Hydrosilylation of a Molecular Molybdenum Nitride Provides Mechanistic Insights into Photodriven Ammonia Synthesis from N₂and H₂

TY - JOUR

T1 - Hydrosilylation of a Molecular Molybdenum Nitride Provides Mechanistic Insights into Photodriven Ammonia Synthesis from N2and H2

AU - Kim, Junho

AU - Kaul, Nidhi

AU - Pecoraro, Matthew V.

AU - Chirik, Paul J.

N1 - Publisher Copyright: © 2026 The Authors. Published by American Chemical Society. This article is licensed under CC-BY 4.0. https://creativecommons.org/licenses/by/4.0/

PY - 2026/2/25

Y1 - 2026/2/25

N2 - Addition of Ph2SiH2 to [(depe)2Mo(N)][BArF4] (depe = 1,2-bis(diethylphosphino)ethane, BArF4 = B(3,5-(CF3)2C6H3)4) at 60 °C generated the silyl imido molybdenum hydride complex, trans-[(depe)2Mo(NSiHPh2)H][BArF4], 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][BArF4] with blue light under H2 produced free amine along with [(depe)2MoH5][BArF4] 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)][BArF4] to ammonia and the role of the photocatalyst in this transformation.

AB - Addition of Ph2SiH2 to [(depe)2Mo(N)][BArF4] (depe = 1,2-bis(diethylphosphino)ethane, BArF4 = B(3,5-(CF3)2C6H3)4) at 60 °C generated the silyl imido molybdenum hydride complex, trans-[(depe)2Mo(NSiHPh2)H][BArF4], 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][BArF4] with blue light under H2 produced free amine along with [(depe)2MoH5][BArF4] 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)][BArF4] to ammonia and the role of the photocatalyst in this transformation.

UR - https://www.scopus.com/pages/publications/105030921349

UR - https://www.scopus.com/pages/publications/105030921349#tab=citedBy

U2 - 10.1021/jacs.5c22220

DO - 10.1021/jacs.5c22220

M3 - Article

C2 - 41666383

SN - 0002-7863

VL - 148

SP - 7761

EP - 7771

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 7

ER -