Synthesis, characterization and catalytic activity of N-heterocyclic carbene ligated Schiff base palladacycles

A series of N-heterocyclic carbene (NHC) ligated Schiff base palladacycles were synthesized by the reaction of ?-acetato-bridged Schiff base palladacycles (PdL1-2) with imidazolium salts (a-c). The new NHC ligated palladacycles were fully characterized using 1H NMR, 13C NMR, infrared spectroscopy, MS analysis, and single-crystal X-ray diffraction for one complex (PdL1). Further exploration of the catalytic application of the palladacycles for Suzuki-Miyaura cross-coupling reactions of aryl bromides with phenylboronic acid was carried out. It was determined that the new dimeric imine-palladacycle (PdL2) exhibits the highest catalytic activity among the coupling compounds in this study.