The Reactive Sites of Methane Activation: A Comparison of IrC(3)(+) with PtC(3)(+)

The activation reactions of methane mediated by metal carbide ions MC(3)(+) (M = Ir and Pt) were comparatively studied at room temperature using the techniques of mass spectrometry in conjunction with theoretical calculations. MC(3)(+) (M = Ir and Pt) ions reacted with CH(4) at room temperature forming MC(2)H(2)(+)/C(2)H(2) and MC(4)H(2)(+)/H(2) as the major products for both systems. Besides that, PtC(3)(+) could abstract a hydrogen atom from CH(4) to generate PtC(3)H(+)/CH(3), while IrC(3)(+) could not. Quantum chemical calculations showed that the MC(3)(+) (M = Ir and Pt) ions have a linear M-C-C-C structure. The first C–H activation took place on the Ir atom for IrC(3)(+). The terminal carbon atom was the reactive site for the first C–H bond activation of PtC(3)(+), which was beneficial to generate PtC(3)H(+)/CH(3). The orbitals of the different metal influence the selection of the reactive sites for methane activation, which results in the different reaction channels. This study investigates the molecular-level mechanisms of the reactive sites of methane activation.