A 10^6‑Fold Enhancement in N_2‑Binding Affinity of an Fe_2(μ-H)_2 Core upon Reduction to a Mixed-Valence Fe^(II)Fe^I State
Abstract
Transient hydride ligands bridging two or more iron centers purportedly accumulate on the iron–molybdenum cofactor (FeMoco) of nitrogenase, and their role in the reduction of N_2 to NH_3 is unknown. One role of these ligands may be to facilitate N_2 coordination at an iron site of FeMoco. Herein, we consider this hypothesis and describe the preparation of a series of diiron complexes supported by two bridging hydride ligands. These compounds bind either one or two molecules of N_2 depending on the redox state of the Fe_2(μ-H)_2 unit. An unusual example of a mixed-valent Fe^(II)(μ-H)^2Fe^I is described that displays a 10^6-fold enhancement of N_2 binding affinity over its oxidized congener, quantified by spectroscopic and electrochemical techniques. Furthermore, these compounds show promise as functional models of nitrogenase as substantial amounts of NH_3 are produced upon exposure to proton and electron equivalents. The Fe(μ-H)Fe(N2_) sub-structure featured herein was previously unknown. This subunit may be relevant to consider in nitrogenases during turnover.
Additional Information
© 2014 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: July 21, 2014. Publication Date (Web): September 3, 2014. This work was supported by the N.I.H. (GM 070757) and the Gordon and Betty Moore Foundation. J.R. was supported by an N.S.F. graduate research fellowship. We thank Larry Henling for crystallographic assistance, Prof. Michael T. Green and Elizabeth Onderko for assistance with the collection and analysis of EXAFS data, Dr. Angelo di Bilio for assistance with EPR measurements, and Prof. George Rossman for assisting with near-IR spectrophotometry measurements.Attached Files
Published - ja507217v.pdf
Supplemental Material - ja507217v_si_001.pdf
Supplemental Material - ja507217v_si_002.cif
Supplemental Material - ja507217v_si_003.cif
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Additional details
- PMCID
- PMC4183624
- Eprint ID
- 50072
- Resolver ID
- CaltechAUTHORS:20140926-134453593
- NIH
- GM 070757
- Gordon and Betty Moore Foundation
- NSF Graduate Research Fellowship
- Created
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2014-09-26Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field