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

In this study, we have developed two novel imine-palladacyclic dimer complexes (PdL1-2) and six novel imine-Pd-NHC complexes (PdL1a-c and PdL2a-c) which showed moderate to high activity in the coupling of aryl bromides and phenylboronic acid. [Display omitted] •Six N-heterocyclic carbenes (NHCs) ligated Schiff base palladacycles were synthesized.•The role of Pd(II)-NHC complexes were screened in Suzuki-Miyaura cross-coupling reactions.•The new dimeric imine-palladacycle (PdL2) was found to be an active catalyst. A series of N-heterocyclic carbene (NHC) ligated Schiff base palladacycles were synthesized by the reaction of μ-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.