Synthesis, Characterization, and Catalytic Activity of N-Heterocyclic Carbene (NHC) Palladacycle Complexes

Palladacycle dimers possessing bridging halides can be easily cleaved by using N-heterocyclic carbenes (NHCs) to generate novel monomeric complexes. The structure of one of these was determined by single-crystal diffraction study and consists of a square-planar coordination around the palladium center where the NHC ligand is trans to the amine of the palladacycle. The complex was found to be equally active in aryl amination and α-arylation of ketones even at very low catalyst loading (0.02 mol %). Primary and secondary alkyl/arylamines are equally active partners in coupling reactions.