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.