Cobalt(III) dicarboxylato bis-ethylenediamine nitrates: Preparation and characterization by thermal analysis and other analytical methods

Abstract

Compounds with the general formula cis or trans-[Coen 2 (RCOO)2 ]NO3 were prepared by modifications of known procedures; R was H, CH~, C~H s or C3H~, and en was ethylenediamine. The compounds were characterized by TLC and UV-Vis spectrophotometry, and their thermal behaviour was examined via TG and DTA, and via IR spectra on heated samples.The thermal stabilities are discussed in terms of the strengths of the bonds in the solids [1] and steric hindrance; the thermal decompositions are described with the aid of hypothesized intermediates and IR spectra.Reaction steps axe identified and the thermal stability sequence is discussed: the cis compounds are less stable than the corresponding trans compounds, due to the lower reticulation effect; the sequence of the cis compounds is the reverse of the sequence of carboxylate ion basicity, while the sequence displalyed by the trans compounds can be interpreted in terms Of solid lattice stabilization.

Thermoanalytical behaviour of some dicarboxylato-α-diiminecobalt(III) complexes

“…The data obtained for the Co(III)-o-phen complexes can be compared with those reported in a previous paper following an analogous investigation of the cis-[Co(III)-en-OCOR] complexes [2]. This comparison allows us to formulate some considerations on the influence of the nature of the nitrogen ligand on the thermal stability of the examined complexes: i) in both cases, the first decomposition process involves the breaking of Co-N bonds and elimination of the nitrogen ligand;…”

“…These two series were chosen because they offer an opportunity for study of the effects of the pyridine rings and/or the length of the allphatic chain in the carboxylato ligands on the thermal stability of the complexes. Furthermore, a comparison of the results with those of the corresponding ethylenediamine series can give information on the effect of the ring [2]. Nitrate was chosen as th.~ counter-ion, in order to minimize anation reactions.…”