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Crystal structure, thermal stability, and the process of scandium tris-methylcyclopentadienyl Sc(MeCp)3 evaporation are studied. It is shown by XRD that crystals of this compound with the C2/c space group and the following parameters at 150 K are formed from the gas phase and from the solution: a = 7.9568(4) Å, b = 13.7620(6) Å, c = 28.239(2) Å, β = 107.4860(10)°, V = 2949.3(3) Å3, Z = 8, Dcalc = 1.217 g/cm3. The violation of the crystal packing order is manifested as diffuse scattering accompanied by single-crystal Bragg diffraction. The obtained data suggest that the complex has the Sc(η5-MeCp)2(η1-MeCp) structure with Sc–Z distances equal to 2.26-2.37 Å, where Z is the center of the η5-MeCp species or the C atom (for η1-MeCp). The NMR data obtained for the Sc(MeCp)3 samples, which were kept for 7 days at 423 K, 453 K, and 483 K, indicate that the substance undergoes noticeable decomposition only at the highest temperature. Temperature dependences of the saturated vapor pressure of the complex are measured independently by the flow method (transpiration) (392-469 K) and by the static method (441-514 K). As a result of joint processing of the tensimetry data, the following thermodynamic parameters of Sc(MeCp)3 evaporation are determined: ΔevH0(458.5) = 82.5±1.1 kJ/mol, ΔevS0(458.5) = 135±2 J/(mol·K). [ABSTRACT FROM AUTHOR]

Scandium(III) benzoyltrifluoroacetonate [Sc(btfac)3] was synthesized, purified, and characterized by elemental analysis and 1H 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) Å. 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, = 36.8 ± 1.3 kJ/mol, and = 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: = 135 ± 4 kJ/mol, and = 212 ± 9 J/(K mol). The structure and thermal properties of scandium benzoyltrifluoroacetonate were compared to those of similar scandium tris-β-diketonate complexes. [ABSTRACT FROM AUTHOR]

To expand the library of volatile magnesium precursors certified for effective use in chemical gas-phase deposition of the corresponding oxide or fluoride layers, a thermodynamic study of the mixed ligand complex Mg(tmeda)(btfac)2 (tmeda is N,N,N',N'-tetramethylethylenediamine, btfac is benzoyl trifluoroacetonate) have been performed. The melting process has been studied using DSC (Tm = 459.4 ± 0.3 K, = 42.9 ± 0.4 kJ/mol); the sublimation process has been studied using the flow (transfer) method in the temperature range 407–447 K ( = 163 ± 6 kJ/mol, ΔsublS427 = 293 ± 14 J/(mol K)). The substance passes into the gas phase with partial decomposition. Thermodynamic modeling of the composition of condensed phases formed from Mg(tmeda)(btfac)2 with the addition of H2 or O2 has been performed depending on the temperature (700–1300 K), total pressure (133–13 332 Pa), and the ratio of the reagent gas to the precursor (0–300). The data obtained can be used to determine the experimental parameters of the processes for obtaining functional layers. Comparison of the results with a similar trifluoroacetylacetonate complex made it possible to quantitatively reveal the effect of replacing the methyl group in the anionic ligand with a phenyl one. [ABSTRACT FROM AUTHOR]