Kinetic analysis of TG data XXXV. Spectroscopic and thermal studies of some cobalt(III) chelates with ethylenediamine

摘要

A number of 30 [Co(en)_3]Y_3, [Co(en)_2X_2]Y and [Co(en)_2X(amine)]Y_2 type complexes (X = Cl, Br; Y = Cl, Br, I, NCO, NCS, NO_3, ClO_4 etc.; amine = aromatic and alkylamines) were obtained from trans-[Co(en)_2Cl_2]Cl by double decomposition and by substitution reactions, respectively. The structure of the complexes was proved by means of far and middle FTIR spectra. The thermal decomposition was studied by TG, DTA and DSC measurements. Mass spectra were also recorded. In the case of[Co(en)_3]Y_3 complexes the nitrate, perchlorate and dimesoperiodates decompose suddenly, frequently explosion like. The halides and thiocyanates seem to substitute an ethylenediamine ligand, yielding a rather unstable intermediate. The pyrolysis of [Co(en)_2X_2]Y type derivatives yields no relatively stable intermediates, but the decomposition temperatures may be correlated with the nature of Y and with the cis or trans configuration of the compound. With the [Co(en)_2X(amine)]Y_2 type complexes one observes the formation of [Co(en)_2XY]Y as intermediate product. From the TG curves kinetic parameters were derived for some dehydration and deamination processes, by using the nomogram method. The validity of a nonlinear kinetic compensation law was observed.