Electrochemical synthesis of palladium N-heterocyclic carbene (NHC) complexes

A novel electrochemical method for the preparation of Pd-NHC (N-heterocyclic carbene) catalysts has been developed. Unlike previously reported procedures, the present method does not employ soluble sacrificial anodes as a metal source but makes use of well-defined Pd-containing precursors instead. Importantly, oxygen was observed to play a key role acting as an electrogenerated base. A superoxide anion is formed via the reduction of oxygen at the cathode. The subsequent deprotonation of the imidazolium salts and reaction of NHCs with the Pd species occurs either in a sequential or in a concerted manner resulting in the formation of the final organopalladium product.