Get access

Mechanistic Insight into the Reactivity of Oxotransferases by Novel Asymmetric Dioxomolybdenum(VI) Model Complexes

Authors

  • Dr. Ramasamy Mayilmurugan,

    1. Institut für Chemie, Bereich Anorganische Chemie, Karl-Franzens-Universität Graz, Schubertstrasse 1, 8010, Graz (Austria), Fax: (+43) 316-380-9835
    Search for more papers by this author
  • Bastian N. Harum,

    1. Institut für Chemie, Bereich Anorganische Chemie, Karl-Franzens-Universität Graz, Schubertstrasse 1, 8010, Graz (Austria), Fax: (+43) 316-380-9835
    Search for more papers by this author
  • Dr. Manuel Volpe,

    1. Institut für Chemie, Bereich Anorganische Chemie, Karl-Franzens-Universität Graz, Schubertstrasse 1, 8010, Graz (Austria), Fax: (+43) 316-380-9835
    Search for more papers by this author
  • Prof. Dr. Alexander F. Sax,

    1. Institut für Chemie, Bereich Physikalische und Theoretische Chemie, Karl-Franzens-Universität Graz, Heinrichstrasse 28/VI, 8010, Graz (Austria)
    Search for more papers by this author
  • Prof. Dr. Mallayan Palaniandavar,

    1. School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024 (India)
    Search for more papers by this author
  • Prof. Dr. Nadia C. Mösch-Zanetti

    Corresponding author
    1. Institut für Chemie, Bereich Anorganische Chemie, Karl-Franzens-Universität Graz, Schubertstrasse 1, 8010, Graz (Austria), Fax: (+43) 316-380-9835
    • Institut für Chemie, Bereich Anorganische Chemie, Karl-Franzens-Universität Graz, Schubertstrasse 1, 8010, Graz (Austria), Fax: (+43) 316-380-9835
    Search for more papers by this author

Abstract

The asymmetric molybdenum(VI) dioxo complexes of the bis(phenolate) ligands 1,4-bis(2-hydroxybenzyl)-1,4-diazepane, 1,4-bis(2-hydroxy-4-methylbenzyl)-1,4-diazepane, 1,4-bis(2-hydroxy-3,5-dimethylbenzyl)-1,4-diazepane, 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)-1,4-diazepane, 1,4-bis(2-hydroxy-4-flurobenzyl)-1,4-diazepane, and 1,4-bis(2-hydroxy-4-chlorobenzyl)-1,4-diazepane (H2(L1)–H2(L6), respectively) have been isolated and studied as functional models for molybdenum oxotransferase enzymes. These complexes have been characterized as asymmetric complexes of type [MoO2(L)] 1–6 by using NMR spectroscopy, mass spectrometry, elemental analysis, and electrochemical methods. The molecular structures of [MoO2(L)] 1–4 have been successfully determined by single-crystal X-ray diffraction analyses, which show them to exhibit a distorted octahedral coordination geometry around molybdenum(VI) in an asymmetrical cis-β configuration. The Mo[BOND]Ooxo bond lengths differ only by ≈0.01 Å. Complexes 1, 2, 5, and 6 exhibit two successive MoVI/MoV (E1/2, −1.141 to −1.848 V) and MoV/MoIV (E1/2, −1.531 to −2.114 V) redox processes. However, only the MoVI/MoV redox couple was observed for 3 and 4, suggesting that the subsequent reduction of the molybdenum(V) species is difficult. Complexes 1, 2, 5, and 6 elicit efficient catalytic oxygen-atom transfer (OAT) from dimethylsulfoxide (DMSO) to PMe3 at 65 °C at a significantly faster rate than the symmetric molybdenum(VI) complexes of the analogous linear bis(phenolate) ligands known so far to exhibit OAT reactions at a higher temperature (130 °C). However, complexes 3 and 4 fail to perform the OAT reaction from DMSO to PMe3 at 65 °C. DFT/B3LYP calculations on the OAT mechanism reveal a strong trans effect.

Ancillary