A heterogeneous route for transfer hydrogenation reactions of ketones using Ru(II)Cymene complex over modified benzene-organosilica (PMOB)

Abstract

An inorganic-organic hybrid catalyst, Ru(II)Cym@PMOB, was synthesized by anchoring of [Ru(II)Cl2(p-cymene)]2 complex which is derived from a reaction between hydrated ruthenium(III) trichloride and α-phellandrene over aminofunctionalized benzene-organosilica (PMOB). In the context of secondary alcohol synthesis from ketones, transfer hydrogenation (TH) reactions are convenient compared to conventional hydrogenation reactions owing to its lower activation energy and ambient pressure and mild temperature reaction conditions. The synthesized catalysts were characterized by CHN analysis, XRD, ICP, N2-sorption analysis, TG & DTA, FTIR, 13C &29Si solid NMR, UV–vis, TEM, SEM and XPS. The catalytic activities of neat [Ru(II)Cl2(p-cymene)]2 complex and Ru(II)Cym@PMOB were evaluated in transfer hydrogenation (TH) of ketones (∼97%) and compared with conventional hydrogenation reactions (∼5%) where molecular H2 was used. The results showed Ru(II)Cym@PMOB as highly active catalyst towards transfer hydrogenation (TH) reaction of acetophenones compared to neat [Ru(II)Cl2(p-cymene)]2 complex. The heterogeneity of Ru(II)Cym@PMOB was confirmed by Sheldon’s test.