Scandium(III) 1,1,1-Trifluorohexane-2,4-dionate Complex: Synthesis, Structure, and Thermal properties

A new scandium(III) 1,1,1-trifluorohexane-2,4-dionate complex [Sc(5Htfac)] was synthesized, purified, and characterized by elemental analysis, NMR spectroscopy, and mass spectrometry. Its structure was determined at 150 K by X-ray diffraction analysis (CCDC No. 2433044). The complex has a molecular structure in which the bidentate cyclic ligands are arranged according to the α-sisomer. Shortened H...F interactions were identified in the structure. The thermal properties were studied by TGA and DSC, and the fusion temperature (309.3 ± 0.5 K), enthalpy (ΔH°(T) = 36.0 ± 1.4 kJ mol), and entropy (ΔS°(T) = 116.5 ± 4.5 J mol K) of fusion were determined. The temperature dependence of the saturated vapor pressure was measured by the flow method (343–433 K) and the static method with a membrane null manometer (410–470 K). On this basis, the thermodynamic characteristics of evaporation at average and standard temperatures were calculated (ΔH°(298.15 K) = 100.2 ± 1.3 kJ mol, ΔS°(298.15 K) = 201.8 ± 2.8 J mol K). From these data, the sublimation parameters of the complex were obtained (ΔH°(298.15 K) = 135.3 ± 1.9 kJ mol, ΔS°(298.15 K) = 315.3 ± 5.4 J mol K). The structure and thermal properties of [Sc(5Htfac)] were compared with those of two scandium(III) β-diketonates bearing methyl and tert-butyl substituents in the ligand.