d-Electron Attraction-Induced Reactivity Variants in Gas-Phase Reactions of ReM+ (M = Os, Ru, Fe) with Small Molecules.

Gas-phase reactions of [ReM]⁺ (M = Os, Ru, and Fe) with methane (CH₄), nitrogen (N₂), and carbon dioxide (CO₂) at ambient temperature have been studied by using Quadrupole-Ion Trap (Q-IT) mass spectrometry combined with quantum chemical calculations. [ReOs]⁺ effectively dehydrogenates CH₄ while it absorbs N₂ and CO₂ at ambient conditions; simple addition was observed in the thermal reaction of [ReRu]⁺ with all three substrates. By contrast, [ReFe]⁺ is inert with any of the interested molecules. The preferred reaction sites and optimal spin states of [ReM]⁺ (M = Os, Ru, and Fe) complexed small molecules were analyzed by a combination of frontier molecular orbital, absolute electronegativity analysis, electrostatic potential distribution, orbital interaction, and energy decomposition analysis. The differences in valence d-orbital radius and absolute electronegativity between dopant atoms and the Re unit are critical determinants for small molecule activation. The absolute electronegativity of the cluster is influenced by the dopant atoms on the valence d orbitals of Re. This property facilitates the thermodynamic activation of σ-bonds in small molecules.