The preparation of Ru5C(CO)15 and Os5C(CO)15

C82

Joumal of Orgunomerallic Chemistry, 57 (1973) C82-C83 0 E4sevier Sxpoia Sk, Lausanne - Printed in The Netherlands

Preliminary communication The preparation of Ru~C(COJ~~ and OS~C(CO)~~

C.R. EADY,

B.F.G. JOHNSON,

J. LEWIS and T. MATHESON

University C3remical Labomtory, Lensfield Road, Cambridge, CB2 IEW (Great BrilainJ (Received June 27th, 1973)

a

SUhfMARY

The carbido carbonyl complexes and characterised.

Rus C(CO)rs and Oss C(CO),s

have been prepared

Following the initial report by Braye and coworkers’ of the synthesis and structural characterisation of the first transition metal carbonyl carbide FesC(CO)rs came reports of the preparation and X-ray analysis of the anion* Fe6C(C0)r6*and the neutral Ru&(CO)r, q4 and Ru&(CO)r4 (arene) 3y5. More recently the rhodium anion6 Rh6C(CO)152’ has been identified by full X-ray analysis and an improved synthetic route to FesC(CO)rs has been given’. In the case of the neutral Ru6C(CO)r7 evidence8 has been presented to suggest that the source of the carbon atom is a carbonyl group whereas the carbon in the Rh& system apparently arises from CHCla 6. We now report the preparation and characterisation of the ruthenium and osmium analogues of Fe&(CO)rs. atm) at 13O’C for -1 h yields Reaction of ~&&Ru~(CO)~~ with ethylene (lo-12 a dark browrrorangesolution. After filtration and removal of solvent in vacua a dark brown residue is obtained. Separation by column chromatography on silica using hexane as eluent gives at least eight products amongst which are Ru6C(CO)r7 and Ru&(CO)~~_ Yields of these materials are moderate and very low (30% and -1%) respectively. Although no evidence has yet been obtained for the formation of the pentanuclear carbide from the direct pyrolysis of a-H4Ru4(CO)rs it is likely that the ethylene plays no part in the formation of this derivative. Pyrolysis of 0s6(CO)18 ’ in an evacuated Carius tube at 2515~ gives a dark brown material. Extraction into ethyl acetate, followed by filtration through kieselguhr gives a yellow solution whichafter removal of the solvent yields OssC(CO)rs as yellow crystals (yield -40%). Alternatively the carbide may be obtained from the direct pyrolysis of Osa(C0)1a but in this case yields are low (-10%) and the reaction obviously proceeds via the intermediate formation of 0s6(CO)r8.

PRELIMINARY

TABLE

COMMUNICGTION

C83

1

INFRARED SPECTRA QF M,C(CO),, COMPOUNDS(CYCLOHEXANE) (2200-1600 Compound

v (CO) (cm -I)

Fe5CKO),,a

2098w

Ru,C(CO),, ~,C(CO),,

-

2066~s 2034s

2012m 2016m

2078~s

2019m

2050s

2031s 2038s

cm-‘)

1991m b b

aRef_ 7. bA very weak absorption is observedin this region. The infrared spectra of RusC(C0)

rs and OQC(CO)~~ in the carbonyl stretching region (see Table 1) are related to that of Fe&(CO)rs recorded by Graham and coworkers’. Under electron impact the parent ion MsC(CO)rs” together with ions Ms C(CO>:,, (?I = l-l 5) corresponding to the stepwise loss of fifteen CO groups are observed. As was observed in the mass spectrum of FesC(CO)rs the most intense ion corresponds to the simple carbide MsC+ but unlike the iron complex fragmentation of this unit does no’foccur except for the formation of small amounts of Ru&+. In keeping with the enhanced stability observed with clusters of the 2nd and 3rd row transition metals the doubly-charged ions Ms C(CO)E and Ms C(CO)ls-n*+ are observed in relatively high abundance. The synthetic routes employed in this work, particularly in the case of the osmium system, would again indicate that the source of the carbidocarbon is from the reduction of a coordinated carbonyl group. Pyrolysis of higher osmium carbonyl compounds based on Os, and Oss units also yields carbido complexes and these will be reported in due course. The chemistry of the “carbon atom” in these and other carbide systems is currently under investigation_ ACKNOWLEDGEMENTS We thank Johnson, Matthey and Co. Ltd. for their generous loan of RuCls and Os04 and the S.R.C. for financial support (C.R.E.

and T.M.).

REFERENCES 1 E.H. Braye, L.F. DabI, W. Hiibeland D.L. Wampler,J. Amer. Chem. Sot., 84 (1962) 4633. 2 MR. ChurcbiB, J. WormaId, J. Knight and M.J. Mays, J. Amff. Chem. Sot., 93 (1971) 3073. 3 B.F.G. Johnson, J. Lewisand LG. Williams,J. C&em. Sot. (A), (1970) 901. 4 A. Sir&u, M. Bianchi and E. Benedetti, Chem. Commun., (1969) 596. S R. Mason and W.R. Robinson, aem. Commun., (1968) 468. .

6 V.G. Albano, M. Sansoni, P. Chini and S. Martinengo, J. aem. Sot (Daiton), (1973) 651. 7 RP. Stewart, U. Anders and WAG. Grabam, J. Organometal. Gem., 32 (1971) C49. 8 CR. Eady, B.F.G. Johnson and J. Lewis,L Orgnnometal. aem., 37 (1972) C39.