Scandium(III) Benzoyltrifluoroacetonate: Structure and Thermal Properties

Scandium(III) benzoyltrifluoroacetonate [Sc(btfac)(3)] was synthesized, purified, and characterized by elemental analysis and H-1 NMR spectroscopy. Its structure was determined by single-crystal X-ray diffraction at 150 K. The complex has a molecular structure and is an axial isomer. All ligands in it are bidentate-cyclic coordinated; scandium is in a distorted octahedral environment, d(Sc-O) = 2.0681(2)-2.094(2) & Aring;. There are two types of stacking interactions. The thermal properties in the condensed phase were studied by thermal analysis and differential scanning calorimetry (DSC). The temperature, enthalpy, and entropy of melting of the complex were determined as 399.1 +/- 0.5 K, Delta(m) H-Tm(degrees)= 36.8 +/- 1.3 kJ/mol, and Delta(m) S-Tm(degrees) = 92.2 +/- 3.3 J/(K mol), respectively. The temperature-dependent saturated vapor pressure of [Sc(btfac)(3)] was determined in the temperature range 413-443 K by the flow (transpiration) method. The thermodynamic characteristics of vaporization at an average temperature were calculated: Delta(vap) H-430(degrees) = 135 +/- 4 kJ/mol, and Delta(vap) S-430(degrees) = 212 +/- 9 J/(K mol). The structure and thermal properties of scandium benzoyltrifluoroacetonate were compared to those of similar scandium tris-beta-diketonate complexes.