Use of a Ru/Os-CO-diiodide precursor to synthesize heteroleptic 1-alkyl-2-(arylazo)imidazole complexes: The structural characterization, electrochemistry and catalytic activity

Abstract

Trans-(I,I)-[MI2(CO)2(RaaiR′)] (M=Ru, Os) (RaaiR′=1-alkyl-2-(arylazo)imidazoles) complexes have been synthesized by the reaction of RaaiR′ and [Ru(CO)4I2] or [Os(CO)4I2] in acetonitrile solution and the complexes have been characterized by elemental analysis and spectral (FT-IR, UV–Vis, 1H NMR) data. The structural confirmation has been determined by single crystal X-ray diffraction of trans-(I,I)-[MI2(CO)2(HaaiEt)] (M=Ru, 3b; Os, 5b) (HaaiEt=1-ethyl-2-(phenylazo)imidazole) and has shown a distorted octahedral geometry with a trans-I,I and cis-CO, CO configuration. The complexes show a M(III)/M(II) couple and the reduction of the chelated azoimine ligand. These complexes act as catalysts in the oxidation of PhCH2OH to PhCHO, 2-butanol (C4H9OH) to 2-butanone, cyclopentanol (C5H9OH) to cyclopentanone and cyclohexanol to cyclohexanone by N-methylmorpholine-N-oxide (NMO). The molecular orbital diagram has been drawn by density functional theory (DFT) using the optimized geometry from the single crystal X-ray parameters. The assignments of electronic spectra have been carried out by TD-DFT calculations both in the gas and acetonitrile phases.