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The reaction between thallium(I) and [CoIIIW12O40]5- in the presence of ruthenium(III) as catalyst proceeds viainitial outer-sphere oxidation of the catalyst to ruthenium(VI). The ruthenium(IV) thus generated will oxidize thallium(I)
to an unstable thallium(II) which by reacting with oxidant gives the final product, thallium(III). The formation of ruthenium(II)
by direct two-electron reduction of the catalyst by thallium(I) is thermodynamically less favorable. The reaction rate is
unaffected by the [ H+ ], whereas it is catalyzed by chloride ion . The formation of reactive chlorocomplex,TlCl, in a prior equilibrium is the
reason for the chloride ion catalysis. Increasing the relative permittivity of the medium increases the rate of the reaction,
which is attributed to the formation of an outer-sphere complex between the catalyst and oxidant.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
The reaction between CrVI and 12-tungstocobaltate(II) was carried out in 2.0 mol dm–3 HCl and followed a simple second order rate law. The reaction was catalysed by hydrogen ion due to the formation of active H2CrO4 and was inhibited by chloride ion as, in its presence, conversion of the active species into inactive chlorochromate occurs. Chromium(V) and chromium(IV) were generated in situ by the use of CrVI—VIV or CrVI—2-ethyl-2-hydroxybutyric acid and CrVI—i-PrOH reactions respectively, and the oxidation of 12-tungstocobaltate(II) by these atypical oxidation states, was also studied. The rate constants for the oxidation of 12-tungstocobaltate(II) by CrVI, CrV and CrIV were found to be in the ratio 1:1.2:5.2 respectively. The ionic strength did not affect the reaction, while decrease in the solvent polarity increased the rate of the reaction. The activation parameters were also determined and the values H
, G
and S
were found to be 52.4 ± 6 kJ mol–1, 100.8 ± 7 kJ mol–1, –151.7 ± 10 J K–1 mol–1 respectively, supporting the mechanism proposed. 相似文献
3.
The reaction between TlI and [CoIIIW12O40]5– proceeds in two one-electron steps, involving formation of unstable TlII in a slow first step followed by reaction with oxidant in a fast step. The reaction rate is unaffected by the [H+] as protonation equilibria are not involved with either reactant, whereas the accelerating effect of chloride ion is due to the formation of an active chloro-complex of the reductant, TlCl3
2–. Increasing the ionic strength and decreasing the relative permittivity of the medium increases the rate of the reaction which is attributed to the formation of an outer sphere complex between the reactants. The activation parameters were also determined and the values support the proposed mechanism. 相似文献
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