Direct Room-Temperature Conversion of Methane into Protonated Formaldehyde: The Gas-Phase Chemistry of Mercury among the Zinc Triad Oxide Cations.

In thermal reactions of methane with diatomic metal oxides [MO].+ of the zinc triad (M=Zn, Cd, Hg), protonated formaldehyde [CH2 OH]+ is generated as the major product only for the [HgO].+ /CH4 couple. Mechanistic insight is provided by high-level quantum-chemical calculations, and relativistic effects are suggested to be the root cause for the unexpected thermal production of [CH2 OH]+ from [HgO].+ /CH4 .