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Redox Properties and Basicity of Keggin-Type Polyoxometalate Complexes

2005; Oxford University Press; Volume: 78; Issue: 1 Linguagem: Inglês

10.1246/bcsj.78.95

1348-0634

Sadayuki Himeno, Masayo Takamoto, R. Santo, Akio Ichimura,

Vanadium and Halogenation Chemistry

Abstract For Keggin-type polyoxometalate complexes (α-[XMo12O40]n− (X = S, P, As, Si, Ge; n = 2–4) and α-[XW12O40]n− (X = S, P, As, Si, Ge, B, Al; n = 2–5)), the conversion processes of the first two one-electron waves into a two-electron wave were investigated in dipolar aprotic solvents containing H+, Li+, or Na+ as a Lewis acid. A simulation of the cyclic voltammogram indicated that the potential difference (ΔEmid) between the first one- and two-electron redox waves served as a useful criterion for the basicity of the Keggin anions. According to the ΔEmid values, the Keggin anions were classified into the following four groups: (1) [SW12O40]2−; (2) [SMo12O40]2−, [XW12O40]3− (X = P, As); (3) [XMo12O40]3− (X = P, As), [XW12O40]4− (X = Si, Ge); (4) [XMo12O40]4− (X = Si, Ge), [XW12O40]5− (X = B, Al). The voltammetric properties of the Keggin anions were systematized with reference to their basicities.