Kinetic investigation of the electrochemical oxidation of Bis(benzene)chromium(0) in Diethyl ketone/N,N-Dimethylformamide

摘要

The cyclic voltametric technique utilizing a platinum working electrode was applied for the investigation of the electrochemical oxidation of bis(benzene)chromium(0), (C_6H_6)_2Cr to bis(benzene)chromium(I), (C_6H_6)_2Cr~+ in diethyl ketone (DEK), N,N-dimethylformamide (DMF), and DEK/DMF binary mixtures containing n-tetrabutylammonium hexafluorophosphate (TBAPF_6) as the supporting electrolyte at T=298.15 K. The half-wave potentials (E _(1/2)) of the (C_6H_6)_2Cr~(+/0) redox couple in DEK, DMF and DEK/DMF binary mixtures, were determined. The variation of E _(1/2) with the solvent composition was found to be almost linear. The E _(1/2) results were analyzed in terms of the electron-donating power of the solvent medium. The diffusion coefficients, D, were calculated using the Randles-Sevcik equation. The kinetics of the electrode reaction were investigated through the determination of the heterogeneous electron-transfer rate constants, k _s, according to the electrochemical rate equation proposed by Nicholson. Furthermore, the activation Gibbs energies for the electron-transfer process (ΔG ~≠) were also calculated. The results indicate that the redox couple (C _6H_6)_2Cr~(+/0) exhibits an electrochemically reversible and diffusion-controlled process in all the investigated solvent media.