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    Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions

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    mitra-et-al-2015-nonheme-fe(iv)-oxo-complexes-of-two-new-pentadentate-ligands-and-their-hydrogen-atom-and-oxygen-atom.pdf (2.105Mb)
    Date
    2015-07-22
    Author
    Mitra, Mainak
    Nimir, Hassan
    Demeshko, Serhiy
    Bhat, Satish S.
    Malinkin, Sergey O.
    Haukka, Matti
    Lloret-Fillol, Julio
    Lisensky, George C.
    Meyer, Franc
    Shteinman, Albert A.
    Browne, Wesley R.
    Hrovat, David A.
    Richmond, Michael G.
    Costas, Miquel
    Nordlander, Ebbe
    ...show more authors ...show less authors
    Metadata
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    Abstract
    Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L<sup>1</sup>) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L<sup>2</sup>), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [Fe<sup>II</sup>(CH<inf>3</inf>CN)(L)]<sup>2+</sup> (L = L<sup>1</sup> (1); L<sup>2</sup> (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [Fe<sup>IV</sup>(O)(L)]<sup>2+</sup> (L = L<sup>1</sup> (3); L<sup>2</sup> (4)), which were characterized by UV-vis spectroscopy, high resolution mass spectrometry, and Mössbauer spectroscopy. Complexes 3 and 4 are relatively stable with half-lives at room temperature of 40 h (L = L<sup>1</sup>) and 2.5 h (L = L<sup>2</sup>). The redox potentials of 1 and 2, as well as the visible spectra of 3 and 4, indicate that the ligand field weakens as ligand pyridyl substituents are progressively substituted by (N-methyl)benzimidazolyl moieties. The reactivities of 3 and 4 in hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) reactions show that both complexes exhibit enhanced reactivities when compared to the analogous N4Py complex ([Fe<sup>IV</sup>(O)(N4Py)]<sup>2+</sup>), and that the normalized HAT rates increase by approximately 1 order of magnitude for each replacement of a pyridyl moiety; i.e., [Fe<sup>IV</sup>(O)(L<sup>2</sup>)]<sup>2+</sup> exhibits the highest rates. The second-order HAT rate constants can be directly related to the substrate C-H bond dissociation energies. Computational modeling of the HAT reactions indicates that the reaction proceeds via a high spin transition state.
    URI
    https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84938401764&origin=inward
    DOI/handle
    http://dx.doi.org/10.1021/ic5029564
    http://hdl.handle.net/10576/52496
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    • Chemistry & Earth Sciences [‎601‎ items ]

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