Oxido-alcoholato/thiolato-molybdenum(VI) complexes with a dithiolene ligand generated by oxygen atom transfer to the molybdenum(IV) complexes

Abstract

Oxido-alcoholato- and oxido-thiolato-molybdenum(VI) complexes bearing two ene-1,2-dithiolate ligands (cyclohexene-1,2-dithiolate) are prepared as synthetic models of molybdenum(VI) reaction centers of dimethyl sulfoxide reductase family of molybdenum enzymes. These complexes are prepared by oxygen atom transfer from tertiary amine N-oxide (trimethylamine N-oxide and N,N-dimethylaniline N-oxide) to the five-coordinate alcoholato- and thiolato-molybdenum(IV) complexes, and are characterized by UV–vis, cold-spray-ionization mass, resonance Raman, and 1H NMR spectroscopies. The oxygen atom transfer reactions are studied kinetically at a low temperature (−40 °C) to demonstrate that the reactivity of the thiolato-molybdenum(IV) complex is higher than that of alcoholato-molybdenum(IV) complex by about 7 times, and that the oxygen atom transfer reactivity increases with increasing the electron withdrawing ability of the p-substituent of N,N-dimethylaniline N-oxide derivatives. Mechanistic details are discussed based on the reactivity studies.