New Molybdenum(V) Complexes Prepared by the Oxidation of Dinuclear Quadruply-Bonded Molybdenum(II) Monothiocarboxylates

Oxidation of molybdenum(II) thiopivalate and thiobenzoate in the presence of -picoline or pyridine results in the formation of dinuclear molybdenum(V) complexes of the general formulae [Mo₂O₂(-O)₂(-SO₄)L₄] with L = -picoline or pyridine and [Mo₂O₂(-O)(-S)(-SO₄)L₄] with L = -picoline. As determined by X-ray structure analysis, two complexes with -picoline differ in their bridging cores: In one complex, two Mo atoms are doubly bridged through two oxygen atoms; in the other, one Mo atom is doubly bridged through oxygen and sulfur atoms. However, they both crystallize together. The product is solvated with -picoline and water molecules. Molybdenum atoms exhibit distorted octahedral coordinations. The same complexes were prepared also through direct reactions of [Mo₂O₃(O₂CCH₃)₄] with thiopivalic and thiobenzoic acid in the presence of -picoline or pyridine. The appearance of the oxo-oxygens and sulfido-sulfur as well as sulfato ligand is explained by the molybdenum-catalyzed oxidation of thiocarboxylates.