The migratory insertion of carbon monoxide (CO) into M–C bonds has been known for several decades and is invoked in many industrially-important reactions. However, analogous reactivity with isoelectronic dinitrogen (N2) has yet to be realized. Recently, our group reported the iron-mediated coupling of arenes with N2 to yield anilines. We proposed that the N–C bond formation step occurs after silylation of iron-bound N2 to give a formally iron(IV) hydrazido(2–) species. This high-valent intermediate subsequently undergoes migratory insertion of the aryl group to the hydrazido group, but this proposed species was not isolated. Here, we explore the mechanism of this umpolung reaction in which the previously nucleophilic N2 ligand becomes an electrophile through silylation. A formally iron(IV) hydrazido complex has been successfully isolated and characterized, and theoretical calculations along with kinetic analysis of a series of hydrocarbyl migrations offers insight into the generality of this novel route of N–C bond formation to N2.

Making N2 electrophilic: Hydrocarbyl migration to a doubly-silylated hydrazido(2–) ligand at iron(IV)

ACS Spring 2022

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