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 degrees 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 x 10(-9) to 17 x 10(-9) M(-1) s(-1), with an average value of 5 x 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 approximately 0.02 A.