Reduction of [ Cp 2 ∗ Mo 2O 5] by mercaptopropionic acid in an aqueous medium. Isolation and characterization of a dinuclear oxo- and 3-sulfido-proprionato(2-)-bridged molybdenum(IV) compound

Compound HSCH 2CH 2COOH reduces and coordinates molybdenum upon interaction with Cp 2 ∗ Mo 2O 5, to yield Cp 2 ∗ Mo 2(μ-O)(μ-SCH 2CH 2CO 2) 2 but, unlike the closely related HSCH 2COOH substrate, does not lead to C–S bond cleavage. Reaction of Cp 2 ∗ Mo 2O 5 with HSCH 2CH 2COOH in acidic (by CF 3COOH) 50:50 MeOH–H 2O solvent at room temperature yields compound Cp 2 ∗ Mo 2(μ-O)(μ-SCH 2CH 2CO 2) 2, a dinuclear diamagnetic Mo IV compound with a two-leg-sharing bis(four-legged piano stool) structure and a Mo–Mo distance of 2.6833(6) Å. A reaction monitoring by ESI MS shows the formation of an intermediate 18 mass units heavier, interpreted as a dihydroxo analogue. Electrochemistry shows a reversible, pH independent oxidation process and an irreversible, pH-dependent reduction process. Contrary to a recently published analogous reaction with the closely related HSCH 2COOH substrate, this process does not lead to C–S bond cleavage.