Diamine bis(phenolate) and pendant amine bis(phenolate) ligands: catalytic activity for the room temperature palladium-catalyzed Suzuki–Miyaura coupling reaction

Abstract

A series of amine bis(phenolate) ligands bearing aryl substituents of varying steric bulk are reported and characterized using single-crystal X-ray diffraction, NMR spectroscopy and high-resolution mass spectrometry experiments. Palladium complexes derived in situ from these ligands are evaluated as catalysts for the Suzuki–Miyaura coupling of phenylboronic acid and aryl bromides. High conversions are observed for these reactions in methanol solvent at low catalyst loadings (0.01 mol%), short reaction times (30 min) and mild temperatures (30°C). Conversion is observed for a range of substrates, and is found to depend on the nature of the external base and solvent employed. These findings demonstrate the utility of catalysts derived from late transition metal complexes of amine bis(phenolate) ligands, particularly those bearing bulky cumyl substituents.