Modeling the cis-Oxo-Labile binding site motif of non-heme iron oxygenases: Water exchange and oxidation reactivity of a non-heme iron(IV)-Oxo compound bearing a tripodal tetradentate ligand

Anna Company, Irene Prat, Jonathan R. Frisch, Dr Ruben Mas-Ballesté, Mireia Güell, Gergely Juhász, Xavi Ribas, Dr Eckard Münck, Josep M. Luis, Lawrence Que, Miquel Costas

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Abstract

The spectroscopic and chemical characterization of a new synthetic non-heme iron(IV)-oxo species [FeIV(O)(Me,HPytacn)(S)] 2+ (2, Me,HPytacn=1-(2′-pyridylmethyl)-4,7-dimethyl- 1,4,7-triazacyclononane, S=CH3CN or H2O) is described. Complex 2 was prepared by reaction of [FeII(CF3SO 3)2(Me,HPytacn)] (1) with peracetic acid. Complex 2 bears a tetradentate N4 ligand that leaves two cis sites available for binding an oxo group and a second external ligand but, unlike the related iron(IV)-oxo species with tetradentate ligands, it is remarkably stable at room temperature (t1/2>2a h at 288a K). Its ability to exchange the oxygen atom of the oxo ligand with water has been analyzed in detail by means of kinetic studies, and a mechanism is proposed on the basis of DFT calculations. Hydrogen-atom abstraction from C-H bonds and oxygen-atom transfer to sulfides by 2 have also been studied. Despite its thermal stability, 2 proves to be a very powerful oxidant that is capable of breaking the strong C-H bond of cyclohexane (bond dissociation energy=99.3a kcala mol-1). A powerful oxidant: A non-heme oxo-iron(IV) complex (see picture), containing a labile site cis to the terminal oxo group, has been prepared and characterized. The complex is unusually stable (t1/2>2a h at 288a K). Water exchange, oxo transfer, and Ha abstraction reactions have been studied. Despite its thermal stability, the complex is a very powerful oxidant.

Original languageEnglish (US)
Pages (from-to)1622-1634
Number of pages13
JournalChemistry - A European Journal
Volume17
Issue number5
DOIs
StatePublished - Feb 1 2011

Keywords

  • bioinorganic chemistry
  • iron
  • oxygenases
  • reaction mechanisms
  • tetradentate ligands

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

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