Synthesis of bridged palladium-PEPPSI complexes and catalytic studies in C–C cross-coupling reactions

Abstract

A series of dimetallic NHC-Pd-PEPPSI complexes with phenylene-bridged N-heterocyclic carbenes (NHC) were synthesized and fully characterized by 1H NMR, 13C NMR, HRMS, FTIR, and elemental analysis. The N tags were 2,3,4,5,6-pentamethylbenzyl, 3,5-dimethylbenzyl, 4-tert-butylbenzyl and 3-methoxybenzyl groups. The catalytic properties of the complexes were investigated in the Suzuki-Miyaura reactions of aryl bromides with arylboronic acid and in the Heck coupling reactions of aryl bromide with styrene and in the Sonogashira reactions of aryl bromides with phenylacetylene. Generally, dimetallic complexes exhibit good catalytic activities in the Suzuki-Miyaura, Heck, and Sonogashira coupling reactions.