Tensimetric Study of the Tris(2,2,6,6-tetramethylheptan-3,5-dionato)yttrium(III) Dissociation in a Gas Phase

The saturated and unsaturated vapor pressures of tris(2,2,6,6-tetramethylheptane-3,5-dionato)yttrium(III), Y(thd) 3 , were measured by the static method with a membrane null-manometer in wide ranges of temperature (179.5–418°C) and pressure (300–5220 Pa). The average molecular weight of the compound in unsaturated vapor calculated from the obtained data unambiguously indicates that the gas phase above the liquid compound consists of the Y 2 (thd) 6 dimer molecules. It follows from the temperature dependence of the molecular weight that in the unsaturated vapor the dimer dissociates into the monomers Y(thd) 3 , and at a higher temperature, the monomer dissociates to form Y(thd) 2 . Thermodynamic characteristics of the dissociation processes were calculated, and the thermodynamic parameters of the Y(thd) 3 evaporation were refined to give the results, which agree well with the mass spectrometry and electron diffraction data for the Y(thd) 3 vapor.