Kinetic studies of tris(2,2′-bipyridine)iron(III) perchlorate with cobaloxime, [Co(dmgBF2)2(H2O)2]

The kinetics of the reduction of View the MathML sourceFe(bipy)33+ by Co(dmgBF2)2(H2O)2 in 0.041 M HNO3/NaNO3 was found to be first-order in both the oxidizing and reducing agents and the second-order rate constant is given by k obs = k 1 + k 2K [Cl−], with k 1=1.59 × 106 M−1 s−1and k 2K = 1.83 × 108 M−2 s−1, at 25 °C. The term that is first-order in [Cl−] is attributed to the formation of an ion-pair between View the MathML sourceFe(bipy)33+ and Cl−. For k 1, the activation parameters ΔH * and ΔS * are 2.22 ± 0.02 kcal mol−1 and −22.7 ± 0.8 cal mol−1 K−1, respectively. The self-exchange rate constant of k 22 ≈ 8.7 × 10−3 M−1 s−1 for View the MathML sourceCo(dmgBF2)2(H2O)2+/0 was estimated using Marcus theory and the known self-exchange rate constant for View the MathML sourceFe(bipy)33+/2+