Structure and stereochemistry in some sulfoxide complexes of Pt(II) and Pd(II)

INORC.

t~UCL

CHEM.

LETTERS

Vol. 4.

pp. 691o696t

1968.

Pergornon

STRUCTURE AND STEREOCHEMISTRY

SULFOXIDE COMPLEXES OF e t ( I i )

William Kitching* Oept. of Chemistry,

University

Sulfoxide since infra-red

complexes

of Queensland,

other metals investigated Although PdCI2.2DMSO

pectively, sulfoxide

report infra-red

J. Moore

Brisbane

and Pd(ll)

region suggested

of the Rh(ll)

have been den~o~strated

and Pd(ll).

and p.m.r, measurements

of Cotton and co-workers

since a substantial

res-

on a range of new sulfoxide

infra-red

and configurations.

and structural

studies

that for acyclic

peculiar structural

features,

data in Table i, this appears

sulfur On the

to be tile case,

increase in frequency of the vibration

691

(2,3)

and bonding in other

be the donor atom towards Pt([l) and Pd(ll).

basis of the infra-red

(5)

In this Communication we

(1,2) we anticipated

not incorporating

(4)

(i).

to have trans and cis configurations

Following on the pioneering

would generally

complex

appear to co-ordinate via oxygen

of Pt(ll)

(i),

acetate -DMSO complex

complexes which confirm their S-bonded structures

sulfoxides

4067, Australia.

are of interest

(lll)-dimethylsulfoxide

little is known of the structures complexes

Britain

(2,3) that sulfur was the donor atom.

and Pd(NO3)2.2DMSO

by X-ray determinations

Great

August 1968).

of Pt(ll)

witn the exception of an iridium and the possible exception

In

Ai~D P d ( I I )

studies in the S-O stretching

and some X-ray work confirmed

Printed

IN SOME

and Christopher

(Received 23

Press.

predominantly

692

SULFOXIDE COMPLEXES

Vol. 4,Ho. 12

TABLE 14 SULFOXIDE

~S-O (Free)

VS_o(PtCI2.2L)

~S_o(PdCI2.2L)

~S_o(Me2SnCI2.2L)

DMSO

1055

1135, 1160

1116

945*

(CH3CH2)2SO

1030 (broad)

1125, 1140

1135

940

CH3SOCH2C6H 5

1035

1120; 1150, 1170

iii0; 1152, 1162

945, 975

(C6H5CH2)2SO

1030

1150 (broad)

1120, 1130; 1177

9855

CH3SOCH(CHj) 2

1020, 1040

ll30(sh); 1145

1105; 1130

930, 955**

US_O in cm

-i

for nujol mulls.

In the Pt(ll) and Pd(ll) complexes

splitting of the band commonly occurred, and one explanation has been offered (3).

In some cases distinction between VS_ 0 and

bands of similar energy was difficult in the more complex sulfoxides, but ~S-O doubtlessly increases. The structure of this complex has been confirmed by an actual X-ray study (see N. Isaacs, C.H.L. Kennard and W. Kitching, Chem. Comml. (1968), in press) and is 0-complexed. In this case, the complex has the five coordinate structure Me2SnCI2.L (6), but this does not alter the validity of the argument. Refers to the complex ¢2SnCI2.2L.

derived from S-O stretching is observed.

Sulfur donation would

increase O+S p-d bonding, the S-O bond order and consequently the frequency

(I).

The opposite is true for O-coordination,

~S-O for the organo tin complexes

as judged by

(6) of types Me2SnCI2.2L where

a = sulfoxide. Nothing has been reported on the p.m.r, spectra of S-bonded sulfoxide complexes.

The actual resonance positions of protons on

carbon attached to sulfur in complexed sulfoxides would be anticipated to depend on whether oxygen or sulfur was the donor atom.

An appreciable

Yol. 4, Ho. 12

SULFOXIDE COMPLEXES

693

TABLE 2% S ULFOXIDE

T FREE

T (PtCI 2 •2L)

DMSO

7.5

6.45*

(CH3CH2)2SO

7.3

6.41

CH3SOCH2C6H5 (C6H5CH2)2SO CH3SOCH(CH3) 2

7.68, 6.15

(TPdCI 2 .2L)

7.47 6.86

6.75, ca 5.3

6.13

5.55**

7.7, 7.4

6.66, 5.86

Relative to tetramethylsilane

T (Me2SnCI 2 •2L)

7.35

insoluble

7.45, 5.87

~

6.0

6.92, 6.36

7.62, 7.19

(i0~) or chloroform (2.73K).

Only

a-proton resonances are tabulated, and positions correspond to centres of multiplets in certain cases. Pyridine solvent.

Pyridine displacement of DMSO in the Pt(ll)

complex was slowly occurring as judged by the increasing intensity of the free DMSO signal.

Pyridine displacement of DMSO in

PdCI2.2DMSO occurred before a spectrum could be obtained. This complex could not be synthesised by the usual procedure. See text. The preparation of this compound which is poorly soluble, appears irreproducible.

downfield shift would be expected for S-coordination, while little movement should accompany 0-coordination.

The data in Table 2 is

again impressively consistent with S-bonding for Pt(II) and Pd(II), and O-bonding for the tin complexes. S-bonding in the Pt(II) and Pd(II) complexes appears to be associated with downfield proton shifts of c_aa1 p.p.m., while O-coordination scarcely has any effect.

This increased acidity of a-hydrogens

resulting from S-coordination implies that Pt(II) and Pd(II) salts may be useful catalysts for H-D exchange in sulfoxides. currently being checked.

This point is

Another spectral feature nicely consistent

694

SULFOXIDE COMPLEXES

Vol. 4, Ho. 12

with S-coordination is the presence of 1 9 5 p t - ~ spin coupling (195pt has I = i/2; 33% natural abundance).

On the other hand no llgsn,

IITsn-IH coupling (I = 1/2, each ca 8% natural abundance) has been observed in any of a large number of organo-tin sulfoxide complexes, a result consistent with O-coordination. while in PtCI2.(CH3SOCH2C6H5)2,

JCH 3

For PtCI2.2DMSO , J = 21 H Z

23 H Z.

Substituent effects in

the ligand appear to greatly influence this coupling since in PtCI 2. (CH3SOCH(CH3)2)2, JCH 3 = 24 H Z while JCB < 6-8 H Z. derived from decoupling experiments).

(This result was

This latter effect is probably

a consequence of conformational preference.

No 195pt coupling to

B-protons was observed, and 195pt-!H coupling in sulfoxide complexes is substantially smaller than in the corresponding sulfide complexes (8).

195pt coupling to the benzylic and methylene protons also occurs

but these regions of the spectra are quite complex (due primarily to methylene proton inequivalence) and will be treated in detail elsewhere (9).

The isopropyl methyl groups are clearly non-equivalent in

these complexes.

Far infra-red studies indicated that the Pd(ll) complexes were uniformly trans since a single vPd_C 1 in the region of 350 cm was observed. at ca 310 cm

-i

-i

In contrast, the Pt(ll) complexes showed two VPt_C I and 330 cm

-i

consistent with a cis ligand array.

The

X-ray powder photographs of the Pt(ll) and Pd(ll) DMSO complexes were quite different.

Thus the known mono-nuclear sulfoxide complexes of

Pd(ll) appear to be trans while ti~ose of Pt(ll) appear to be cis.

PdCI2.(C6H5CN)2 in benzene reacted with (C6H5CH2)2SO (ratio 1:2) to yield a complex analysing as PdCI2.(C6H5CH2)2SO , which on the basis of i.r. spectra in tge Pd-CI stretching region (i0),

Vol. 4, No. 12

SU/FOXIDE

COMPLEXES

695

displacement and cleavage reactions (see below) with triphenyl phosphine (~3 P) is suggested to have structure (I).

L\

/ C1 \ Pd

/ Cl

\

/

/ C1

~3Px --

Pd

2~3P

\

,

C1

L

/ C1 \ Pd

/ CI

(I)

/ C1 Pd

"\

1

2~3P

C1

PdCI2-(~3P)2

)

\ P~3

(II) +2 (C6H5CH2) 2S0

L = (C6H5CH2)2SO

Compounds of type (I) have been prepared where L = DMSO, (C6H5CH2)2SO , (CoH5)2SU and C6H5CH2SOCH 3.

These compounds are deep red brown in

color in contrast to the yellow orange mononuclear complexes, and infra-red spectra indicate S-coordination.

Low solubility prevented

conventional molecular weight measurements, and no parent ion appeared in the mass spectrum.

Yellow PdCI2(C6H5CN) 2 which is mononuclear and

trans in the solid (ii), dissolves in benzene or chloroform to yield deep red solutions which show two C-N stretching frequencies at 2230 -i cm

and 2295 cm -1, the former coincident with VC_ N for free benzonitrile.

Intensity considerations suggest that in solution disproportionation is substantially complete to yield a complex of type I, since this will react with the calculated amount of #3 P to yield the known (II) (i0). This then rationalises the formation of the corresponding binuclear sulfoxide complexes and may help to explain the formation of other dimeric products when PdCI2.(C6H5CN)2 is the source of Pd(ll).

All compounds had satisfactory elemental analyses.

ACKNOWLEDGEMENTS.

We are grateful to Mr. V.G. Kumar Das for some

exploratory work and to Dr. J. Macleod of the Australian National University for mass spectra.

696

SULFOXlDE COMPLEXES

Vol. 4, N,. 12

REFERENCES 1.

F.A. Cotton and R. Francis, J. Amer. Chem. Soc., 82, 2985 (1960) and related references.

2.

M.J. Bennett, F.A. Cotton and D.L. Weaver, Nature, 212, 286 (1966).

3.

D.A. Langs, C.R. Hare and R.G. Little, Chem. Comm., 1080 (1967).

4.

M. McPartlin and R. Mason, Chem. Comm., 545 (1967).

5.

S.A. Johnson, H.R. Hunt and H.M. Ne-m~un, Inorg. Chem., 2, 960, (1963).

6.

W. Kitching and C.J. Moore, to be puhllshed.

7.

We thank Mr. D. Doddrell, Indiana University,

8.

P.C. Turley and P. Haake, J. Amer. Chem. Soc., 89, 4617 (1967).

9.

W. Kitchlng, C.J. Moore and D. Doddrell, to be published.

i0.

for this experiment.

R.C. Goodfellow, P.L. Goggin and L.M. Venanzl, J. Chem. Sot., 1897 (1967).

it

J.R. Holden and N.C. Baenziger, Acta Cryst., 9, 194 (1956).

(A),