Thermogravimetric analysis (TGA) which provides valuable information about thermal stability of compounds and influence of temperature on their structure has been widely used for the characterization of different materials, including coordination cluster compounds. Thermal properties of four new heterometallic tetranuclear coordination clusters with general formula [Fe2Ln2(piv)6(L)2(MeOH)4]∙solvent (Ln3+ = Dy (1), Tb (2), Nd (3), Pr (4); Hpiv = pivalic acid; L = 1,1,1-tris(hydroxymethyl)propane (1, 2) and 1,1,1-tris(hydroxymethyl)ethane (3, 4); solvent = H2O (1), MeOH (2)) have been investigated by TG/DTG/DTA measurements. The heterometallic {Fe2Ln2} clusters based on pivalic acid and polyalcohol ligands have been prepared by ultrasonic (1, 2) and solvothermal (3, 4) methods. All compounds have also been characterized by single-crystal X-ray diffraction analysis and infrared spectroscopy. Thermogravimetrical analyses showed that the thermal decomposition of clusters 1-4 proceeds through several weakly resolved steps (Fig. 1). As 1 and 2 have solvent molecules, the first weight loss is related to removal of these solvents, followed by removal of four coordinated methanol molecules. Due to the absence of solvent molecules in outer sphere, thermal decomposition of 3 and 4 begins with elimination of coordinated methanol molecules from inner sphere. Further heating to 500 oC results in the decomposition of the remaining six pivalate groups and two molecules of polyalcohol ligands. Above 520oC the decomposition of these compounds is completed, giving expected oxides.figureFigure 1. TG/DTA curves (left) and structure of 3 (right).