Reactivity of Nb3N3-xOx+ (x = 0-3) toward Methane: Ligand-Controlled Modulation of Nb-Nb σ Bonds

Mild activation of methane remains a fundamental challenge due to its chemical inertness. While metal-metal σ-bond-mediated pathways have recently emerged as an effective strategy, how mixed ligands regulate reactivity of dual-metal centers remains poorly understood. Herein, we investigate the reactivity of Nb3N3-xOx+ (x = 0-3) clusters toward CH4 using time-of-flight mass spectrometry combined with theoretical calculations. A clear evolution of reactivity is observed upon stepwise substitution of N with O, with reaction channels shifting from exclusive adsorption (Nb3N3+) to concurrent adsorption and dehydrogenation (Nb3N2O+, Nb3NO2+), and ultimately to efficient dehydrogenation (Nb3O3+). Mechanistic analysis reveals that methane activation occurs at Nb-Nb dual-metal centers, whose reactivity is governed by ligand-controlled number and distribution of Nb-Nb σ bonds. Nitrogen ligands disrupt σ bonding and reduce active sites, whereas oxygen ligands preserve intact dinuclear motifs and promote synergistic C-H activation. These findings clarify how ligand coordination controls metal-metal bonding and governs dual-metal site reactivity, providing molecular-level insights into methane activation.