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Reversible modulation of the redox characteristics of acid-sensitive molybdenum and tungsten scorpionate complexes

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Abstract

The large-scale synthesis of the scorpionate ligand Ttz (hydrotris(1,2,4-triazol-1-yl)borate) is reported as well as syntheses of Group VI complexes K[M(L)(CO)3] and M(L)(NO)(CO)2 (L = Ttz or Tp (hydrotris(pyrazol-1-yl)borate), M = Mo or W). The redox characteristics of the metal in these Ttz complexes are shown to be reversibly modulated by interactions between the exo-4-N lone pairs of the triazolyl rings and Brønsted or Lewis acids. The basicity of the scorpionate ligand in [M(Ttz)(CO)3] is quantified (pKaH2O values range from 1.1 to 4.6) and found to be dependent on both the oxidation state and identity of the metal. In the presence of Brønsted acids, the observed redox behavior for the one-electron oxidation of the Group VI metal center is consistent with a proton-coupled electron transfer (PCET). Indeed, for both Mo and W derivatives, a one-electron oxidation decreases the pKa by ∼3.5 units.

Graphical abstract: Reversible modulation of the redox characteristics of acid-sensitive molybdenum and tungsten scorpionate complexes

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Publication details

The article was received on 13 Feb 2018, accepted on 21 Mar 2018 and first published on 27 Mar 2018


Article type: Paper
DOI: 10.1039/C8DT00598B
Citation: Dalton Trans., 2018, Advance Article
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    Reversible modulation of the redox characteristics of acid-sensitive molybdenum and tungsten scorpionate complexes

    A. J. Heyer, P. J. Shivokevich, S. L. Hooe, K. D. Welch, W. D. Harman and C. W. Machan, Dalton Trans., 2018, Advance Article , DOI: 10.1039/C8DT00598B

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