The Cr(II) reduction of Co(ptdn)3 (ptdn pentane- 2,4-dionato) was studied in various acetone/water mixtures. The activation parameters were measured over a temperature range of 25-45 °C and were found to vary in a complex, non-linear fashion. Three pathways for reduction were observed: outer sphere, mono-bridged inner-sphere and di-bridged innersphere. Only the di-bridged pathway showed an acid dependence. The results are discussed in terms of the nature of the solvent mixture and its effect on the reactants and the transition state. The δH‡ and δS‡ tend to change in such a manner that deviations in δG‡ are minimized, although the existence of any isokinetic relationships could not be established. This behavior is compared with that of other redox systems reported to be studied in mixed solvents. Possible reasons for the observation of the di-bridged pathway, which is not observed in water, are presented.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry