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(<em>η</em>⁴-<strong>L</strong>)Cl] (<strong>1a</strong>) has been isolated from the reaction between RhCl₃.3H₂O and salophen ligand [<strong>L</strong> = N,N<strong>^′</strong>-bis(salicylidene)-1,2-phenylenediamine (<strong>a</strong>)] in 1:1 molar ratio in dichloromethane solution. The complex <strong>1a </strong>has been characterized by FT-IR, UV-vis, ESI-MS, ¹H and ¹³C NMR spectroscopy. Theoretical calculations (B3LYP) and spectroscopic evidence recommends that the ligand <strong>a</strong> coordinates to the Rh centre through imine N and phenolic O donor atoms. The complex <strong>1a</strong> emerged out to be an effective catalyst for oxidation of alcohols in water. Excellent yields of carbonyl compounds have been 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.