Hydrazine Formation via Niᴵᴵᴵ-NH₂ Radical Coupling in Ni-Mediated Ammonia Oxidation
- Creators
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Gu, Nina X.
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Oyala, Paul H.
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Peters, Jonas C.
Abstract
Given the diverse mechanistic possibilities for the overall 6e⁻/6H⁺ transformation of ammonia to dinitrogen, identification of M(NHₓ) intermediates involved in N–N bond formation is a central mechanistic challenge. In analogy to water oxidation mechanisms, which widely invoke metal oxo intermediates, metal imide and nitride intermediates have commonly been proposed for ammonia oxidation, and stoichiometric demonstration of N–N bond formation from these metal-ligand multiply bonded species is well-precedented. In contrast, while the homocoupling of M–NH₂ species to form hydrazine has been hypothesized as the key N–N bond forming step in certain molecular ammonia oxidation systems, well-defined examples of this transformation from M–NH₂ complexes are essentially without precedent. This work reports the first example of net ammonia oxidation mediated by a molecular Ni species, a transformation carried out via formal Niᴵᴵ/Niᴵᴵᴵ oxidation states. The available data are consistent with a Nᴵᴵᴵ–NH₂ intermediate featuring substantial spin at N undergoing N–N bond formation to generate a Niᴵᴵ₂(N₂H₄) complex. Additional and structurally unusual Ni_x(N_yH_z) species – including a Ni₂(trans-N₂H₂) complex – are characterized and studied as intermediates in the Ni-mediated ammonia oxidation cycle described herein.
Additional Information
The content is available under CC BY NC ND 4.0 License. The authors acknowledge Dr. Michael Takase and Lawrence Henling for assistance with X-ray crystallography. This work was supported by the National Institutes of Health (General Medical Sciences, grant GM070757) and an NSF-GRFP to N.X.G. The Caltech EPR facility is supported by the Dow Next Generation Educator Fund. The X-Ray Crystallography Facility in the Beckman Institute at Caltech has been supported by a Dow Next Generation Instrumentation Grant. The authors declare no competing financial interests.Attached Files
Submitted - hydrazine-formation-via-ni-iii-nh2-radical-coupling-in-ni-mediated-ammonia-oxidation.pdf
Supplemental Material - ni-nh2-si-chem-rxiv.pdf
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Additional details
- Eprint ID
- 120400
- Resolver ID
- CaltechAUTHORS:20230324-457084000.3
- NIH
- GM070757
- NSF Graduate Research Fellowship
- Dow Next Generation Educator Fund
- Created
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2023-03-30Created from EPrint's datestamp field
- Updated
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2023-03-30Created from EPrint's last_modified field