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Issue 2, 2001
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Electrosynthesis and solution structure of six-electron reduced forms of metatungstate, [H2W12O40]6−

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Abstract

Metatungstate salts α-[R4N]5H[H2W12O40] (R = Pr or Bu) were produced by phase transfer methods. Two one-electron reduction processes (E1/2 −1100, −1590 mV versus Ag–AgCl (saturated KCl in MeCN)) are seen for [Bu4N]5H[H2W12O40] in MeCN (Bu4NClO4, 0.1 M) solution. They convert into a single two-electron process in MeCN–water (95∶5 v/v) upon the addition of acid. Controlled potential electrolysis in aqueous HCl at the two electron potentials resulted in isolation of the six-electron reduced salt [NH4]4H8[H2W12O40] in which one of the oxidised WVI3 trinuclear caps of metatungstate is reduced to a WIV3 trinuclear cap. [Bu4N]3H9[H2W12O40] and related salts were generated by phase transfer. The anion [H2{WIV3(OH2)3}WVI9O34(OH)3]3− is obtained by dissolving [Bu4N]3H9[H2W12O40] in dry CD3CN. The distribution of the eleven protons present in this anion is mapped by 1H and 183W NMR, allowing assessment of the structural changes which accompany reduction. Cs point symmetry is observed and imposed by the association of the three surface hydroxyl protons with the reduced WIV3 trinuclear cap and one of the oxidised WVI3 trinuclear caps. Three WOW links appear to be converted into longer W(OH)W links to accommodate the significant shortening (≈0.7 Å) in W  W separation anticipated to occur upon reduction.

Graphical abstract: Electrosynthesis and solution structure of six-electron reduced forms of metatungstate, [H2W12O40]6− [ ]

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Publication details

The article was received on 02 Aug 2000, accepted on 08 Nov 2000 and first published on 13 Dec 2000


Article type: Paper
DOI: 10.1039/B006264M
Citation: J. Chem. Soc., Dalton Trans., 2001,0, 187-196
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    Electrosynthesis and solution structure of six-electron reduced forms of metatungstate, [H2W12O40]6−

    C. Boskovic, M. Sadek, R. T. C. Brownlee, A. M. Bond and A. G. Wedd, J. Chem. Soc., Dalton Trans., 2001, 0, 187
    DOI: 10.1039/B006264M

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