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Million-fold activation of the [Fe2(µ-O)2] diamond core for C–H bond cleavage

Nature Chemistry volume 2, pages 400–405 (2010)Cite this article

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Abstract

In biological systems, the cleavage of strong C–H bonds is often carried out by iron centres—such as that of methane monooxygenase in methane hydroxylation—through dioxygen activation mechanisms. High valent species with [Fe2(µ-O)2] diamond cores are thought to act as the oxidizing moieties, but the synthesis of complexes that cleave strong C–H bonds efficiently has remained a challenge. We report here the conversion of a synthetic complex with a valence-delocalized [Fe3.5(µ-O)2Fe3.5]3+ diamond core (1) into a complex with a valence-localized [HO–FeIII–O–FeIV=O]2+ open core (4), which cleaves C–H bonds over a million-fold faster. This activity enhancement results from three factors: the formation of a terminal oxoiron(iv) moiety, the conversion of the low-spin (S = 1) FeIV=O centre to a high-spin (S = 2) centre, and the concentration of the oxidizing capability to the active terminal oxoiron(iv) moiety. This suggests that similar isomerization strategies might be used by nonhaem diiron enzymes.

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Figure 1: Interconversions among high-valent diiron complexes described in this study.
Figure 2: Ultraviolet–visible (UV–vis) and EPR spectra showing the reduction of 3 to 4.
Figure 3: Characterization of 4 by Mössbauer spectroscopy.
Figure 4: Graphic comparison of oxidative reactivities of various iron(iv) complexes.
Figure 5: Reaction of 4 with DHA studied by UV–vis spectroscopy.

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Acknowledgements

This work was supported by NIH grants GM38767 (to L.Q.) and EB-001475 (to E.M.).

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Affiliations

  1. Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, 55455, Minnesota, USA

    Genqiang Xue & Lawrence Que Jr

  2. Department of Chemistry, Carnegie Mellon University, Pittsburgh, 15213, Pennsylvania, USA

    Raymond De Hont & Eckard Münck

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  1. Genqiang Xue
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Contributions

G.X., E.M. and L.Q. conceived and designed the experiments; G.X. and R.D.H. performed the experiments and analysed the data; G.X., R.D.H., E.M. and L.Q. co-wrote the paper.

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Correspondence to Eckard Münck or Lawrence Que Jr.

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Xue, G., De Hont, R., Münck, E. et al. Million-fold activation of the [Fe2(µ-O)2] diamond core for C–H bond cleavage. Nature Chem 2, 400–405 (2010). https://doi.org/10.1038/nchem.586

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