Abstract
The kinetics of oxidation of cis-[Cr-III(phen)(2)(H2O)(2)](3+) (phen = 1,10-phenanthroline) by IO4- has been studied in aqueous acidic solutions. In the presence of a vast excess of [IO4-], the reaction is first order in the chromium(III) complex concentration. The pseudo-first-order rate constant, k(obs), showed a very small change with increasing [IO4-]. The dependence of k(obs) on [IO4-] is consistent with Eq. (i).
k(obs) = a[IO4-]/(b + c [IO4-]) (i)
The pseudo-first-order rate constant, k(obs), increased with increasing pH, indicating that the hydroxo form of the chromium(III) complex is the reactive species. An inner-sphere mechanism has been proposed for the oxidation process. The thermodynamic activation parameters of the processes involved are also reported. (C) 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 563-568, 2011