A new water-soluble Rh(III)-Salophen complex as efficient catalyst for alcohol oxidation in aqueous medium

Abstract

A new water-soluble rhodium(III) complex [Rh(η⁴-L)Cl] (1a) was synthesized by reacting RhCl₃.3H₂O with Salophen ligand  [L = N,N^′-bis(salicylidene)-1,2-phenylenediamine (a)] in 1:1 molar ratio in dichloromethane solution. The complex 1a was characterized by FT-IR, UV-Vis, ESI-MS, ¹H and ¹³C NMR spectroscopy. Theoretical calculations (B3LYP) and spectroscopic evidence recommends that the ligand a coordinates to the Rh centre through imine N and phenolic O donor atoms. The complex 1a emerged out to be an effective catalyst for oxidation of alcohols in water. Magnificent yields of carbonyl compounds are acquired for a comprehensive assortment of substrates with H₂O₂ as oxidant at a relatively low loading of catalyst. Thus, the Rh(III)-H₂O-H₂O₂ catalytic system could act as an environmentally benign alternative to oxidation methods in conventional organic solvents.