Ammonia formation by metal–ligand cooperative hydrogenolysis of a nitrido ligand

Abstract

Bioinspired hydrogenation of N2 to ammonia at ambient conditions by stepwise nitrogen protonation/reduction with metal complexes in solution has experienced remarkable progress. In contrast, the highly desirable direct hydrogenation with H2 remains difficult. In analogy to the heterogeneously catalysed Haber–Bosch process, such a reaction is conceivable via metal-centred N2 splitting and unprecedented hydrogenolysis of the nitrido ligands to ammonia. We report the synthesis of a ruthenium(IV) nitrido complex. The high nucleophilicity of the nitrido ligand is demonstrated by unusual N–C coupling with π-acidic CO. Furthermore, the terminal nitrido ligand undergoes facile hydrogenolysis with H2 at ambient conditions to produce ammonia in high yield. Kinetic and quantum chemical examinations of this reaction suggest cooperative behaviour of a phosphorus–nitrogen–phosphorus pincer ligand in rate-determining heterolytic hydrogen splitting. One of the hurdles facing the development of effective catalysts to produce ammonia from nitrogen is the stability of the metal nitrides that form during the reaction. Now, the hydrogenolysis of nitride ligands with hydrogen is reported and attributed to PNP pincer ligand cooperativity.

Cite this article

Askevold, B., Nieto, J., Tussupbayev, S. et al. Ammonia formation by metal–ligand cooperative hydrogenolysis of a nitrido ligand. Nature Chem 3, 532–537 (2011). https://doi.org/10.1038/nchem.1051

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