How and Why Do Cluster Size, Charge State, and Ligands Affect the Course of Metal‐Mediated Gas‐Phase Activation of Methane?

Recent progress in the gas‐phase activation of methane is discussed. We demonstrate that cluster size, charge state, and ligands crucially affect both the reactivity and selectivity of metal‐mediated bond activation processes. We outline the important role that relativistic effects and spin densities play and discuss the paradigm of two‐state reactivity in thermal reactions. State‐of‐the‐art mass‐spectrometry based experiments, in conjunction with electronic structure calculations, permit identification of the elementary steps at a strictly molecular level and thus allow to uncover mechanistic features for four types of reactions: (i) metal‐mediated dehydrogenation of methane, (ii) ligand‐switch processes of the type ML + CH 4 → M(CH 3 ) + HL, (iii) hydrogen‐atom abstraction as the crucial step in the oxidative coupling of methane, and (iv) the mechanism of the challenging CH 4 →CH 3 OH conversion.