On the Origin of the Distinctly Different Reactivity of Ruthenium in [MO] /CH Systems (M=Fe, Ru, Os).

The thermal gas-phase reactions of [RuO] with methane have been explored by FT-ICR mass spectrometry and high-level quantum-chemical calculations. In contrast to the previously studied [FeO] /CH and [OsO] /CH couples, which undergo oxygen/hydrogen atom transfers and dehydrogenation, respectively, the [RuO] /CH system produces selectively [Ru(CH) ] and H O, albeit with much lower efficiency. Various mechanistic scenarios were uncovered, and the associated electronic origins were revealed by high-level quantum-chemical calculations. The reactivity differences observed for the [MO] /CH couples (M=Fe, Ru, Os) are due to the subtle interplay of the spin-orbit coupling efficiency, orbital overlap, and relativistic effects.