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Issue 2, 2017
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Reactivity of the copper(III)-hydroxide unit with phenols

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Abstract

Kinetic studies of the reactions of two previously characterized copper(III)-hydroxide complexes (LCuOH and NO2LCuOH, where L = N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridine-dicarboxamide and NO2L = N,N′-bis(2,6-diisopropyl-4-nitrophenyl)pyridine-2,6-dicarboxamide) with a series of para substituted phenols (XArOH where X = NMe2, OMe, Me, H, Cl, NO2, or CF3) were performed using low temperature stopped-flow UV-vis spectroscopy. Second-order rate constants (k) were determined from pseudo first-order and stoichiometric experiments, and follow the trends CF3 < NO2 < Cl < H < Me < OMe < NMe2 and LCuOH < NO2LCuOH. The data support a concerted proton–electron transfer (CPET) mechanism for all but the most acidic phenols (X = NO2 and CF3), for which a more complicated mechanism is proposed. For the case of the reactions between NO2ArOH and LCuOH in particular, competition between a CPET pathway and one involving initial proton transfer followed by electron transfer (PT/ET) is supported by multiwavelength global analysis of the kinetic data, formation of the phenoxide NO2ArO as a reaction product, observation of an intermediate [LCu(OH2)]+ species derived from proton transfer from NO2ArOH to LCuOH, and thermodynamic arguments indicating that initial PT should be competitive with CPET.

Graphical abstract: Reactivity of the copper(iii)-hydroxide unit with phenols

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Publication details

The article was received on 11 Jul 2016, accepted on 08 Sep 2016 and first published on 27 Sep 2016


Article type: Edge Article
DOI: 10.1039/C6SC03039D
Citation: Chem. Sci., 2017,8, 1075-1085
  • Open access: Creative Commons BY-NC license
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    Reactivity of the copper(III)-hydroxide unit with phenols

    D. Dhar, G. M. Yee, T. F. Markle, J. M. Mayer and W. B. Tolman, Chem. Sci., 2017, 8, 1075
    DOI: 10.1039/C6SC03039D

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