Reaction of Ta 3 - Clusters with Molecular Nitrogen: A Mechanism Investigation.

Because of the inertness of molecular nitrogen, its practicable activation under mild conditions is a fundamental challenge. Ta 3 - is an exceptionally small cluster that reacts with N 2 at room temperature, leading finally to Ta 3 N 2 - ; Ta 3 N 2 - also could react with N 2 at room temperature, leading finally to Ta 3 N 4 - , a product of interest in its own right because of its potential as a nitrogen fixation medium. The mechanisms of the Ta 3 - - and Ta 3 N 2 - -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 N 2 /Ta 3 - 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 Ta 3 N 2 - /N 2 system may be of paramount importance in both applied and fundamental studies.