New Mn(II) and Cu(II) chiral C 2-multidentate complexes immobilised in zeolites (USY, MCM41) : Reusable catalysts for selective oxidation reactions

Abstract

Heterogenisation of the manganese(II) and copper(II) complexes bearing a triethoxysilyl group on zeolites (modified ultrastable Y zeolite (USY), MCM-41) through covalent bonding to support and the preparation of the respective Mn-complex encapsulated into the supercages of large pore sized Y zeolite are reported. The chemical environment of the metal in these materials does not change after heterogenisation as we confirm by FT-IR, diffuse reflectance and thermogravimetric (TG) analysis. All catalysts, homogeneous and heterogenised, are active and selective in the oxidation of alkyl phenyl sulfides and nerol at low temperatures using sodium hypochlorite or IOPh as terminal oxidant. The catalytic activity of the anchored USY and MCM41 complexes is higher than the corresponding homogeneous or encapsulated ones, yielding sulfoxides and epoxyalcohols with excellent yields and selectivity and moderate enantioselectivity. Life time of heterogenised catalysts has been examined by repeated use of the complexes leading similar rates and yields of sulfoxide or epoxide, whilst no appreciable loss of metal has been observed over several runs.