Mechanochemical solid state synthesis of a bifunctional copper(I)/N-heterocyclic carbene complex and its catalytic activity in hydrogenative transformations

A sophisticated bifunctional catalyst bearing a copper(I)/N-heterocyclic carbene and a guanidine organocatalyst has been prepared by a mechanochemical synthesis in a ball mill. This approach circumvents commonly employed silver(I) complexes which are associated with significant and undesired waste formation. Due to the bifunctional nature of the desired complex, earlier mechanochemical conditions were not applicable and a new protocol based on cheap and readily available K3PO4 as base has been developed. The resulting complex has been shown to be active in a variety of reduction/hydrogenation transformations employing dihydrogen as terminal reducing agent.