Methane activation by heteronuclear diatomic AuRh+ cation: comparison with homonuclear Au2+ and Rh2+†
The ability to activate methane differs appreciably for different transition metals, and it is attractive to find the most suitable metal for the direct conversion of methane to value-added chemicals. Herein, we performed a comparative study on the reactions of CH4 with Au2+, AuRh+ and Rh2+ cations by mass-spectrometry based experiments and DFT-based theoretical analysis. Different reactivity has been found for these cations: Au2+ has the lowest reactivity, and it can activate methane but only produce H–Au2–CH3+ without H2 release; Rh2+ has the highest reactivity, and it can produce both carbene-type Rh2–CH2+ and carbyne-type H–Rh2–CH+ with H2 release; AuRh+ also has high reactivity to produce only AuRh–CH2+ with H2, avoiding the excessive dehydrogenation of CH4. Our theoretical results demonstrate that Rh is responsible for the high reactivity, while Au leads to selectivity, which may be caused by the unique intrinsic bonding properties of the metals.