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 27.10.2011   Карта сайта     Language По-русски По-английски
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27.10.2011

Structure and reactivity of a mononuclear non-haem iron(III)–peroxo complex





Journal name:

Nature

Volume:

478,

Pages:

502–505

Date published:

(27 October 2011)

DOI:

doi:10.1038/nature10535


Received


Accepted


Published online



 






Oxygen-containing mononuclear iron species—iron(iii)–peroxo, iron(iii)–hydroperoxo and iron(iv)–oxo—are key intermediates in the catalytic activation of dioxygen by iron-containing metalloenzymes1, 2, 3, 4, 5, 6, 7. It has been difficult to generate synthetic analogues of these three active iron–oxygen species in identical host complexes, which is necessary to elucidate changes to the structure of the iron centre during catalysis and the factors that control their chemical reactivities with substrates. Here we report the high-resolution crystal structure of a mononuclear non-haem side-on iron(iii)–peroxo complex, [Fe(iii)(TMC)(OO)]+. We also report a series of chemical reactions in which this iron(iii)–peroxo complex is cleanly converted to the iron(iii)–hydroperoxo complex, [Fe(iii)(TMC)(OOH)]2+, via a short-lived intermediate on protonation. This iron(iii)–hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(iv)(TMC)(O)]2+, via homolytic O–O bond cleavage of the iron(iii)–hydroperoxo species. All three of these iron species—the three most biologically relevant iron–oxygen intermediates—have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(iii)–hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(iv)–oxo complex in C–H bond activation of alkylaromatics. These reactivity results demonstrate that iron(iii)–hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes.





Figures at a glance


left


  1. Figure 1: X-ray crystal structure of 1.


    Structure of [Fe(TMC)(OO)]+ (1), with thermal ellipsoids drawn at the 30% probability level, produced using ORTEP software. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å): Fe–O1 1.906(4), Fe–O2 1.914(4), Fe–N1 2.192(4), Fe–N2 2.256(5), Fe–N3 2.180(5), Fe–N4 2.273(4), O1–O2 1.463(6). Selected angles (°): O1–Fe–O2 45.03(17), Fe–O1–O2 67.8(2), Fe–O2–O1 67.2(2).




  2. Figure 2: Ultraviolet–visible spectra and XAS data of 1, 2 and 3.


    In ac, data for 1, 2 and 3 are shown respectively in blue, red and green. a, Ultraviolet–visible spectra of 1, 2 and 3; arrows indicate spectral changes for the conversion of 2 to 3 in the reaction of 1 (1 mM) and 3 equiv. HClO4 in acetone/CF3CH2OH (3:1) at –40 °C. b, Main panel, Fe K-edge XAS data; inset, expanded pre-edge region. Dotted black line shows starting material, high-spin [Fe(ii)(TMC)]2+, for reference. c, Main panel, Fourier transform of EXAFS data (k = 2–16). R, bond length; Δ, phase shift of the scattered wave. Inset, EXAFS data (solid lines) with final fits (dashed lines); y axis shows EXAFS intensity multiplied by k3. These data show striking differences across the series, most of which are the result of changes to the first coordination sphere.




  3. Figure 3: Iron–oxygen intermediates.


    Generation, structural and spectroscopic characterization, and reactivities of mononuclear non-haem iron–oxygen intermediates detected in the reactivity studies of 1.




  4. Figure 4: Reactivity studies of 2 with aldehydes.


 


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  • Chen Wev .  honorary member of ISSC science council

  • Harton Vladislav Vadim  honorary member of ISSC science council

  • Lichtenstain Alexandr Iosif  honorary member of ISSC science council

  • Novikov Dimirtii Leonid  honorary member of ISSC science council

  • Yakushev Mikhail Vasilii  honorary member of ISSC science council

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