On the feasibility of N2 fixation via a single-site FeI/FeIV cycle: Spectroscopic studies of FeI(N2)FeI, FeIV=N, and related species
Abstract
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.
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.Attached Files
Published - HENpnas06.pdf
Published - HENpnas06fig7.pdf
Published - HENpnas06fig8.pdf
Published - HENpnas06fig9.pdf
Published - HENpnas06supp.pdf
Files
Name | Size | Download all |
---|---|---|
md5:ff1b8399c72c23862e3513646a77cbcc
|
148.9 kB | Preview Download |
md5:67b4b5c5f7b5fb192512ccbef48a89d3
|
1.1 MB | Preview Download |
md5:cd738cf5056a0a02378b3e620c36508c
|
148.8 kB | Preview Download |
md5:f2c0265797dd5551dc2edf7865bd42f7
|
85.4 kB | Preview Download |
md5:ac6ca7127124d2ba73bc46c8f5073fc6
|
172.5 kB | Preview Download |
Additional details
- PMCID
- PMC1693871
- Eprint ID
- 11127
- Resolver ID
- CaltechAUTHORS:HENpnas06
- MIH
- GM-070757
- NIH Postdoctoral Fellowship
- GM-072291
- NIH
- GM-077387
- Herman Frasch Foundation Fellowship
- Arnold and Mabel Beckman Foundation
- Alfred P. Sloan Foundation
- Created
-
2008-07-16Created from EPrint's datestamp field
- Updated
-
2021-11-08Created from EPrint's last_modified field