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Characterization of Three Members of the Electron-Transfer Series [Fe(pda)2]n (n=2−, 1−, 0) by Spectroscopy and Density Functional Theoretical Calculations [pda=Redox Non-innocent Derivatives of N,N′-Bis(pentafluorophenyl)-o-phenylenediamide(2−, 1.−, 0)]

  1. Marat M. Khusniyarov Dr.1,2,
  2. Eckhard Bill Dr.1,
  3. Thomas Weyhermüller Dr.1,
  4. Eberhard Bothe Dr.1,
  5. Klaus Harms Dr.2,
  6. Jörg Sundermeyer Prof. Dr.2,
  7. Karl Wieghardt Prof. Dr.1

Article first published online: 7 JUL 2008

DOI: 10.1002/chem.200800546

Issue

Chemistry - A European Journal

Chemistry - A European Journal

Volume 14, Issue 25, pages 7608–7622, August 28, 2008

Additional Information

How to Cite

Khusniyarov, Marat M., Bill, E., Weyhermüller, T., Bothe, E., Harms, K., Sundermeyer, J. and Wieghardt, K. (2008), Characterization of Three Members of the Electron-Transfer Series [Fe(pda)2]n (n=2−, 1−, 0) by Spectroscopy and Density Functional Theoretical Calculations [pda=Redox Non-innocent Derivatives of N,N′-Bis(pentafluorophenyl)-o-phenylenediamide(2−, 1.−, 0)]. Chem. Eur. J., 14: 7608–7622. doi: 10.1002/chem.200800546

Author Information

  1. 1

    Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34–36, 45470 Mülheim an der Ruhr (Germany), Fax: (+49) 208-306-3951

  2. 2

    Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35032 Marburg (Germany), Fax: (+49) 6421-28-28917

Publication History

  1. Issue published online: 25 AUG 2008
  2. Article first published online: 7 JUL 2008
  3. Manuscript Received: 25 MAR 2008

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Keywords:

  • density functional calculations;
  • iron;
  • Moessbauer spectroscopy;
  • non-innocent ligands;
  • redox chemistry

Abstract

The four-coordinate iron complexes, [FeIII(pda2−)(pda.−)] (1) and [AsPh4]2[FeII(pda2−)2] (2) were synthesized and fully characterized; pda2− is the closed-shell ligand N,N′-bis(pentafluorophenyl)-o-phenylenediamido(2−), and pda.− represents its one-electron-oxidized π-radical anion. Single-crystal X-ray diffraction studies of 1 and 2 performed at 100(2) K reveal a distorted tetrahedral coordination environment at the iron centers, as a result of the intramolecular π–π interactions between C6F5 rings. The electronic structures of 1 and 2 were unambiguously determined by a combination of 57Fe Mössbauer and electronic spectroscopy, magnetic susceptibility measurements, X-ray crystallography, and DFT calculations. Compound 1 contains an intermediate-spin FeIII ion (SFe=3/2) strongly antiferromagnetically coupled to a π-ligand radical (SR=1/2) yielding an St=1 ground state. Complex 2 possesses a high-spin FeII center (SFe=2) with two closed-shell dianionic ligands. Complexes 1 and 2 are members of the redox series [Fe(pda)2]n with n=0 for 1 and n=2− for 2. The anion n=1− has been reported previously in the coordination salt [Fe(dad)3][Fe(pda)2] (3; dad=N,N′-bis(phenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene). A complicated temperature-dependent electronic structure has been observed for this salt. Here, DFT calculations performed on 3 confirm the previous assignments of spin- and oxidation-states. Thus, [Fe(pda)2]n (n=0, 1−, 2−) constitutes an electron-transfer series, which has also been established by cyclic voltammetry; the mono- and dications (n=1+ and 2+) are also accessible in solution, but have not been further investigated. The 57Fe Mössbauer spectra of [Fe(pda)2]n species in 1 and 3 show extremely large quadrupole splitting constants due to addition of the valence and covalence contributions that have been confirmed by DFT calculations.

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