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

Abstract

The reaction of MoO 2(mes) 2 with S-H 2BINOL (mes = 2,4,6-Me 3C 6H 2; H 2BINOL = 1,1′-bi-2-naphthol) and (CF 3) 2MeCOH in THF yielded the novel dioxo-molybdenum(VI) complexes MoO 2( S-BINOL)(THF) 2 and MoO 2[OCMe(CF 3) 2] 2(THF), respectively. Similar tungsten derivatives WO 2( S-BINOL)(THF) and WO 2[OCMe(CF 3) 2] 2(THF) have been prepared by the reaction of WO 2Cl 2(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 MoO 2( 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 MoO 2( S-BINOL)(THF) 2 and MoO 2[OCMe(CF 3) 2] 2(THF) in the hydrosilylation of carbonyl groups has been explored.