Methane activation by gold-doped titanium oxide cluster anions with closed-shell electronic structures

The reactivity of closed-shell gas phase cluster anions AuTi₃O₇^- and AuTi₃O₈^- with methane under thermal collision conditions was studied by mass spectrometric experiments and quantum chemical calculations. Methane activation was observed with the formation of AuCH₃ in both cases, while the formation of formaldehyde was also identified in the reaction system of AuTi₃O₈^-. The cooperative effect of the separated Au⁺ and O^2- ions on the clusters induces the cleavage of the first C-H bond of methane. Further activation of the second C-H bond by a peroxide ion O₂^2- leads to the formation of formaldehyde. This study shows that closed-shell species on metal oxides can be reactive enough to facilitate thermal H-CH₃ bond cleavage and the subsequent conversion.