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

Abstract

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., and 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.

CexOy– (x = 2–3) + D2O Reactions: Stoichiometric Cluster Formation from Deuteroxide Decomposition and Anti-Arrhenius Behavior

“…34 Ce 2 O − is the most reduced cluster in the x = 2 series, and the reaction with water is expected to follow the rate law…”

Molybdenum Oxide Clusters: Structure, Stability, and Electronic Properties

“…Gas-phase clusters with controlled composition, size, and structure provide a convenient tool for improving catalytic activity by better understanding the aforementioned relationships. Studies have been conducted by applying various gas-phase cluster generation techniques on oxide surfaces, including fast atom bombardment, , evaporation from the Knudsen effusion cell, − and laser irradiation. − In these studies, important results have been achieved in establishing the relationships between cluster size and composition, catalytic activity, and selectivity in chemical processes such as CO oxidation and bond cleavage in small hydrocarbons and alcohols.…”

Observation of the Reaction Intermediates of Methanol Dehydrogenation by Cationic Vanadium Clusters

“…[10] Such model systems are amenable to the state-ofthe-art theoretical models and methods,a nd the fitting of experimental data with calculated results allows also to verify the reliability of theory. [11] Much previous efforts have been put on the reactions of metal oxide clusters,f or example, [12] [13] and M x O y (M = V, Fe), [14] with methanol. Thef ormation of formaldehyde and reactive intermediates like CH 3 OC and CH 3 C have been postulated, [15] and their connection with related bulk metal oxide surface reactions has been revealed.…”