Palladium(ii) complexes containing ONO tridentate hydrazone for Suzuki–Miyaura coupling of aryl chlorides in aqueous-organic media

Abstract

Facile synthesis of three new palladium(II) complexes bearing heterocyclic hydrazone ligands are presented along with their structural characterization using IR, ¹H and ¹³C NMR spectra. Molecular structures of the complexes determined by single-crystal XRD revealed a distorted square-planar geometry around the metal ion to which the hydrazone was attached in a tridentate fashion. Catalytic activity of these complexes tested towards the Suzuki–Miyaura cross coupling reaction of substituted aryl boronic acids with aryl chlorides in a water–toluene system (90 : 10%) without using any promoting additives or phase transfer agents, proved that they are highly active with 0.01 mol% loading under optimized conditions to afford 99% yield of the coupled product. Effects of temperature, solvent and base on the cross-coupling reaction were carried out as well. These complexes showed significant catalytic activity up to five cycles.