Dinuclear N-heterocyclic carbene palladium(II) complexes as efficient catalysts for the Buchwald-Hartwig amination

A series of dinuclear N-heterocyclic carbene (NHC) palladium complexes [PdCl2(NHC)](2)(mu-L) (1-6, L = diphosphine ligands) has been synthesized and fully characterized by H-1 NMR, C-13 NMR and P-31 NMR spectroscopies, elemental analysis, IR spectroscopy, and X-ray crystal structural study. The solid-state structures of 1-6 show dinuclear frameworks with two palladium(II) centres were held together by bridging diphosphine ligands. Each palladium centre was coordinated by an N-heterocyclic carbene ligand, a phosphorus atom and two chloro ions in a trans-arrangement. Further explorations of the catalytic potential of the dinuclear carbene palladium complexes as catalysts for Pd-mediated transformations have been examined under microwave irradiation conditions and the title complexes (1-6) displayed good catalytic activities in Buchwald-Hartwig aminations of aryl chlorides. (C) 2014 Elsevier B. V. All rights reserved.