Reaction mechanisms of metal-metal bonded carbonyls. Part VII. Reaction of alkynes with \u3bc-carbonyl-\u3bc-diphenylgermanio-bis(tricarbonylcobalt)(Co-Co)

Alkynes [C2Ph2, MeC2Ph, PhC2H, and C2(CO2Et)2] displace the bridging GePh2 group from [(OC)3Co(\u3bc-GePh2)(\u3bc-CO)Co(CO)3], (I), to form the well known complexes [(OC)3(Co(\u3bc-alkyne)Co(CO)3] together with (GePh2)n (n = 4-7). The kinetics of reaction of complex (I) with diphenylacetylene in decalin have been studied over a range of temperature. The rate of reaction is first order in [Complex] and [C2Ph2] and the reaction is greatly retarded by carbon monoxide. The results are consistent with a reaction mechanism that involves initial reversible ring opening to form [(OC)3Co(\u3bc-GePh2)Co(CO)4], a process that is also involved in a reactions of complex (I) with carbon monoxide and triphenyl- and tributyl-phosphine. A mechanism involving intermediates with terminally co-ordinated GePh2 groups cannot be conclusively ruled out but is considered to be less probable