Toward an Understanding of the Mechanism of Metal Exchange in (Propargyl Alcohol)Co2(CO)6 Clusters: Syntheses and Structures of [η5-C5Ph2R2−C⋮C−TMS)(Fe(CO)2(μ-H)]Co2(CO)6, R = Ph or Et

The reaction of (5-alkynylcyclopentadienol)Co2(CO)6 clusters with iron pentacarbonyl in acetone does not yield the expected product in which the hydroxyl substituent is lost and a tricarbonylcobalt vertex is replaced by an Fe(CO)3 group. Instead, the product contains an (η5-C5Ph2R2)Fe(CO)2H moiety that is bridged to one of the cobalt vertexes of the intact dicobalt-alkyne cluster. The process is rationalized in terms of a decarboxylation rather than a dehydroxylation process, and the relevance to the mechanism of substitution of one metal vertex by another is discussed.