The reduction of metal nitrides has received considerable research interest in the context of catalytic homogeneous ammonia synthesis, and a major challenge is the lack of thermodynamic driving force (&lt; 50 kcal/mol) in the N–H bond-forming step. A method for the reduction of a manganese nitride to ammonia has been discovered, where light-driven proton-coupled electron transfer (PCET) enables N–H bond formation. Photoreduction of (sal-tBu)Mn(V)N (sal-tBu = (S,S)-(+)-N,N’-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine) to ammonia and a Mn(II) complex has been accomplished using 9,10-dihydroacridine and a combination of an appropriately matched photoredox catalyst and weak Brønsted acid. Acid-reductant pairs with effective Bond Dissociation Free Energies (BDFE) between 35 and 46 kcal/mol led to efficient ammonia production. Understanding the mechanism of this light-driven method may provide a blueprint for new approaches to catalytic ammonia synthesis under ambient conditions. Extension of these studies to N<sub>2</sub>-derived molybdenum(VI) nitrides will also be presented.

N–H bond formation from metal nitrides yields ammonia by light-driven proton-coupled electron transfer

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.