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-CCBut)(CO)9

Reactions of Cp*WRu 2 (CCPh)(CO) 8 ( 1a ) with excess Cp*W(CO) 3 H, Cp* = C 5 Me 5, affords a carbido−alkylidyne cluster Cp* 3 W 3 Ru 2 (μ 4 -C)(μ 3 -CPh)(CO) 9 ( 5 ) alone with three byproducts, which are identified as hydride cluster Cp*WRu 3 (μ-H) 3 (CO) 11 ( 2 ), vinylidene cluster Cp* 2 W 2 Ru 2 (CCHPh)(CO) 9 ( 4 ), and a pentanuclear oxo−carbido cluster Cp* 2 W 2 (O)Ru 3 (μ 5 -C)(CO) 11 ( 3 ). In contrast, the respective condensation using tert -butyl derivative Cp*WRu 2 (CCBu t )(CO) 8 ( 1b ) gives an acetylide cluster Cp* 3 W 3 Ru 2 (μ 3 -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 μ 4 -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.