Counterion Dependence of Dinitrogen Activation and Functionalization by a Diniobium Hydride Anion

We report the synthesis of anionic diniobium hydride complexes with a series of alkali metal cations (Li + , Na + , and K + ) and the counterion dependence of their reactivity with N 2 . Exposure of these complexes to N 2 initially produces the corresponding side‐on end‐on N 2 complexes, the fate of which depends on the nature of countercations. The lithium derivative undergoes stepwise migratory insertion of the hydride ligands onto the aryloxide units, yielding the end‐on bridging N 2 complex. For the potassium derivative, the N−N bond cleavage takes place along with H 2 elimination to form the nitride complex. Treatment of the side‐on end‐on N 2 complex with Me 3 SiCl results in silylation of the terminal N atom and subsequent N−N bond cleavage along with H 2 elimination, giving the nitride‐imide‐bridged diniobium complex.