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 R. O. ; et al. J. Phys. Chem. Lett. 2010, 1, 3066 ; Ramabhadran R. O. ; et al. J. Am. Chem. Soc. 2013, 135, 17039 ], the reactivity of molybdenum oxo–cluster anions, Mo x O y – (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 Mo x O y – + H2O/D2O reactivity studies, with particular emphasis on the Mo2O y – and Mo3O y – series. In general, sequential oxidation, Mo x O y – + ROH → Mo x O y+1 – + RH, and addition reactions, Mo x O y – + ROH → Mo x O y+1 RH–, largely corresponded with previously studied Mo x O y – + 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 Mo x O y – + 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.