The homopolynuclear coordination compound [CoL · 2.5H2O]n with L=C2O42− was synthesized by a new unconventional method. It consist in the redox reaction between 1,2-ethanediol and cobalt nitrate
in presence of nitric acid. The coordination compound was characterized by chemical analysis, electronic and vibrational spectra
respectively, thermal analysis. In the coordination compound the Co(II) ion exists in a high spin octahedral configuration
and oxalate anion acts as double-bridge ligand, tetradentate, similar as in CoC2O4 · 2H2O obtained by the classical method. Nonstoichiometric oxide, Co3O4+0.25 with deficit in cobalt and normal spinel Co3O4 where identified as thermal decomposition intermediates. As final product of decomposition, the oxide CoO was obtained.