Kinetics of the Reductions of (Ethylenediaminetetraacetato)cobaltate(III) by 4,4-Dipyridylamine Complexes of Pentacyanoferrate(II) and Pentaammineruthenium(II) |
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Authors: | Chiu-Feng Chien Andrew Yeh |
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Abstract: | The reactions of Fe(CN)5dpa3? and Ru(NH3)5dpa2+ (dpa = 4,4′-dipyridylamine) with Co(edta)? have been investigated kinetically. For Fe(CN)5dpa3? complex, a linear relationship was observed between the pseudo-First-order rate constants and the concentrations of Co(edta) which leads to a specific rate 0.876 ± 0.006 M?1S?1 at T = 25°C., μ = 0.10 M and pH = 8.0. For the Ru(NH3)5dpa2+ system, the plots kobs vs Co(edta)?] become nonlinear at concentrations of Co(edta) greater than 0.01 M and the reaction is interpreted on the basis of a mechanism involving the formation of an ion pair between Ru(NH3)5dpa2+ and Co(edta)? followed by electron transfer from Ru(II) to Co(III). The nonlinear least squares fit of the kinetic results shows that Qip = 10.6 ± 0.7 M?1 and ket = 93.9 ± 0.7 s?1 at pH = 8.0,μ = 0.10 M and T = 25°C. |
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Keywords: | Outer-sphere electron transfer Marcus theory Ion-pair formation |
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