1971 Volume 44 Issue 3 Pages 705-708
The complex, cis,trans-[CoCl2(NH3)2en]ClO4, regardless whether its state is monohydrate or anhydride, was isomerized to trans,cis-form by heating in a solid phase. In the kinetic study on perchlorate in a closed system, it was found that the isomerization of the hydrated compound proceeded through a second order reaction with respect to the remaining fraction of the starting compound with the activation energy, E≠=29.5 kcal mol−1, while that of the anhydrous one proceeded through a first order reaction with E≠=51.4 kcal mol−1. On the other hand, derivatographic analyses showed that the enthalpy change in the dehydration partly including isomerization was ΔH=13.9 kcal mol−1 for the monohydrated perchlorate and the activation energy was E≠=39.9 kcal mol−1, whereas the enthalpy change of isomerization of the anhydrous perchlorate was ΔH=−2.1 kcal mol−1. From the results, it is believed that the “Aquation-anation” mechanism on the crystal surface is predominant in the isomerization for the hydrate, but it proceeds through some intramolecular reactions for the anhydride.
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