Derivatographic Studies on Transition Metal Complexes. VII.Thermal cis, trans-to-trans, cis Isomerization of [CoCl2(NH3)2en]Br·H2O in Solid Phase

Abstract

Abstract The cis, trans-to-trans, cis isomerization as well as dehydration of [CoCl2(NH3)2en]Br·H2O were investigated by using derivatographic, isothermal, and sealed tube methods. Isomerization in a solid phase proceeded regardless of whether its state was monohydrate or anhydride. Two distinct processes were found for isomerization, one being accompanied by the liberation of water of crystallization and the other taking place after complete liberation of water of crystallization. Both reactions were of the first order. The thermochemical functions were obtained to be ΔH=(12±2) kcal/mol, E\eweq=(28±3) kcal/mol and ΔS\eweq=(−10±4) e.u. for dehydration. The values E\eweq=(28±3) kcal/mol and S\eweq(−4±2) e.u. were estimated for isomerization in the first process, and E\eweq=(28±3) kcal/mol and ΔS\eweq=(−12±3) e.u. for that in the second process. As a possible reaction mechanism for isomerization, an “aquation-anation mechanism” was introduced for the first process and an “intramolecular mechanism” for the second.