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O: Fachverband Oberflächenphysik

O 7: Heterogeneous Catalysis: Experiment

O 7.3: Talk

Monday, March 12, 2018, 11:00–11:15, MA 141

Evolution of the reactivity of gas-phase cationic tantalum-2 oxide clusters with methane — •George Goddard^1,2, Jan Eckhard¹, Tsugunosuke Masubuchi¹, Martin Tschurl¹, and Ueli Heiz¹ — ¹Chair of Physical Chemistry, Department of Chemistry & Catalysis Research Center, Technische Universität München, Lichtenbergstr. 4, 85748 Garching, Germany — ²Department of Chemistry, Durham University, Durham, U.K. DH1 3LE

Metal clusters have long been looked at as model catalysts, particularly in the activation of C-H bonds. It is also known that the presence of ligands can have large effects on reactivity. Here the reaction pathway and kinetics of Ta₂O_x⁺ with methane were investigated for x = 0-6. Ta₂O₃⁺ purely shows molecular adsorption, as does Ta₂O₄⁺ and Ta₂O₆⁺. Conversely, Ta₂O⁺ is unreactive, whilst Ta⁺ eliminates H₂ to give a carbene adsorbate, and Ta₂O₂⁺ shows both intact adsorption and dehydrogenated products of methane. Finally the stoichiometric Ta₂O₅⁺, which occurs with the lowest abundance causes hydrogen atom abstraction. The reaction was repeated using deuterated methane to confirm mass assignments and to calculate the kinetic isotope effect for each reaction step. This has led to an elucidation of the mechanism and of the structure of the clusters in question.