Thermal decomposition of iron cyano complexes in an inert atmosphere

The thermal decomposition of K3[Fe(CN)6] (1), [Co(NH3)6][Fe(CN)6] (2), [Co(NH3)6]4[Fe(CN)6]3•13H2O (3), Ni3[Fe(CN)6]2•20H2O (4), and [Ni(NH3)6]3[Fe(CN)6]2 (5) was studied in an inert atmosphere (argon and nitrogen) in the temperature range from 20 to 1000 °С. The TG—DSC—DTG curves were obtained. The analyses of solid thermolysis products of compounds 1—5 and gaseous thermolysis products of compounds 1 and 5 were carried out using IR spectroscopy. Depending on temperature, the solid thermolysis products of K3[Fe(CN)6] (1) are K4[Fe(CN)6], Fe4[Fe(CN)6], KCN, Fe3C, and C, and the gaseous thermolysis products are (CN)2 and N2. A deficient of potassium is observed in the residues obtained at ≥800 °С. The thermal decomposition of compounds 2—5 is accompanied by the evolution of Н2О (3, 4), NH3, N2, and HCN. Free metals Co and Fe and intermetallic compounds CoFe, FeNi, and Ni3Fe in a mixture with carbon (25—60% of the initial C content in the complex) are formed in the solid state. Gaseous (CN)2 is formed only in the case of compound 1. The thermolysis of the hydrogen-containing complexes gives HCN.