RH and H2 Production in Reactions between ROH and Small Molybdenum Oxide Cluster Anions

To test recent computational studies on the mechanism of metal oxide cluster anion reactions with water [Ramabhadran, It O.; et al. J. Phys. Chem. Lett. 2010, I, 3066; Ramabhadran, R. O.; et al. J. Am. Chem. Soc. 2013, 13S, 17039], the reactivity of molybdenum oxo-cluster anions, MoxOy- (x = 1 - 4; y <= 3x) toward both methanol (MeOH) and ethanol (EtOH) has been studied using mass spectrometric analysis of products formed in a high-pressure, fast-flow reactor. The size-dependent product distributions are compared to previous MoxOy- + H2O/D2O reactivity studies, with particular emphasis on the Mo2Oy- and Mo3Oy- series. In general, sequential oxidation, MoxOy- + ROH -> MoxOy+1- + RH, and addition reactions, MoxOy- + ROH -> MoxOy+1RH-, largely corresponded with previously studied MoxOy- + H2O/D2O reactions [Rothgeb, D. W.; Mann, J. E.; Jarrold, C. C. J. Chem. Phys. 2010, 133, 054305], though with much lower rate constants than those determined for MoxOy- + H2O/D2O reactions. This finding is consistent with the computational studies that suggested that -H mobility on the cluster-water complex was an important feature in the overall reactivity. There were several notable differences between cluster-ROH and cluster-water reactions associated with lower R-OH bond dissociation energies relative to the HO-H dissociation energy.