A comparative study on the reactivity of ditantalum deuteride cluster anions Ta 2 D 2 - and Ta 2 D 4 - toward N 2 .

The activation and transformation of molecular nitrogen (N 2 ) by metal hydride species has attracted widespread attention due to its critical role in nitrogen fixation. Herein, the reactions between tantalum deuteride cluster anions Ta 2 D 2,4 - and N 2 were investigated experimentally and theoretically. An unprecedented reaction channel of the liberation of a single D atom was observed and much superior reactivity was identified for Ta 2 D 4 - . Theoretical investigations indicate that the releasing of D atoms benefits from the completely dissociative adsorption of N 2 on the dinuclear metal centres. The extra D atoms in Ta 2 D 4 - compared to Ta 2 D 2 - are helpful to create sufficient electron density at the adsorption site and modify the symmetry of active orbitals to facilitate a further reduction of N 2 . This comparative study provides a molecular-level insight to understand the high structure-modulating capability of the additional hydride ligands in polyhydride species in the adsorption and activation of nitrogen molecules.