(n-Bu)₄NBr-Promoted N₂ Splitting to Molybdenum Nitride

Abstract

Splitting of N₂ via six-electron reduction and further functionalization to value-added products is one of the most important and challenging chemical transformations in N₂ fixation. However, most N₂ splitting approaches rely on strong chemical or electrochemical reduction to generate highly reactive metal species to bind and activate N₂, which is often incompatible with functionalizing agents. Catalytic and sustainable N₂ 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)₄NBr can promote N₂-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 N₂ fixation kinetically and thermodynamically, compared with the quartet Mo^III counterpart. Especially, computational studies reveal a distinct heterovalent {Mo^II-N₂-Mo^III} dimeric intermediate for the N≡N triple bond cleavage.