title: Factors affecting the carboxylate shift upon formation of nonheme diiron-O2 adducts.
abstract: Several [Fe(II)2(N-EtHPTB)(μ-O2X)](2+) complexes (1·O2X) have been synthesized, where N-EtHPTB is the anion of N,N,N'N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane and O2X is an oxyanion bridge. Crystal structures reveal five-coordinate (μ-alkoxo)diiron(II) cores. These diiron(II) complexes react with O2 at low temperatures in CH2Cl2 (-90 °C) to form blue-green O2 adducts that are best described as triply bridged (μ-η(1):η(1)-peroxo)diiron(III) species (2·O2X). With one exception, all 2·O2X intermediates convert irreversibly to doubly bridged, blue (μ-η(1):η(1)-peroxo)diiron(III) species (3·O2X). Where possible, 2·O2X and 3·O2X intermediates were characterized using resonance Raman spectroscopy, showing respective νO-O values of ∼850 and ∼900 cm(-1). How the steric and electronic properties of O2X affect conversion of 2·O2X to 3·O2X was examined. Stopped-flow analysis reveals that oxygenation kinetics of 1·O2X is unaffected by the nature of O2X, and for the first time, the benzoate analog of 2·O2X (2·O2CPh) is observed.
authors: Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, United States.
authors: Jonathan R
authors: JR
authors: Frisch
authors: Ryan
authors: R
authors: McDonnell
authors: Elena V
authors: EV
authors: Rybak-Akimova
authors: Lawrence
authors: L
authors: Que
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010100:Oxygen / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D005296:Ferrous Compounds; D007501:Iron; D010100:Oxygen