Thermal decomposition of trans-difluoro bis-(ethylenediamine) chromium (III) chloride 1.5 hydrate and μ-[(ethylenediamine) chromium (III) dichloro-(ethylenediamine)] chloride

Abstract

Two complexes trans-difluoro bis-(ethylenediamine) chromium (III) chloride 1.5 hydrate and μ-[(ethylenediamine) chromium (III) dichloro (ethylenediamine)] chloride were isolated and were characterized by elemental analysis and IR spectroscopy. The thermal behaviour of the two complexes on heating up to 800°C in nitrogen atmosphere was examined by thermogravimetry (TG), DTG and differential thermal analysis (DTA). Thermal analysis showed three stages of decomposition of trans-[Cr(en)2F2]Cl·1.5H2O in the following order: (i) dehydration, (ii) deamination or loss of amine and (iii) total disruption of the complex to form Cr2O3. As for [(Cr2(en)3Cl4)]Cl2, its decomposition involved: (i) loss of the bridged ethylenediamine, (ii) loss of the two other ethylene diamines and (iii) disruption of the complex to form the oxide. Activation parameters were evaluated using the theory of absolute reaction rate and values of activation energy were found to be 38.3 and 103kJmol-1for the dehydration and deamination of trans-[Cr(en)2F2]Cl·1.5H2O respectively, and 88.7 and 203kJmol-1for the loss of bridged ethylene diamine and the other two ethylenediamines of [Cr2(en)3Cl4]Cl2molecules, respectively. © 1999 Elsevier Science B.V.