Half-sandwich ruthenium(II) complexes containing O, N bidentate azo ligands: Synthesis, structure and their catalytic activity towards one-pot conversion of aldehydes to primary amides and transfer hydrogenation of ketones

Abstract

The ruthenium(II) complexes of the general formula [Ru(η6‒p‒cymene)(Cl)(L1‒5)] (L = O, N-donors of biphenylazo derivatives), formed by reacting 2‒(biphenylazo)phenol (HL1‒ HL4) and 1‒(biphenylazo)naphthol ligands (HL5) with [{η6‒p‒cymene)RuCl}2(μ‒Cl)2] have been synthesized. The compositions of the complexes have been established by IR, UV–Vis, 1H NMR spectral methods and X-ray crystallography. The synthesized complex could act as an efficient, reusable homogeneous catalyst for transformation of aldehydes to the corresponding primary amides in the presence of NH2OH·HCl, thus resulting an expansion of Beckmann rearrangement. The effect of solvent, base, temperature, time, catalyst loading and recyclability was also investigated. They also effectively catalyze the transfer hydrogenation reaction of various ketones with 2-propanol.