Half-sandwich para-cymene ruthenium(II) naphthylazophenolato complexes: Synthesis, molecular structure, light emission, redox behavior and catalytic oxidation properties

Abstract

A series of conformationally rigid half-sandwich organoruthenium(II) complexes with the general formula [(η 6- p-cymene)RuCl(L)] (where L = mono anionic 2-(naphthylazo)phenolato ligands) have been synthesized from the reaction of [{(η 6- p-cymene)RuCl} 2(μ-Cl) 2] with a set of 2-(naphthylazo)phenolato O,N-donor ligands. All the ruthenium complexes were fully characterized by FT-IR, 1H NMR, and UV–Vis spectroscopy as well as elemental analysis. In dichloromethane solution all the metal complexes exhibits characteristic metal-to-ligand charge transfer bands (MLCT) and emission bands in the visible region. The molecular structure of one of the complexes [Ru(η 6- p-cymene)(Cl)(L2)] ( 2) was determined by X-ray crystallography. Electrochemical data of all the ruthenium complexes show a two metal centered voltammetric responses with respect to Ag/AgCl at scan rate 100 mV s −1. Further, the complex ( 2) efficiently catalyzes the oxidation of a wide range of alcohols to their corresponding carbonyl compounds in the presence of N-methylmorpholine- N-oxide (NMO) up to 97%.