Reactivity of [CoIIIW12O40]5– with organic radicals in aqueous solution. Evidence for an electron transfer mechanism

Abstract

The rate constants for reaction of the [12-tungstocobaltate(III)]^5– ion [Co^IIIW₁₂O₄₀]^5– in aqueous solution with a large number of carbon-centered cyclic and acyclic radicals, among them radicals of the alkyl, α-hydroxyalkyl, α-alkoxyalkyl, α-amidoalkyl and benzyl type, have been measured by pulse radiolysis. Except for methyl and ethyl radical and α-carboxyalkyl radical anions, the radicals react with rates of the order (1–5)× 10⁹ dm³ mol^–1 s^–1, which corresponds to or is close to diffusion control. From a comparison with oxidants that are able to react by ligand transfer, the oxidant [Co^IIIW₁₂O₄₀]^5– is concluded to react by electron transfer.