Intermediates in the conversion of [Os3(CO)11(PRPh2)](R = Me or Ph) into [Os3(µ3-C6H4)(µ3–PR)(CO)9]: crystal and molecular structures of [Os3-(µ-H)(µ3-C6H4PMePh-o)(CO)9] and [Os3(µ3-C6H4PMe-o)(CO)10]

Abstract

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.