Hydrosilylation of a Molecular Molybdenum Nitride Provides Mechanistic Insights into Photodriven Ammonia Synthesis from N2 and H2

Kim, Junho; Kaul, Nidhi; Pecoraro, Matthew V.; Chirik, Paul J.

doi:10.1021/jacs.5c22220

Hydrosilylation of a Molecular Molybdenum Nitride Provides Mechanistic Insights into Photodriven Ammonia Synthesis from N₂ and H₂

Journal Article · Tue Feb 10 00:00:00 EST 2026 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/jacs.5c22220· OSTI ID:3020795

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Princeton Univ., NJ (United States)

Addition of Ph₂SiH₂ to [(depe)₂Mo(N)][BAr^F₄] (depe = 1,2-bis(diethylphosphino)ethane, BAr^F₄ = B(3,5-(CF₃)₂C₆H₃)₄) at 60 °C generated the silyl imido molybdenum hydride complex, trans- [(depe)₂Mo(NSiHPh₂)H][BAr^F₄], a surrogate for a proposed intermediate complex in the photodriven hydrogenation to free ammonia. Irradiation of a THF solution of trans-[(depe)₂Mo(NSiHPh₂)H]- [BAr^F₄] with blue light under H₂ produced free amine along with [(depe)₂MoH₅][BAr^F₄] in 76% yield. This transformation occurred in the absence of a precious metal photocatalyst, suggesting that it was needed only for the initial addition of H₂ to the molybdenum nitride during the first N−H bond-forming step in the photodriven hydrogenation. Deuterium labeling and crossover studies support concerted Si−H bond addition across the Mo≡N bond, enabled by the nucleophilicity of the nitride. Subsequent hydrogenation involves an intramolecular H migration from Mo to the imido ligand, as supported by electronic absorption spectroscopy, transient absorption spectroscopy, initial rate measurements, and deuterium kinetic isotope effect measurements. These findings provide insights into the photodriven hydrogenation of [(depe)₂Mo(N)][BAr^F₄] to ammonia and the role of the photocatalyst in this transformation.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Univ., NJ (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

Grant/Contract Number:: SC0006498; SC0019370

OSTI ID:: 3020795

Journal Information:: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 7 Vol. 148; ISSN 0002-7863; ISSN 1520-5126

Publisher:: American Chemical Society (ACS)Copyright Statement

Country of Publication:: United States

Language:: English

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Hydrosilylation of a Molecular Molybdenum Nitride Provides Mechanistic Insights into Photodriven Ammonia Synthesis from N2 and H2

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Hydrosilylation of a Molecular Molybdenum Nitride Provides Mechanistic Insights into Photodriven Ammonia Synthesis from N₂ and H₂