Methane activation by heteronuclear diatomic AuRh + cation: comparison with homonuclear Au 2 + and Rh 2 .

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 Au-2(+), AuRh+ and Rh-2(+) cations by mass-spectrometry based experiments and DFT-based theoretical analysis. Different reactivity has been found for these cations: Au-2(+) has the lowest reactivity, and it can activate methane but only produce H-Au-2-CH3+ without H-2 release; Rh-2(+) has the highest reactivity, and it can produce both carbene-type Rh-2-CH2+ and carbyne-type H-Rh-2-CH+ with H-2 release; AuRh+ also has high reactivity to produce only AuRh-CH2+ with H-2, 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.