(<i>n</i>‑Bu)₄NBr-Promoted\nN₂ Splitting to Molybdenum Nitride

Abstract

Splitting of N₂ via six-electron reduction\nand further\nfunctionalization to value-added products is one of the most important\nand challenging chemical transformations in N₂ fixation.\nHowever, most N₂ splitting approaches rely on strong chemical\nor electrochemical reduction to generate highly reactive metal species\nto bind and activate N₂, which is often incompatible with\nfunctionalizing agents. Catalytic and sustainable N₂ splitting\nto produce metal nitrides under mild conditions may create efficient\nand straightforward methods for N-containing organic compounds. Herein,\nwe present that a readily available and nonredox (<i>n</i>-Bu)₄NBr can promote N₂-splitting with a Mo­(III)\nplatform. Both experimental and theoretical mechanistic studies suggest\nthat simple X^– (X = Br, Cl, etc.) anions could induce\nthe disproportionation of Mo^III[N­(<i>TMS</i>)­Ar]₃ at the early stage of the catalysis to generate a catalytically\nactive {Mo^II[N­(<i>TMS</i>)­Ar]₃}⁻ species. The quintet Mo^II species prove\nto be more favorable for N₂ fixation kinetically and thermodynamically,\ncompared with the quartet Mo^III counterpart. Especially,\ncomputational studies reveal a distinct heterovalent {Mo^II–N₂–Mo^III} dimeric intermediate\nfor the NN triple bond cleavage.