Reaction of Ta₃ ^- Clusters with Molecular Nitrogen: A Mechanism Investigation

Because of the inertness of molecular nitrogen, its practicable activation under mild conditions is a fundamental challenge. Ta₃ ^- is an exceptionally small cluster that reacts with N₂ at room temperature, leading finally to Ta₃N₂ ^-; Ta₃N₂ ^- also could react with N₂ at room temperature, leading finally to Ta₃N₄ ^-, a product of interest in its own right because of its potential as a nitrogen fixation medium. The mechanisms of the Ta₃ ^-- and Ta₃N₂ ^--mediated activation of the N≡N triple bond have been investigated. Our extensive computations elucidate mechanisms for the ready reactions, leading to stepwise cleavage of the N≡N bond. Initial isomeric N₂/Ta₃ ^- complexes, N≡N elongation, undergo a N≡N split over generally low barriers in a highly exothermic process. The nitrogen-atom or molecular exchange reactions found in the Ta₃N₂ ^-/N₂ system may be of paramount importance in both applied and fundamental studies.