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

Abstract

Alkynes [C₂Ph₂, MeC₂Ph, PhC₂H, and C₂(CO₂Et)₂] displace the bridging GePh₂ group from [(OC)₃[graphic omitted]o(CO)₃], (I), to form the well known complexes [(OC)₃[graphic omitted]o(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(µ-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.