Zinc-bis(imino)pyridine Complexes as Catalysts for Azide-Alkyne Cycloaddition in Water

Abstract

Two new zinc(II) complexes, [2,6-bis(methylphenyliminomethyl)pyridine]ZnBr2 (2 a) and [2,6-bis(triflouromethylphenyliminomethyl)pyridine]ZnBr2 (2 b) were synthesized by the reactions of corresponding 2,6-bis(imino)pyridine based [NNN]-pincer ligand and anhydrous ZnBr2 in acetonitrile as a solvent. The catalytic properties of zinc(II) complexes were examined in azide-alkyne cycloaddition reactions in water. The zinc(II) complexes were characterized by UV-Vis, 1H NMR, IR, elemental analysis and mass spectroscopy. The zinc complex [2,6-bis(triflouromethylphenyliminomethyl)pyridine]ZnBr2 was characterized by X-ray crystallography. The zinc(II) complexes efficiently catalyzed the azide-alkyne cycloaddition reaction for the synthesis of 1,2,3-triazoles (mixture of 1,4- and 1,5-disubstituted 1,2,3-triazoles) in water with good to excellent yields. © 2022 Wiley-VCH GmbH.