Synthesis and structural studies on the chiral phosphine-NHC rhodium and palladium complexes for their performances in the metal-catalyzed reactions

Abstract

Diverse chiral rhodium and palladium complexes ligated with phosphine-functionalized N-heterocyclic carbene ligands based on 1,1′-binaphthyl backbone have been synthesized. The structures of these phosphine-NHC rhodium and palladium complexes have been confirmed by X-ray diffraction analysis. The different sizes of the N-substituents from the NHC-P rhodium complexes had an inverse relationship with their ability of chiral induction, which was accounted by the Rh-catalyzed asymmetric hydrosilylation of acetophenone to afford corresponding chiral alcohol with up to 72% ee. The NHC-P palladium complexes connected with different kinds of coordination anions were also applied in the Suzuki and Heck reactions. The acetate-coordinated NHC-P palladium complex exhibited better catalytic activity to give the products in excellent yield under mild conditions.