The study of chemical reactions between gold-containing heteronuclear oxide clusters and small molecules can provide molecular level mechanisms to understand the excellent activity of gold supported by metal oxides. While the promotion role of gold in alkane transformation was identified in the clusters with atomic oxygen radicals (O^−.), the role of gold in the systems without O^−. is not clear. By employing mass spectrometry and quantum chemistry calculations, the reactivity of Au₂VO₃⁺ clusters with closed-shell electronic structures toward ethane was explored. Both the dehydrogenation and ethene elimination channels were identified. It is gold rather than oxygen species initiating the C−H activation. The Au−Au dimer formed during the reactions plays important roles in ethane transformation. The reactivity comparison between Au₂VO₃⁺ and bare Au₂⁺ demonstrates that Au₂VO₃⁺ not only retains the property of bare Au₂⁺ that transforming ethane to dihydrogen, but also exhibits new functions in converting ethane to ethene, which reveals the importance of the composite system. This study provides a further understanding of the reactivity of metal oxide supported gold in alkane activation and transformation.

Metal carbide species have been proposed as a new type of chemical entity to activate methane in both gas-phase and condensed-phase studies. Herein, methane activation by the diatomic cation MoC⁺ is presented. MoC⁺ ions have been prepared and mass-selected by a quadrupole mass filter and then allowed to interact with methane in a hexapole reaction cell. The reactant and product ions have been detected by a reflectron time-of-flight mass spectrometer. Bare metal Mo⁺ and MoC₂H₂⁺ ions have been observed as products, suggesting the occurrence of ethylene elimination and dehydrogenation reactions. The branching ratio of the C₂H₄ elimination channel is much larger than that of the dehydrogenation channel. Density functional theory calculations have been performed to explore in detail the mechanism of the reaction of MoC⁺ with CH₄. The computed results indicate that the ethylene elimination process involves the occurrence of spin conversions in the CC coupling (doubletquartet) and hydrogen atom transfer (quartetsextet) steps. The carbon atom in MoC⁺ plays a key role in methane activation because it becomes sp³ hybridized in the initial stages of the ethylene elimination reaction, which leads to much lower energy barriers and more stable intermediates. This study provides insights into the CH bond activation and CC coupling involved in methane transformation over molybdenum carbide-based catalysts.

The activation of CH bonds in alkanes is currently a hot research topic in chemistry. The atomic oxygen radical anion (O^−.) is an important species in CH activation. The mechanistic details of CH activation by O^−. radicals can be well understood by studying the reactions between O^−. containing transition metal oxide clusters and alkanes. Here the reactivity of scandium oxide cluster anions toward n-butane was studied by using a high-resolution time-of-flight mass spectrometer coupled with a fast flow reactor. Hydrogen atom abstraction (HAA) from n-butane by (Sc₂O₃)_NO⁻ (N=1–18) clusters was observed. The reactivity of (Sc₂O₃)_NO⁻ (N=1–18) clusters is significantly sizedependent and the highest reactivity was observed for N=4 (Sc₈O₁₃⁻) and 12 (Sc₂₄O₃₇⁻). Larger (Sc₂O₃)_NO⁻ clusters generally have higher reactivity than the smaller ones. Density functional theory calculations were performed to interpret the reactivity of (Sc₂O₃)_NO⁻ (N=1–5) clusters, which were found to contain the O^−. radicals as the active sites. The local charge environment around the O^−. radicals was demonstrated to control the experimentally observed size-dependent reactivity. This work is among the first to report HAA reactivity of cluster anions with dimensions up to nanosize toward alkane molecules. The anionic O^−. containing scandium oxide clusters are found to be more reactive than the corresponding cationic ones in the CH bond activation.