High-valent nonheme iron intermediate. Structure and properties of [Fe{sub 2}({mu}-O){sub 2}(5-Me-TPA){sub 2}](ClO{sub 4}){sub 3}

Journal Article · Wed Mar 15 04:00:00 EST 1995 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja00115a013· OSTI ID:35483

Dong, Y; Fujii, Hiroshi; Hendrich, M P; Leising, R A; Pan, G; Randall, C R; Wilkinson, E C; Zang, Y; Que, L Jr ^[1]; Fox, B G; Kauffmann, K; Muenck, E ^[2]

---

1. Univ. of Minnesota, Minneapolis, MN (United States)
2. Carnegie Mellon Univ., Pittsburgh, PA (United States)

In our efforts to model oxidizing species of diiron enzymes, we observed a transient high-valent species in the reaction of a ({mu}-oxo)diiron(III) TpA complex with H{sub 2}O{sub 2} in CH{sub 3}CN at -40{degree}C. This intermediate exhibits an S = 3/2 EPR spectrum and a Moessbauer isomer shift of 0.11 mm/s, i.e., the complex has properties very similar to those of synthetic oxoiron(IV) porphyrin radical cation species. Because the initial EPR quantitations gave spin concentrations of 0.3 spin for samples that contained 30% of the iron associated with the S = 3/2 species, we formulated the intermediate as [Fe-(TPA)O]{sup 3+}; however, this mononuclear formulation has turned out to be incorrect. The use of 5-alkyl-TPA ligands in place of TPA has allowed the isolation of the high-valent species as a solid; the spectroscopic properties of the isolated solid identify it as [Fe{sub 2}(O){sub 2}(5-R-TPA){sub 2}](ClO{sub 4}){sub 3}, a bis({mu}-oxo)diiron(III,IV) complex. We detail the spectroscopic studies in this paper. Among the models considered, the only one that could possibly explain the observed site equivalence, isomer shift. and other properties consists of a valence-delocalized low-spin (S = 1/2) Fe{sup III}-low-spin (S = 1) Fe{sup IV} pair coupled by Heisenberg as well as double exchange. 70 refs., 15 figs., 4 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 35483
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 10 Vol. 117; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ABSORPTION SPECTRA
AMINES
ELECTRON SPIN RESONANCE
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
IRON COMPLEXES
IRON COMPOUNDS
METHYLAMINE
NUMERICAL DATA
ORGANOMETALLIC COMPOUNDS