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Journal of Thermal Analysis and Calorimetry
Authors: E. Filatov, S. Sysoev, Ludmila Zelenina, Tamara Chusova, V. Logvinenko, P. Semyannikov, and I. Igumenov

Abstract  

Thermal behaviour of a series of lithium β-diketonates: Li(dpm) (dpm=dipivaloylmethanate (2,2,6,6-tetramethylheptane-3,5- dionate)), Li(pta) (pta=pivaloyltrifluoracetonate (2,2-dimethyl-6,6,6-trifluoro-3,5-hexanedionate)), Li(tfa) (tfa=trifluoracetylacetonate (1,1,1-trifluoro-2,4-pentandionate)), Li(hfa) (hfa=hexafluoracetylacetonate (1,1,1,5,5,5-hexafluoro-2,4-pentandionate)) has been investigated. Gas phase composition of these complexes has been established. Temperature dependences of vapor pressure of lithium compounds were obtained by static and dynamic methods, and thermodynamic parameters were calculated. Dependence of compound volatility on ligand structure is shown. For Li(dpm) detailed investigation has been done by differential scanning calorimetry (DSC).

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Journal of Thermal Analysis and Calorimetry
Authors: Ksenia Zherikova, Natalia Morozova, Ludmila Zelenina, S. Sysoev, Tamara Chusova, and I. Igumenov

Abstract  

Five volatile hafnium(IV) and zirconium(IV) β-diketonates: hafnium(IV) acetylacetonate, hafnium(IV) trifluoroacetylacetonate, hafnium(IV) pivaloyltrifluoroacetonate, hafnium(IV) 2,2,6,6-tetramethylheptane-3,5-dionate and zirconium(IV) 2,2,6,6-tetramethylheptane-3,5-dionate were obtained, purified and identified. Thermal behavior of solid compounds was investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC) in helium atmosphere and in vacuum. DSC method was also used for definition of thermodynamic characteristics of melting processes. Using the static method with quartz membrane zero-manometer and the flow method the temperature dependencies of saturated vapor pressure for hafnium(IV) complexes was obtained. The standard thermodynamic characteristics ΔH T 0 and ΔS T 0 of sublimation and evaporation processes were calculated from the temperature dependences of saturated vapor pressure.

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Abstract  

The volatile scandium-β-diketonates are synthesised using acetylacetone (acac) and tetramethylheptanedione (tmhd) as coordinative ligands for CVD application. The X-ray powder patterns are indexed and analysed and found to be orthorhombic and monoclinic phases for Sc(acac)3(1) and Sc(tmhd)3(2) respectively. The sublimation and evaporation kinetics have been analyzed using three calculating techniques. The non-isothermal based activation energy values are found to be 38 ± 2 and 73 ± 2 kJ mol−1 by Flynn–Wall technique for (1) and (2) respectively. The measured Ea values are close to the value obtained using Kissinger method.

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DSC and vapour pressure measurements are presented on some Be, Al and Cr complexes with 2,4-pentanedione tetramethyl-3,5-heptanedione, 1,1,1-trifluoro-2,4-pentanedione and hexafluoro-2,4-pentanedione. Thermodynamic functions are given for the sublimation, vaporization and melting processes of the substances.

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The standard molar enthalpies of formation of the crystalline lanthanum(III) chelate complexes with pentane-2,4-dione (acetylacetone, Hacac) and 1-phenylbutane-1,3-dione (benzoylacetone, Hbzac) were determined by the solution calorimetry method. The following values ofΔH

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Thermal dissociation processes ofβ-diketonate adducts with the composition ML2 · 2B (L = acetylacetone and its substituted derivatives;M = Ni, Co;B = H2O, BuNH2CH3OH, Py, NH3) were investigated. Kinetics of dissociation were studied in a flow reactor. For dehydration processes a compensation relationship is observed (lgA=E+b), demonstrating analogous mechanisms.

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Abstract  

57Co Mössbauer emission spectra of cobalt benzoylacetonate and 3-substituted acetyl-acetonates have been studied. All spectra reveal the same stabilized57Fe forms, though in a ratio depending on the substituent in the ligand. This dependence is interpreted in terms of the substituent effect on the nature of metal-ligand bonding.

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