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

Abstract

AbstractM(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 NiII2(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.