Di- and tri-nuclear-palladium complexes bearing piperidoimidazolin-2-ylidenes: synthesis, characterization, and catalytic applications

A series of di- and tri-nuclear Pd(II) complexes with piperidoimidazolin-2-ylidenes anchored to benzene ring via methylene spacers were synthesized. The obtained complexes were fully characterized by IR, H-1 NMR, C-13 NMR spectroscopy and elemental analysis. Molecular structures of two of the products have been determined by means of X-ray crystallography. Their catalytic performances in Suzuki-Miyaura and Mizoroki-Heck cross-coupling reactions were thoroughly investigated. The catalytic reactivity of new di- and tri-metallic complexes was compared with the monometallic systems. It is observed that the activities of the tri-nuclear Pd(NHC) complexes were higher than the corresponding mono- and di-nuclear complexes under the same conditions. (C) 2015 Elsevier Ltd. All rights reserved.