Nonclassical oxygen atom transfer reactions of an eight-coordinate dioxomolybdenum(vi) complex

Abstract

The dioxomolybdenum(VI) complex MoO₂Cl₂(dmf)₂ reacts with Pb(DOPO^Q)₂ (DOPO = 2,4,6,8-tetra-tert-butyl-1,9-dioxophenoxazinate) to give MoO₂(DOPO^Q)₂, which has an eight-coordinate structure with normal molybdenum-oxo bond distances and angles but elongated distances to the dioxophenoxazine ligand. The dioxo complex is deoxygenated by phosphines to produce octahedral Mo(DOPO^Cat)₂, in which reduction has taken place at the ancillary ligands. This compound in turn reacts with trimethylamine-N-oxide to regenerate MoO₂(DOPO^Q)₂, allowing a catalytic cycle for phosphine oxidation. This represents an example of four-electron nonclassical oxygen atom transfer in which both the oxidized and reduced forms of the metal complexes can be observed.