Dioxo-molybdenum(VI) and -tungsten(VI) BINOL and alkoxide complexes: Synthesis and catalysis in sulfoxidation, olefin epoxidation and hydrosilylation of carbonyl groups

The reaction of MoO2(mes)2 with S-H2BINOL (mes = 2,4,6-Me3C6H2; H2BINOL = 1,1′-bi-2-naphthol) and (CF3)2MeCOH in THF yielded the novel dioxo-molybdenum(VI) complexes MoO2(S-BINOL)(THF)2 and MoO2[OCMe(CF3)2]2(THF), respectively. Similar tungsten derivatives WO2(S-BINOL)(THF) and WO2[OCMe(CF3)2]2(THF) have been prepared by the reaction of WO2Cl2(DME) with the corresponding lithium salts of BINOL and 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, respectively. Catalytic experiments have shown that MoO2(S-BINOL)(THF)2 is an active catalyst in the sulfoxidation of methyl phenyl sulfide and in the epoxidation of cis-cyclooctene with tert-butylhydroperoxide, under mild conditions. The BINOL complex was, however, not found to be enantioselective. In addition, the catalytic activity of the molybdenum species MoO2(S-BINOL)(THF)2 and MoO2[OCMe(CF3)2]2(THF) in the hydrosilylation of carbonyl groups has been explored.