Mechanistic Aspects of Gas-Phase Hydrogen-Atom Transfer from Methane To [CO]+ and [SiO]+: Why Do They Differ?

The reactivity of the two diatomic congeneric systems [CO]C+ and [SiO]C+ towards methane has been investigated by means of mass spectrometry and quantum-chemical calculations. While [CO]C+ gives rise to three different reaction channels, [SiO]C+ reacts only by hydrogen-atom transfer (HAT) from methane under thermal conditions. A theoretical analysis of the respective HAT reveals two distinctly different mechanistic pathways for [CO]C+ and [SiO]C+, and a comparison to the higher metal oxides of Group 14 emphasizes the particular role of carbon as a second-row p element