Kinetics and mechanism of the reaction between 4-t-butylphenolate anion and tetrahydroxoargentate(III) in aqueous alkaline media

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The reaction of [Ag(OH)4]- with 4-t-butylphenolate (L-) follows a biphasic absorbance change, each phase exhibiting pseudo-first-order kinetics under limiting conditions of the silver(III). A subsequent, slow, and very small absorbance increase (t0.5 > 1 h) is accompanied by the precipitation of metallic silver. In the [L-] range 0.5 × 10-3 - 10 × 10-3 and [OH-] range 0.12-1.2 mol dm-3 at 25°C and in aqueous medium, the pseudo-first-order rate constant for the initial, faster phase, Kf (in s-1), corresponds to the first one-electron transfer from L- to the initial silver(III) species and obeys the relation (i). The pseudo-first-order rate constant for the second, kf = (0.330 ± 0.09) + (1.26 ± 0.09) × 103[L-] + (2.64 ± 0.28) × 102[L-]/[OH-] (i), slower phase, Ks (in s-1), represents the second one-electron transfer from L- to an intermediate silver(II) species produced as a result of the first one-electron transfer and satisfies an [OH-]-independent expression (ii). The kf and ks values are not influenced by the ionic strength (0.3-1.2, ks = (1.46 ± 0.02) × 102[L-]/{1 + (56.0 ± 3.5)[L-]} (ii) mol dm-3) of the medium nor by the presence of added pyrophosphate or silver(I) ions. Kinetic and spectral results are interpreted as suggesting that each of the processes mentioned most probably proceeds by a substitution-controlled mechanism at the silver centre.

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Journal of the Chemical Society, Dalton Transactions