Electrostatic and Charge-Induced Methane Activation by a Concerted Double C-H Bond Insertion.

A mechanistically unique, simultaneous activation of two C-H bonds of methane has been identified during the course of its reaction with the cationic copper carbide, [Cu-C]+. Detailed high-level quantum chemical calculations support the experimental findings obtained in the highly diluted gas phase using FT-ICR mass spectrometry. The behavior of [Cu-C]+/CH4 contrasts that of [Au-C]+/CH4, for which a stepwise bond-activation scenario prevails. An explanation for the distinct mechanistic differences of the two coinage metal complexes is given. It is demonstrated that the coupling of [Cu-C]+ with methane to form ethylene and Cu+ is modeled very well by the reaction of a carbon atom with methane mediated by an oriented external electric field of a positive point charge.