Synthesis and Thermal Stability of Manganese(III) Acetylacetonate

Abstract

The dependence of the stability of Mn(C5H7O2)3 modifications on the properties of the solvent chosen for recrystallization is considered. Low-polarity solvents with a low dielectric permittivity enhance intermolecular interactions, which leads to the formation of the β-Mn(C5H7O2)3 modification during the synthesis of Mn(C5H7O2)3 from chloroform solutions. The use of mixtures of chloroform with petroleum ether makes it possible to control supersaturation, the rate of formation, and growth of phase nuclei due to the evaporation of chloroform under isothermal conditions. The use of polar solvents for recrystallization favors the formation of γ-Mn(C5H7O2)3. The composition of the thermal decomposition products of β‑Mn(C5H7O2)3 in a dry inert atmosphere has been determined by X-ray powder diffraction, IR spectroscopy, thermogravimetric and mass spectral analysis, and differential scanning calorimetry. In the temperature range 140–240°C, β-Mn(C5H7O2)3 melts to form Mn(C5H7O2)2. At temperatures of 500–550°С, Mn(C5H7O2)2 decomposes to a mixture of MnO, Mn3O4, Mn2O3, and carbon.