Use of a molybdenum(VI) dioxide complex as a homogeneous and heterogeneous magnetically recoverable epoxidation catalyst

A Mo(VI) complex, [MoO2HL(HOCH3)], HL = 2-[(2-hydroxy-benzylidene)-amino]-3-(4-hydroxy-phenyl)-propionic acid, was reacted with 3-(chloropropyl)-trimethoxysilane-functionalized silica that had been fused with magnetite to yield a magnetically separable catalyst in which the Mo complex was covalently linked to the silica matrix through a silane linkage. Both the free [MoO2HL(HOCH3)] and the immobilized complex function as efficient catalysts for the oxidation of olefins in the presence of tert-butylhydroperoxide as primary oxidant. The Fe3O4@SiO2/[MoO2L(HOCH3)] showed lower catalytic activity and turnover numbers compared to its homogeneous counterpart. However, the immobilized catalyst could be readily recovered from the reaction mixture by using a magnet and could be reused up to seven times without any loss of activity.