Synthesis and Catalysis of NHC Coordinated Cyclometalated Palladium(II) Complexes with Bridging Hydroxide Ligands

Abstract

1,2-Addition reactions using organoboron compounds are one of the useful syntheses of various functionalized alcohols, but they generally require a large quantity of bases. In this study, we attempted to solve this problem by synthesizing unsymmetrical 1,3-diarylimidazoline-type N-heterocyclic carbene (NHC)-coordinated C^C* cyclometalated palladium(II) complexes with bridging hydroxide ligands (CYPOHs) in two steps and one pot from the corresponding Cl bridged dimer and using them as catalysts. 2,6-di(pentan-3-yl)aniline (IPent)-based NHC coordinated PhS-IPent-CYPOH acted as a highly efficient catalyst for the 1,2-addition of (hetero)arylboronates to a large number of aldehydes and ketones, including unactivated ketones, under base-free conditions. (Figure presented.).