Synthesis and catalytic activity of binuclear Mn(III, III)–BINOL complexes for epoxidation of olefins

Abstract

The novel binuclear complexes [Mn2(III, III)(BINOL)3L2]2H2O, where, L = 2, 2′-bipyridine (Bpy) or 1,10-phenanthroline (Phen) and BINOL = 1, 1′-bi-2-naphthol were synthesized and characterized by elemental analyses, magnetic susceptibility and various spectral methods. The catalytic activity of these complexes was studied for the epoxidation reaction of unfunctionalized olefins like styrene, 1-hexene, 1-octene and 1-decene. The products thus obtained were analyzed by GC. The epoxidation reactions were carried out, in the presence of catalyst with different oxidants, to study the effect of the nature of the oxidant on the reactions. The different oxidants used were the peroxide oxygen donor (e.g. TBHP and H2O2), mono oxygen donor (e.g. PhIO) and dioxygen donor (e.g. molecular O2). TBHP was found to be the best oxidant for the epoxidation reaction. To study the effect of the solvent on the epoxidation, the reactions were carried out in different media, such as a polar media (e.g. with CH3OH as solvent), non-polar media (e.g. with CH2Cl2 and C6H6 as solvents) and coordinating solvent (e.g. CH3CN). The maximum epoxide formation was observed in CH2Cl2 medium. The epoxidation reactions with optically active BINOL catalysts under optimum established conditions were carried out to examine the enantioselectivity of the catalysts. The complexes were, however, found not to be enantioselective. Copyright © 2006 John Wiley & Sons, Ltd.