Reaction of Copper(II) with Ferrocene and 1,1‘-Dimethylferrocene in Aqueous Acetonitrile: The Copper(II/I) Self-Exchange Rate

The kinetics of the reactions of copper(II) with ferrocene (Fc) and 1,1‘-dimethylferrocene (Dmfc) have been studied
at 25 °C in aqueous acetonitrile (AN) containing 50−97.5 vol % AN. With increasing % AN, the rate constant increases along with the driving-force for the reaction. The results are analyzed in terms of Marcus theory to estimate
the Cu(II/I) electron self-exchange rate constant (k11) for the system. Over the solvent range studied, the calculated
k11 changes from 1.1 × 10-9 to 17 × 10-9 M-1 s-1, with an average value of 5 × 10-9. In addition, the structures
of the trifluoromethanesulfonate salts of [Cu(AN)4]+, [Cu(OH2)2(AN)2]2+, and [Cu(AN)4]2+ are reported. It is found
that the Cu−NCCH3 bond-length difference between the Cu(I) and Cu(II) oxidation states is only ∼0.02 Å.