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On the feasibility of N2 fixation via a single-site FeI/FeIV cycle: Spectroscopic studies of FeI(N2)FeI, FeIV=N, and related species

Hendrich, Michael P. and Gunderson, William and Behan, Rachel K. and Green, Michael T. and Mehn, Mark P. and Betley, Theodore A. and Lu, Connie C. and Peters, Jonas C. (2006) On the feasibility of N2 fixation via a single-site FeI/FeIV cycle: Spectroscopic studies of FeI(N2)FeI, FeIV=N, and related species. Proceedings of the National Academy of Sciences of the United States of America, 103 (46). pp. 17107-17112. ISSN 0027-8424. PMCID PMC1693871. doi:10.1073/pnas.0604402103.

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PDF (Fig. 7. Mössbauer spectra of toluene solutions of 38 mM [PhBPiPr3]Fe(H)3(PMe3) (5) (A) and 40 mM [PhBPiPr3]FePMe3 (6) (B) at 140 K and zero applied magnetic field.) - Published Version
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PDF (Fig. 8. Isofield parallel magnetization (cT, dots) for a powder sample of 4 at the magnetic fields listed on the plot. The simulations (solid lines) use: SA = SB = 3/2, J = +4 cm-1, DA = DB = -53 cm-1, E/DA = E/DB = 0.10, g) - Published Version
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PDF (Fig. 9. EPR spectrum (solid line) and simulation (dashed line) of 46 mM [PhBPiPr3]FePMe3 in toluene) - Published Version
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The electronic properties of an unusually redox-rich iron system, [PhBPR 3]FeNx (where [PhBPR 3] is [PhB(CH2PR2)3]−), are explored by Mössbauer, EPR, magnetization, and density-functional methods to gain a detailed picture regarding their oxidation states and electronic structures. The complexes of primary interest in this article are the two terminal iron(IV) nitride species, [PhBPiPr 3]FeN (3a) and [PhBPCH2Cy 3]FeN (3b), and the formally diiron(I) bridged-Fe(μ-N2)Fe species, {[PhBPiPr 3]Fe}2(μ-N2) (4). Complex 4 is chemically related to 3a via a spontaneous nitride coupling reaction. The diamagnetic iron(IV) nitrides 3a and 3b exhibit unique electronic environments that are reflected in their unusual Mössbauer parameters, including quadrupole-splitting values of 6.01(1) mm/s and isomer shift values of −0.34(1) mm/s. The data for 4 suggest that this complex can be described by a weak ferromagnetic interaction (J/D < 1) between two iron(I) centers. For comparison, four other relevant complexes also are characterized: a diamagnetic iron(IV) trihydride [PhBPiPr 3]Fe(H)3(PMe3) (5), an S = 3/2 iron(I) phosphine adduct [PhBPiPr 3]FePMe3 (6), and the S = 2 iron(II) precursors to 3a, [PhBPiPr 3]FeCl and [PhBPiPr 3]Fe-2,3:5,6-dibenzo-7-aza bicyclo[2.2.1]hepta-2,5-diene (dbabh). The electronic properties of these respective complexes also have been explored by density-functional methods to help corroborate our spectral assignments and to probe their electronic structures further.

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Peters, Jonas C.0000-0002-6610-4414
Additional Information:© 2006 by the National Academy of Sciences. Edited by Richard R. Schrock, Massachusetts Institute of Technology, Cambridge, MA, and approved August 29, 2006 (received for review May 30, 2006). Published online before print November 7, 2006. This article is a PNAS direct submission. Squid data were collected at the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. This work was supported by National Institutes of Health Grant GM-070757 (to J.C.P.), Postdoctoral Fellowship GM-072291 (to M.P.M.), and Grant GM-077387 (to M.P.H.). R.K.B. is grateful for a Herman Frasch Foundation Fellowship, and M.T.G. acknowledges the Arnold and Mabel Beckman Foundation and the Alfred P. Sloan Foundation. Author contributions: M.P.H., M.T.G., and J.C.P. designed research; M.P.H., W.G., R.K.B., M.T.G., M.P.M., T.A.B., C.C.L., and J.C.P. performed research; M.P.H., W.G., R.K.B., M.T.G., M.P.M., and J.C.P. analyzed data; and M.P.H., M.P.M., and J.C.P. wrote the paper. The authors declare no conflict of interest. Complete materials and methods are provided in Supporting Materials and Methods.
Funding AgencyGrant Number
NIH Postdoctoral FellowshipGM-072291
Herman Frasch Foundation FellowshipUNSPECIFIED
Arnold and Mabel Beckman FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:dinitrogen activation; high-valent iron; nitrogenase; high-valent iron nitride; spectroscopy
Issue or Number:46
PubMed Central ID:PMC1693871
Record Number:CaltechAUTHORS:HENpnas06
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11127
Deposited By: Tony Diaz
Deposited On:16 Jul 2008 22:27
Last Modified:08 Nov 2021 21:33

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