Ammonia is currently produced industrially by hydrogenation of dinitrogen using fossil-fuel-derived hydrogen. A sustainable ammonia synthesis based on renewable resources could impact global food, energy, and water systems — but advances in fundamental chemical reactivity are needed. A two-part electrochemical approach to ammonia synthesis is proposed based on a thermodynamic analysis of electrochemical N2 fixation: (1) reductive N2 splitting to form a metal nitride complex; (2) proton-coupled electron transfer (PCET) reduction of the nitride complex to release ammonia. Electroanalytical studies of N2 splitting by (PNP)Re(Cl)2 (PNP is N(CH2CH2PtBu2)2]−) provide insight into the first process. A combined experimental-computational study of protonation of (PNP)Ru(N) identifies a new metal-ligand cooperative PCET mechanism for nitride conversion to ammonia.

Mechanisms of dinitrogen cleavage and nitride reduction to ammonia at pincer complexes

255th National Meeting (2018)

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