Dual functionalized task specific ionic liquid promoted in situ generation of palladium nanoparticles in water: synergic catalytic system for Suzuki–Miyaura cross coupling

Abstract

Herein we report the synthesis of a novel, dual functionalized task specific ionic liquid possessing cation with hydroxyl functionality which induces reaction in water and acts as a reducing agent as well as an anion with prolinate functionality serves as ligand and stabilizes and/or activates the in situ formed palladium nanoparticles (Pd-Nps) thus act as palladium(0) reservoirs. The generated palladium nanoparticles were characterized by UV-visible spectroscopy, high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDX) analysis. These in situ synthesized palladium nanoparticles with particle size between 3 to 9 nm exhibited a high catalytic activity in the Suzuki–Miyaura cross-coupling of aryl halide with aryl boronic acid without using external phosphine ligand. Less activated aryl chlorides also coupled smoothly with aryl boronic acid. It is noteworthy that, isolation of the products were performed by the simple extraction in diethyl ether, and the aqueous system containing ionic liquid along with Pd-NPs was recycled for seven times, without significant loss of catalytic activity.