Air-stable Pd(0) catalyst bearing dual phosphine ligands: a detailed evaluation of air stability and catalytic property in cross-coupling reactions

Abstract

We have synthesised an air-stable Pd(0) catalyst bearing donor and acceptor phosphine ligands (Complex 1). This study revealed the long-term air stability and catalytic property of Complex 1 as a catalyst for cross-coupling reactions, where it was stable in air for eight months. DFT calculations revealed that the acceptor ligands in Complex 1 decreased the HOMO energy level, which provided the observed air stability. Complex 1 successfully served as a catalyst for direct C–H arylation reactions and Suzuki–Miyaura cross-coupling reactions, and catalysed the reaction of a relatively inactive substrate, 2-chrolopyridine, which could not be achieved by conventional, air-stable Pd(0) catalysts. Isolating the intermediates of the coupling reactions revealed that each intermediate possessed the donor ligand (PCy₃), which was determined to be responsible for imparting the high catalytic activity exhibited by Complex 1.