Dinitrogen Activation and Cyanide Release by the Gas-Phase Cluster Anions InNbC₂^-: Synergistic Effects of the p-Block Indium and the d-Block Niobium

Transforming N₂ into valuable C-N bond-containing products at room temperature is of great importance, yet it remains highly challenging because of the inherent inertness of N₂ and the complexity in designing effective catalytic active sites. In this study, we investigate the structure and reactivity of InNbC₂^- using mass spectrometry, photoelectron spectroscopy, and theoretical calculations. Remarkably, at room temperature, InNbC₂^- can completely cleave the N≡N triple bond to form two C-N bonds in the intermediate product Nb(CN)₂^-, accompanied by the release of the In atom. Subsequently, one cyanide (CN) molecule is liberated during the oxidation reaction of Nb(CN)₂^- with O₂. Comparative analysis with the inert Nb₂C₂^- cluster reveals two critical roles of the In atom in the N₂ reduction process: (1) the In atom enhances the negative charge on the Nb site, facilitating N₂ adsorption and reduction. (2) The In atom enables the flexible formation and cleavage of the In-Nb bond during the reaction. In this N₂ transformation, the metal atoms act as electron reservoirs, and the C₂ unit is another important electron donor during C-N bond generation. The formation of strong Nb-O bonds provides the driving force for releasing cyanide as the final product in the subsequent oxidation reaction. This work presents the first gas-phase example of a heteronuclear bimetallic anion, InNbC₂^-, capable of releasing cyanide as a product under thermochemical conditions. Our findings propose a novel strategy for designing N₂ transformation catalysts by integrating p-block main group metals with d-block transition metals, offering new insights into the activation and functionalization of N₂.