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The kinetics of the reduction of Fe ( bipy ) 3 3 + 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 kobs = k1 + k2K[Cl−], with k1=1.59 × 106 M−1 s−1and k2K = 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 Fe ( bipy ) 3 3 + and Cl−. For k1, 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 k22 ≈ 8.7 × 10−3 M−1 s−1 for Co ( dmgBF 2 ) 2 ( H 2 O ) 2 + / 0 was estimated using Marcus theory and the known self-exchange rate constant for Fe ( bipy ) 3 3 + / 2 + . |
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