Synthesis and skeletal isomerization of the phosphinidene acetylide cluster complexes [Ru₄(CO)₁₀(μ₄-PPh)(CCPh){WL(CO)}] where L = C₅Me₅ or C₅H₅

Reactions of the phosphinidene cluster [Ru₄(CO)₁₃(μ₃-PPh)] with tungsten acetylide complexes [WL(CO)₃(CCPh)] (L = C₅Me₅ or C₅H₅) gave interconvertible isomers of formula [Ru₄(CO)₁₀(μ₄-PPh)(CCPh){WL(CO)}]. The structures of the two C₅Me₅ derivatives were determined by X-ray diffraction, showing a novel WRu₄P octahedral core arrangement, in which the acetylide ligand is co-ordinated to a WRu₂ triangle with its C-C vector bridging the Ru-Ru edge. For one isomer the phosphinidene ligand is located at the position trans to the W atom, while in the second isomer it is at the cis position. Possible mechanisms for this rare example of skeletal isomerization are suggested.