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    Isolation and Assessment of the Molecular and Electronic Structures of Azo-Anion-Radical Complexes of Chromium and Molybdenum. Experimental and Theoretical Characterization of Complete Electron-Transfer Series


    Joy, Sucheta and Krämer, Tobias and Paul, Nanda D. and Banerjee, Priyabrata and McGrady, John E. and Goswami, Sreebrata (2011) Isolation and Assessment of the Molecular and Electronic Structures of Azo-Anion-Radical Complexes of Chromium and Molybdenum. Experimental and Theoretical Characterization of Complete Electron-Transfer Series. Inorganic Chemistry, 50 (20). pp. 9993-10004. ISSN 0020-1669

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    Abstract

    The reaction of 3 equiv of the ligand 2-[(2-chlorophenyl)azo]pyridine (La) or 2-[(4-chlorophenyl)azo]pyridine (Lb) with 1 equiv of Cr(CO)6 or Mo(CO)6 in boiling n-octane afforded [Cr(La/b)3]0 (1a and 1b) and [Mo(La/b)3]0 (2a and 2b). The chemical oxidation reaction of these neutral complexes with I2 in CH2Cl2 provided access to air-stable one-electron-oxidized species as their triiodide (I3–) salts. The electronic structures of chromium and molybdenum centers coordinated by the three redox noninnocent ligands La/b along with their redox partners have been elucidated by using a host of physical methods: X-ray crystallography, magnetic susceptibility measurements, nuclear magnetic resonance, cyclic voltammetry, absorption spectroscopy, electron paramagnetic resonance spectroscopy, and density functional theory. The four representative complexes, 1a, [1a]I3, 2a, and [2a]I3, have been characterized by X-ray crystallography. The results indicate a predominant azo-anion-radical description of the ligands in the neutral chromium(III) species, [CrIII(L•–)3], affording a singlet ground state through strong metal–ligand antiferromagnetic coupling. All of the electrochemical processes are ligand-based; i.e., the half-filled (t2g)3 set of the CrIII d3 ion remains unchanged throughout. The description of the molybdenum analogue is less clear-cut because mixing between metal- and ligand-based orbitals is more significant. On the basis of variations in net spin densities and orbital compositions, we argue that the oxidation events are again primarily ligand-based, although the electron density at the molybdenum center is clearly more variable than that at the chromium center in the corresponding series [1a]+, 1a, and [1a]−.

    Item Type: Article
    Keywords: Isolation; Assessment; Molecular; Electronic Structures; Azo-Anion-Radical Complexes; Chromium; Molybdenum; Experimental; Theoretical Characterization; Complete Electron-Transfer Series;
    Academic Unit: Faculty of Science and Engineering > Computer Science
    Faculty of Science and Engineering > Research Institutes > Hamilton Institute
    Item ID: 15521
    Identification Number: https://doi.org/10.1021/ic200708c
    Depositing User: Tobias Kraemer
    Date Deposited: 16 Feb 2022 13:09
    Journal or Publication Title: Inorganic Chemistry
    Publisher: American Chemical Society
    Refereed: Yes
    URI:
    Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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