Competitive Acetylide C-C Bond Scission vs Formation of a Quadruply Bridging Carbonyl Ligand. X-ray Crystal Structures of the Two Pentanuclear Clusters Cp*₃W₃Ru₂(μ₄-C)(μ₃-CPh)(CO)₉ and Cp*₃W₃Ru₂(μ₃-CCBu^t)(CO)₉

Reactions of Cp*WRu₂(CCPh)(CO)₈ (1a) with excess Cp*W(CO)₃H, Cp* = C₅Me₅, affords a carbido-alkylidyne cluster Cp*₃W₃Ru₂(μ₄-C)(μ₃-CPh)(CO)₉ (5) alone with three byproducts, which are identified as hydride cluster Cp*WRu₃(μ-H)₃(CO)₁₁ (2), vinylidene cluster Cp*₂W₂-Ru₂(CCHPh)(CO)₉ (4), and a pentanuclear oxo-carbido cluster Cp*₂W₂(O)Ru₃(μ₅-C)(CO)₁₁ (3). In contrast, the respective condensation using tert-butyl derivative Cp*WRu₂-(CCBu^t)(CO)₈ (1b) gives an acetylide cluster Cp*₃W₃Ru₂(μ₃-CCBu^t)(CO)₉ (6). The X-ray structural determinations of 5 and 6 reveals the existence of an edge-bridged tetrahedral core, in which the butterfly crater is occupied by a μ₄-carbide in 5 or a quadruply bridging CO ligand in 6. A plausible mechanism leading to the formation of these two cluster compounds is also presented.