Spectroscopic and Electrochemical Characterization of 18-Molybdodisulfate(VI)(4−), S2Mo18O624−

Abstract

The formation conditions of a yellow Dawson-type S2Mo18O624− anion have been investigated as functions of the concentrations of Mo(VI), H2SO4, organic solvents, the nature of the organic solvents used, temperature of the solution, and the reaction time. For a 50 mM Mo(VI)/50% (v/v) acetonitrile system, the yellow S2Mo18O624− anion formed in 0.2–1.0 M H2SO4, while a pale-yellow Mo6O192− anion did in 0.04–0.3 M H2SO4. The yellow heteropolyanion is electrochemically reduced in six successive steps to mixed-valence heteropoly blues at the glassy carbon electrode. Each of the first four waves corresponds to a reversible two-electron transfer. The mixed-valence blue species were characterized by their inherent visible and infrared (IR) spectra.