DUGi

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

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@2072@@297574

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(CF3SO3)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>2 h at 288 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[BOND]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[BOND]H bond of cyclohexane (bond dissociation energy=99.3 kcal mol−1)

Financial support for this work was provided by MEC-Spain (Projects CTQ2009–08464/BQU and CTQ2008–06696/BQU), and the US National Institutes of Health (GM-33162 to L.Q. and EB-001475 to E.M.). M.C. acknowledges Generalitat de Catalunya for an ICREA-Academia Award and SGR 2009 SGR 637. A.C., I. P., and M.G. thank MEC for FPU PhD grants. We thank RahuCat for a generous gift of tritosyl tacn. We thank W. Han and L. Noodleman for providing the utility programs to compute the Mçssbauer parameters of the iron complexes and M. Swart for his useful comments about the Mçssbauer calculations

Wiley-VCH Verlag