Intermediates in the conversion of [Os 3 (CO) 11 (PRPh 2 )](R = Me or Ph) into [Os 3 (µ 3 -C 6 H 4 )(µ 3 –PR)(CO) 9 ]: crystal and molecular structures of [Os 3 -(µ-H)(µ 3 -C 6 H 4 PMePh-o)(CO) 9 ] and [Os 3 (µ 3 -C 6 H 4 PMe-o)(CO) 10 ]

The thermal conversion of [Os3(CO)11(PRPh2)](R = Me or Ph) into [Os3(µ3-C6H4)(µ3-PR)(CO)9](3) by loss of carbon monoxide, and probably benzene, has been reported. By carrying out the reactions at lower temperatures we have been able to isolate [Os3(µ-H)(µ3-C6H4PMePh)(CO)9](1a) and [Os3(µ3-C6H4PMe)(CO)10](2a) from the methyldiphenylphosphine compound and corresponding derivatives (1b) and (2b) from the triphenylphosphine derivative. Both (1) and (2) convert thermally to the µ3-C6H4 clusters (3) and are deduced to be intermediates in the formation of (3). The single-crystal X-ray structures of (1a) and (2a) are reported. In (1a), µ3-C6H4PMePh-o is a five-electron donor bonded through P to one Os atom, by a σ-Os–C bond to another, and by an η2 interaction of the C6H4 ring to the third. Compound (2a) contains the µ3 ligand C6H4PMe-o, as a four-electron donor, and a bridging CO ligand. In the degradation of PRPh2 into the components C6H4, PR, and C6H6, ortho-metallation is the first step, but probably follows an initial loss of CO.