Rates and Mechanisms of Electron Transfer/Nickel-Catalyzed Homocoupling and Carboxylation Reactions. An Electrochemical Approach.

Abstract

A review with 20 refs. on the conceptual analogies existing between electrochem. initiated homogeneous reactions and their equiv. taking place at the surface of metal particles. An electrochem. approach is proposed to the investigation of the rates and mechanisms of homocoupling and carboxylation of aryl halides catalyzed by nickel complexes where redn. is the driving force. It is thus shown that nickel catalysis of the homocoupling reaction occurs via an efficient sequence involving both paramagnetic (NiI and NiIII) and diamagnetic (Ni0 and NiII) organometallic nickel complexes. In the presence of carbon dioxide, this chain is annihilated and a new chain develops which affords high carboxylation yields. The transposition of these results to 'homogeneous' conditions, involving metal particles instead of a cathode, is discussed and its validity is examd. on the basis of previously reported kinetic results. [on SciFinder(R)]