title: X-ray absorption spectroscopy and reactivity of thiolate-ligated Fe(III)-OOR complexes.
abstract: The reaction of a series of thiolate-ligated iron(II) complexes [Fe(II)([15]aneN(4))(SC(6)H(5))]BF(4) (1), [Fe(II)([15]aneN(4))(SC(6)H(4)-p-Cl)]BF(4) (2), and [Fe(II)([15]aneN(4))(SC(6)H(4)-p-NO(2))]BF(4) (3) with alkylhydroperoxides at low temperature (-78 °C or -40 °C) leads to the metastable alkylperoxo-iron(III) species [Fe(III)([15]aneN(4))(SC(6)H(5))(OOtBu)]BF(4) (1a), [Fe(III)([15]aneN(4))(SC(6)H(4)-p-Cl)(OOtBu)]BF(4) (2a), and [Fe(III)([15]aneN(4))(SC(6)H(4)-p-NO(2))(OOtBu)]BF(4) (3a), respectively. X-ray absorption spectroscopy (XAS) studies were conducted on the Fe(III)-OOR complexes and their iron(II) precursors. The edge energy for the iron(II) complexes (∼7118 eV) shifts to higher energy upon oxidation by ROOH, and the resulting edge energies for the Fe(III)-OOR species range from 7121-7125 eV and correlate with the nature of the thiolate donor. Extended X-ray absorption fine structure (EXAFS) analysis of the iron(II) complexes 1-3 in CH(2)Cl(2) show that their solid state structures remain intact in solution. The EXAFS data on 1a-3a confirm their proposed structures as mononuclear, 6-coordinate Fe(III)-OOR complexes with 4N and 1S donors completing the coordination sphere. The Fe-O bond distances obtained from EXAFS for 1a-3a are 1.82-1.85 Å, significantly longer than other low-spin Fe(III)-OOR complexes. The Fe-O distances correlate with the nature of the thiolate donor, in agreement with the previous trends observed for ν(Fe-O) from resonance Raman (RR) spectroscopy, and supported by optimized geometries obtained from density functional theory (DFT) calculations. Reactivity and kinetic studies on 1a- 3a show an important influence of the thiolate donor.
authors.affiliation: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Jay
authors.initials: J
authors.lastname: Stasser
authors.forename: Frances
authors.initials: F
authors.lastname: Namuswe
authors.forename: Gary D
authors.initials: GD
authors.lastname: Kasper
authors.forename: Yunbo
authors.initials: Y
authors.lastname: Jiang
authors.forename: Courtney M
authors.initials: CM
authors.lastname: Krest
authors.forename: Michael T
authors.initials: MT
authors.lastname: Green
authors.forename: James
authors.initials: J
authors.lastname: Penner-Hahn
authors.forename: David P
authors.initials: DP
authors.lastname: Goldberg
mesh_terms: D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011522:Protons; D013455:Sulfur / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D011522:Protons; D013455:Sulfur; D007501:Iron