl(CO)Pg (where F =tertiary phosphine) give complexes ofgeneral formulaM ™ C l g P ( C O ) P g (M.Rh or Ir,P-tertiary phosphine)

Thus, in these reactions, SF^Cl behaves as achlorofluorinating agent.This should be compared with

17the reaction of SF^Cl with cyclohexene, when 1-chloro- 2-fluorocyclohexane is obtained as one of the products.

X \ ». SF3Ç 1 I SF4

It seems possible that metal-pentafluorosulphur bonds are formed in these cases, and that the complexes,M Clg(SF^)(CO)Pg, disproportionate, giving M ClgFtCO)?^,

and SF^.All complexes of the type M^igF(CO)Pg show the

increased frequency of vCO on going from the starting material trans M^Cl(CO)Pg. This increase is due to the smaller back donation of electrons from the complex,onto the carbon monoxide, due to the increased positive charge, thus increasing the CO bond order, and increasing the stretching frequency of the carbon-oxygen double bond,

- 15-

The complex irC 1 gP.(CO)(Ph P)p shows one strong band

at 330cm~‘ in the region(400-200cm ), which has been

assigned to a metal-chlorine mode. This implies a transarrangement of chloride ligands within the complex. The

addition of CIF to the complex could take place either

cis or trans. Assuming that the trans configuration of

the tertiary phosphin.es is retained during the addition,

then there are only two possible configurations(I ) and

(II) for the octahedral complex formed on addition of

CIF to trans IrCl(CO)(Ph^P)2 (see diagram). The assumption

that the phosphines retain their trans configuration, has30a 31been made by Bennett et al. and Vaska, who have pointed

out that a cis configuration of phosphines requires a

substantial rearrangement of the ligands. Also, in all

except one, of the established structures of adducts of

trans IrX(C O )(Ph^P)p (X=Cl,Br,l), the tertiary phosphines

have been found trans to one another. The exception, the

complex, hromocarbonyltetracyanoethylenebis(triphenyl-: '' ' 32phosphine)iridium(I), may be regarded as an unusual case,

53however. Baddley has suggested that, although the trans

configuration would appear sterically preferable, the

strong X-acidity of tetracyanoethylene forces the cis

configuration. Otherwise, with tetracyanoethylene, and

carbon monoxide, trans to one another, there would be

a competition between these two strong X-acids for

electron density.

—16 —

Obviously, configuration(I) can result from eithercis or trans addition of CIF. The configurâtion(II), however, can only result from a cis addition of CIF.As the far infrared spectrum 6f the complex Ir^Cl ^ F ( C O )- (Ph_P)g shows only one fIr-Cl , this implies a trans arrangement of chloride ligands, and suggests that the complex has configuration(II). Thus the reaction of the SF^Cl with trans IrCl(CO)(Ph^P)2 , involves cis addition of CIF to the d^ complex. Similarly, for the complex RhClgF(CO)(Ph_P)p, the structure(II) (M=Rh) has been assigned, on the basis of the far infrared spectrum, which also shows only one strong band in the region, (400-200cm"l).

However, in the case of the complex trans RhCl(CO)(PMSgPh)2 » the far infrared spectrum shows two

bands, and addition of CIF may have occurred, via cis or trans attack. The proton nuclear magnetic resonance of this complex has also been of little assistance in determination of the configuration of the complex. A complex pattern was obtained , which may be due to anoverlapping triplet and doublet,suggesting a mixture of

P Clcis and trans isomers.Confjg. CII

+SF_C1

COCIS addition of

CIF

ClCl

nrstereo chem. of f » d 4nof _clPL.to trans MC1(C0)P.,

ClL

COCIS ,or TRANS

addition of CIF

- 17 -

fȈct-S)jqm

Mc\

a"3"oMOO

n TON *03 3-ON WfO

M0f1roOnO

M•vlNOà

SOr-IM\0O

co

N)M

%. y

M-viVIIM00O

%"OyVI.MMMMINNVI O

H Æ- f ON ON VI VI VI VI VI NJl 4P 4P "9 OM VI H M tO VI VI 4P to to to 00 NO 0 *cVI O -Ni VI H to VI H 03 H 4P O 3 O? ON-Ni -0 to VI f ND NO to NO NO H a as f .f VI VI VI VI 4P VI VI VI o3 0 *a VI f VI -Ni -o ON ON ON M ON VI 4- cMro

o esM M

4?- M o ro VI VI VI VI NO VI 3O. Oa.0- 00 00 00 00 00 00 00 00 4P "9 oO 0 000 VI M to VI 4 VI 4P VI VI VI O C i-iO ON o 03 4P O -Ni ON NO ON lO

H M

3a.-*3

maoVI VI to to to 4P 4P 4P 4P O o 0 *

03 00 - cVI VI to ■Ni VI ON VI -4 -Ni 3 OVI to o VI 00 to NO ON NO H Ni O.q

anH H N ■Ni -Ni ■Ni ■Ni -Ni o »M tO GVI 4P 4P 4P too 3 nVI »P-to ON o to 03 00 NO to

N4 VI

Q."qo

ao*1 1 1 1 1 1 1 1 1 1 4P ON 4P VI

G3Q.s->Oa

%

18-

TABLE 2 Character 1stic^Infrared absorptions, (cw** ) of new complexes,

COMPLEX vM^Çl ÇO < S-F Others

A 315s - 685VS,780s. 423m,

316s,293s. - - ^ P t - P N.A.

342s - - yPt-P N.A.

331s 2057VS - ^Pt-P 439m,

343s 2046vs - V Pt-P 437m.

324m,305m 208IVS - vPt-P N.A.

m=medium s=strông sh=shoulder br=broad vs=verystrong

N.A." not assigned w=weakA=cis PtCl(SF_)(PPh,)2 BaPtClgFglPPh^)^

C=PtCl2Fg(PPh )g D=IrClgF(C0)(PPh^)2

R=PhClgF(C0)(PPh_)2.CgHg F=RhCl2F(C0)(PPhMe2)p

e = absorption bands due tô co-ordinated phosphine ligandsomitted.

- 19-

EXPERIMENTAL '

Analytical data for new compounds is presented in

Table 1-. Analytical data for known or unidentified

complexes are shown in this section. Melting points are

also shown in Table I. Melting points are uncorrected,

and were recorded on a Reichart hot-stage apparatus.TI nuclear magnetic resonance spectra were recorded on

a Varian Associates A60 spectrometer, at bOMc/s.

nuclear magnetic resonance spectra were recorded on

a Varian Associates DA60 spectrometer, at 56.4 Mc/s. The

nuclear magnetic resonance spectra results obtained, are

shown for the relevant complexes in this section.

Infrared spectra were recorded from Nujol mulls, on a

Perkin-Elmer 225 spectrophotometer, using KBr(3700~400cm ^ )

and polythene (400-200cm ^ ) windows, and the results are

shown in Table 2 .

AnalaR benzene, and AnalaR diethyl ether, were

dried over sodium wire, before use. Other solvents used

were of reagent grade, except where stated. All solvents

used in reactions were saturated with nitrogen before use.

Triphenylphosphine was obtained from Albright and

Wilson Ltd, and recrystallised from ethanol before use.

Platinum, rhodium, and iridium salts were obtained , on

loan, from Johnson Matthey Ltd.

Sulphur chloride pentafluoride/was generously given by

■ 20”

Dr. H.L.Roberts, Mond Division,Imperial Chemical IndustriesLtd., Heath Laboratory, Runcorn, Cheshire.

3 34> The complexes, Pt(PRh_)^, Pt(PPh^)„trans(PhHC=CHPh ) ,2 9 3 5 13Pt(PPh ) (PhCHCPh), trans IrCl(CO)(Ph„P) ,RhCl(Ph P ) ,

36 ^ ' 36trans RhCl(CO)(Ph„P)2 , trans RhCl(CO)(PhMe P )g , trans 37 38PtHCl(Ph„P)g , and trans PtHCl(PEt^)^ , were prepared by

literature methods.

1. Reaction of sulphur chloride pentafluoride with;

a) Trans-stilbenebis(triphenylphosphine)platinum(0);

0«90g. of the complex, in benzene,(25mls.), was

introduced into a thick glass walled tube. Excess sulphur

chloride pentafluoride was introduced, and the tube sealed

in vacuo. The tube was heated to 70° for twelve hours. The

yellow solution became orange, and an orange precipitate

was formed. The tube was.opened, and the orange solid was

filtered off, washed with more benzene, and diethyl ether,

to give cis PtCl(SF^)(PPh^)^ ,(A ),as an orange solid.

(0 723.87#).b ) Tetrakis ( triphenylphosphine )platin.um(0 ) ;

.1 « 30g., in benzene, (15mls.), was introduced into a

thick glass walled tube. Excess sulphur chloride penta-

fluoride was introduced, and the tube sealed in vacuo.

The tube was heated to 60° for two days. The yellow

solution became orange, and an orange precipitate if as

21

formed. The tube was opened, and the orange solid was

filtered off, washed with more benzene, and diethyl ether,

to give slightly impure cis PtClSF^(Ph^P)^, as an orange

solid. (0'8 5 g • 8 7 # ) .

c ) - Diphenylacetylenebis ( triphenylphosphine ) plat inuin( 0 ) ;

Using the same method as in b), the complex (0 .50g .), in 15mls. benzene, gave cis PtClSF^(Ph^P)^ (0.30g.63#)»

2. Reaction between cis P t C l (SF^)(Ph^P )^ , and m e thylenechloride or acetone

Cis PtCl(SF^)(Ph^P)p(0.8g .), was dissolved in

methylene chloride,(40mls.), to give a pale orange

solution. The s.olution was evaporated to half volume, and

methanol was added. The solution was then evaporated to

small volume.(approx.lOmls.), and allowed to cool, giving

pale yellow crystals of dichlorodifluorobis(triphenyl­

phosphine )platinum(IV),B,(0.32g.40 %),

A similar procedure-, using A,R. acetone, also gave the

product. The complex is soluble in benzene, acetone, and

methylene chloride, and insoluble in diethyl ether,

alcohols, and petroleum spirit.

3. Reaction between trans hydridochlorobis(triphenyl-

phosphine)platinum(II), and SF^C]

Trans PtHCl (Ph^P) , (0.68g.), was dissolved in

benzene(13mls.), and heated at 40 , with excess SF^Cl, in

a sealed tube for twenty four hours. The colourless

solution turned pale yellow, and a pale yellow solid ,-22-

precipitated out. The pale yellow solid was recrystallised

from hot benzene, giving pale yellow crystals of

Dichlorodifluorobis(triphenylphosphine)platinurn(IV),C,

(0 , 62g .84 #) .4. Reaction between trans hydridochlorobis (triethylphosphine )

platinum(Il) and SF^C l .

Trans PtHCl(PEt^)p , (0„50g.), in .benzene(lOmls,) ,0was heated, at 40 , with, excess SF^Cl, in a sealed tube,

for twenty four hours. After a few hours, the colourless

solution had turned yellow, and a red oil had formed. The

tube was opened, and the red-brown oily solid was filtered

off, All attempts to isolate this product,as a solid,

failed. The yellow benzene filtrate was evaporated to

smaller volume, when golden-yellow crystals of the known

complex, trans tetrachlorobis(triethylphosphine)platinum(IV)

(0 .2g.32%), identified by melting point, infrared spectrum

and analysis, were obtained.^.p . 154-156 . Lit.152-153 •

(Found: 0,24.86; H,5"22; 01,24*67. C^gH^gCl^PgPt, requires

0,25* 14; LI, 5 • 28 ; Cl, 24 • ?4%) .5. Reaction between trans IrCl(CO)(Ph„P)„ and SF_C1

Trans chlorocarbonyIbis(triphenylphosphine)iridium(I )

(l.Og.), in benzene, was heated, at 75 , with excess

SF^Cl in a sealed tube for twenty four hours. The yellow

solution became paler, and a pale yellow precipitate

formed, after several hours. The tube was opened, the

precipitate(0 ,87s .), was filtered off and washed with

diethyl ether. The complex was.recrystallised from hot

-23-

benzene, and pale yellow crystals of IrCl^F(CO)(Ph^P)2 (configoII),D , were obtained. The complex is soluble in

acetone, and benzene, but insoluble in diethyl ether, and-> . . .

alcohols.

6 . Reaction betif een _t.r.a_ns_RhCl (CO ) (Ph P) and SF^C l .

Trans Chlorocarbonylbis(triphenylphosphine)rhodium(I )

(0,6go), in 15mls. benzene, was heated to 50 , with

excess of sulphur chloride pentafluoride, in a sealed

tube, for six hours. After two hours, the solution had

turned orange, and a bright orange precipitate had formed.

The tube was opened, and the complex(0.4lg.) was filtered

off, and washed with diethyl ether. The complex,(0.4lg.),

was obtained pure, by chromatography, using a Florsil-

packed column. The crude complex, in 40% benzene,-60%

petroleum spirit(40-60 ), was added to the column, and

the yellow-orange band formed.was eluted with 80% benzene, -20% petroleum spirit(40-60 ). Pale orange crystals of

the complex, containing one mole of soIvent,RhCl^F(G O )-

(Ph^P)gC^H^, E, were obtained. The complex is soluble in

acetone, and benzene, but insoluble in diethyl ether, and

alcohols.

7. Reaction between trans RhCl (CO ) (PMe^Ph ) and SF^Cl.

Trans Rh C 1(CO)(PMe gPh)^ , (0 ° 50 g .) , in benzene, (lOmls)

was heated with excess of sulphur chloride pentafluoride

for two days, in a sealed tube. The yellow solution had

turned orange after several hours. The tube was opened,

and the orange solution evaporated down to half volume,

“24 —

and methanol /ifas added. On further evaporation, orange

crystals of RhClgF(CO)(PMe^Ph)^ , F , were obtained.(0•23g.

4l%). The complex is very soluble in benzene and acetone,

and moderately soluble in alcohols.19The F nuclear magnetic resonance spectrum of the

complex showed one signal at + 5613 c.p.s., relative to

benzotrifluoride.

The .n.m.r. showed a broad signal, centred at T

2°35, due to the phenyl absorption of the phosphine, and

a complex signal centred' at "C8 «15, relative to TMS, whichcould be due to an overlapping triplet and doublet.

8. Reaction of RhCl(PPh..)„ with SF^Cl ^—RbCl (PPh,^ ) „ , ( 1 <: Og . ) , and excess SF^Cl, were heated

together in a sealed tube at 40° for twenty four hours,

and the deep red solution turned orange. The complex,

(0«6g.), was filtered off and recrystallised from acetone.

Elemental analyses gave an approximate C1:F ratio of 2:1.

(Pound: C,51-30; H, 3'74; Cl,14-72; F,3'82%)

The infrared spectrum of the complex in the region,

(400-200cm~^) showed two bands at 339cm ^(ms) and 303cm ^ ,

(ms). '

.9 . Reaction between Triphenylphosphine and SF^Cl

Triphenylphosphine(0 ° 6g.) in benzene,(20mls.) , was,

heated to 80° with excess SF^Cl in a sealed tube.

The colourless solution had become pale yellow after

several hours.. Evaporation of the solution under reduced

pressure gave a white crysta 1 1 n ne soi ,i d , ( 0 • g . ) , i d(?nt i f i ed

- 25-

' 39as difluorotriphenylphosphorane by infrared spectrum and

melting point. , ,

M.p. 135-140°. Lit. I36pl40°.

26-

PART 2.REACTIONS OP SULPHUR HEXAPLUORIDE WITH SOME TRANSITION METAL COMPLEXES

INTRODUCTIONSulphur hexafluoride, SFg, is chemically rather inert,

thus it is unaffected by aqueous or fused alkali, ammonia,1 hoor oxygen,and alkali metals only react at high temperatures

Roberts^has shown that this lack of chemical reactivity must be explained in terras of a kinetic effect, rather than a thermodynamic effect, since the sulphur-fluorine bond energy in sulphur hexafluoride differs little from that in sulphur tetrafluoride. Thus the free energy of hydrolysis of sulphur hexafluoride is favourable.

="6 * 3"2°(s) ------

A G * = -48 k.cal.mole ^

The octahedral symmetry of sulphur hexafluoridemeans that ordinary nucleophilic reagents cannot ^co-ordinate to form a S^2 type transition state, whereas,with the co-ordinatively unsaturated sulphur tetrafluoride,attack may readily occur. This argument is supported bythe fact that isotopic fluorine exchange occurs readily in

41the case of sulphur tetrafluoride, but not sulphur-42 1hexafluoride. Roberts has also pointed out

- 27-

that the reluctance of combined fluorine atome to Interact with nucleophiles is also of importance,since, in the caseof sulphur chloride pentafluoride, where one fluorine atom has been replaced by a chlorine atom, hydrolysis by OH is rapid, and, in the case of sulphur bromide penta­fluoride, hydrolysis occurs, even in acidic media. Sulphurhexafluoride, however, does react with certain

43electrophiles, e.g. aluminium trichloride,

Sfë» AICI3- -a S g — >. AIF3 . Clg . SgClg

the remaining volatile material containing no compound with a sulphur-fluorine bond. Reaction also occurs between SFg and sulphur trioxide

In many ways SFg behaves like carbon tetrafluoride and other saturated fluorocarbons,with respect to chemical reactivity.

It was hoped, however, that with certain transition metal complexes, sulphur-fluorine bonds might be broken and new complexes formed.RESULTS

Sulphur hexafluoride did not react with trans chlorocarbonylbis(triphenylphosphine)iridium(I ), in benzene, at temperatures up to 100**, the unchanged

- 28-

starting materials being obtained even after ten days.Sulphur hexafluoride and trans hydridochlorobis-

( triphenylphosphine)platinuin(lI ) similarly failed to0react at temperatures up to 100 , and the unchanged

starting materials were obtained even after ten days.

Infrared spectra of the products confirmed in each

case that.no reaction had occured,

DISCUSSION ■

The failure of SFg to react with the transition

metal complexes was not surprising, in view of it's

general chemical properties-. Possibly reaction with

certain electrophilic transition metal complexes might

prove more successful.

EXPERIMENTALa) SF^+ trans PtHCl(Ph^P)g

Trans PtHCl(Ph^P)g(l.Og.) in benzene (20 mis.), and

excess SF^, were sealed in a thick glass tube, No colour

change in the colourless solution was apparent at room

temperature, and the tube was heated to 100° for ten days,

when the colourless solution turned slightly pale yellow.

The tube was opened, and the solution was evaporated to

dryness under reduced pressure. Recrystallisation of this crude solid yielded colourless crystals of a solid

-29

identified by melting point and infrared spectrum as

trans PtHCl(Ph^P)p . The pale yellow colouration is

probably due to slight decomposition of the

trans PtHCl (Ph^P)^ at 100°.

M.p, 209°. Lit. 210°.

b) SFg + trans IrCl(CO)(Ph^P)p

Trans IrCl(CO)(Ph^P)^ (0°6g.), and excess SF^, were

heated at 100°, in a sealed tube for ten- days, in benzene,

(SOmls.-), No apparent colour change occurred in the yellow

solution. On allowing the tube to cool, large yellow

crystals were formed. The tube was opened, and the crystals

filtered off. The yellow crystals were identified by

melting point and infrared spectrum as transIrCl(CO)(Ph^P)„ By evaporating down the yellow benzene solution from this

reaction, a further amount of trans IrC1(C O )(Ph^P)2 was obtained.

M.p. }300°. Lit. 323°.

.30.

PART 3 .THE REACTIONS OF SOME SULPHUR-NITR06EN--FLU0RJNE COMPOUNDS

WITH TRANSITION-METAL COMPLEXES-

INTRODUCTION44,45,2

A wide range of new sulphuf-nitrogen-fluorine ■

compounds have been synthesised in recent years.

Compounds with sulphur in oxidation state + 2,-{- 4, and

4- 6, have been prepared. However, until recently, no

metal containing sulphur-nitrogen-fluorine compound was46,47known. Clemser et al. have recently prepared mercury

di-iminosulphur difluoride, HgfNSFg)^ and shown that

it is a useful intermediate in the preparation of new

sulphur-nitrogen-halogen compounds. Little attention has

been paid to the reactions of these compounds with i ra

transition-metal complexes, which could yield complexes

having interesting structural properties.The compounds

formed between sulphur-nitrogen-fluorine compounds and

transition metal complexes,might also prove useful

intermediates,in the preparation of new sulphur-nitrogen

compounds.

This section describes the reactions of some sulphur-

nitrogen-f luorine compounds in oxidation state 4-4 and -h6

with transition metal complexes of palladium, platinum,

rhodium, and iridium.

-31- .

RESULTS AND DISCUSSIONa ) REACTIONS OP THIAZYL TRIFLUORIDE NSP___

Thiazyl trifluoride, NSF^, is a derivative of sulphur hexafluoride in which the three fluorine atoms are replaced by a nitrogen atom. The P-S-F angle is only approximately 4°greater, and the S-F distance about O.OIA shorter in thiazyl trifluoride than in sulphur- hexafluoride , and the three fluorine atoms in NSF^ are

45in a configuration not too different from an octahedron.The chemical properties of NSF_ also suggest it isreasonable to compare it with sulphur hexafluoride, asit is stable in glass vessels at up to 200°, only reactswith sodium at 400°and is unattacked by dilute acids.^

48However, boron trifluoride has been shown to react with thiazyl trifluoride to form a 1:1 complex NSF^. BF^» The complex is believed to have structure a) in the liquid state, and structure b) in the solid state.

F_SN ----------> BP^ (N S F g )* (B P ^ )"

a) ' b)

Two moles, of hydrogen fluoride may be added across the sulphur-nitrogen triple bond in NSF, to give

49pentafluorosulphanyliminosulphur difluoride.

46 ^ HgONSF, ♦ 2HF s Ô» FgSNHg NS?;

One fluorine atom in NSF^ may also be replaced by reaction of NSP_ with diethylamine, phenol or

513-pyrroline.

NSPg + ^ N =S P g - N (C g H ^ )g

NSP_ + C,H_OH > N = S F g -0 -C g H g

NSP_ + H N C .H , ^ ^ 4 ^ 6

These reactions suggest that thiazyl trifluoride could react with transition metal complexes in severalways.

& ? & FM <— III M-N.SF Mf- I M(NSP_)SPg 2 3 n

i ) ii) iii) iv) v)

In i) NSP_ is co-ordinated to a metal atom, via theX bond of the sulphur-nitrogen triple bond, in a similar

52way to the reactions of carbon disulphide,hexafluoro-but -2-yne and perfluorothioacetone with tetrakis(triphenyl­

phosphine )platinum( 0 ) , to form the complexes shown over-, leaf.

- 35-

(PhgPigPt I (Ph^Pig ft. (phgPigptH

In ii), one of the fluorine atoms in NSF^ has co-ordinated to the metal, and a reaction similar to the reaction between NSF^ and diethylamine has occurred.

In iii), a typical co-ordinative dissociation reaction has occurred, with formation of meta1-fluorine and metal-iminosulpburdifluoride bonds.

In iv), thiazyl trifluoride has rearranged,at or prior to, co-ordination, to give N-fluoroiminosulphur- difluoride, a compound which has not previously been synthesised, and co-ordination to the metal atom, through the sulphur-nitrogen double bond, has occurred.

In v), polymerisation of the thiazyl trifluoride has occurred, on co-ordination to the metal. Reaction of trifluoroacetonitrile with tetrakis(triphenylphosphine)- platinum (0); has been shown, by an X-ray stud^,^ to have the structure shown below.

H .CF.=/. ^

; ' ^*3In this reaction, dimérisation of trifluoroaceto-

nitrile, has occurred, and co-ordination of the dimer to

— 3 4 —

the platinum has followed.Similarly, carbon subsulphide undergoes an

oxidative-addition reaction with trans chlorocarbonyl- bis(diphenylethylphosphine)iridium(I), with polymerisation

54of the carbon subsulphide onto the metal, to give the complex jlrCKCO ) (EtPhgPi) Also, many complexesin which a polymeric sulphur-nitrogen system is bound

55to a metal, are known. Piper has prepared such a complex frem nickel(I I )chloride and tetrasulphur tetranitride, and postulates the structure.

1

Therefore, the possibility of a complex of type v) must be considered.

The reactions of thiazyl trifluoride,NSF^, with complexes of rhodium, iridium, and platinum, have been studied.

Trans stilbenebis(triphenylphosphine)platinum(0), inbenzene, reacted with an excess of thiazyl trifluoride, to give a complex of stoichiometry, Pt(Ph_P)gNSF^, as an orange solid, stable in air. The infrared spectrum ofthe complex ( see Table 2 ) showed a bond at l44l cm“l

in the region associated with V-N=S, o r v N = S , ruling out structure iv). Although the band at l44l cm ^ is normally

- 55-

associated with r N=S , rather than V* , structure ii ) cannot be ruled out, because of the possibility of back bonding from the sulphur-nitrogen triple bond onto platinum, with consequent decrease in sulphur-nitrogenbond order, and drop in v IfeS.

19The F nuclear magnetic resonance spectrum of the complex ( see Expt * 1. ) shows two signals, eliminating structure of type i). The complex reacts readily with lithium chloride, in acetone, to give cis dichlorobis- (triphenylphosphine) platinumdl ) . This also suggests a structure of type i ) is unlikely, since, to give cis PtClg(Ph_P)g with lithium chloride, it would presumably have to rearrange to a complex containing Pt-SF^N, or Pt-NSFg bonds, before further reaction, to give cis* PtClg/PhgPlg.

From these results, no distinction may be made between the structures of type ii) and iii), e.g.

S = N .N=SF_(Ph^P) 2 or (PPh^)gPt^^

(Type ii) (Type iii)

and it would seem an X-ray study is required to determine the structure of the complex.

Trans chlorocarbonylbis(triphenylphosphine)iridium(I) in benzene, reacted with excess thiazyl trifluoride to

- 36-

give a purple solid with y'CO characteristic of an iridium (III) complex. This purple complex appears stable in the solid in air, but solutions of the complex rapidly decompose to give a brown solution, from which a dark brown solid may be obtained. The purple complex analysed approximately for the formula,IrCl(CO)(Ph^P)g- NSFj. The complex showed a band at l440cm assigned to a sulphur-nitrogen multiple bond stretching frequency, and once again the results do not distinguish between the possible structures of typeii) and iii),(ignoring otherpossible isomers).

ClPh P

ClCO

I *5

PPh_. -------- 5 F

Ii*

CO

IPPh.N=SP, .FSSN

The purple complex, chlorotris(triphenylphosphine)- rhodium(I), in benzene, reacted with excess of thiazyl trifluoride to give an orange solid, which analysed for the stoichiometry RhCl(NSF g )g (Ph_P)g . This suggests that either another rhodium(III)fluoro-complex is formed in the reaction, or displaced triphenylphosphine from the rhodium(I) complex reduces thiazyl trifluoride. The possible structures for this complex are shown overleaf•

- 17-

Cl Cl(Ph P) (Ph P) Rh/^ ' ^ ^ 2 (fh P)" % . S P g*2 ^ F

a) b) c) ^Structure c) contains sulphur, in two different

oxidation states, (IV), and(VI), and this structure isunlikely. No distinction can be made between thesestructures from the results obtained.

Trans hydridochlorobis(triphenylphosphine)platinum(II) reacted with excess thiazyl trifluoride to give a pale orange solid, which analysed approximately for the stoichiometry PtHCl(Ph_P)g. NSF_. The complex exhibited bands due to r P t - H , r P t - C l , andyS-F, together with characteristic bands due to co-ordinated triphenylphosphine, although no band could definitely be assigned to VNmS.The complex could not be recrystallised, owing to decomp­osition in solution, end the analytical data obtained on the complex suggest the presence of impurities in the crude product,which, presumably, has structure of type ii ) or type iii), similar to the other complexes of thiazyl- trifluoride.

b) REACTIONS OF N-FLUOROPORMYLIMINOSULPHURDIFLUORIDE F_S m NCOF.

56N-fluoroformyliminosulphurdifluoride is one member

- 38-

of the group of compounds containing the iminosulphur- difluoride, N=SFg, group, and some chemical properties of the compound have been previously investigated.

N-fluoroformyliminosulphurdifluoride, FgSNCOF, isreadily converted into thiazyl trifluoride, by the action

57of silver(II)difluoride.

FgSNCOF + 2AgPg ------- NSF_ + COFg + 2AgF

Reaction of FgSNCOF at room temperature, with. caesium fluorine,’^however, gives the S(IV) derivative, thiazyl fluoride.

PgSNCOF - > COFg ♦ NSF.

has suggested that this reaction occurs viaformation of the NSF- anion.

FgSNCOF + F ------- > COFg + NSFg er > NSF ♦ F

46Glemser, Mews and Roesky, have recently reported

the preparation of mercury di-iminosulphurdifluoride, Hg(NSFg)2, by reaction of FgSNCOF with mercuric fluoride.

FgSNCOF + HgFg -----» Hg(NSFg)g

An 4?X-ray study of this compound has shown it has a structure

39-

containing mercury-nitrogen bonds.The infrared spectrum of this compound shows V N»S at 1 3 1 3 cm ^ , on d y S - P at 680cm ^ , and 574cm ^ .

This compound is a useful intermediate for preparation of new suIphur-nitrogen-fluorine compounds. Thus HgtNSPg)- may be used to prepare N-chloroimino- sulphurdifluoride and N-bromoiminosulphurdifluoride.

Hg(NSPg)g + 2Clg ------> 2ClNSFg + HgClgHg(NS^Pg)g + 2Brg --- > 2BrNSFg t HgBrg

There are several possible ways that FgSNCOF could react with a transition metal,M, complex, and these are shown below in diagrammatic form.

Mf— ^^2 M tN-Ç-F Ç-F p S = = W-C-F

(A) & (B) NSFg

. & F . S%N ^@-N.SFM ^ N . S F g

(D) ° (E) (F)S.N-C-F

«{p MCSFjNCOF)^

(G) (H)

—4o—

A , B, and C, all involve bonding through the sulphur- nitrogen double bond, and, or, carbon-oxygen double bond, to the metal, M. D , _E_, _F_, and _Gj are all typical co-ordlnative-dissociâtion reactions, with cleavage of different bonds in the FGSNCOF molecule. H shows the case where polymerisation of the FgSNCOF has occurred, prior to, or at co-ordination to, the metal.

The reaction of FgSNCOF with transition metal phosphine complexes of rhodium, iridium, palladium, and platinum, has been studied. The reactions of some carbonyls of iron, ruthenium, and tungsten, have also been briefly investigated.

Tetrakis(triphenylphosphine)platinum(0), reacted with excess FgSNCOF, at room temperature, to give a red-orange solid, with stoichiometry Pt(Ph^P)gSFgNCOF, amongst other products, containing higher percentages of sulphur and nitrogen. The infrared spectrum of this complex showed bands characteristic of?CO( of a fluoroformyl groupf^Y- S-F, v-C-F, and vC-N. Therefore, structures of type B, (no>rCO), C, (noV-cO), D , ( n o v- C-N) ,E ,(no f C - N ) , F,(noy'C-F), and H, ( analysis shows only one SFgNCOF per Pt atom) may be eliminated.

The decrease of v CO in the FgSNCOF complexed to the metal, compared with thefCO in the free FgSNCOF, suggests some back bonding, from the carbonyl grouping onto the platinum, occurs, with consequent decrease in carbon-oxygen

bond order, and drop in CO.Therefore, the complex Pt (Ph_P)gPgSNCOP, has the

structure of type G or type A.

(Ph,P.Pt (Ph,P).Ptf-^^ ^ ^S"N-C-P ^ ^ N-C-P

Although no band can be definitely assigned to V N=S, the structure of type G cannot be definitely ruled out, as it may be obscured by other bands in this region, due to the co-ordinated tertiary phosphine ligands.

The complex reacts with lithium chloride in acetone, to give cis PtCl,, (Ph^P) g . As mentioned in the notes below table4 , no information upon configuration,from stretchingfrequencies of platinum-phosphorus bonds may be obtained, as in addition to bands due to co-ordinated phosphine, bands due to ^Pt-N, and f Pt-S, occur below 600cm ^. The other product from the reaction between FgSNCOF and tetrakis(triphenylphosphine)platinum(0), containing a higher percentage of sulphur and nitrogen, may be similar to the products obtained from FgSNCOF, and tetrakis(triphenylphosphine}palladium(0) and tetrakis- (diphenylmethylphosphine)platinum(0) discussed below.

Cis dichlorobis(triphenylphosphine)platinum(II) did not react with FgSNCOF at temperatures up to 50° and unchanged cis PtCl_(Ph_P)„ was obtained after several

-42-

days. This is not surprising, as the platinum-chlorine bond is very strong, and the product P t (Ph^P)gFgSNCOP, itself, reacts with lithium chloride, to give cis- PtClg(Ph_P)g.

Trans chiorocarbonyIbis(triphenylphosphine)iridium(I ) reacted,with excess FgSNCOF,to give a yellow-green solid, stable in the air, but decomposing rapidly in solution, to give a brown solid. This ready decomposition prevented recrystallisation, and determination of molecular weight. Elemental analyses corresponded to a ratio of N:S;F 4:2:3 , and percentages of sulphur and nitrogen were much higher than those required for a 1:1 complex. The complex showed Y CO at 2021 cm ^ , characteristic of an iridium(IIl) complex, and characteristic bands assigned to V C O ( of a fluoroformyl group), vS-P, r C-N, v N=S, vlr-Cl, and y C-F, in it’s infrared spectrum.

Reaction of FgSNCOF, at room temperature, with di-iron ennearcarbonyl, triruthenium dodecacarbonyl, and tungsten hexacarbonyl, gave unchanged starting materials, even after periods of up to a week. This is not altogether

surprising, as the iron and ruthenium polynuclear carbonyls ! contain strong metal-metal bonds , and tungsten- hexacarbonyl is also a very stable compound.

Trans hydridochlorobis(tripbenylphosphine)platinum(II) in benzene, at room temperature, reacted with excess FgSNCOF to give a complex, which analysed approximately

-4-3“ ■

for the stoichiometry PtHGl (.Ph^P) gFgSNCOF. Once again, the product, an orange solid, appeared stable in air, but decomposed in solution. The complex had bands in it's infrared spectrum; assigned to v" N=S , V'S-F , Y'Pt-H , "J'C-N,V" CO ( of a fluoroformyl group), V'Pt-Cl, and-fC-F, suggesting an octahedral structure, analogous to that of the complex, Pt(Ph^P)^FgSNCOF, with platinum, in an oxidation state of +4.

Chlorotris(triphenylphosphine)rhodium(I), reacted with excess FgSNCOF, to give a brown complex, having characteristic bands assigned to S-F , V" C-F , w'CO (of a fluoroformyl group), and V'C-N. However, elemental analyses showed that the complex contained high percentages of sulphur and nitrogensuggesting polymerisation of the ligand,onto the metal, had occurred,

10The reaction 6f FgSNCOF, with the zerovalent d phosphine complexes, tetrakis(triphenylphosphine)- palladium(O), and tetrakis(diphenylmethylphosphine)- platinum(O), in each case, gave a bright orange solid, containing a high percentage of sulphur and nitrogen.Once again, recrystallisation or determination of molecular weight was impossible, because of the instability of the complexes in solution. The infrared spectra of these products showed characteristic bands, assigned to Y'N=S, yC-F, (in the case of reaction of Pd (PPh^ ) ) , -y C-N , Y'CO (of a fluoroformyl group), and

. 44“

y S - F e The high percentage of sulphur and nitrogensuggested that, in these cases, and also the reaction ofFgSNCOF with trans IrCl(CO)(Ph^P)g , polymerisation of thesulphur-nitrogen compound onto the metal, had occurred.This reaction would be similar to the reaction of carbon

54subsulphide with trans IrCl(CO)(PhgEtP)g , and the reaction53of trifluoroacetonitrile with Pt(PPh^)^, where ^

polymerisation onto the metal also occurs. Clifford et al. report the formation of a light tan solid in the preparation of FgSNCOF from silicon tetraisocyanate, and sulphur tetrafluoride, at 123°. This solid also gave, on pyrolysis, volatile products, which were not identified.

46Recently, Glemser et al. have obtained 95% yield of FgSNCOF, from the same reaction, at room temperature, for a longer reaction time, and have suggested that, at the . higher temperature, polymeric sulphur-nitrogen-fluorine compounds are formed, lowering the yield. These results suggest that FgSNCOF can, under suitable conditions, polymerise, and it seems, probable polymerisation of FgSNCOF onto the metals has;occurred in these reactions.

-4 5

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.47.

EXPERIMENTAL

Section a)- Reactions of Thiazyl 'IVifluoride

Analytical and melting point data are shown in table

3, for new complexes. Analytical data for uncharacterised

complexes c\re shown in the relevant experimental section.

nuclear megnetic resonance results are reported in the

appropriate experimental section. Characteristic

absorptions in the infrared spectra, for new complexes,are

shown in table 4, and for unidentified complexes in the

relevant experimental section.

N-fInoroformyliminosulphur difluoride was prepared56by the method of Clifford and Kobayasbi, using sulphur

tetrafluoride, prepared by the method of Fawcett and

Tullock^ "silicon tetraisocyanate was purchased from

Fluka Products, Thiazyl trifluoride was prepared from

N-fluoroforinyliniinosulphur difluoride, by oxidation with57silver(II) difluoride,(prepared by direct fluorination61of silver(I)chloride)•Other reagents, solvents and

instruments etc, used, were as in the Experimental SectionV 4 X 62Chapter 1, Part 1. Pt(PPhgMe)^, cis PtClg(PPh )g, and

other transition metal complexes were yirepared by

.literature methods. All so]id products were washed with

diethyl ether after filtration,

I am indebted to Miss G, Warren for assistance in

preparation of the sulpî)ur~nitrogen-f3uorine compounds u s e d i n t li i s w o r Ic, „ g „

i) Reaction between Trans stilbenebis(triphenylphosphine)-

platinum(II) and thiazyl trifluoride.

Trans stilbenebis(triphenylphosphine)platinum(0)(1.3g)

in benzene(20mls.) was treated with excess thiazyl

trifluoride in a sealed glass tube, at room temperature, for four days. After several hours the yellow solution

had turned orange, and an orange solid had precipitated

out. After several days the tube was opened, and the

orange solid was filtered off, affording slightly impure

Pt(NSF^)(Ph^P)g,(O.95g«), which could be recrystallised

from acetone-petroleum spirit.(100-120 ). The complex

is soluble in benzene, acetone and chlorinated solvents

in which it slowly decomposes, and insoluble in19petroleum spirit, ether, and alcohols. The F n.m,r.spectrum

of the complex in acetone showed two signals at -825c.p.s and-862-5c.p .s .(relative to C^F^)(relative intensities 2:1)ii) Reaction between trans chlorocarbonylbis(triphenyl­

phosphine ) iridium ( I )' and thiazyl trifluoride.

Trans IrCl(CO)(PPh^ )2 (iOg.) in benzene(25mls.)

and excess thiazyl trifluoride, were shaken together in

a sealed glass tube for several days. After several hours

the initial yellow solution had turned a deep purple

colour. After several days the tube was opened, and a

small amount of brown benzene-insoluble material was

filtered off from the solution. The purple benzene

solution was rapidly evaporated to small volume under

.49-

reduced pressure, and a purple solid was filtered off.This complex analysed approximately for the

stoichiometry, JrCl ( CO ) (NSF^ ) ( PPh.^ ) 2 ( 0. 8g. ) . Attempts, to recrystallise this complex from chlorinated solvents and alcohols gave yellow-brown solutions, from which an unidentified brown solid could be isolated.

iii) Reaction between trans hydridochlorobis(triphenyl­

phosphine ) plat inum (II) and thiazyl trifluoride.

Trans PtHCl(PPh^)2 (0.9g»),. in benzene(20mls.) was

treated with excess thiazyl trifluoride, in a sealed

tube for five days, at room temperature. The colourless

solution had turned an orange-red after fourteen hours,

and some orange precipitate had formed. The tube was

opened and the orange solid filtered off. The benzene

solution was evaporated under reduced pressure, to give

a further amount of orange solid. The complex(0.7g.) could

be purified by addition of excess diethyl ether to an

acetone solution of the complex^ Elemental analyses

approximate to the stoichiometry PtHCl(NSF^)(PPh^ )2 >and the infrared spectrum of the complex

supports this formulation.

50.

iv) Reaction between chlorotris(triphenylphosphine)- rhodiuin(l) and thiazyl trif luoride.

The complex RhCl ( PPh^ )( 1. 5g . ) » in benzene (SOmla.),

was heated to 60°, with excess thiazyl trifluoride^ in a

sealed glass tube for seven days. After two days the

deep red solution had turned a very dark brown, and a

dark brown solid had precipitated. The tube was opened,

and the brown solid (l.3g«) was filtered off. Elemental

analyses showed the complex had the stoichiometry

RhCl(NgSgF^)(PPh^)2» Removal of the benzene solvent

from the filtrate, and recrystallisation of the off-

white solid from ethanol afforded triphenylphosphine,

: identified by melting point and infrared spectrum.

The complex RhCl (NgS2!'' ) (PPh^ ) 2 is soluble in iacetone and chlorinated solvents with decomposition, and insoluble in diethyl ether and petroleum spirit.

v) Reaction of Pt(PPh„ )„NSF^ with lithium chloride.

A'solution of lithium chloride (0.4g«), in acetone,

was added to the complex Pt(Ph^P)gNSF^ (0.5g«) in

acetone solution, and the pink solution was boiled for

a few minutes. The solution was evaporated to dryness

under reduced pressure, and the crude product was

extracted with water and ethanol. The pinkish white.solid

remaining was recrystallised from methylene chloride, to

give slightly.impure cis dichlorobis(triphenylphosphine)-

platinum(ll) (0»3g.), identified by melting point 282-288 (lit. 310° ) and infrared spectrum(4000-200cm ^ ).

b. REACTIONS OF N-FLUOROFORMYLIMINOSULPHUR DIFLUORIDE

i)Reaction between Tetrakis(triphenylphosphine)platinum(O)

and FgSNCOFTetrakis(triphenylphosphine)platinum(0) (2°0g.),in

benzene, was reacted with excess N-fluoroformylimino- .

sulphur difluoride in a sealed glass tube, at room

temperature, for two days. The tube was vigorously shaken

during this period. After several hours the yellow solution

had turned orange-red, and an orange-red solid had

precipitated from the solution. The tube was opened after

two days, and the orange solid was filtered off. Elemental

analyses corresponded to the stoichiometry Pt(PPh^)gSFgNCOF

(1'Ig.). Concentration of the filtrate gave a red solid.

Elemental analyses on this complex showed it had high

sulphur and nitrogen content. A melting point suggested

that this product was a mixture.

The complex Pt(PPh^)^SFgNCOF is soluble in acetone and

chlorinated solvents with decompositionand is insoluble

in ether and petroleum spirit.

il) Reaction between trans chlorocarbonylbis(triphenyl­

phosphine ) iridium ( I ): and FgSNCOF

The complex trans IrCl (CO ) (PPh^ ) 2 ( 1. 7g • ), in

benzene(20mls.), was treated with excess FgSNCOF, in a

sealed glass tube, at room temperature, for two days. The

tube was vigorously shaken during this period. After

several hours the yellow solution had become a green colour

The tube was opened and removal of the solvent gave

a dark green product. Attempted recrystallisation'of

this product from hot benzene-methanol mixtures resulted

in decomposition to a dark brown solid. However, a quick

recrystallisation by adding petroleum spirit(40-60°) to

a cold benzene solution of the product gave an olive

green solid, showing characteristic vC O of an iridium(IIl)

complex.

Elemental analyses on this product and on the crude

product suggested that the ratio of both sulphur and

nitrogen to iridium was at least two. M.p.185-190°.

■ (Found :C,44 ; 19 ;H,5.53 IF,3.16;N,6 .95;5,5.92%)The i.r.spectrum shows characteristic absorption bands at

2021 (yCO) ,1755b'C0F) ,1385('/N=S) ,8 51(y-C-N) , 790 , 715 (yS-F ) (cm“^).iii) Reaction between Tetrakis(diphenylmethylphosphine)-

platinum(O) and FgSNCOF.

The complex Pt (PMePhg ) (1.5g.) in benzene , (12mls , )

was reacted,with excess FgSNCOF,in a sealed tube at room

^3-

temperature for seven days. The yellow solution had

turned orange after eight hours. The tube was opened,

and a small amount of orange material was filtered off.

The filtrate was evaporated under reduced pressure to

a small volume, and addition of a gO% diethyl ether,

50% ethanol mixture gave a precipitate(0.6lg.) of a

bright orange solid.

Elemental analyses of this compound showed high

percentages of sulphur, nitrogen and fluorine in the s

complex. Additional purification of the complex,attempted

by recrystallisation from acetone-methanol mixtures,

resulted in decomposition to a brown oily solid,which

was not investigated.

The complex is soluble in benzene, acetone and

chlorinated solvents, and insoluble in diethyl ether and

petroleum spirit.

(Pound: C ,32.4l;H,3.6 l ; f]11.8 ;N,7.71;S,9.54%)The i.r.spectrum shows characteristic absorption bands at 1701(vC0;of COP) ,134l('i'N=s) ,845(y C-N) ,730(v'S-F) . (cm”^).

iv) Reaction between Tetrakis(triphenylphosphine)-

palladium(O) and F gSNCOF.The complex Pd(PPh^)^ (2.0g.), in benzene, (lOinls. )

was treated with excess FpSNCOFin a sealed glass tube for

two days. The tube was vigorously shaken during this period

After 1 day the yellow solution had turned a bright

orange, and some orange solid had precipitated out.

) 4“

The tube was opened, and the orange solid was filtered

off. Concentration of the filtrate by evaporation under

reduced pressure,and addition of diethyl ether,gave

additional amounts of this orange solid. Elemental

analyses on this product (l.09g.) showed high percentages

of sulphur and nitrogen. Attempted recrystallisation of

the orange' solid from acetone-methanol mixtures gave

a dark brown product which also contained high percentages

of sulphur and nitrogen.

The complex could however be recrystallised without

apparent decomposition, by dissolving in benzene, filtering,

and adding excess hexane.

The complex is soluble in benzene, acetone and ,

chlorinated solvents, although insoluble in diethyl ether

and petroleum,spirit. (Found; 0,54.42; H ,5.64 ; F,2.65;

,N,5.33; 5,10.46%)The I.r,s p e c t m m shows characteristic absorption bands at iyoK-rCO of COF group) ,1345 (yN=S) ,1183 (yC-F) ,760 (vS~F) (cm )

v) Reaction between Cis dichlorobis(ti-iphenylphosphine)- platinum(Il) and FgSNCOF.

The complex cis PtCl2(Ph^P)g(1.5g«)» suspended in

benzene ( 30mls. ) was treated with excess FgSNCOF.' in a sealed glass tube. The tube was heated at temperatures

oup to 60 for several days. The tube was. opened after

six days, and the white insoluble complex was filtered off

and identified by melting point and infrared spectrum

(4000-200cm ^ ) as unchanged cis PtCl^(Ph^P)^ (1.4g.)

v i ) Reaction between metal carbonyls and F GSNCOF

Tungsten hexacarbonyl in xylene was treated with

excess FgSNCOF in a sealed glass tube for several days.

The tube was opened and the solution evaporated down,

under heduced pressure, to gitre unchanged tungsten

hexacarbonyl, identified by infrared spectrum and melting

point.

This experiment was repeated, using di-ironennear~

carbonyl and trirutheniumdodecacarbonyl in. benzene. In

each case unchanged metal carbonyl was identified by an

infrared spectrum.

v i i )Reaction between RhCl(PPh„)„ and SFGNCOFThe complex (1.5g.), in benzene,(25mls.), was reacted

with excess SF-NCOF in a sealed tube for two days. A brown solid(0.8g.) precipitated out, which contained high percentages of sulphur and nitrogen. (Found: P,4;86|N, 9.93 ;S,4,08%).The i.r.spectrum shows characteristic absorption bands at 1?68,1?04 (YCO of COF group),1398(vN=S), 1164(f C-F) ,845(YC-N) ,785,735(^S-F) (cm"^).viii) Reaction between trans PtHCl(PPh^ )gand SFgNCOF

The complex ( 1. Og..) in benzene ( 20mls . ) and excess

56-

SFgNCOF were heated at 40 in a sealed tube for two days,

An orange solid,(0*46g.) , precipitated out, which was

filtered off. The complex analysed approximately for the

stoichiometry PtHCl(PPh^)gSFgNCOF.

ix) Reaction of Pt(PPh^ )^SFgNCOF with lithium, chloride.

The procedure, as for the reaction between

Pt(PPh^)gNSF^ and lithium chloride in acetone, gave cis

.PtClg(PPh^)2 , identified by infrared spectrum and melting

point.

57-

CHAPTER 2

THE PREPARATION AND PROPERTIES OF TERTIARY PHOSPHINE

METAL FLUORIDE COMPLEXES.

INTRODUCTION > ,

Phosphine complexes of the transition metals have

been known for over a century, and in recent years have63received extensive study. Complexes have now been prepared

from salts of most transition metals, and many other

types of complex derivatives have also been obtained.

Generally, the most stable phosphine complexes are

obtained from salts of elements to the right of thé

transition metal series. This is due to the character of

the phosphine ligand, which acts both as ir -bond donor

and a X-bond acceptor. The vacant 3d orbitals of the

phosphorus are capable of interaction with filled

nonbpnding d orbitals of a transition metal. In many

cases, the acceptor character may be as important as the

donor character, thus in the case of the complexes of

trifluorophosphine,PF^, the highly reduced donor

properties of the ligand are amply compensated by the

increased electron affinity of the vacant ,d orbitals on

the phosphorus. The high ligand-field strength of

tertiary phosphines ensures a large energy difference

between the low energy,and high energy d orbitals of

the metal. Generally, the most stable complexes are

those in which the metal has it's low energy orbitals

completely occupied by electrons, it's high energy

orbitals vacant, and also the energy difference is large

— q 8 ™

enough to prevent promotion of electrons from low to high orbitals. Thus the stability of transition metal phosphine complexes increases from left to right across the transition metal series.

The phosphine metal halide complexes are usually amongst the most stable complexes for metal M and their chemistry has been extensively studied. However, phosphine metal fluoride complexes are less well known, and have received little attention.

Trifluorophosphine complexes containing metal-fluorinetio 65

64bonds were originally prepared by Moissan, by the reactionof phosphorus pentafluoride on platinum metal. Peacockhas suggested that Moissan's platinum compound should bewritten as PtFp(PF^), in view of the similarities inproperties of phosphorus trifluoride and carbon monoxide,

66Cbatt and Williams have suggested that the compound isdimeric with fluorine bridging groups, and is analogousto Schutzenberger'8 complex ( PCl^PtClg)

The first alkyl or aryl phosphine metal fluoride68complex was prepared by Muetterties. Reaction of tungsten

hexafluoride with triphenylphosphine gave a product which was formulated as the ionic compound,(WF^PPh^f(F f.

- 59-

69Subsequently, Moss studied the reaction of tertiary phosphine metal hydrides with anhydrous hydrogen fluoride and prepared,difluorohydridotris(triphenylphosphine)iridium(III), IrHFg(PPh_)g, by reaction of hydrogen fluoride with trihydridotris(triphenylphosphine)iridium(II),

IrHgtPPhg)^ — — » IrHPgfPPh,)^

69': 'Moss also studied the reactions of complexes70 69formulated as PtHg(PPh^)^, and PdHg(PPh^)^, with liquid

hydrogen fluoride, and obtained complexes formulated as PtFg(PPh_)g and PdFg(PPh_)g, respectively. However, since this work, it has been shown that the palladium(ll) and platinum(II)"hydrido" complexes are the zerovalent

71,72phosphine complexes, Pd(PPh^)^ and Pt(PPh^)^, respectively.McAvoy^reported the preparation of phosphine metal

fluoride complexes of ruthenium and osmium, by a similar75method. McAvoy et al. also extended the study of the

complex formulated as PtFg(PPh_)g, and have reported the reactions of this complex with carbon monoxide, triphenylphosphite, and other compounds.

—6O—

50Clark et al. have reported the preparation of a complex, chlorofluorobis(trlethylphoaphine)platinum(II),as a minor product in the reaction of trans hydrido­chlorobis ( triethylphosphine )platlnum(II ) with trifluoro- ethylene. Vaska has also studied the reaction of gaseoushydrogen fluoride with crystals of the complexes trans

74 75IrCl(CO)(Ph^P)g, and IrH(CO)(Ph^P)_.This chapter describes the attempted preparation of

some new phosphine metal fluorides, using liquid hydrogen fluoride, hydrofluoric acid, elemental fluorine, silver(I) fluoride, and thalloua fluoride. The reaction of, tetrakis(triphenylphosphine)platinum(O) with liquid hydrogen fluoride,and the reactions of the product, previously reported by McAvoy et al .^%ave been reinvestigated.

Part 1 describes the preparation and properties of the new phosphine metal fluoride complexes, using liquid hydrogen fluoride and other methods. Part 2A ) includes a study of the reaction between tetrakis- (triphenylphosphine)platinum(0) and liquid hydrogen fluoride. The reactions of other zerovalent phosphine complexes,with liquid hydrogen fluoride,are also discussed in this section.The chemical properties of the complex obtained from the reaction between tetrakis(triphenyl- phosphine)platinum(O) and liquid hydrogen fluoride, are also discussed in Part 2B .

- & Î -

PART 1RESULTS AND DISCUSSION ;

The results may he conveniently discussed in three

sections;

A. The reactions of platinum(II), palladium(Il), and

nickel(Il), complexes, with liquid hydrogen fluoride.

B. The reactions of other complexes with liquid hydrogen

fluoride.

C. Other attempted methods of preparation of new tertiary

phosphine métal fluoride complexes.

All experiments, involving liquid hydrogen fluoride,

were performed using the same method. Liquid hydrogen

fluoride was condensed onto the transition metal complexo

in a polythene beaker, at . The reaction vessel was

then, allowed to warm to room temperature. After several

hours, excess acid was removed in a stream of dry nitrogen,

SECTION A

The reactions of plat inum(l.I ) , palladium(Il), and

nickel(Il), complexes with liquid hydrogen fluoride.

Reaction of liquid hydrogen fluoride with

cis dichlorobis(triphenylphosphine)platinum(II), gave a

colourless solution. Removal of the excess acid gave a

white solid, soluble in acetone, and benzene, which was

identified as cis chlorofluorobis(triphenylphosphine)-

platinum(II).

■6 2-

The complex has one strong band in the infrared spectrum (400-200cm”^ ). This band has been assigned t o V P t - C l .The infrared spectrum of the complex, between 450 cm ^ , and 400cm shows two bands assigned to V'Pt-P, andsuggests the complexes have the cis configuration. The complex is essentially a non-conductor in nitromethane, and nitrobenzene solutions. The complex reacts with chlorinated solvents, or a solution of lithium chloride, in acetone, to-give cis dichlorobis(triphenylphosphine)- platinumdl ) .

cis PtCl_(PPh_)g — ^ cis PtClF(PPh )^ ^ 'CHgClg V

or LiCl/acetone

Reaction of trans hydridochlorobis(triphenylphosphine)- platinumdl), with liquid hydrogen fluoride, gave a pale yellow solid, after removal of excess acid. The product was reCrystallised from acetone, and identified as cis chlorofluorobis(triphenylphosphine)pl a t i n u m d l ), identical to the product obtained from cis PtClg(PPhj)2, and liquid hydrogen fluoride.

Few chloro-fluoro complexes of platinum are known. Complexes containing the trichlorotrifluoroplatinate( I V ) ,

ion, (PtCl^F^)^", have previously been prepared?^These complexes were prepared by the reaction of bromine trifluoride, with the hexachloroplatinatedV) ion,

-hi-

2— ® 30(PtCl^) , at 20 ♦ Clark et al. have reported the preparation of chlorofluorobis{triethylphosphine)- platinum(Il), as a minor product in the reaction between trifluoroethylene and trans hydridochlorobis- (triethylphosphine)platinum(II).

The preparation of cis chlorofluorobis(triphenyl- phosphine)platinum(II) presumably involves an intermediate Pt(IV) complex, which could then lose hydrogen chloride, giving the product. It should be noted that hydrogen

77chloride is insoluble in liquid hydrogen fluoride.

cl«PtCl.(PPh.). iliî— » PtHCl.F(PPh.).^S^l»PtClF(Ph.P).

Chatt et al. have shown that addition of hydrogen chloride to trans hydridochlorobis(triethylphosphine)- platinum(Il) gives the complex, dihydridodichlorobis- (triethylphosphine)platinum(IV), which slowly loses hydrogen chloride, even in the solid.

trans PtHCl(PEt_)g + HCl < PtH2Clg(PEt^)g.

Recently, the complex dihydridodichlorobis(triphenyl- phosphine)platinum(IV), has been isolated from the reaction of trans hydridochlorobis(triphenylphosphine)- pletlnum(IV); with hydrogen chloride.

trans PtHCKPPh )g + HCl F = ^ P t H g C l g ( P P h ^ ) g

The Pt(IV) complex slowly loses hydrogen chloride in the solid, and more quickly in solution.

Similarly, in the reaction between trans hydrido­chlorobis ( triphenylphosphine )platinum(II ) , and hydrogen fluoride, a platinum(IV) complex is probably an intermediate. This intermediate then loses hydrogen, and after isomérisation, the complex cis PtClF(PPhj)g is obtained.

♦HF -H„trans PtHCl(PPh^)g PtHgClF(PPh^)g-^-4 cis PtClP(PPh )g

This reaction is similar to the reaction between hydrogen chloride and trans hydridochlorobis(triethyl­phosphine ) platinum (II ), which, on heating, react to give cis dichlorobis(triethylphosphine)platinum(II) 7^^

trans PtHCKPEt )g PtHgClg(PEt^)g-^^cisPtClg(PEt^)g

The pale yellow complex cis dibromobis(triphenyl­phosphine )platinum( II ) , appeared initially to turn white on addition of liquid hydrogen fluoride. After an hour, the solution had turned red. Removal of the excess acid

— 65—

gave a pale yellow solid, which was identified as cis bromofluorobis(triphenylphosphine)platinum(II).

cis PtBrg(PPh^)g — — > c ^ PtDrF(PPh_)g

The complex showed only one strong band in the region(240-190cm"^), which was assigned toV'Pt-Br, and it wasessentially a non-conductor in nitromethane. The complexis probably formed via a similar mechanism to thatpostulated for the chloride analogue, involving a Pt(IV)intermediate, which loses hydrogen bromide, which is

77insoluble in liquid hydrogen fluoride.The displacement of chloride and bromide from the

complexes cis PtClg(Ph_P)g, and cis PtBrg(Ph_P)g, should also be contrasted with the inability of fluoride to displace chloride, bromide or iodide, from the relevant (PtXg)^” , ion, (X=Cl,Br,I) in aqueous solution?^

The reactions of other dichloro-platinum(II)phosphin# complexes, were also studied, in an attempt to prepare other chlorofluoroplatinum(II)phosphine complexes.

Trans dichlorobis(tri-n-butylphosphine)platinum(II), gave a rather oily yellow solid, which, however, consisted mainly of the starting material trans PtClg(n-Bu^P)g.

Cis dichlorobis(diphenylmethylphosphine)platinum(II), reacted with liquid hydrogen fluoride, to give a red solution. Removal of excess acid gave a pink so]id, which,

-66-

after recrystallisation from acetone, had turned a

slightly yellowish colour. Elemental analyses, and. an

infrared spectrum,(400-200cm ^ ), of the product, showed

that the principal constituent of the crude reaction

mixture was, in fact, the starting material,

cis PtClg(PPhgMe)2 , although a small amount of a fluorine ,

containing complex was also present, as indicated by

elemental analyses of the crude product.

Similarly, reaction of cis dichlorobis(triphenyl-

arsine)platinum(ll)% with liquid hydrogen fluoride,gave

mainly unchanged starting material. The complex,

cis PtClntAsPh^)^, was not very soluble in liquid hydrogen

fluoride. The insolubility of this complex,in liquid

hydrogen fluoride^probably explains why no reaction had

occurred.

Reaction of trans dichlorobis(triphenylphosphine)-

palladium(Il), with liquid hydrogen fluoride, gave an

orange solid. The complex trans PdClg(Ph^P)g, was not

very soluble in liquid hydrogen fluoride. Recrystallis­

ation of this product from acetone, yielded a product,

which was identified as trans PdClg(PPh^)g. However, a

small amount of a fluorine containing complex was

indicated by elemental analyses of the crude product.

Reaction of cis dichioro 1 ,2-bis(diphenylphosphino)= ethanenickel(II), also gave mainly unchanged starting

material.

67.

An attempt to prepare an iodofluorobis(tertiary-

phosphine)platinum(II) complex, by reaction of trans hydridoiodobis( triphenylphosphine)platinum(II with

liquid hydrogen fluoride, gave a bright yellow solid. This

crude product was a mixture, containing a large proportion

•of the bright yellow cis di-iodobis(triphenylphosphine)-

platinùm(Il); in addition to a pale yellow product, which

was not identified. .

Reaction of cis di-iodobis(triphenylphosphine)-

platinum(Il), with liquid hydrogen fluoride, gave mainly

unchanged cis PtIg(PPh^)g, as indicated by melting point,

and,elemental analyses of the product.

Reaction of trans iodomethylbis(triphenylphosphine)-

platinum(II), with excess liquid hydrogen fluoride, gave

an orange solution. A light tan solid was obtained, after

removal of excess acid. This crude product contained

some cis PtIg(PPh^)g, and a pale yellow product, which

was not identified, although elemental analyses indicated

that it contained fluorine.

The reactions of these iodine containing complexes

are interesting in that, in every case, some cis

PtIg(PPh^)g, was obtained. The presence of this complex

in the products of all the reactions suggests that, if

an intermediate iodofluoro complex is formed, it is

unstable, and reacts further, possibly with another

molecule of the same intermediate, giving the di-iodo

.68.

complet.A possible reaction scheme for the formation of the

di-iodo complex from the hydridoiodo complex, is shown below;

trans P t H I ( P P h _ ) g - ^ PtHgPI(PPh^)g::^^ PtPKPPh^ig

x2

.Fluorine containing Pt complex + cis PtIg(PPh_)gThe bright orange complex,trans dichlorodiammine-

pall a d i u m d l ), did.not go into solution in liquid hydrogen fluoride, and unchanged trans PdClg(KH^)g was identified by an infrared spectrum and melting point, after removal of excess acid.

SECTION BTHE REACTIONS OF OTHER COMPLEXES WITH HYDROGEN FLUORIDE.

Chlorotriphenylphosphinegold(I),AuCl(PPhj ), did not go into solution in liquid hydrogen fluoride. An infrared spectrum of the compound obtained after removal of excess acid indicated that the compound was unchanged chloro- triphenylphosphinegold(I).

Trans chlorocarbonylbis(triphenylphosphine)iridium(I) was not very soluble in liquid hydrogen fluoride. Main]y unchanged starting material was obtained after removal of excess acid, although a small amount of another complex was indicated by an infrared spectrum, which showed one band above POCOcm"^'

-An-

74Vaska has previously studied the reaction of gaseous hydrogen fluoride with crystals of trans IrY(CO)(Ph_P)g (y=Cl,Br,l), and has deduced the molecular structure of the products from their vibrational spectra, although no complete analyses were obtained for these complexes.

The general reaction for addition of gaseous hydrogen fluoride to these solid complexes is shown below.

trans IrY(CO)(Ph^P)g + HP ------> IrHPY(CO)(PPh^)g

The six co-ordinate adduct was obtained under these conditions. Chlorotris(triphenylphosphine)rhodium(I ) reacted with liquid hydrogen fluoride to give an orange solid, which contained fluorine, but was not characterised. The complex showed one strong band in the region (400-200cm”^ ), in an infrared spectrum, assigned to<Pt-Cl.Chiorotris(triphenylphosphine)rhodium(I) reacts

13with hydrogen chloride in benzene to givehydridodichlorobis(triphenylphosphine)rhodium(III).

RhCl(PPh_)^ + HCl -------^ RhHClg(PPh^)g + PPh^.

The orange product, obtained in this work, from the reaction of RhCltPPh^), with liquid hydrogen fluoride, however, does not show a rhodium-hydrogen stretching mode

-70-

in it * s infrared spectrum, so' a similar reaction has

not occurred. ~

SECTION C ■ . :OTHER ATTEMPTED METHODS OF PREPARATION OF PHOSPHINE

METAL 'FLUORIDE COMPLEXES.

i) Methods using silver(I )fluoridë, AgF

Freshly prepared yellow silver(I )fluoride and trans

chlorocarbonylbis(triphenylphosphine)iridium(I) were

refluxed together,in acetone,for an hour. After filtration

to remove insoluble silver salts, the solution was

evaporated to dryness, and the crude mixture was extracted

with benzene to give a yellow solution. Evaporation of the

benzene solution to small volume, under reduced pressure,

and addition of methanol, afforded a yellow crystallineI - 1product. This product had a strong band at 1947cm ,

assigned to Y C O characteristic of an iridium(I) complex,l'The product had no strong bands in the region 400-200cm ,

in comparison to the strong band at 317cm ^ (3H c m ^sh), shown in the infrared specfrum of trans I r C K C O ) (PPh„ ) „.

Elemental analyses identified this product as trans

, fluorocarbonylbis(triphenylphosphine)iridium(I).

71-

The infrared spectrum of the complex IrF(CO)(Ph^P)^

is identical in the region 430-400cm to all complexes

of the type, trans IrX(CO)(PPh^)2 ,(X=C1,Br,I ), in that

only one medium band is observed, apart from the weak

absorption due to triphenylphosphine itself near 4l5cm”^«

This band has been assigned to an iridium-phosphorus

stretching mode, and the similarity of the infrared

spectrum of the complex IrF(CO)(Ph^P)2 ^to other related halide complexes in this region, coupled with the fact

that no cis complexes of formula IrY(C O )P ^ ,(P=phosphine,

Y=halide), have been prepared, suggests that the fluoride

complex also has a trans configuration.

Trans IrCl(CO)(Ph^P)2 has f CO at 1951cm (nujol),*=• Tand the complex trans IrF(C O )(Ph„P)_ h a s f C O 4cm lower

-1at 1947cm . This decrease in f CO on going from a chloride

to a fluoride trans to the carbon monoxide group may be

explained in terms of the acceptor properties of the trans

halide. Thus, in the fluoride complex, the fluoride ligand

has no available d-orbitals, thus no electron density

from the d and d orbitals on the iridium atom can be

accepted. Therefore, a greater filling,than in the chloride

complex,, of the antibonding orbitals of the trans carbon

monoxidejoccurs, with consequent decrease in bond order,

and drop in TCO from chloride complex to fluoride complex.79

While this work was in progress, Grinberg et al,

reported the preparation of the rhodium analogue of this

-72-

complex, by a similar method, and it's reaction with

sulphur dioxide.

Cis dichlorobis(tri-n-butylphosphine)piatinum(II)

also reacted with silver(I)fluoride, in methanol, but

the product could only be obtained as an intractable oil.

Similarly, trans hydridochlorobis(triphenylphosphine)-

platinum(II) reacted with siIver(I )fluoride, but the

product did not contain a platinum-hydrogen bond,

(YPt-H absent in infrared spectrum), and the product

was not further investigated,

ii) Method using thallous fluoride

Thallous fluoride is slightly soluble in methanol

and thallous chloride is insoluble in tbip solvent. It

was hoped to prepare new complexes by a similar method

to those methods, using silver(I)fluoride, However, no

new complexes were obtained by this method, unchanged

starting materials being obtained from a refluxing

solution of freshly prepared thallous fluoride and

IrCl(CO)(Ph„P)„ in methanol.Possibly, new complexes could

be prepared using a different solvent, as the iridium

complex trans IrCl(CO)(PPh^ )2 was not very soluble in methanol.

-73-

iii) Methods using 40 w/v hydrofluoric acid

Trans chlorocarbonylbis(triphenylphosphine)ifidium(I)

was obtained unchanged from reaction with hydrofluoric: • . 7 4acid. This should be compared with the work of Vaska,

who studied the reaction of gaseous hydrogen fluoride

with solid trans IrCl(CO)(PPh^)2 .

iv) Methods using elemental fluorine , .

The difficulty encountered in direct fluorination

of phosphine metal complexes is that of finding an inert

solvent medium for the complex. The solvent 1,1,2 trichloro

1,2,2 trifluoroethane("Genetron 113”) was found to be

inert to the slow passage of fluorine diluted with

nitrogen. However, the phosphine complexes used were not

very soluble in this solvent, and reactions were generally

found to be incomplete,

A suspension of cis dichlorobis(triphenylphosphine)-

platinum(Il) in "Genetron 113” was placed in a Dreschel

bottle. Fluorine diluted with nitrogen was slowly bubbled

through the system for two hours. After filtering off

unchanged cis PtCl^(PPh^ )21 that had not gone into solution, the filtrate was evaporated down to give a

small yield of a pale yellow solid. The infrared spectrum

(4000"»200cm"^ ) , of this complex was very similar to

cis PtCl2(PPh^)2 , with strong bands at 315cm ^ , and

- 74-

«.1 '291cm in theYPt-Cl region. The yield of this complex

was insufficient for elemental analyses, however.

If a suitable solvent could be found, reactions

might be similar to the reactions of elemental chlorine,

with square planar Pt(ll) complexes^^which give the

corresponding Pt(IV) complexes.

Reaction of elemental fluorine with trans

chlorocarbonylbis(triphenylphosphine)iridium(I), using

the same technique, gave only unchanged trans ■

IrCl(CO)(Ph„P)_. The complex was insoluble in the solvent "Genetron 113”«

EXPERIMENTAL

Analyticali melting point and infrared data for

new complexes are shown in this section.

All reactions using liquid hydrogen fluoride were

performed using the same method. Liquid hydrogen fluoride

w;as condensed onto the transition metal complex contained

in a polythene beaker at -78°» After several hours,

excess acid was removed in a stream of dry nitrogen.^ 3 ■ 38Cj^ PtBrg(Ph,P)2 , cfs Ptl2 (Ph^P)2 , trans PtHl(PPh^)j81 82 TTtrans PtI(CH„)(PPh„)„» AuCl(PPh„), and other Pt dichioro

62 ^.complexes were prepared by literature methods. Trans

PdClgCPPh^)^, was prepared from trans PdClg(NH^)g, by

treatment with hot ethanolic triphenylphosphine.

75-

, , 83 84Silver!I)fluoride and thallous fluoride were alsoprepared by literature methods.

Section AReactions of platinum(II), palladiuw(II), and nickel(II).

complexes with liquid hydrogen fluoride.

a) cis PtClgCPPh^)^

Removal of excess acid gave a white solid, which, after recrystallisation from acetone/diethyl ether mixtures gave the product cis chlorofluorobis(triphenyl­phosphine )platinum(II ).

M.p. 134-137°. (Yield 7896).(Found: C.SS'OS; H,3'98; Cl,4'77; F,2 63; CIFP Pt3b 30 2requires C,55'86; H,3'91; Cl,4'58; F,2'45%)The complex exhibits a band at 302cm ^ , assigned to VPt-Cl, and two bands at 443cm ^ , and 422cm ^ , assignedto VPt-P.

b)trans PtHCKPPh-)^

Removal of excess acid gave a pale yellow solid,

-76-

which, after recrystalligation from acetone/diethyl, ether

mixtures, gave the product cis chlorofluorobis(triphenyl­

phosphine )platinum(II) .

M.p.136-139° (Yield=64%)»

The complex had an infrared spectrum identical to the

product in a), '

(Pound: C,55'21; H:, 4 ' 38 ; Cl, 4 *38; F,2'6?; C_&H QClFPgPt

requires; C,33-86; H,3'91; Cl,4-38; F,2-43%).

c) cis PtBf^(PPh )_

Removal of excess acid gave a pale yellow solid,

which, after recryst'allisation from acetone/diethyl ether

mixtures, gave cis bromofluorobis(triphenylphosphine)-

platinum(II).

M.p.229-234°. (Yield=58%).

(Found: C,52-29; H,3“755 Br,10«06; C^gH^QBrFP^Pt requires

C,52'2; H,3'69; Br,9'76%).-1The complex exhibits a band at 192cm assigned to

Y Pt-Br, and two bands at 444cm ^ , and422cm ^ , assigned

toYPt-P.

d) cis PtClg(PPhgMe)g

Removal of excess acid gave a pink solid, which

after recrystallisation from acetone/diethyl ether

mixtures, had turned a yellowish colour. An infrared

spectrum of this product (2000-200cm ^ ) showed clearly

-77-

the presence of jci^PtClgCPPhgMe)g, as a main constituent

of this product. Elemental analyses also suggested that

the mixture largely contained unchanged starting material

together with a small amount of a fluorine containing

product.

(Found: c , 47*69; H,4°30; Cl,9*87; F,l*47; '

^ 2 6 ^ 2 6 ^ ^ 2^ 2^^ requires C,46-86; H,3*93; Cl,10-64%)

e )trans P t Ci^ (n -Bu ^P)^The product, a rather oily yellow compound,after

thorough washing with diethyl ether, was recrystallised

from ethanol to give unchanged starting material,

identified by melting point 58-6I ° (Lit, 63-6^ ) and

infrared spectrum (2000-200cm ).

f ) cis PtCl2 (AsPh^ )2 /The product, a pale yellow solid, was identified as

unchanged starting material by an infrared spectrum(4000'

200cm" )

g ) trans PdCl2 (Ph^P)2The orange product, after removal of excess acid,

was recrystallised from acetone/diethyl ether mixtures.

An infrared spectrum showed that j.ViC principal

constituent was unchanged starting complex. Elemental

analyses confirmed that the product was a mixture

containing mainly trans PdCl^(Ph_P)_, and a small amount

.78.

of an unidentified fluorine containing complex. The

complex trans PdClnCPh^P)^ was not very soluble in liquid

hydrogen fluoride. '

(Found: C,59*70; H,4*03; 01,9*20; P.l'OO.^36^y0^^2^2^^ requires C,6l*6; H,4"31; 01,10*10%)

h) NiClg(Ph2PC2H^PPh2) ,

The reaction product contained mainly unchanged

starting complex, identified by infrared spectrum(2000-»

200cm ^ ) and elemental analyses.(Found: 0,58-45; H,4-42; 01,13*71. Cg^Hg^ClgNiPg requires

C,59'l4; H.4'58; 01,13*43%)

i) cisPtlntPPh.).The complex was not very soluble in liquid, hydrogen

fluoride, T^e yellow product, after removal of excess

acid, contained mainly unchanged cis Ptl2 (PPh^)g, as

indicated, by elemental analyses and melting point of the

crude product.

M.p. 282-287° (Lit. 283I(Found: 0,45.81; H,3-l4; 1,24.39. C.gH^QlgPgPt requires

0,44*42; H,3'll; 1 ,26-07%)

*79*

j ) trans PtHI(PPh^)g .

The bright yellow solid obtained after removal of

excess acid was dissolved in boiling benzene, and the

solution was filtered. The yellow solution was cooled.,

and concentrâted,giving cis PtlgCPPh^)^, identified by

melting point 281-282 ° (Lit.285° ) and infrared spectrum,/

Concentration of the mother-liquor gave a small amount

of paie yellow solid which was not identified,

M.p. 181° (decomp. )

1 1 trans Ptl(CH^ ) (PPh )g

A light tan product was obtained after removal of

excess acid. The crude product was dissolved in boiling

benzene and filtered. Cone entrâtion of the yellow solution

gave bright yellow crystals of cis Ptl2(PPh^)2 , identified

by melting point, 28O-285 °(Lit. 285°), and infrared

spectrum as cis Ptl2 (PPh^)2 « Addition of methanol to the

mother liquor and removal of solventjunder reduced

pressure,gave a pale yellow product which was not

identified, although elemental analyses showed the

presence of fluorine.

(M.p.181-185°.(Found ; c , 51*27; H,3°95; 1 ,3 -29; f,7»6i%)

.80-

1 )trans PdCl„(NH_)_

The orange complex did not go into solution in liquid

hydrogen fluoride and after removal of excess acid,

unchanged starting complex was identified by an infrared

spectrum (4000-200cm ^ ) and melting point,o ,

M.p. 263-8 °(decomp.) Lit. 210(Decomp.)

2. Reaction of lithium chloride in acetone with cis

■PtClF(PPh^)^

Lithium chloride (0.3g.) in acetone was added to

cis PtClFtPPh^)^ (0 «3g.), in acetone solution.

Immediately, a white precipitate was formed. The mixture

was shaken for two hours and the solvent removed under,

reduced pressure. The crude white product obtained was

washed thoroughly with water. An infrared spectrum of

the product (2000-200cm ^ ) showed the presence of

cis PtClg (PPh^ ),,, which could he obtained pure, by

recrystallisatiion from methylene chloride/petroleum

spirit mixtures, (0?42g, ) Similarly,

recrystallisation of cis PtClF(PPh„)„ from methylene,' i -chloride/petroleum spirit mixtures also gave cis PtClgtPPh^/g

identified by infrared spectrum (2000-200cm”^) and melting

point. ■ -

.81.

SECTION B > ,■REACTIONS OF OTHER COMPLEXES WITH LIQUID HYDROGEN

FLUORIDE

a) trans AuCl(PPh^)

The complex was not soluble in liquid hydrogen

fluoride and unchanged starting material was identified

by an infrared spectrum(2000-200cm ^ ) and melting point

M.p.237-239°. (Lit. 243-24^)

b) trans IrCl(CO)(PPh^ )2The complex was not very soluble in liquid hydrogen

fluoride. The product obtained contained mostly unchanged

trans IrCl(CO)(PPh^ )2 and a small amount of complex showing a band at 2030cm ^ ,

c) RhCl(PPh^)^ :

An orange solid was obtained after reaction with

excess liquid hydrogen fluoride, which contained fluorine

and did not show any bands in an infrared spectrum in

the region associated with y Rh-H. The complex showed a“ 1strong band at 334cm assigned tor Rh-Cl

M.p. 240-2 5 0 ° (decomp.)Found; C,51*79; H,4'll; Cl,6-6l; F,22*70 ,

82.

Section CReaction of silver fluoride with trans IrCl(CO)(PPh„)„ ------------------------------ ---- -----— ------------------- 5— 2—

Preshly prepared yellow silver (1) f Ivioride (0 • 40g. )

and trans IrCl(CO)(PPh^ )2 (O-ySg.), were added to

acetone (50mls.) and the solution was heated under reflux

for one hour. A black precipitate was filtered off, and

the solution was evaporated to dryness under reduced

pressure. The crude mixture was extracted with benzene,

ev£»poration of this yellow benzene solution to small

volume, and addition of methanol, afforded the product,

trans IrF(CO)(PPh^)„ (0'34g.)

M.p. 241—246

(Found: C,58

C,58'l8; H,3*96; F,2«49%).

The complex exhibits a band, at 1947cm ^ assigned to

/CO.and the pattern of the infrared spectrum in the

region 450-400cm"^ is identical to other complexes of

the formula, trans IrX(CO)(Ph_P)_, (X=Cl,Br,l)

(Found: C,38*48; H,3*93j F,2°38; C^yH^gFIrOPg requires

• 83-

PART 2

Section A includes the reaction of zerovalent

tertiary phosphine complexes of nickel, palladium, and

platinum, with liquid hydrogen fluoride» In particular,

the reaction of tetrakis(triphenylphosphine)platinum(0),73with liquid hydrogen fluoride, reported by McAvoy et al.

has been reinvestigated. The chemistry of the product from

this reaction has also been studied, and is reported in

Section B.

SECTION A

REACTIONS OF ZEROVALENT METAL TERTIARY PHOSPHINE COMPLEXES

WITH LIQUID HYDROGEN FLUORIDE

RESULTS AND DISCUSSION73 ’McAvoy et al. prepared the complex formulated as

cis difluorobis(triphenylphosphine)platimun(ll), by

bubbling hydrogen fluoride through a solution of Pt(PPh^)^

in benzene, or by reaction of liquid hydrogen fluoride with

solid Pt(PPh^)^ in. a polythene beaker or in a stainless

steel bomb.

Pt(PPh_)^ 2HF. — ---- bi£ PtFgfPPhglg Hg •(. 2Ph^P

■> ' ■ ' . ■ . The isomérisation of the product to the trans isomer

in methylene chloride and the reactions of this complex

with triphenylphosphite and carbon monoxide were also

. reported.

McAvoy et a.i. T^repor ted that all products, including

. '

cis PtFg(PPh^)g,were recrystallised from methylene

chloride,by precipitation with diethyl ether.However, the results obtained from a study of the

reaction of methylene chloride with cis chlorofluorobis-

(triphenylphosphine)platinum(II), had suggested that the metal-fluorine bond in tertiary phosphine platinum fluoride complexes was readily cleaved in chlorinated solvents, with formation of cis dichlorobis(triphenyl­

phosphine ) pla tinum (II ) .

CH^Clgcis PtClP(PPh_)_ cis PtClg(PPh_)_— ^ z —— ti J ^

73In fact, McAvoy et al. also reported that, if a

solution of cis PtF2 (PPh_)2 in chlorinated solvents was kept for some hours, the solution became fluorinated and dichlorobis(triphenylphosphine)platinum(II) was formed,

(isomer not specified).

Therefore, it was thought advisable to attempt recrystmllisation of the crude product, from the reaction of Pt(PPh*)^ with liquid hydrogen fluoride,from some other, non-chlorinated, solvent. The complex was found to be soluble in acetone and the crude complex, after thorough washing with benzene and diethyl ether, was recrystallIsed from acetone.

Elemental analyses on the complex recrystallised this way, however, were in disagreement with those of

-8n-

McAvoy et al.; and the results calculated t o r P t F ^ i P P h ^ )

In particular, the elemental analyses for platinum metal showed a large difference from those found by these workers and calculated for PtFgCPPh^)g :

Calculated for PtFg(PPh_)g Pt, 25'7%.73Found by McAvoy et al. for product

recrystallised from methylene chloride Pt, 25*9%*Calculated for PtClg(PPh )g Pt, 24'7*.Found in this work for productrecrystallised from acetone P t , 18*2%.

These results led to the investigation of reaction and the reaction product more thoroughly.

In the proposed reaction scheme,

Pt(PPh_)^ + 2HP -------> cis PtFg(PPh2 )2 + Hg + STPh^.

one mole, of the zerovalent platinum complex Pt(PPh^)^ should yield two moles. of free triphenylphosphine. However, in two separate determinations of the weight of free triphenylphosphine obtained after reaction, weights, corresponding to under one mole, of free triphenylphosphine per mole. of Pt(PPh^)^, were obtained Further in three determinations of percentage yield of cis PtF„(Ph_P)„, based upon the above equation, values in excess of 100% were obtained. This suggested that

-86-

the platinumClX) .complex contained not two, but three

moles, of‘triphenylphosphine. Therefore, to confirm this,

tris(triphenylphosphine)platinum(0) was reacted with

liquid hydrogen fluoride. From this reaction no free

triphenylphosphine could be isolated, and a complex,

identical to the product obtained from reaction of

Pt(PPh^)^ and liquid hydrogen fluoride, was obtained.

Also, the platimim(ll) fluoride complex was reacted

with excess,lithium chloride in acetone to yield cis

dichlorobis(triphenylphosphine)platinum(II) and free

triphenylphosphine, confirming that the complex contained

three moles, of co-ordinated triphenylphosphine per

platinum atom.

Elemental analyses of the complex suggested the

formula PtF_(PPh_)_.3 3 3Vask%^has studied the reaction of gaseous hydrogen

fluoride with crystalline hydridocarhonyltris(triphenyl­

phosphine ) lridium( I )■ and obtained the ionic products A, and B; -

A: : IrH(CO)(Ph^)^ + HF >|lrHg(CO)(Ph^P)^.

B(with excess HP):

IrH(CO)(Ph^P)^ +^HF --- ^ rHg(CO)(Ph^P)^excess

HFg,

depending upon whether excess acid is used.

-87-

6Cariati, üfo and Bonatl have also studied the reactions of zerovalent phosphine complexes of platinum with inorganic acids. In certain cases, reactions of the t}n^ shown below occur.

Pt(PPh^)^ + HX -i^tHtPPhg)]*.X=BF^", CIO^", HSO^", CH-OSOg".

In these reactions also, ionic complexes are formed. ' ' 73McAvoy et al. did not report conductivity

measurements on the fluoro-complex. In view of the abovereactions of hydrogen fluoride, in which ionic products

/were obtained, the possibility of the complex of stoichiometry PtF_(PPh_)*, being ionic,has to be considered. Conductivity measurements in nitromethane, nitrobenzene, and acetone, confirmed that the complexwas ionic and had a conductivity similar to those shown by other uni-univalent electrolytes in these solvents. However, an infrared spectrum of the complex failed to show the presence of a Y Pt-H, and although vPt-H is sometimes obscured or very weak, it suggests that a complex of formulation PtHCPPhgXg HgF^ with cationidentical to those complexes obtained by Cariati et al.^ is unlikely.

Addition of sodium tetraphenylborate in ethanol to an ethanolic solution of the complex caused immediate

—88—

precipitation of a white solid. Recrystallisation from acetone gave * complex which analysed as |^tF(PPh^)^]BPh^ . Similarly, a complex analysing as |ptP(PPh_) j wasobtained from the fluoro-complex and lithium tetrafluoro- borate. These results suggest the cation is in fact |ptP(PPh_)_l*.

85Grim et al. have prepared complexes of the type {ptP_x]Y, (X=C1,Y=C1, P=PPhgMe,andX=Cl,Y»Cl or BPh^, P=PPhgPr.), by reaction of one mole, of tertiary phosphinewith the cis dichlorobis(tertiary phosphine)platinum(II) complex, and, in the case of the complex,jjPtCl(PrPhgP) jnPh^, by addition of sodium tetraphenyl-borate to a solution of the iPtCl(PrPh.P)Cl complex.

86Church and Mays have also prepared complexes of the type |ptXL(PEt^)gj*C10^" (X=C1, Br, L=PPh^,PRt^,P(OPh)^,P(OMe)^ by reaction of the type

cis PtXg(PEt^)g + L + NaClO^ ^|ptXL(PEt^) CIO^"

87Clark et al. have also prepared similar complexes by reaction of cis dichiorobis(triethylphosphine)-platinumdl ) with triethylphosphine, in the presence of sodium tetraphenylborate.

cis PtC]g(PRt^)^ + PRt^ + NaBi=h^ »|ptCl(PEt2 )jBPh^

-89-

ComplëXëg edAimlnin# eêtîleM,(%ehAlid#)hâve also heen obtained by reaction of the corresponding

68platinumdl )dihalide complex with boron trifluoride, e.g.

cis PtlgCPRt^)^ + DF^ ---- fptl(PEt^)J BF^

Therefore, the complex obtained from reaction of liquid hydrogen fluoride and tetrakis(triphenyJphosphine). platinum(0) may be formulated as, fluorotris(triphenyl- phosphine)platinum(II) hydrogen difluoride. The infrared spectrum of the complex showing a band that may be assigned to the hydrogen difluoride ion, although bands in this region are somewhat obscured by absorptions due to the co-ordinated triphenylphosphine ligand. Molecular weight measurements on the complex also.gave reasonable agreement, with those expected,for an ionic compound of the formulation {^PtF(PPh^) J HF^.

The reactions of other zerovalent tertiary phosphine complexes of nickèl, palladium and platinum with liquid hydrogen fluoride have also been studied. Conductivity measurements suggest that ionic compounds are formed in most cases.

Tetrakis(diphenylmethyIphosphine)platinum(0) reacted with excess liquid hydrogen fluoride to give a pale yellow product. Recrystallisation from acetone gave a white solid identified as fluorotris(diphenylmethyIphosphine )- platinumdl) hydrogen difluoride.

-90-

PtF(PPhgMe)^^HP2.

The yellow colour of the crude initial product is probably due to the presence of unreacted Pt(PPhgMe)..

product showed a conductivity in acetonein agreement with that required for a uni-univalent electrolyte.

Tetrakis(triphenylphosphine)palladiura(0) reacted with liquid hydrogen fluoride to give a crude yellow product. The ether-soluble portion of this crude product was shown to contain free triphenylphosphine. Recrystallisation of the diethyl ether-insoluble portion gave a pale yellow complex which analysed as PdFgCPh^P)^. However, conductivity measurements in acetone showed a conductivity in agreement with that required for a uni- bivalent electrolyte. The complex possibly has the structure shown below.

(Ph PigP^^ ^fd(PPh 2 )g

2+

,F„

Di %,2-bis(diphenylphosphino)ethan«J platinum(O), reacted with excess liquid hydrogen fluoride to give a greyish compound, after removal of excess acid. However, after thorough washing with diethyl ether, the product was seen to contain some metallic platinum.

-91-

Recrystallisation from acetone gave a white product which analysed as PtP-tPhgPCgH^PPhg). The diethyl ether washings of the crude complex contained displaced 1 , 2 -bis (diphenylphosphino)ethane. The conductivity of the complex in acetone suggested the complex was a uni-bivalent electrolyte. The structure of the complex is possibly,

P^"^= 1,2 bis(diphenylphosphino)ethane.Complexes containing the cationic species

2 +i;t2Xg(R,P)4 have been prepared by other workers.Druce et al. have reported the reaction.

-KL2cis PtXgLg + 2BX_—

L*(n-Bu)_ P , X=C1 or Br.

90Clark et al. have also reported the reaction,

2cis PtClg(Ph^P)g + 4BP^ ^tgClg(Ph^P)^ (BP4)2

+2(BPpCl)

Addition of liquid hydrogen fluoride to tetrakis- (triphenylarsine)platinum(0 ) gave a colourless solution. After removal of excess acid a yellow solid was obtained

-yn-

which, after recrystallisation from acetone, gave a pale

yellow solid analysing approximately as PtFg(AsPh_)g. It was concluded by analogy with the above reactions that the

complex had the structure.

2 +

^2(Ph2As)gPt^ ^^ft(AsPh2)g

The zerovalent nickel complex, dicarbonylbis(tri­phenylphosphine )nickel (0 ) reacted with excess liquid hydrogen fluoride to yield a dark greyish solid containing a little metallic nickel, after removal of excess acid.

4This product contained free triphenylphosphine, identified

by elemental analyses, infrared spectrum, and melting

point. A compound insoluble in all common solvents and,showing no bands in the infrared spectrum characteristicof co-ordinated carbon monôxide or triphenylphosphine,was probably nickeKII)difluoride. This reaction has

73also been studied by McAvoy et al. who also report the formation of nickel(II)fluoride.

—93—

EXPERIMENTAL

Analytical data and melting points are shown below<

Characteristic infrared absorptions, and nuclear

magnetic data are shown in the relevant experimental

section. Conductivity .measurements were obtained on a91Wayne-Kerr conductivity bridge. PtXPhgPCgHj^PPhg)^,

3 ' 92Pt(AsPh^)^, N i (CO)^(PPh^)2 , and other complexes were

prepared by literature methods.

Reaction of liquid hydrogen fluoride with various

zerovalent metal complexes

i) Pt(PPh,) _.Removal of excess acid gave a white solid, which,

after thorough washing with benzene and diethyl ether, was

recrystallised from acetone, giving the product

jptP(PPh^)^ HFg. The.complex is soluble in ethanol, acetone

and chlorinated solvents, but insoluble in diethyl ether,

benzene, and petroleum spirit.

M.p,184-190°, to yellow oil.(turning deep red at 210°.)

‘ F^^ nuclear magnetic resonance spectrum showed a band at

+432OC.p .s .from benzotrifluoride. The complex shows an

2 °i.r. absorption band at l4lOcm~"^, assigned to YHF,(Found: C,61-53; H,4'56; F,5'40; Pt,l8-20,

C54 H46P 3P!>t ,1 8 ’ 76%)

H,fF_P_Pt requires C,62-37; H,4-46; F,5'48; P,8-94;5 A 4 0 3

-94-

Oamometric molecular weighta,(determined on a Mechrolab vapour pressure osmometer in acetone solution) (Found: 467, 432, 343.

Required fmr PtPfPRbg)^ (HF2),104o).

Conductivity dataSolvent conductivity

Nitrometbane glohm ^cm^mole ^Nitrobenzene 1 9 ohm ^cm^mole ^Acetone 9 0 ohm ^cm^raole ^

Percentage Yields, based on equations,(1) and(2)

1) Pt(PPh_)^ +' 2HF ------> PtFgCPPh.)^ + 2PPh^ + H 2

2) Pt(PPh^)^ + 3HF------- >^tF(PPh^)^ HFg + PPh^+ " 2 -

Wt.of Pt(PPh,),. (g). Wt.of product,(g), % yield ;(washed with Based

on eqn(2 )

2.93 2-04 . 116 95I'OO 0-79 129 912 ' 0 0 1-43 113 83

Pt(PPh2 )2 ,1 - 5 0 l'4l 119 87

The percentage yields of triphenylphosphine. displaced

-95-. i

in two determinations, were,46 and 4 l , based on

equation (i-) , and 92 and, 82, based on equation(2). No

triphenylphosphine was isolated from the reaction of

Pt(PPh^)^. with liquid hydrogen fluoride.

The complexes, Jl->tF ( PPh Me ) , JPd^Fg (Ph^P ) ,

[r42"3(PhgPCgH^PPh2gHFg g. and |ingFg (Ph^As ),J (HFg)g, were prepared from the corresponding zerovalent phosphine

complexes,ii) Pt(PPhgMe)^, iii) PdfPPh^)^, iv)

Pt (PhpPCgH^^PPhg ) 2 5 v) Pt(AsPh_)^ respectively, using the

same method as above for the preparation ofjptFPPh^)^ HF^,

All complexes were recrystallised from acetone.

Cheiracterisation. data for these complexes is shown below.

|ptF(PPh2Me) j HFg M.p. 12%-130°. Colour, white. ,

(Found: C,56«6; H,4- $6 ; F,6-38; P t , 21 • 79.

C.gH^QP-P-Pt requires C,54'82; H,4'72; F,6-68; Pt,22.83%)Conductivity in dry A.R.acetone = 78ohm ^cm^mole”^.

IQThe F ■'n.m.r. spectrum showed a signal at + 5070c. p. s.

relative to benzotrifluoride.

P t F 2 ( Ph PC PPh g ) 2 ( 2 2 M.p.2l4-2l8 . Colour, white,

(Found: C , 44 - 72 ;, R ,3 - 65 ; F,9-02.

^ requires C,4?'93;,H,3.87; F,8.73%).Conductivity in acetone = 244ohm ^cm^mole ^ .

96-

^2-2-~-3-4l-^2- M.p. 205-210°. Colour, yellow.

(Pound: c,64'46; H,4'32; P,5'87; P,8.94.

CL^HggP^P^Pdg requires C,64°63; H ,4•32 ;, F ,5•68 ; P,9.26%)

Couductivi ty in acetone = 175ohro'"^cm^mole'”''.19The F n.m.r. spectrum showed a band at + 5200c.p.s.,

relative to benzotrifluoride,

p t g F g fAsPh^)^ F2 M.p. 132-136°. Colour, yellow,

(Found: C,48«4l; H,3”.40; F , 4 ' 83. CypH^gASgF^Ptg requires

C,51'l4; H,3'58; F,4-49%).

The yields of fluoride complexes obtained, were

variable, as in some cases^"a small amount of unchanged

zerovalent metal complex was left in the reaction vessel,

after removal of excess acid. In these cases, yields might

be improved,by bubbling hydrogen fluoride through benzene

solutions of the complexes.

V i ) Ni(co)_ (PPh,)nRemoval of excess acid gave a grey solid, which

appeared to contain a little metallic nickel. The solid

was thoroughly washed with ether. This ethereal extract

was evaporated to small volume to give triphenylphosphine,i' ' '; identified by elemental analyses, melting point and

, infrared spectrum.

97-

M.p. 77 <■ M.p. of pure sample of PPb^, 79-80 .

(Found: 0 ,81»8 2 ; H,5«79. C ^ g H ^ P requires 0,82-43; H,5’86%)

The acetone-insoluble solid was also insoluble in all other

common organic solvents,and an infrared spectrum showed

no bands that could be assigned to-Y C O . The complex was

pale green in colour. This product is probably nickel(Il)

fluoride.

98.

SECTION BREACTIONS OP THE COMPLEX FLUOROTRIS(TRIPIIENYLPHOSPHINE)- PLATTNUM(II) HYDROGEN DIFLUORIOE

RESULTS AND DISCUSSIONThe reactions of the complex PtF(PPh_),HPg are

discussed in the following sub-sections;

i) Reactions involving reduction of the Pt(Il) complex.

ii) Reactions with alkali metal salts.

iii) Reactions with tertiary phosphines.

iv) Miscellaneous reactions of the Pt(II) complex.

i) Reactions involving reduction of the Pt(Il) complex

to Pt(0).

The complex,fluorotris(triphenylphosphine)-

platinumdl ) hydrogen difluoride, reacted with ethanolic potassium hydroxide and free triphenylphosphine to give the zerovalent d^^ tetrakis(triphenylphosphine)platinum( 0 )

KOH/C_H OHPPh^t [ptF(PPh^) J HFg ;---=-2— » P t (PPh^)^,

This reaction is similar to the reaction of

-99-

ethanolic potassium hydroxide with hydridotris(triphenyl-

phosphine)platinum(II) chloride, giving the zerovalentcomplex, tris(triphenylphosphine)platinum(0).

r TT 1 KOH/C_H_OHPt H(PPh^)^l-------- ^ Pt(PPh^)^.

Ugo et al^^ have also shown that cis dichlorobis-

(triphenylphosphine)platinum(II) may also be reduced, via

trans hydridochlorobis(triphenylphosphine)platinum(11), to zerovalent phosphine complexes, by reaction with

ethanolic potassium hydroxide in the presence of free triphenylphosphine.

cis PtClgCPPh-jg trans PtHCl(PPh^)g2 5

KOH/CgH^OH/PPh^ Pt(PPh_)^^ (n-3 or4 ).

94Deeming and Shaw have also reported the preparationfi Iof the d iridium(l) complexes of formula Ir X(CO)Pg.

(X=C1,Br,P=PMe_, PEt^ jPMe^Ph), by dehydrohalogenation

of the corresponding hydridodichlorocarbonylbis(tertiaryphosphine)iridium(III) complexes, lrHXg(CO)Pg, using

methanolic potassium hydroxide, or sodium methoxide.

KOH/C H OH Ir^^HXg(C 0 )P2 ---- =-2 ^ Ir^X(CO)Pg.

Other zerovalent complexes may be readily obtained

from the complex jptP(PPhg)J HPg. Thus reaction of the complex with ethanolic potassium hydroxide,in the presence of tetrachloroethylene,gave tetrachloroethylenebis(tri­

phenylphosphine ) pi at inum ( 0 ), together with a small amount

of c h lor op er ch loro viny Ibis ( triphenylphosphine ) pla ttinum( II ).

The latter product is probably formed after the formation of the zerovalent olefin complex, as this isomerises tothe chloroperchlorovinyl complex, in the presence of

, 26ethanol.

Ptr<PPh,), HF, >’t(C2Cl^)(PPh,)2.PtCl(C,Cl,): 4 (PPh,,2.

Similarly, the complex diphenylaoetylenebis(tri­phenylphosphine )platinum(0 ) was obtained,by reaction ofjlptF(PPh^) j HFg^with ethanolic potassium hydroxide in the presence of diphenylacetylene.

-, KOH/C_H OH Pf^-^F(PPh^)^ HFg phC&bPh Pt(PhC=CPh)(PPh^)g

Zerovalent platinum complexes of the type Pt(acetylene)(Ph_P)g were fjrst prepare^%y reduction of platinumdl) complexes, in the presence of the free acetylene.

N.,H./EtOHPtcqqPhjP)^ Pt(<.c.tylen.)(Ph,P)^

-lOl-

ii) Reactions with alkali metal salts.

The complex |ptF (PFh^ ) J h F ^ reacted with lithium halides, in acetone solution, to yield the corresponding bis(tertiary phosphine)platinum(II) halide complexes.Thus, lithium chloride reacted with the complex,in acetone, to give cis dichlorobis(triphenylphosphine)platinum(11). The free triphenylphosphine formed in the reaction was also isolated in this reaction.

r n (CH_)_COIPtF(PPh^) jHFg ) cis PtClg(PPh^)^ + PPh^.

Similarly, with lithium bromide in acetone, the complex cis dibromobis(triphenylphosphine)platinum(II) wasformed.

(CH )„C0ptF(PPhj)jjHFj T T t o V » PtBrgCPPhj)^ . PPhj.

A white solid was obtained after reaction of ethanolic solutions of lithium tetrafluoroborate and ^tF(PPh^)^!HFg. Recrystallisation of the product from acetone gave the complex fluorotris(triphenylphosphine)-platinumdl ) tetraf luoroborate.

jl'tF(PPh^) j h F g + NaBF^ ?|^tF(PPh^) j s F ^ + NaHFg.

-102-

The complex shows a conductivity in acetone, characteristic

of a uni-univalent electrolyte. The infrared spectrum of the product shows a strong broad band, centred at lOglcm"^ which may be assigned to an unco-ordinated tetrafluoro- borate ion.

Cariati et al. have also prepared platinum(II) complexes containing an unco-ordinated tetrafluoroborate ion, by reaction of tetrafluoroboric acid with tetrakis- ( triph eny Iphosph in e.)p la tinum(O) ,

Pt(PPh^)^ + HBF^ -----> jptH(PPh^) J BF^

although, in these reactions, a platinum hydride complex is formed. Addition of sodium tetraphenylborate in ethanol to an ethanolic solution of the complex resulted in immediate precipitation of a white solid. The precipitate

was recrystallised from acetone, and identified as fluorotris(triphenylphosphine)platinum(II) tetraphenyl­

borate .

[ptF(PPh^)^HFg + NaBPh^ >-|ptP(PPh^)^BPh^ + NaHFg.

The complex shows a conductivity in acetone, characteristic of a uni-univalent electrolyte.

-103-

85Grim et al. have also prepared similar platinumdl ) complexes, containing an uneo-ordinated tetraphenylborate ion, although the complex has a platinum-chlorine bond.

cis PtClg(PPhgMe)g4.pPhgMe+NaBPh^— ^tCl(PPhgMe)J BPh^+NaCl.

6Cariati et al. have also prepared similar complexes by simple exchange of anion X, by the tetraphenylborateanion.

PtH(Ph^P)Jx + NaBPh^ >' t H ( P h ^ P ) ^ B P h ^ + NaX.(X*C1, NO^, or HSO^).

The addition of lithium perchlorate to the complexjptF(PPh^)J HFg, in ethanolic solution, causedprecipitation of a white solid. The reaction mixture wasshaken for twenty four hours, to give a white crystallinesolid. Recrystallisation of this solid,from acetone,gavea product which analysed approximately as PtF(ClO^)(PPh^)gThe infrared spectrum, however, shows a band due tounco-ordinated perchlorate ion, and the complex has aconductivity characteristic of a uni-bivalent electrolyteand a formula of type i) may be rejected.(Ph P) Pt(

^ O-CIO Type i)

— 104 —

F,. 1^*Type ii)

The complex possibly has structure ii), similar tothe structure postulated for the complex obtained fromreaction of di j l , 2-bis ( dipbenylpbosphinoethane ) J platinum(O)and liquid hydrogen fluoride. Platinum(II) complexescontaining unco-ordinated perchlorate ion have previously

86been prepared by Church and Mays.

cis PtXg(PEt^)g + L + NaClO^------ >|ptXL(PEt^)JciO^.L=PEt^, PPh_, P(OPh)^.

iii) Reactions with tertiary phosphinesDiphenylmethyIphosphine was added to an ethanolic

solution of the complex [ p t F ( P P h ^ ) a n d the mixture was shaken vigorously for twenty four hours. The colourless solution had turned slightly yellow after this time. Removal of solvent,at reduced pressure, gave a rather oily off white product, which was extracted thoroughly with diethyl ether. The reaction vessel,containing this oily product, was evacuated on a vacuum line for four hours to give an off white solid. This solid was recrystmllised from acetone, and identifded as

fluorotris(diphenylmethylphosphine)platinum(II) hydrogen difluoride, identical to the product obtained by reaction of tetrakia(diphenylmethylphosphine)platinum(0 ), with anhydroum hydrogen fluoride.

PPhgMePtFCPPhj^HFj C„H

rngwe - -i[_PtF(PPh,M.)jHF^ . PPh,.

The diethyl ether extracts from the reaction contained free triphenylphosphine.

Similarly, reaction of 1,2-bis(diphenylphosphino)- ethane with the complex jptF(PPh^)^ HF^ gave a product identical to that obtained from reaction of di-^,2-bis (diphenylphosphino)ethanej platinum(O) with liquid hydrogenfluoride, which possibly has the structure shown below.

2 + p^p = 1,2 bis(diphenylphosphino^

ethane

When trl-n-butylphomphine was shaken with the complex p^iFfPPhgj^HPg in ethanolic solution, the solution, after eight hours, had turned slightly yellow. Removal of solvent,at reduced pressure,gave an off-white oil, which was extracted with petroleum spirit. All attempts to obtain a solid from the oil failed. However, the petroleum spirit extracts contained free triphenylphosphine, suggesting that a reaction,similar to those above had.

-106-

at least partially, occurred.

' _ n-Bu_P/C_H OH|PtF(PPh^)^jHFg -^ ------> PtF(n-Bu^P) HFg,

An infrared spectrum and proton nuclear magnetic resonance spectrum of the oil, after thorough washing with petroleum spirit,(free tri-n-butylphosphine soluble in petroleum spirit) , showed that the complex contained co-ordinated tri-n-butylphosphine.

A similar reaction between dimethylphenylphosphine and the complex, jptF(PPh^)^ HP^, in ethanol, also gave a yellow solution after shaking for fourteen hours. However, only an intractable oil could be obtained from the reaction mixture, although, if the oil was extracted with petroleum spirit, free triphenylphosphine could be identified in the petroleum spirit extracts, suggesting that replacement of the triphenylphosphine ligand by dimethylphenylphosphine had, at least partially, occurred.

[ p t r C P P h j j j jH F , . PM.^Ph M f L . [ P t F ( P M e ^ P h ) , ] H F ^ .P P h , .

-107-

iv) Miscellaneous reactions of the complex^PtP(Prh,)^ H P m.

When a stream of hydrogen chloride gas i as bubbled through an ethanolic solution of the complex,|ptF(PPh^)^Jh f ^ , a white crystalline solid was precipitated. An infrared spectrum of this product, melting point, and elemental analyses, identified the product as cis dichlorobis(triphenylphosphine)piatinum(II)

Reaction of hexafluoropropene, CF^CF=CFg with the complex, in acetonitrile, in a stainless steel pressure vessel at 60°, for thirty six hours, gave art off-white solid. An infrared spectrum and melting point of the product showed that it was the unchanged |PtP^Ph_) HFg complex. Similarly, reaction of tetrafluoroethylene,CgFr, with the complex under the same conditions,gave unchanged |ptF(PPh_)_lHFg.

Reaction of the complex tP(PPh^^)HFg ,in acetonitril e, with carbon monoxide at a pressure of 100 atmospheres, for twenty four hours, in a stainless steel vessel, gave an orange-yellow product, showing two strong bands at 198lcm"^ and 1 9 4 2 c m a s s i g n e d to VCO. The complex showed no conductivity in acetone. A single crystal X-ray structure determination is being performed on this complex.

73McAvoy et al. also studied the reaction of carbon monoxide in anhydrous hydrogen fluoride with the complex

-108-

formulated by these workers as PtFg(PPh_)g , and obtained a complex of formula PtFg(CO)g(PPh_)g , although this complex showed bands assigned t o V C O at 2152, 2105, end 2085cm"l.

When ethanolic solutions of stannous chloride or bromide were added to the complex |ptF(PPh^) HFg in ethanol, an immediate formation of a yellow precipitate was observed. The complexes were recrystallised from

* Yacetone/ethanpi mixtures. Infrared spectra(400-200cm" ), of these products showed the presence of the trichloro- stannato, SnCl^ and tribromostannato, SnBr_" anions. Elemental analyses showed that these complexes containedboth fluorine and chlorine or bromine, but the complexes were not completely characterised.

The reaction of carbon di-sulphide with an ethanolic solution of the complex [ptF(P P h ^ ^ j HFg gave a pale yellow crystalline solid, analysing as PtF^(CSg)(PPh^)g. The infrared spectrum of this complex showed a band at 1176cm”^ which can be attributed to the stretching frequency of the carbon-sulphur double bond. The structure of this complex,(B), may be similar to that postulated for the complex bis(triphenylphosphjne)(carbon disulphide)-

52platinumdl), (A), prepared from the reaction oftris(triphenylphosphine)piatinum(0), with carbon disulphide

fin diethyl ether.

(Ph^P)gPt j (PhgPlgP

Aj_ 111-109-

1 ' T)'rl" fi"M' rgm toN 13133"VIt3" f-VJ

oI o"n fM to

N M to toCTN\ji M O(0 CD C\0

t ri^«+ rf"q13 1313 135" O'VI VI

&a_j03 00133"4P w

CDVI 0N'1MoVI

VI VI VI VI -o ~0 ON VI ■*J oH to to M o o O \D 0 a>g M0\ o f VI VI \o VI ON 3 nO VI VI vO CO ON VI to Q. aVI VI VI VI 4P 4P 4P 4P 5Ç O0 3^ o\ CD C\ \0 V£l O H G0\ 3\ \0 N 4P ON

o o

05 «V

H O

3 o a a"9 O 0 31 1 1 1

Æ» 4P

\D 05 VI to M SO ■Nl SO3 H 3 m a aNg o0 31 1 O to4P VI

1 1 1 1 P M 3 o a a?\ C\ to to M M CD CO m0 33\3\ M to VI 4P SO -V SO CD

-O -V

4P-J \0 4P VI VI 3 o a a"4 m 0 3VI VI \0 M 1 1 1 1 1 1 G 1- 3 n

(/)

110.

( 4-

EXPERIMENTALAnalytical data and melting points,(nncorrected), for

new complexes are shown in Table 1. Analytical and melting point data for unidentified complexes are shown in the relevant experimental section. Characteristic absorptions in the infrared spectra of the complexes are also shown in the relevant experimental section, together with

nuclear magnetic resonance data. All reactions were performed in an atmosphere of dry nitrogen.

Reactions of QptF(PPh^ )j HF^ with various compounds.1 . Triphenylphosphine, in the presence of ethanolic potassium hydroxide.

Ethanolic solutions of the complex,(O* 37g»), and triphenylphosphine (0 *39g«), were mixed together under nitrogen. Ethanolic potassium hydroxide,(0*20g.), was slowly added, with vigorous stirring of the solution, the solution being warmed to about 60° . The solution

turned yellow, and a yellow crystalline solid precipitated from solution. The solid was filtered off, and washed with ethanol. Tve product was identified by melting point and infrared spectrum as tetrakis(triphenylphosphine)- platinui f 0 ) .M.p.95-99°' M.p. of complex Pt(PPh_)^ prepared by literature m e t h o d 8 7 - 9 0 °*

-111-

2. Tetrar.bloroethylene in the presence of ethanolic

potassium hydroxide.

An ethanolic solution containing the complex,(0°15g,),

tetrachloroethylene,(0 »lOg.), and potassium hydroxide,

(O'lOg.), was refluxed in ethanol. An off-white solid,

that precipitated from the solution, was filtered off and

recrystallised from benzene/petroleum spirit mixture,

affording a mixture,(0 °10g.), of tetrachloroethylenebis-

(triphenylphosphine)platinum(0 ) and chloro(perchloro-

vinyl)bis(triphenylphosphine)platinum(II), identified by

melting point and infrared spectra.

M.p. Bulk of complex melts at l80-18 5° ( Li t . Pt ( CgCly^ ) (PPh^ )

190° ). A little melts at 285° . (Lit.PtCl(CgCl_)(PPh )g

286°).

3 .Diphenylacetylene in the presence of alcoholic potassium hydroxide.

An ethanolic solution containing the complex,(0 » 37g»)

diphenylacetylene,(Oil5g«), and potassium hydroxide, was

refluxed in ethanol for fifteen minutes. The solution

was allowed to cool, and fine yellow crystals were

deposited. The yellow complex,(0«23g.), was identified as

(diphenylacetylene)hi s (triphenylphosphine)platinum(0 ) , by melting point and infrared spectrum.

M.p. 139-167°. Lit. 161-169°.

■11 2,-

4. Lithium cblVjridè or bromide. .

'The. lithium hcilicle, (0 • 20g. ) , in acetone,, was added

with stirring, to the complex,(0 «36g.), in, acetone solution,

causing immediate precipitation of a white solid. The

solution was boiled, evapopated to dryness, and washed

thoroughly with water. The crude product was extracted

.with petroleum spirit, and then methylene chloride.

Cis di chlorobis(triph enylphosphine)platinum(IT)(0 «19g.)

and cis dibromobis(triphenylphosphine)platinum(II) were

identified by melting point and infrared spectra.

Triphenylphosphine was also identified by infrared spectrum

and melting point,, in the petroleum spirit extract of the

crude product.

Cis PtCl^(PPh,)^ M.p. 298-300°decomp. (Lit. 310°)\ o

Cis PtBr2 (PPh_)2 M.p. 297-303 decomp.( Lit. 300 )

5, Lithium tetrafluoroborate

Ethanolic solutions of the complex,(0 »?5g«), and

lithium tetraf Itioroborat e , ( 0 . 30g . ) , wer e mixed and the solution was heated to boiling. The solution was cooled,

diethyl ether was added, and the solution was shaken

vigorously for forty eight hours. A white solid had

precipitated out after this period, which was recrysta]lised from acetone/diethyl>et her mixtures, and

identified as f1uorotris(trinh enyipho sph ine)p1a t i num(II) • tetrafluorobora te. (Q .gig.).

-113-

Conductivity in acetone - 94ohm"^cm^ mole~^.

A characteristic infrared absorption band was observed at .11051cm “ (s br ) assigned to

6. Sodium tetraphenylborate

Ethanolic solutions of sodium tetraphenylborate,

(0»20g„), and the complex, (0»35g«), were mixed, causing

immediate formation of a white precipitate, which was

filtered off, crystallised from acetone/petroleum spirit

mixtures, and identified as fluorotris(triphenylphospbine) •

platinum(II)tetraphenylborate.(0 »30g .).Conductivity in acetone = 8^ohms”“cm^mole’"^

7. Lithium perchlorate

Ethanolic solutions of lithium per chlorate ,( 0 » 6g . )•,

and the complex,(0 °71g.), were mixed, and. a white solid

was precipitated. The reaction mixture was shaken for

twenty four hours, and the white precipitate was filtered

off, and recrystallised from acetone, giving a product

which analysed approximately for the stoichiometry

PtE(C10^)(PEh^)p.

. ~ n 4-

Conductivity in acetone = l,36obtns ^'cm^mole ^ .

A characteristic absorption band in the infrared spectrum

was observed at 1090cm ^ (,s br), assigned to vClO^.

8 . Tertiary phosphin.es

The general procedure for these reactions is given

below. To the complex in ethanol,(im.mole.),tertiary

phosphine,(3m . mole.) was added, and the solution turned

slightly yellow. The solution was then vigorously shaken

for twenty four hours. Tpe solvent was removed under

reduced pressure, and the product washed thoroughly with

petroleum spirit. The flask containing the product was.

then connected to a ^iVdcuum line, and heated in vacuo for

à' few.hours. Diethyl ether was added to the product, which

was then filtered off. In this way , |~PtF ( PPhgMe ) HFg ,

and, jl^t^^(Ph^PC^Hj^PPh^) (HF^)^, identical to the products

obtained by reaction of liquid hydrogen fluoride with the

appropriate serovalent platinum complex, were obtained.

The reactions of tri-n-butylphosphine and dimethyl-

phenylphosphine with the complex gave intractable oils,

although displaced triphenylphospbine was identified in

the petroleum spirit extracts of the crude products.

M.p. ptF(PPhgMe)^lHF^. 118- 123°. '

M .p . {p t^ g ( P h g P C g H ^ P P h g )J (H F g ) 2 . 226-228 .

nuclear magnetic resonance spectrum of the product,

-.1 .1 5 -

from the reaction between tri-n-butylphosphine and the

Pt(Il). complex, showed a broad multiplet centred at

1«20 pprn(d) from trimethylsilane , (TMS ) , as internal

standard.

9 . Hydrogen chloride

A' stream of hydrogen, chloride gas was passed through

an ethanolic solution of the complex,(0 »5g• )» for fifteen

minutes. A white crystalline product/(0°31g°), was

precipitated, which was identified as cis dichlorobis-

(triphenylphospbine)platinum(II ) by infrared spectrum,

melting point, and analyses.

(Found: C,53'88; H,3'77; Cl,8'8l,C»^H^QClgPgPt requires; C,54-69; H,3 -8 2 ; ci,8-97%)

: : '

10. Hexafl\ioroprop-2-ene and TetrafluoroethyleneThe fluorocarbon was condensed into a stainless steel

pressure vessel containing the complex,in acetonitrile

solution. The vessel was heated to 60 for thirty six 'hours. Unchanged starting complex , j PtF (PPh„ ) HF„ , was3.identified in each case,by melting point and infrared

snec'trum. .

-116-

11. Carbon monoxide

Carbon monoxide, at a pressure of 100 atmospheres,

was admitted to à stainless steel vessel containing the

complex (0°8g.), in acetonitrile solution. The vessel was

heated to 60° for eight hours, and left at room

temperature for ten hours. Filtration of the a,cetonitrile

solution gave an orange crystalline product and an orange-

yellow solution, from which further amounts of an orange-

yellow product could be obtained, by addition of diethyl

ether. Elemental analyses of this product,(0»49g.),

indicated the stoichiometry PtF^(CO)^(PPh^)2 .(Found : C,56°36; H , 4 » 08 ; F,4”50. C^gly^^FgOpPgPt requires

C,56'09; H,3'72; P,4.679^)

The orange product was a non-electrolyte in acetone

solution. The infrared spectrum of the product shows-1 _icharacteristic absorptions at 1942cm (s),and 198lcm (s)

assigned to TCO,

12. Stannous chloride or bromide

On addition of ethanolic solutions of stannous

chloride or bromide, to the complex in ethanol, a yellow

precipitate was immediately formed. The yellow solid

was filtered off and recrystallised from acetone/diethyl

ether mixtures. Infrared spectra of these products showed

■11

characteristic bands at 322cm .( s ) , 299cm ^(s),272cm ^(s)262cm ^(s), assigned to y-fenCl^ and %tPt-Cl for the stannous

chloride reaction product, and at 222cm ^(m),2l6cm ^(m ) 210cm '(m s;h ), 203cm ^(m), assigned toV'SnBr^ and

"f Pt~Br for the stannous bromide reaction product.

SnClg/^tF(PPh^) HP2 reaction product:(Found: 0 ,52°20; H,3°55; Cl,ll'75; F,o°85; Pt,23.37%)SnBr g/jPtF (PPh^ ) J HFg reaction . product :(Found: C,45'l8; H,3'31; Br,17-26; F,l'32%)

13. Carbon disulphide

To an ethanolic solution of the complex,(0°6lg.)

carbon disulphide (3mls.) was added. The solution was

shaken for two days. Removal of solvent, under reduced

pressure, gave a yellow solid , which was thoroughly washed

with ether. This product had stoichiometry corresponding to

PtF^CSg(PPh^ )2 . The complex showed a characteristic band

at 1176cm ^(ms), assigned to T'C=S.

- 1,1 8

CHAPTER 5

REACTIONS OF ORGANIC ACCEPTOR AND DONOR COMPOUNDS WITH

TRANSITION METAL COMPLEXES.

GENERAL INTRODUCTION

In the course of our investigations of the chemistry

of the complex fluorotris(triphenylphospbine)platinum(II)

hydrogen diflnoride, the interaction between' the platinum(II)

complex and 2 , 3~dichloro~,5 , 6~dicyano-p-ben7,oquinone , was

studied. Addition of the.pale yellow acetone solution of

the quinone,to a colourless acetone solution of the

'platinum(II) complex,gave an immediate intense red

colouration. The,visible absorption spectrum of this

solution showed new bands which could be attributed to the

2,3-dichloro-5j6-dicyano-p-benzoquinone anion. Similarly,

visible absorption spectra of the platinum(Il) complex in

acetone solution,with p-benzoquinone or tetracyanoethylene,

showed the presence of bands attributable to the p-benzo- quinone and tetracyanoethylene negative ions respectively.

This chapter describes the investigation of these

interactions by visible absorption and electron spin

resonance spectroscopy, and the extension of the

investigation to other transition metal complexes. In>

particular, the interaction of quinones and transition metal

,dithiolene complexes has been studied.

- 1 ) 9 -

PART 1 k

THE INTERACTION BETWEEN TRANSITION METAL DITHIOLENE COMPLEXES AND ORGANIC ACCEPTORS.

RESULTS AND DISCUSSIONIn this chapter, the interaction of metal dithiolene

complexes with organic acceptors is discussed. The nomenclature of the metal dithiolene complexes follows that used by NcClevert^dn a review of these complexes.The formal oxidation state of the metal in these complexes is taken,in this work,to be that derived from consideration of the dithiolato lig»nds as dianions, e.g.(Et.N)g |Nifs2Cg(ÇN)2 ] 2 ]^", oxidation state, of Ni» + 2.

The term 'charge transfer' is generally used rather loosely, end,in this work, is used to imply that an ultra­violet or visible absorption spectrum of a complex, ( A D ) ,

formed from molecules A and D , shows bands due to transfer of charge within that complex. The term electron transfer is used in cases where complete transfer of an electron from one species to another has occurred, ( A * + D ).

A + n ^ ( AD) -------------- > A" + D*

In solution, particularly in strongly solvating

-]20-

solvents, formation of an ionic species, rather then a 'charge transfer' adduct, will be favoured.

On mixing methylene chloride solutions of the transition metal dithiolene complexes and 2 ,3 -dichloro- 5 ,6 -dicyano-p-benzoquinone, an immediate colour change occurred. The wavelengths of maximum absorption for new peaks which appear in the 5 0 0 - 7 0 0 m ^ region on mixing the solutions, are shown in Table 1.

Table la) shows the results for complexes of thegeneral formula, (Et^Njg « (M *Co,Ni,Cu,Z n,Pd and Pt). These results show clearly that the visible absorption spectra do not vary with change in metal.

Table lb) shows the wavelengths of maximum absorption for complexes of the general formula, (Et^N) M^SgCg(CN (M=Ni,Pd.Pt,Cu). The results for M=Pd, Pt , Cu , show no variation in the wavelength of maximum absorption ,from those of the corresponding complexes, where the metal is

in the +2 oxidation state. In the case for M=Ni, the complex

fails to generate the A ion, and is therefore a weaker donor than the others in this series.

Table Ic) shows the wavelengths of maximum absorptionfor complexes of the general formula, (R )g Ni^SgCg(CN)2 ^Jj (R=n-Bu or Et). These results show that no difference -occurs on varying the gegenion of the complex.

Tableld) shows the wavelengths of maximum absorption for complexes of the general formula, (Rt^N)gfNi (S^CgRg)^ (R=CN or CF.^). In this case also, variation of the

-121-

TABLE 1Wayelengths of maximum absorption for new bands observedin visible region 5 0 0 -7 0 0 m ^ o n adding 2 , 3 dicbloro-5 , 6 dicyano-p-benzoquinone to transition metal dithiolenecomplexes, in methylene chloride solution.

la)-Absorption spectra of complexes of general formula

.....

Anion[co^gCg(CN)g]2 2 - )) max.

544 ,(mdf)584

[n 1 [s2C2(CN)j]g 2 - 544 , 585[cufSgC^CCNJ^]^ 2- 542 , 584[znfSjC^CCN)^]- 2- 544 , 585p d f S g C g ( C N ) J g 2- 542 , 583p t [SjC^iCN)^^ / - 540 , 584

lb) Absorption spectra of complexes of generalEt.N * |N™^ fs.,Cm(CN)

tr :2- 2- 242 + 2,3 dichloro- 5 , 6 dicyano-p-benzoquinone in CH ^Clg solution

Anion ?lr,ax

NO NEW BANDS OBSERVED

540sh , 590sh 542 ,'5845359h , 581

-)22_1 '4 V , ..

le) Absorption spectra for complexes of general formule+ 2 ,3 -dichloro-5 ,6 -dicyano-p-

benzoquinone in' CH^Cl» solution.

Cation X

(n-C^H^)^N +

(Rt^N +

max ("f) 544 , 585

544 , 585

Id)- Absorption spectra for complexes of general formula Et,^N Z dichloro-5 ,6 -dicyano-p-

benzoquinone in CH„Cl„solution.

Anion

2-

Am.,

544 , 585

544, 586

-123-

TABLE 2Wavelengths of maximum absorption for new bends observed on adding other organic acceptors. A, to complexes ofgeneral formula, (Et,^N)m_

a) A=7.7,8,8

Anion

2J 2[?i” [s2C2 (CN)[cuI’ (S,C,(CN)2] 2;

tetracyanoquinodimethane

A max

748 , 7 6 5 , 849 7 4 7 , 762sh,848

7 4 9 , 763sh,850

2-

2-

2-

b ) A=tetracyanoethylene Anion

[sjC2 (CK)|

[Z"“ I2>=2<“ L |[pt”

II r 41h:

Xmax

polybanded **3 74-4 70 " *^390-470

" *%20-470

'* 376-470" 366-470

a) Polybanded at 9-10 m \ intervals.b ) Region 370-390 or 420 m't, obscured by other bands.

-]%4-

dithiolene .ligand, bound to the metal, does not alter

the visible absorption spectra.

The results, as shown in table 1, suggest that the

addition of all the metal dithiolene complexes to a

solution of 2 ,3-dichloro-5 56—dicyano-p-benzoquinone, generate the same species.

Similar results are obtained when the acceptors,

7 ,7 ,8 ,8-tetracyanoquinodimethane, and tetracyanoethylene

are added to transition metal dithiolene complexes.(See

table 2 ) „The visible absorption spectra observed could arise

either from charge-transfer, from a D.A.ground state, to

an ionic D^A excited state, or from internal transitions

within, the D or A ions.

Although all the spectra obtained shown in table 1

have maximum absorptions at very similar wavelengths, the

only common feature of the complexes studied is the

organic acceptor 2 ,3-dichloro-3,6— dicyano-p-benzoquinone. Similarly, for table 2, the only common features are the

organic acceptors tetracyanoethylene or 7 ,7,8,8-tetracyano- quinodime thane . Therefore, the absorption spectra obtained

would seem to be characteristic of the A ion, and the new

bands observed are due to an A -- > A transition. For

most of the acceptors studied, the spectra of the

respective anions have been reported, although often in

different solvents. Table 3 shows a comparison of the

spectra obtained by addition of the complexes,

- 1 2 5 - .

TABLE 3Comparison of wavelengths of maximum mbaorption for new bends observed on odding organic acceptors,A, to comnlexo!of general formula (Et,.N)* ;Ni ^(SnCmR..,]L' with known bands --- — ..... ' " 4 — Z—""'-' " ' Z— Z —'Z-z; — - — — — "for addition of various other donors with these organic

DONOR SOLVENT ABSORPTION REFERENCE

TMPD CHgClg 537sh 582sh This work

CHpClg 544 585 -

C"2Clg 544 586

p-phenylenedi amine acetone 550 596

Ei 552 594

Nal 553 592

553 5943b) A= 7,7,8,8-tetracyanonuinodimethmne

DONOR SOLVENT ABSORPTIONBANDS(A ) max

REFERENCE

Z " bzCe'CN),],]:- CHgCl, 748,765,849 This work

TMPD NeOH 744 844 97

Na*A" T.H.P.

-126-

750,772,836 98

3c) A= tetrachloro-p-benzoquinoTieDONOR SOLVENT ABSORPTION REFERENCE

BANDS

h " k c g (C N )Z ]^ ''

CHgClg

Acetone

TMPD

{Ni^^ |SnCn(CF.2 2 ^ 2]'-[SgCjCCFj^l 2]

TMPD

2-

2-

MeOH

MeCN

TMPD "

X » Band obscured

3d) A = Tetracyanoethylene

DONOR SOLVENT2-

TMPD

TMPD

CHgClg

CH2CI2

X , 450 This work

X , 447 "X , 466 "

419, 446 ''

424, 452 "

426, 452 420, 447

422, 448

97This work

97

ABSORPTION Reference BANDS374-470?

370-470?

H 0,Me0H,MeCN 370-470?

This work

97

y a polybanded at 9-lOtn'ï intervals

-127-

3e) A= 2,5 dichloro-p-benzoquinone

SOLVENT ABSORPTIONDONOR

[Ni^^[s^C2 (CN)2)^

■[''i” &2'^2‘=''3L]

2—CHgCig

2-

2-

ÜANDSNo new bands

4l8 , 442sh

REFERENCE

This work

; ^2 2 '"' 5 ' ^ g

Ni^^ |s^C.,(CP,)

Acetone 420 , 450sh

MeOH 415 , 442sh

444

2~2 '~ 5 '2j

TMPD . HgO 444 9 7

3f) A= 2,6 dichloro-p-benzoqtiinone

DONOR ' SOLVENT ABSORPTION REFERENCE

acetone[N l^ iS jC g C C F jj^ jZ

KI "

[Nd^rs^C^lCFj)^!^^- MeOH

TMPD "

3g) A = p-benzoquinoneDONOR SOLVENT

BANDS426 , 450

425 , 450

425 , 450

427 , 4 5 3

This work

97

ADSORPTION BANDS REP.

Ni^^{^2^2^^^^2]2l^" ^^2^^2 bands This work

[SjC^CCFjjZ]^- CHgCl,3h) A = 2-metbyl-p-benzoquinone

[Ni^^|s^C2 (CFj)2] 2]"'

No new bands

No new bends

CHgClg No new bands

— 128—

(R=CN or CF^), to solutions of a

range of acceptors in a variety of solvents, with those

already reported or obtained in this research, for anions

generated by these acceptors, .by addition of standard

donors. The standard donors include alkali halides and N,N,N^,N “tetrametb.yl-p~phenylenediainine ( TMPD ) .

The complex containing the bis (l,2- dicyanoethylene-

dithiolato)nickel(II) dianion, is a fairly reluctant

donor, and only gives rise to anions with the strongest

acceptors, such as 7 ,7 ,8 ,8-tetracyanoquinodimethane, tetra­

cyanoethylene, and 2 ,3-dichloro-5 ,6-dicyano-p-benzoquinone.The complex containing the b i s (1,2-diperfluoromethyl-

ethylene dithiolato )nickel (II ) dianion. Ni |s ( CF^ ) 2J

however, has a more favourable ionisation potential, and also generates anions with the dichloro-p-benzoquinones. Neither complex is a strong enovgh donor to generate anions from p-benzoquinone or 2-methyl-p-benzoquinone.

To further confirm the presence of the radical anions

A ,'the electron spin resonance spectra of many

combinations of inorganic donors with these acceptors

were measured w-ith the results listed in table 4. The

cases where a signal due to A was detected, as shown in

table 4, are in complete agreement with the results from

visible absorption spectra, as shown in table 3, and confirm

the generation of the cinions A . The electron spin

resonance spectra also give some information upon the

nature of the transition metal complex after formation of-129-

TABLE 4 . E.S.R. spectra for A anion, generated on addition of various acceptors, A , to metal dithiolenecomplexes, in Solution.COMPLEX ACCEPTORS :

2-

2-

(&=2'002)Strongsignal

B a Ç(g=2 '0 0 3 ) (g=2 :0 0 5 )Strong Strongsignal

2-

2-

strongsignal

strongsignai

signal2 ][Ni” {s2C^(CN)J 2]

pi" lsgC2(crpj gj - [pd" [s^C^CCN)^ 2]

[pt" [sjC^CCN)^] 2 ]

[co" [SjCjCCN)^!

[zn" [ssCjlCNj^js]^'

g]2-

[Co" jSgC2 ( C N ) Z ] ‘

Q = 2,3- dichloro-5,6-dicyano-p-benzoquinone.B = tetracyanoethyleneC = p-chloroanil.a= In agreement with previous values obtained for T C N E , * *

and p-chloroanil

N.s.o.strongsignal

N.s.o.

-130-

the A ion.

The data obtained is shown in tabbe 5, together wlth

relevant comments. The evidence obtained suggests that,

in many of the cases, a simple oxidation M? ,

occurs, e.g. for the complex containing the bis(1 ,2- di cyanoethylenedithiolato)nickel(II) dianion, after

interaction with 2,3 dichloro-3,6 dicyano-p-benzoquinone, a typical electron spin resonance spectrum signal for

N i (III) is observed. However, in some cases, e.g.

oxidation of the metal dithiolene complex containing

Pt(Il) no electron spin resonance signal is observed,

although Pt(IIl), if formed, would be expected to show a

signal. In this case it is possible the Pt(ll) complex is

oxidised to Pt(IV).

Similarly, oxidation of the metal dithiolene complex

containing Co(lII), on the basis of a one electron

transfer to the acceptor, should give a Co(IV) snecies,

which should be paramagnetic, and show a signal, however,

no electron spin resonance signal has been observed for

the complex Cn^^. (CF, ) ^^^and it has been suggested

this compound is dimeric with strong metal-metal

interaction, and may have a singlet ground state. A

similar explanation can be postulated for the failure

to observe a signal on oxidation of the bis(l,2 dicyano- ethylenedithiolato)cobalt(III) anion, by the quinone.

.-131-

"" sT ' o'" ' N ' ? 1T0 H" O rt- o. 3 H- 3

w ' ùT H/TN w !\} - 10 M M N N

n o n o O n O nN M N M N lO lO

o n o O n o o nz % % z z z z z

N M roa . j

M M ,M , ,N , ,(0 , ,N \ ,tc ,1 1 N to M M M M

H

H M

mH"M3m

»301"3I3"

3NO

M

S Z o 1 . 3.3 H- 3 0W w H n C 0H w A (* 3m» 3ff a.0 a.Z 3 cm Z !30 ff H- 0 * 3 r*-3 m @ w.m M riq » 3 fi- 0H- Il i-> H- 01 3M M m M <+ H3 3 te 0» c H m a M|H CT\ H- H-3 H- M

m 3"

3 3 O 0 ta. 'd Z O H. cmO o n H- 0 H- o m g

« Mf) 3 3 M H M@H- <3 3 3 < A

3 cm 3 3 w- a. & fi 3Z M f- en H- 3" H- H- W*

M O - 3 M 0: 3 Wfi3 (0 4T* 3 % 3 3 *

rt- fi- B: 3a» n 3 H- M Oe 0w. M «TJ 0 3 3 f Xm 3 V: 3 3 3 3 fi H-3 O fi- fi M CLm 3 "O 0 H- H" <3M 3

0.- 0H- 3

O n fiH-

O 3" fi- o O(f 3 3 o 3te 3 O. H(0 3 3 a <3 (+ H) M, 3< 3 o o -3(0 3 3 3O. 33

CL

3 OH-33

N 0 "3 Z * H OM3

O.H-

3 O' 3 0 "0 X g 3 m

a: ^ 30 3 H- H-

3 "0 w C3 3 3"n H-fi n

Ha

03 n O

3 < O 03 3 » H* 3 0 33 2 3 3 H B) 3 3 O

m&% & 3 3 3 "3 1a M H 3 » fi WHiax 0 • 03 3 3HO H, 3 3 X

3 3 3 1Z 3 H- • H- 3

a

"13:

The atôichiometry of the Interaction,between2 ,3 -dichloro,5 ,6 -dicynno-p-henzoquinone and several transition metal dithiolene complexes,has also been investigated. This quinone was chosen since it's anion has one band,(5 8 0 -5 9 0 m^),which occurs in a region,where neither the donors used,nor the neutral quinone,have any significant absorption at low concentrations.

The absorbances of the mixed donor-acceptor solutions at the wavelength of maximum absorption for this band are reported in table 6 . The results indicate a 1 :1 stoichiometry, showing that the simple model,D.A.;==r± D* + A , applies to these complexes. The

equilibrium lies close to the right band side of the equation. These results cannot directly be checked against the extinction coefficient of the quinone anion, in methylene chloride solution, since this cannot be determined, as the N,N,N ,N -tetramethyl-p-phenylene- diamine cation (TMPD*), absorbs in the same region. TMPD therefore, cannot he used to generate the quinone anion at known concentration, and weaker donors than TMPD do not

quantitatively convert this quinone to it's anion, whilst alkali metal iodides are too insoluble in methylene chloride to generate this ion. The extinction coefficient may, however, be determined in acetone, by using an alkali metal iodide, and comparing with this, the value obtained by using a complex containing the bia(l, 2 dicyano- ethylenedi thiolatO.)nickel(ll) dianion, |Ni ^

-]?3-

TABLE 6 . Quantitative results for addition of CHgCl^ solutions of known concentration of 2 ,5 , diçhloro-5 , 6

dicyano-p -behzoquinone,(0), to CHr,Cl., solutions of knownconcentrations of metal dithiolene complexes of generalformula, ", D.

a) D= [(n- &2C2(CN)j j

Concn. D Concn. Q . Optical Density Extinction(xlO"^M) (xlo'^M) Observed, 585m/( Coefficient

% Calculated

1'92 0.58 0.24 65001'92 1'15 0.62 54001'42 1.92? 1.01 53601'92 2.70 0.98 51001.92 5" 08 1.0% 57001.92 5.47 0.97 51001'92 5.84 I'll 58005*84 0-77 0.58 50005'84 1.54 0,78 51005'84 2" 51 1'16 51005'84 5' 08 1-53 5000

-154-

6b) 2-

Concn. D . Concn. Q . Optical Density Extinction(xlO-^M) (xlO-^M) Observed _Çoeffi^j^t

0_ Calculated

1'92 O'58 O'25 66001.92 1'15 0-70 61001'92 1'92 1'09 57001'92 2'70 1'17 61001.92 5.47 1'09 57001'92 3'84 1'19 62001"92 4^25 I'll 58<M1.92 8 . 0 7 1'09 5 7 0 0

6°.)■ P.=-

192 5'70 1'15 6000

6 d)P. |Êt, Nlt | P d ^ ^ ^ ^C^(CN)J ^

1.54 1.85 0.96 6200

-135-

as a donor^ using acetone as solvent. Theme results, as presented in table 7 , show good agreement between the values obtained in this way.

The extinction coefficient for the anion,in methylene chloride,was then estimated by adding excess of the

2 - dianion to a quinone solution of knownconcentration. The value obtained is shown in table 7, and is close to that obtained in acetone. The overall consistency of the values of the extinction coefficients in table 7 , with the values calculated in table 6 , confirms the 1 : 1 stoichiometry, with complete electron transfer,from donor to acceptor.

The solvent effects,on the spectra obtained, on

interaction of various donors with 2 ,5-dichloro-5,6 dicyanb-p-benzoquinone, have also been briefly studied. Solvent effects are small, and the most significant feature of Table 8 is not the variation of A max. with solvent, but, the non-appearance of the anion spectrum in poorly solvating solvents, such as benzene. This may be explained in terms of the equilibrium,

s o l v a t e d ) t--------- ^ \ s o l v . ) * ^ (s o l v . )

The equilibrium position will depend mainly on the solvation of the ions on the right hand side, and,in good solvating solvents, anion generation will be favoured, as is found. No change in the electron spin resonance spectrum of the bis(l,2 -dicyanoethylenedithiolmto)palladium(Tl) anion

156.

|CUS,|C,J.(CN)^ 2 -

In a variety of solvents, was observed.The above results confirm that, the metal 1,2

dithiolene complexes,(MS^C^R^)^,(z=0 ,-1 ,-2), are readilyinterconverted by electron-transfer reactions. Previously,

102electron-transfer reactions using iodine, p-phenylene-diamine^^other metal,1 , 2 dithiolene complexes,^^"'^^^

104polarography, and other methods, to effect electron transfer in the dithiolene complexes, have been described. E.g.,

^iS^C^tCN)^^- -^2-- » ^iS^C^CCN)^

^uS^C^(CN)^

N0S,Cg(CF,)g [V(S,C,H,,)3j^2-

It is also of interest to note that the interaction of various metal 8 -hy(^oxyquinoline complexes, with organic acceptors, such as 2 ,3 -dichloro-5 ,6 -dicyano-p-benzoquinone tetracyanoethylene, and p-chloroanil , has been studied.^^^ In these cases, charge transfer adducts are formed and complete electron transfer does not occur. This suggests that the ionisation potential of metal 8 -hydroxyquinoline complexes is higher than that of the metal dithiolene complexes.

-137-

TABLE 7 - Determination of extinction coefficient of2,3-dichloro-5,6 dicyano-p-benzoquinone anion, Q

DONORKI

2 -

2-

SOLVENT CONCN. Q .OPTICAL EXTINCTION/ , DENSITY COEFFICIENT (xlO M) ----- ---------

acetone 2 (33 l'6 l 5 7 0 0

" 2 9 1 1-82 6200

CHgClg 1 9 4 1 19 6100

TABLE 8 SOLVENT EFFECTSVisible absorption spectra obtained on addition of 2,3-dichloro -5,6 dicyano-p-benzoquinone to transition metalcomplexes in various solvents

SOLVENT ptF(PPh^)^Fg cisPtCl^Cpph^)^

MeNOq 546 , 5 8 7 5 4 4 , 5 8 3 5 4 7 , 5 8 7

MeCN 548 , 5 9 0 546 , 5 8 6 5 4 4 , 5 8 9

Acetone 5 5 2 , 5 9 4 5 5 4 , 5 9 4 -CHgCl, 5 4 4 , 5 8 5 5 4 2 , 5 8 2 -PhCl - 540-5 , 5 8 5 NONE

C6"6 Donor insol^ Donor insol. NONE

-138-

PART 2 '

THE INTERACTION BETWEEN TRANSITION METAL PHOSPHINE COMPLEXES AND ORGANIC ACCEPTORS

Part 2 includes the results of the investigation of

the interaction between the complex,fluorotris(triphenyl-

phosphine)platinum(II)hydrogen difluoride, and various

organic acceptors, and the extension of the work to other

transition metal phosphin.e complexes . The interaction of

many other transition metal complexes with, in particular,

the acceptor, 2 ,3~dichloro-5 ,6 dicyanobenzoquinone, have

been studied qualitatively, by visible absorption and

electron spin resonance spectroscopy.

RESULTS AND DISCUSSIONOn adding fluorotris(triphenylphosphine)platinum(II)

hydrogen difluoride to a pale yellow acetone solution of

2 ,3-dichloro-5 56 dicyano-p-benzoquinone,Q, an intense red

colouration is immediately observed. A visible absorption

spectrum of the solution shows the presence of bands due

to o" . An electron spin resonance spectrum confirms the

presence of o". The complex also interacts with tetr'a-

cyanoethylene and even the fairly weak acceptor, p-

benzoquinone, to generate the respective anions. Table 9

shows the visible absorption spectra obtained on mixing the

139-

TABLE 9. Visible absorption spectre for addition of various orgmnic acceptors to fptF(PPh,)_:HF« , in acetonesolution.

Accepto] N^w Bands

2,3-di chlor0 -5 ,6-dicyano-p-benzoquinone 542 582

Te tracyanoethylene polybanded 370-470 at 9-10m intervals

p-benzoquinone 430-450

TABLE 10 Visible absorption spectra for addition of2,3 dichloro-5,6 dicyano-p-benzoquinone,Q, to platinum(II) dihalide phosphlne complexes, in CH^Clÿ soin,

COMPLEX NEW BANDS

. 544 5825 4 4 584

545 585

540 582

None

cis PtCl«(PPh_)« 2 3 2cds PtClgfPPhEtgig

cis PtClglnBu^P)^

cis PtClg(Ph_As)g

transPtCl2(PPh,)g

transPtClm(PEt_)g

transPtClg(nBu_P)g

cis PtBr^(PPb_) ris Pt1n(PPhT)o 54: 584

i4o.

complex with these acceptors. These observations led

subsequently to the investigation of the interaction of

Q with transition metal dithiolene complexes,(Part 1),

and other metal complexes. Usually, interaction to form

Q was accompanied by an immediate colour change. The

visible absorption spectra for addition of Q to various

platinum(ll) phosphine complexes are shown in table 10.Table 11 shows the visible absorption spectra

generated on addition of Q ,to methylene chloride solutions

of other transition metal.halide tertiary phosphine-

complexes.

Table 12 shows the visible absorption spectra

generated on addition of Q,to methylene chloride solutions

of transition metal carbonyl complexes. The only point of

note,in this table,is that the octahedral metal carbonyls,

Cr(CO')^, Mo(CO)^, eind W(CO)^, fail to generate Q .

Table 13 shows visible absorption spectra generated on addition of Q,to methylene chloride solutions of various other transition metal compounds. The ferrocyanide ion (Fe (CN) , as might have been predicted, is readilyoxidised.

Table l4 shows those complexes which, on addition to

solutions of Q, did not generate '.the simple spectrum of Q.

In these cases, it is possible that all three bands

observed are due to a charge-transfer band, due to the

transition DA -- } D'A , However, the coincidence of the

-141-

TABLE 11 Visible absorption spectra generated on additionof Q to CHgClgSols. of other transition metml bmlidephosphine complexes

COMPLEX NEW BANDS

cis NiCl2(PPh^)2 545 586

trans PdCl.,(PPh,)m 546 586

CoClgfPPhgig 545 587AuClPPh- None

TA BLE 12 Visible absorption spectra generated on addition of Q to transition metal carbonyl complexes in CHgCl^soln.

COMPLEX

nuCl2(C0)2<PPh2)2

Fe(CO) (PPhglg

Ni(C0)2(PPh^)2

M o (C O )^ (Ph gPC gH^PPhg)

Mo(CO)^

W(CO)g

Cr(CO)^

NEW BANDS

544

550

559

586

580

585

None

—14 2—

TABLE 13 Visible absorption spectre generated on additionof Q to various other transition metal complexesComplex

Pell(CN),4-

Solvent

Acetone

New Band

354 596

Pt(PPh^)2(CgCl^)

VO ( acec )*

Ix-cplgTiClg

cp=cyclopentadiene

None

CHgClg

acac=acetylacetone

TABLE l4 Visible absorption spectra generated on addition of Q to transition metal complexes, which &ive additional bands to those of Q , in CH-Cl» soln.

Complex

PtlPPhgigCCgF^)

P t K C H ) (PPh^)g

New Bands

534sh 575 64l

529 571 612

TABLE 15 Quantitative results for addition of solutions of known concentration of Q to solutions of known concat of ,cis PtClg(nBu_P)g, Concn D xlO'^M115115115115115

D.Concn. Q xlO M22120216410687

Optical Density " 0.21 (585m4)' O'lG

0'16 0-15 b'l4

14-

lower wavelength band* with those due to A , suggests that the high wavelength band, (above 6 0 0 m;f), is due to thistransition DA------ D A , and the low wavelength bands, aredue to A - '- A trausition, as in the other cases.

A quantitative study of the interaction,(see table 1$) between dichlorobis(tri-n-butylphosphine)platinum(II) andQ,showed that the equilibrium,A + D--- D* + A lies towardsthe left hand side of the equation. This should becompared with the metal dithiolene complexes and Q, where the equilibrium lies mainly to the right hand side of the equation, with nearly complete formation of the 1 ; 1 complex D*A . Thus, the addition of 5 to 20 x 10 ^M,CHgClg solutions of Q to 1 •15xlO~^M solutions of cis dichloro- bis(tri-n-butylphosphine)platinum(H), gave optical densities estimated between 0 * 1 and 0 * 2 at 5 8 5 md,(see table 15). The optical densities being estimated by allowing for the fact that, in strong Q solutions at 585m4\there is some absorption due to Q .(c.f.metal dithiolene complexes where Q solutions are weak, and neglible absorption, due to Q, occurs at 585m'Y) * Hence, using the known value of the extinction coefficient of Q , the concentration, Q , may be calculated using the Beer-Lambert Law.

If the equilibrium is assumed to be,D + A t D* + A"

lO'^M lO'^M 1 0 1 0 M_4a value of approximately 10 for the equilibrium constant

-144-

is obtained.If the equilibrium is assumed to be,

JE . o'" + A-- 2.. 10 10 M

DA 10'"M

a value of approximately 10 ^ for the equilibrium constant is obtained.

Triphenylphosphine,(5 4 9 ,588m^), and other phosphines also generated Q in methylene chloride solutions, as observed in the visible absorption spectra of these solutions. Luckii^^as investigated the reactions between phosphines and quinones, and shown that oxidation of the phosphobetaines(I), obtained by addition of a tertiary phosphine to p-benzoquinone, yields a free-radical phosphobetajne(Il)

APR- + V

(I) (II)Thus, the possibility exists, in the case of

interaction of mental phosphine complexes with 0, that,

i)the tertiary phosphine-metal bond br#aks,and phosphine and n interact to form Q".

-145-

formed by interaction of Q, and the phosphine, to the metal.

iii) is formed by interaction of Q and the metal atom in the metal phosphine complex.

Of these possibilities, i) is unlikely, since Q spectra are also observed in a wide range of other metal complexes, not containing co-ordinated tertiary phosphine, although, in the case of the complex,|ptF(PPh_)_lHFg, this explanation may be correct. Similarly, ii) is unlikely, since 0 is also formed by a wide variety of other metal complexes, other than those containing co-ordinated tertiary phosphine.

The electron spin resonance spectra of many of the transition metal phosphine complexes with Q,in methylene chloride solution,have been obtained. In many cases, only a signal due to Q is observed, but, in some cases, a more complex spectrum is obtained. The results are shown in table l6 a).

Similarly, the interaction of tetracyanoethylene with some transition metal phosphine complexes has been investigated by electron spin resonance.(see table l6 b). These results show clearly that the formation is not due to a co-ordinated triphenylphosphine coming off from the metal, and interacting with tetracyanoethylene, since a more complex pattern than that for the tetracyanoethylene onion alone is observed.

In all the preceeding examples, electron transfer

: -l^h-

TABLE l6 n ) E.s.r. spectra obtained on addition of Q to various tertiary phosphine metal complexes in CH^ClM soins.

ComplexPt(PhC=CPh)(PPh^)g

SignalOne strong line at g= 2 '0 0 2 .

Comments Signal due to

q".

cis PtClgPPh_)g

cis PtIg(PPh^)g

trans PdClgtPPh-)^

RhH(CO)(PPh ^ 2

IrH(CO)(PPh )g

PtfCgF^ltPPh^ig

Pt(C2ClF )(PPh^)g

Pt(C2DrF_)(PPh^)g

trans PtHCl(PPh_)_

Multi-line spectrum 9 lines

Possibly combntn. of Q «-paramagnetic metal species.

TABLE l6 b ) E .m .r .spectra obtained on addition of tetra- cyanoethylene to metal complexes in CH^Clg soins.ComplexPt(CgF^)(PPh^)2

Pt(CgClF^)(PPh^ ) 2

Pt(CgBrF-)(PPh^)g

SignalComplex signal containing more than 1 9 lines

Comment99TCNE shows 9 lines

106TCNE-phosphine complex shows 1 3 lines.Suggests combination o f .TCNE 4- paramagnetic metal species.

.147-

from an inorganic donor to an organic acceptor, hasoccurred. The study was extended to find examples ofelectron transfer^from an inorganic complex,acting as anacceptor.to an organic donor.

The organic donor chosen was N ,N ,N'' ,N-tetramethyl-p-phenylenediamine»(TWPD). Great care had to 'be exerciseain experiments involving TMPD,since the TMPD' ion isreadily formed from TMPD^by the action of oxygen.Therefore acetone was thoroughly saturated with nitrogen,, ’ TMPD Was added to acetone solvent, and the visibleabsorption spectrum obtained, to confirm the absence of

+TMPD , before adding metal complexes in each case. The formation of a deep blue colour, characteristic of TMPD', is observed when a suitable metal complex is added to-the ' colourless acetone solutions of TMPD. The visible absorption spectra of these solutions confirm the presence of TMPD^. Formation of TMPD' was observed for thecomplexes as shown in Table 17»

3 Ü7 'King has previously reported the us e of the powerfultwo-electron reducing agent tetrakis(dimethylamino)-ethylene, in reducing certain metal carbonyl derivatives,giving the corresponding metal carbonyl anions and theoctamethy3.oxamidin.ium cation. E.g.

" c o p c o ) g — ^

148.

TABLE 17. Visible absorption spectra generated onaddition of TMPD to acetonesolutions of metal compounds

ComplexVO(acac)_

NSgPtCl^

NagPdCl^

cis PtCl^tpyig

H%C1_

N ew bands(^max*"')

526sh 568 617

525sh 567 615

520sh 565sh 6l8sh

524sh 568 615

519@h 565 612

Py = pyridineacac a acetylacetùna

-149-

. The work, described above, may be seen as a logicalextension from previous work, showing that many metalcomplexes bad basic properties. The protonation ofhydrido di~ (M-cyc3.opent a dienyl ) rhenium was the first

]08reported example of protonation by acids.of the central metal atom,in a neutral transition metal complex.

+ HCl -----> [ReH2 (/r-C H

This report also showed that the rhenium complex was a base, with base strength in aqueous dioxan, comparable with that of ammonia, A subsequent report showed that ferrocene and- ruthenocene are also basic, although only weakly so, forming the ions Fell and,RuH in boron trifluoride monohydrate as a

protonating solvent. Similarly, di-hydridobis- (Ai-cyclopentadienyl ) tungsten' or molybdenum have been shown to act as bases f^Subseqiiently, many reports of the basic nature of various transition metal complexes have appeared. These include the prhtonation of a wide variety of transition metal carbonyls and substituted carbonyls with sulphuric and other strong acids^^the formation of Lewis acid-base adducts of BF^^^BCl^^^or AlMe^^^with transition metal complexes have also been reported.

The interaction of p-chloroanil and sym-trinitro-115benzene with metallocenes, has also been investigated,

: ' -150-

In acetonit-i , vidence from ultraviolet spectra,for the dissociation of the 1:1 complex,formed between cobeltocene and sym-trinitrobenzene(TNB), has been found.

(:T-C-H_)- C6^ TNB" > (X-C_H_)« Co* + TNS'5 5 2 , 5 5 2

Cobaltocene and p-chloroanil,(CA), however, gave both a 1:2 complex, which was formulated as a charge transfer radical ion salt, (X-C^H^)gCo*CA CA, and a 1:1 complex formulated as a charge transfer complex, wkerein there was only slight charge transfer in the solid state (x-C_H_)_ Co*CA^ . Interaction of nickel-5 5 2ocene and p?»chloroanil, however, gave a complex which was postulated to"have the structure.

p.C^H^)2jCA - CA

The formation of the tetrachlorohydroquinone anion, it was suggested, resulted from the disproportionation shown below.

2CA" -----» CA^" + CA

Formation of the complexes containing the-151-

tetrahydroqvlnone dinegative ion, from the reactions of his(X-crotyl)nickel with p-chloroanil, p-bromoanil and monochloro-p-benzoquinone, have also been recently

116reported. E.g. 0

ClCl2+Ni

ClCl

0

These structures were postulated on the basis of elemental analyses and infrared spectra of the isolated compounds. Recently, twenty five compounds of the salts of the dication ofKN-dimethyl-4,4— bipyridyl, paraquat, (pq)^* with anions of the type^X^^ | , (M= univalent, bivalent or tervelent metal, X=Cl,Br,I.), have been prepared^^fwenty three compounds appeared to be charge transfer adducts pq(MX^) and exhibited a band in the reflectance absorption spectra, assigned to an inter- molecular charge-transfer band from anion to cation.

compound pq^*(FeCl^)^" however, exhibited an absorption band typical of the paraquat radical and electron spin resonance spectroscopy , showed a signal, which could be due to a combination of the signals, of (PeClt)" and (pq')*, of approximately equal Intensity.An electron spin resonance signal was also obtained from the compound(pq)(^u]^Cl/^X which suggested the presence of

-152-

'r TCuT" ions in the lattice arising frb^ electron transfer toTparaquat, from Cu” , although no absorption, snectruii: was

obtained for this complex. It was concluded tha-t in these two compounds completc electron transfer from metal, to •paraquat had occurred.

In this work, many examples of complete electron transfer.from transition metal complexes,to, organic acceptor, have been found, and in many cases it has been confirmed that complete electron transfer between the metal atom in the complex,and organic acceptor has occurred. In conclusion, it would appear that many transition metal complexes may act as electron donors,when a suitably stron.c organic acceptor is used, and, similarly in some cases, transition metal complexes may also act as electron acceptors with'strong organic donors.

-153-

RXJ^ERIMENTAL

Visible absorption spectra were measured on Unicam SP800A, and Beckmann DK-2A spectrophotometers.

In quantitative experiments, the reaction mixtures were contained in 1cm. cells, in a thermostatted cell holder, through which water was circulated from a constant -temperature,bath, equipped with beater and contact thermometer with .electronic relay.

Electron spin resonance measurements, using a Varian Associates E3 spectrometer, were obtained and interpreted by Dr.J .B .Raynor, whose help we gratefully acknowledge.

The transition metal 1,2 dithiolene complexes were kindly supplied by D r.J .B .Cornell.

Other metal complexes were prepared by literature methods. Quinones were obtained from Koch-Light. All

solvents were purified and purged with nitrogen before use

-154.-

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