Synthesis and investigation of catalytic activity of phenylene – And biphenylene bridged bimetallic Palladium-PEPPSI complexes

Abstract

A series of phenylene and biphenylene-bridged N-heterocyclic carbene (NHC) and their bimetallic NHC–Pd-PEPPSI complexes were reported and fully characterized by 1H NMR, 13C NMR, HRMS, FTIR, and elemental analysis. The N tags with different electronic and steric properties were used on the synthesis of bridged bimetallic NHC–Pd-PEPPSI (PEPPSI: Pyridine Enhanced Precatalyst Preparation Stabilization Initiation) complexes. The catalytic properties of the bridged bimetallic NHC–Pd-PEPPSI complexes were investigated in the different C–C coupling reaction such as Suzuki-Miyaura reactions of aryl bromides with arylboronic acid, the Heck coupling reactions of aryl bromide with styrene and in the Sonogashira reactions of aryl bromides with phenylacetylene. Generally, all bridged bimetallic NHC–Pd-PEPPSI complexes showed good catalytic activity in the C–C coupling reactions.