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Title: Electronic Structures of an [Fe(NNR 2 )] +/0/– Redox Series: Ligand Noninnocence and Implications for Catalytic Nitrogen Fixation

Abstract

The intermediacy of metal–NNH 2 complexes has been implicated in the catalytic cycles of several examples of transition-metal-mediated nitrogen (N 2) fixation. In this context, we have shown that triphosphine-supported Fe(N 2) complexes can be reduced and protonated at the distal N atom to yield Fe(NNH2) complexes over an array of charge and oxidation states. Upon exposure to further H +/e equivalents, these species either continue down a distal-type Chatt pathway to yield a terminal iron(IV) nitride or instead follow a distal-to-alternating pathway resulting in N–H bond formation at the proximal N atom. To understand the origin of this divergent selectivity, herein we synthesize and elucidate the electronic structures of a redox series of Fe(NNMe 2) complexes, which serve as spectroscopic models for their reactive protonated congeners.Using a combination of spectroscopies, in concert with density functional theory and correlated ab initio calculations, we evidence one-electron redox noninnocence of the "NNMe 2/ moiety. Specifically, although two closed-shell configurations of the "NNR/ ligand have been commonly considered in the literature-isodiazene and hydrazido(2-)-we provide evidence suggesting that, in their reduced forms, the present iron complexes are best viewed in terms of an open-shell [NNR 2i] •- ligand coupled antiferromagnetically to the Femore » center. Lastly. this one-electron redox noninnocence resembles that of the classically noninnocent ligand NO and may have mechanistic implications for selectivity in N 2 fixation activity.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1];  [3];  [3]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [1]
  1. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Institutes of Health (NIH); National Science Foundation (NSF)
OSTI Identifier:
1558610
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 58; Journal Issue: 5; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Thompson, Niklas B., Oyala, Paul H., Dong, Hai T., Chalkley, Matthew J., Zhao, Jiyong, Alp, E. Ercan, Hu, Michael, Lehnert, Nicolai, and Peters, Jonas C. Electronic Structures of an [Fe(NNR2 )]+/0/– Redox Series: Ligand Noninnocence and Implications for Catalytic Nitrogen Fixation. United States: N. p., 2019. Web. doi:10.1021/acs.inorgchem.9b00133.
Thompson, Niklas B., Oyala, Paul H., Dong, Hai T., Chalkley, Matthew J., Zhao, Jiyong, Alp, E. Ercan, Hu, Michael, Lehnert, Nicolai, & Peters, Jonas C. Electronic Structures of an [Fe(NNR2 )]+/0/– Redox Series: Ligand Noninnocence and Implications for Catalytic Nitrogen Fixation. United States. doi:10.1021/acs.inorgchem.9b00133.
Thompson, Niklas B., Oyala, Paul H., Dong, Hai T., Chalkley, Matthew J., Zhao, Jiyong, Alp, E. Ercan, Hu, Michael, Lehnert, Nicolai, and Peters, Jonas C. Thu . "Electronic Structures of an [Fe(NNR2 )]+/0/– Redox Series: Ligand Noninnocence and Implications for Catalytic Nitrogen Fixation". United States. doi:10.1021/acs.inorgchem.9b00133. https://www.osti.gov/servlets/purl/1558610.
@article{osti_1558610,
title = {Electronic Structures of an [Fe(NNR2 )]+/0/– Redox Series: Ligand Noninnocence and Implications for Catalytic Nitrogen Fixation},
author = {Thompson, Niklas B. and Oyala, Paul H. and Dong, Hai T. and Chalkley, Matthew J. and Zhao, Jiyong and Alp, E. Ercan and Hu, Michael and Lehnert, Nicolai and Peters, Jonas C.},
abstractNote = {The intermediacy of metal–NNH2 complexes has been implicated in the catalytic cycles of several examples of transition-metal-mediated nitrogen (N2) fixation. In this context, we have shown that triphosphine-supported Fe(N2) complexes can be reduced and protonated at the distal N atom to yield Fe(NNH2) complexes over an array of charge and oxidation states. Upon exposure to further H+/e– equivalents, these species either continue down a distal-type Chatt pathway to yield a terminal iron(IV) nitride or instead follow a distal-to-alternating pathway resulting in N–H bond formation at the proximal N atom. To understand the origin of this divergent selectivity, herein we synthesize and elucidate the electronic structures of a redox series of Fe(NNMe2) complexes, which serve as spectroscopic models for their reactive protonated congeners.Using a combination of spectroscopies, in concert with density functional theory and correlated ab initio calculations, we evidence one-electron redox noninnocence of the "NNMe2/ moiety. Specifically, although two closed-shell configurations of the "NNR/ ligand have been commonly considered in the literature-isodiazene and hydrazido(2-)-we provide evidence suggesting that, in their reduced forms, the present iron complexes are best viewed in terms of an open-shell [NNR2i]•- ligand coupled antiferromagnetically to the Fe center. Lastly. this one-electron redox noninnocence resembles that of the classically noninnocent ligand NO and may have mechanistic implications for selectivity in N2 fixation activity.},
doi = {10.1021/acs.inorgchem.9b00133},
journal = {Inorganic Chemistry},
number = 5,
volume = 58,
place = {United States},
year = {2019},
month = {2}
}

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Works referencing / citing this record:

CCDC 1890845: Experimental Crystal Structure Determination
dataset, January 2019


CCDC 1890846: Experimental Crystal Structure Determination
dataset, January 2019