( n -Bu) 4 NBr-Promoted N 2 Splitting to Molybdenum Nitride.

Splitting of N 2 via six-electron reduction and further functionalization to value-added products is one of the most important and challenging chemical transformations in N 2 fixation. However, most N 2 splitting approaches rely on strong chemical or electrochemical reduction to generate highly reactive metal species to bind and activate N 2 , which is often incompatible with functionalizing agents. Catalytic and sustainable N 2 splitting to produce metal nitrides under mild conditions may create efficient and straightforward methods for N-containing organic compounds. Herein, we present that a readily available and nonredox ( n -Bu) 4 NBr can promote N 2 -splitting with a Mo(III) platform. Both experimental and theoretical mechanistic studies suggest that simple X - (X = Br, Cl, etc.) anions could induce the disproportionation of Mo III [N( TMS )Ar] 3 at the early stage of the catalysis to generate a catalytically active {Mo II [N( TMS )Ar] 3 } - species. The quintet Mo II species prove to be more favorable for N 2 fixation kinetically and thermodynamically, compared with the quartet Mo III counterpart. Especially, computational studies reveal a distinct heterovalent {Mo II -N 2 -Mo III } dimeric intermediate for the N≡N triple bond cleavage.