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Characterization of an Fe≡N−NH₂ Intermediate Relevant to Catalytic N₂ Reduction to NH₃

Anderson, John S. and Cutsail, George E., III and Rittle, Jonathan and Connor, Bridget A. and Gunderson, William A. and Zhang, Limei and Hoffman, Brian M. and Peters, Jonas C. (2015) Characterization of an Fe≡N−NH₂ Intermediate Relevant to Catalytic N₂ Reduction to NH₃. Journal of the American Chemical Society, 137 (24). pp. 7803-7809. ISSN 0002-7863. PMCID PMC4603982. doi:10.1021/jacs.5b03432.

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The ability of certain transition metals to mediate the reduction of N₂ to NH₃ has attracted broad interest in the biological and inorganic chemistry communities. Early transition metals such as Mo and W readily bind N₂ and mediate its protonation at one or more N atoms to furnish M(NₓHᵧ) species that can be characterized and, in turn, extrude NH₃. By contrast, the direct protonation of Fe–N₂ species to Fe(NₓHᵧ) products that can be characterized has been elusive. Herein, we show that addition of acid at low temperature to [(TPB)Fe(N₂)][Na(12-crown-4)] results in a new S = 1/2 Fe species. EPR, ENDOR, Mössbauer, and EXAFS analysis, coupled with a DFT study, unequivocally assign this new species as [(TPB)Fe≡N–NH₂]⁺, a doubly protonated hydrazido(2−) complex featuring an Fe-to-N triple bond. This unstable species offers strong evidence that the first steps in Fe-mediated nitrogen reduction by [(TPB)Fe(N₂)][Na(12-crown-4)] can proceed along a distal or “Chatt-type” pathway. A brief discussion of whether subsequent catalytic steps may involve early or late stage cleavage of the N–N bond, as would be found in limiting distal or alternating mechanisms, respectively, is also provided.

Item Type:Article
Related URLs:
URLURL TypeDescription Information CentralArticle
Rittle, Jonathan0000-0001-6241-6253
Hoffman, Brian M.0000-0002-3100-0746
Peters, Jonas C.0000-0002-6610-4414
Additional Information:© 2015 American Chemical Society. Received: April 1, 2015. Published: May 22, 2015. This work was supported by the NIH (GM 070757 to J.C.P., GM 111097 to B.M.H.), the NSF (MCB-1118613 to B.M.H., DGE-0824162 to G.E.C.), an NSERC fellowship (to L.Z.), a Caltech Center for Environmental Microbial Interactions fellowship (to L.Z.), and the Gordon and Betty Moore Foundation. We thank the staff at Beamline 9−3, Stanford Synchrotron Radiation Lightsource (SSRL). SSRL is operated for the DOE and supported by OBER and by the NIH, NIGMS (P41GM103393) and the NCRR (P31RR001209).
Group:Caltech Center for Environmental Microbial Interactions (CEMI)
Funding AgencyGrant Number
NIHGM 070757
NIHGM 111097
NSF Graduate Research FellowshipDGE-0824162
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Caltech Center for Environmental Microbial Interactions (CEMI)UNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Issue or Number:24
PubMed Central ID:PMC4603982
Record Number:CaltechAUTHORS:20150708-084228936
Persistent URL:
Official Citation:Characterization of an Fe≡N–NH2 Intermediate Relevant to Catalytic N2 Reduction to NH3 John S. Anderson, George E. Cutsail, III, Jonathan Rittle, Bridget A. Connor, William A. Gunderson, Limei Zhang, Brian M. Hoffman, and Jonas C. Peters Journal of the American Chemical Society 2015 137 (24), 7803-7809 DOI: 10.1021/jacs.5b03432
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58802
Deposited By: Ruth Sustaita
Deposited On:08 Jul 2015 16:36
Last Modified:03 Jun 2022 19:09

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