TEMPERATURE-DEPENDENCE OF CHIRAL RECOGNITION IN THE OXIDATION OF TRIS(ETHYLENEDIAMINE)COBALT(II) COMPLEX BY OPTICALLY-ACTIVE ANIONIC COBALT(III) COMPLEXES

The temperature dependence of the stereoselectivity in the oxidation o f tris(ethylenediamine)cobalt(II) complex by some chiral anionic cobal t(III) complexes has been studied over the temperature range of 5-45 d egrees C in aqueous solution. The activation enthalpy difference, Delt a Delta H-double dagger, and the entropy difference, Delta Delta S-dou ble dagger, between Delta-Lambda and Delta-Delta pairs show two kinds of Delta Delta H-double dagger/Delta Delta S-double dagger compensatio n behavior, indicating that the electron-transfer proceeds by two diff erent types of reaction mechanisms. The relative importance of Delta D elta H-double dagger and Delta Delta S-double dagger is interpreted in terms of the difference in the stereoselective interactions upon form ation of the precursor complex.