Factors affecting the carboxylate shift upon formation of nonheme diiron-O2 adducts.

ABSTRACT: Several [Fe(II)2(N-EtHPTB)(?-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 (?-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 (?-?(1):?(1)-peroxo)diiron(III) species (2·O2X). With one exception, all 2·O2X intermediates convert irreversibly to doubly bridged, blue (?-?(1):?(1)-peroxo)diiron(III) species (3·O2X). Where possible, 2·O2X and 3·O2X intermediates were characterized using resonance Raman spectroscopy, showing respective ?O-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.

SUBMITTER: Frisch JR 

PROVIDER: S-EPMC3678525 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature