KINETIC INVESTIGATION OF THE REDUCTION FO R CROWDED [CO(TMEN)(3)](3-)() BY [FE(CN)(6)](4)

Kinetic studies of the outer-sphere electron transfer reaction between [Co(tmen)(3)](3+) and [Fe(CN)(6)](4-) have been carried out at variou s temperatures and pH values. The ion-pair formation constant Q(ip) of the precursor complex [Co(tmen)(3)](3+)- [Fe(CN)(6)](4-) is 5.6 X 10( 2) L . mol(-1) and the rate constant k(et) for the electron transfer w ithin the ion-pair is 6.8 X 10(-3) s(-1) at 25 degrees C and I= 0.10 m ol/L. The activation enthalpy Delta H-et(not equal) and the activation entropy Delta H(et)not equal of this reaction are 1.6 X 10(2) kJ/mol and 6.5 X 10(2) J/mol . K respectively. The mechanism of the reaction is discussed.