Hydrazine Formation via Coupling of a Nickel(III)–NH₂ Radical

Abstract

M(NHₓ) intermediates involved in N−N bond formation are central to ammonia oxidation (AO) catalysis, an enabling technology to ultimately exploit ammonia (NH₃) as an alternative fuel source. While homocoupling of a terminal amide species (M‐NH₂) to form hydrazine (N₂H₄) has been proposed, well‐defined examples are without precedent. Herein, we discuss the generation and electronic structure of a NiIII‐NH₂ species that undergoes bimolecular coupling to generate a Ni^(II)₂(N₂H₄) complex. This hydrazine adduct can be further oxidized to a structurally unusual Ni₂(N₂H₂) species; this releases N₂ in the presence of NH₃, thus establishing a synthetic cycle for Ni‐mediated AO. Distribution of the redox load for H₂N‐NH₂ formation via NH₂ coupling between two metal centers presents an attractive strategy for AO catalysis using Earth‐abundant, late first‐row metals.

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