Vibrational spectra of AuF5 complexes with nitrogen fluorides and oxofluorides

Vibrational spectra and structural features of AuF₅ complexes with nitrogen fluorides (NF₃, N₂F₄) and oxofluorides (FNO, NF₃O) are investigated. Vibrational frequency assignment in the solid phase and in solution of anhydrous HF was made. Distinctive features of vibrational spectra of X⁺AuF₆ ^? (X = NF₄ ⁺, N₂F₃ ⁺, NO⁺, NOF₂ ⁺) related to structural transformations of cations and hexafluoroaurate anion due to the influence of the crystal field and cation-anion interactions are discussed.     

Advances in preparative chemistry of oxides and fluorides

A new attempt is made to interpret chemical formulas in the sense of solid state chemistry. Chemical formulas do not reveal the coordination behavior of all particles; therefore, a modified method a la P. Niggli is given to express these terms by formulating “Motifs of Coordination.” Furthermore unexpected new results in inorganic solid state chemistry (oxides and fluorides of metals, e.g., Rb₈[Zn₄O₈], BaNiF₆) have been achieved by using new starting materials and new preparative techniques. Numerous examples are given in detail.     

Thermochemical reactivity of superconducting mixed copper oxides

The importance of thermoanalytical methods for the investigation of superconducting mixed copper oxides is discussed. The thermochemical reactivity of ceramic superconductors adopting the structures of YBa₂Cu₃O_7–x, of K₂NiF₄ as well as of the composite structural frameworks is characterized in dependence of various gas atmospheres. The results give evidence, that depending on the ambient gas atmosphere most of these phases turn out to be remarkably reactive. Moreover, the oxygen stoichiometry proves to be of paramount importance for the superconducting properties. In turn, the range of stability of a superconducting phase with a given oxygen stoichiometry is often very narrow. Therefore, the thermoanalytical monitoring of redox processes and the determination of phase diagrams are indispensable.

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Zusammenfassung Es wird die Bedeutung thermoanalytischer Methoden für die Untersuchung supraleitender Kupfermischoxide beschrieben. In Abhängigkeit verschiedener Gasatmosphären wird die thermochemische Reaktivität von keramischen Supraleitern charakterisiert, die sowohl die Strukturen von YBa₂Cu₃O_7–x, von K₂NiF₄ oder auch von Verbundstrukturgerüsten annehmen. Die Ergebnisse zeigen eindeutig, daß in Abhängigkeit von der umgebenden Gasatmosphäre die meisten von ihnen eine bemerkenswerte Reaktivität aufweisen. Weiterhin scheint der Sauerstoffanteil von äußerster Wichtigkeit für die supraleitenden Eigenschaften zu sein. Der Stabilitätsbereich von supraleitenden Phasen mit einem gegebenen Sauerstoffanteil ist hingegen oft sehr schmal. Eine thermoanalytische Überwachung von Redoxprozessen und die Erstellung von Phasendiagrammen ist somit unentbehrlich.

     

Systematization of the effective ionic charges in the oxides,oxide fluorides,and fluorides of the rare earth metals

Conclusion We can compare the values obtained above and in [9] for the effective ionic charges e^* for all three types of REM compound examined: fluorides, oxides, and oxide fluorides.In spite of the difference in composition, all these substances can be divided into two groups by separating the cubic (or pseudo-isotropic) crystals and the anisotropic compounds. The average values of the effective charges for each of the structural groups are given in Table 7, which also gives in parentheses the values of the ionic character of the bond, calculated according to Pauling's scheme with allowance for only the nearest homogeneous coordination sphere (for example, for CN=5 instead of 11 for the hexagonal LnF₃, etc.).It can be seen from the Table that the effective charges increase on going from the oxides to the fluorides of the REM, as expected in view of the fact that the electronegativity of fluorine is greater than that of oxygen. In all cases, the increase in the values of e^*, noted above, is observed on going from the anisotropic to the cubic crystals of these compounds. This last feature can be attributed to a decrease in the immediate coordination sphere around the REM atoms with change in the structure of the crystal; in this case the coordination sphere is understood to consist of the nearest ligands. Calculation of the degree of ionic character by the EN method with allowance for only the atoms situated at the shortest distances shows much better agreement with experiment than the classical calculation using the formal CN [8].All-Union Scientific-Research Institute for Physicotechnical and Radiotechnical Measurements. Translated from Zhurnal Strukturnoi Khimii, Vol. 14, No. 3, pp. 541–547, May–June, 1973.     

P-type conductivity in transparent oxides and sulfide fluorides

Thin films of CuSc_1−xMg_xO_2+y have been rendered conducting by intercalation of oxygen. Hole conductivities up to of order 10 S/cm can be achieved at the expense of visible transparency, especially in the blue region of the spectrum. Hole conductivities up to 100 S/cm have been achieved in pressed pellets of K-doped BaCuSF, and a band-gap of 3.2 eV has been measured on undoped films.     

Measurements of photo-electron spectra and charging effects in fluorides,iodates and oxides

The ionization energies of inner electron shells have been measured without (I) and including (I′) a correction for the charging effect of non-conducting solid samples (derived from the two different Scotch tape C1s signals observed) for the fluorides, iodates and oxides of 25 elements with a definite oxidation state z. Whereas the difference between the I′ values for the fluoride and the oxide is close to z eV in most cases, this difference almost vanishes in Hg^II and is small in several other post-transition group elements.     

Basicity-acidity and solubility of metal fluorides and oxides in salt melts

The concept relating the basic-acidic properties of compounds (metal fluorides and oxides) to their solubility in salt melts is suggested. The method for estimation of solubility on the basis of thermodynamic calculations is developed. The calculated values agree satisfactorily with experimental data and results of prediction.     

Thermochemical properties of trialkylarsenites

The heats of the reaction of sodium with ethyl and methyl alcohol were determined by calorimetry. The difference in the standard heats of the formation of triethylarsenite and arsenic trichloride was obtained by calorimetration of the reaction of arsenic trichloride with sodium ethylate, the value of which was −382.42 ± 3.60 kJ/mol. The standard enthalpies of formation were determined from a critical analysis of all data on thermochemistry of trialkylarsenites for the following compounds: triethylarsenite Δ_f H ₂₉₈^ℴ [(C₂H₅O)₃As(liquid)] = (−704.38 ± 3.85) kJ/mol; trimethylarsenite Δ_f H ₂₉₈^ℴ [(CH₃O)₃As(liquid)] = (−599.36 ± 1.88) kJ/mol. The values of standard enthalpies of formation were not adjusted for the following substances in liquid state: arsenic trichloride (−321.96 ± 3.85 kJ/mol), tris-(diethylamido)arsenic(III) As(NEt₂)₃(liquid) (−129.81 ± 4.41 kJ/mol), tri-n-propylarsenite (−720.61 ± 4.49 kJ/mol), triisopropylarsenite (−756.11 ± 4.65 kJ/mol), tri-n-butylarsenite (−775.11 ± 4.53 kJ/mol), and triisobutylarsenite (−809.71 ± 4.59 kJ/mol). The use of sodium alcoxide solutions for the calorimetration of halogen anhydrides of various acids was demonstrated.     

Thermochemical investigation of Re2O3—SeO2 systems: III. Yttrium selenium oxides in the pseudo-binary system

Ternary pure phases in the thermodynamical equilibrium Y₂Se_xO_3+2x in the pseudo-binary Y₂O₃-SeO₂ system have been synthesized by solid state reactions and characterized by X-ray powder diffraction, IR spectroscopy and DSC measurements. A new phase Y₂Se_3.5O₁₀ was found besides the known phases Y₂Se₄O₁₁, Y₂Se₃O₉ and Y₂SeO₅. The thermal decomposition properties of the compounds have been determined by total pressure measurements and their thermodynamics data have been derived from their decomposition functions and C_p values. The phase diagram and the phase barogram have been established.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis,properties, and structure of intercalated graphite fluosulfonate fluorides

Graphite fluosulfonate fluorides of the composition C₂F_x−y(SO₃F)_y (x+y≈1) have been synthesized. The new compounds can be treated as derivatives of graphite fluorides C₂F_x(x≈1) in which approximately 1/50 of the F atoms have been replaced by SO₃F groups. The intercalates based on the new matrices have been studied by X-ray phase analysis, IR spectroscopy, mass spectrometry, and thermography. The ability of the intercalates to absorb various substances is investigated. It is shown that the introduction of a few SO₃F groups into the C₂F_x matrices significantly changes the physicochemical properties and the structure of intercalates; in particular, for intercalates of stage II structure this expands the scope of substances that can penetrate into interlayer spacings. The dependence of the penetration ability of the substances on the van der Waals sizes of their molecules makes intercalates resemble zeolites in properties. Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Novosibirsk. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No, 1, pp. 144–151, January–February, 1995 Translated by I. Izvekova     

The fluorination of uranium and vanadium oxides with some metal fluorides

UO₃ reacts with CrF₃ or CuF₂ forming UO₂F₂ and Cr₂O₃ or CuO respectively. Further fluorination occurs above 800°C to form UF₆ though the presence of excess CrF₃ gives mainly UF₄. The fluorination of U₃O₈ with CrF₃ gave UO₂F₂, UF₄ and Cr₂O₃ but with CuF₂ gave UO₂F₂, CuO and Cu₂O. VO₂ reacts with excess CrF₃ forming VF₃, VF₅ and Cr₂O₃. If there is a deficiency of CrF₃ the products are VOF₃, V₃O₅ and Cr₂O₃. CuF₂ and VO₂ form VOF₃, CuO and Cu₂O.     

Thermochemical characteristics of strontium cerate doped by neodymium and indium oxides

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Thermochemical and structural properties of anthraquinones

We have investigated the energetic, structural, and other physical–chemical properties (aromaticity, intrinsic strain, hydrogen bond interaction) of 1,4-anthraquinone (1), its better known isomer 9,10-anthraquinone (2) and the derivatives 9-hydroxy-1,4-anthraquinone (3) and 9-methoxy-1,4-anthraquinone (4). In particular, the standard enthalpy of formation in the gas phase at 298.15 K of 1,4-anthraquinone was determined [ $\Updelta_{\text{f}}^{{}} H_{\text{m}}^{\text{o}} \left( {{\text{g}},{\mathbf{1}}} \right) \, = \, - 4 4. 9 { } \pm { 5}. 7\;{\text{kJ}}\;{\text{mol}}^{ - 1} ]$ . Using isodesmic/homodesmotic reaction schemes, we have experimentally estimated: (i) the stabilization energy of 1 (162.2 ± 7.2 kJ mol^?1) and 2 (193.2 ± 5.2 kJ mol^?1), (ii) strength of intramolecular hydrogen bonding in 3 (HB = 79.8 ± 10.8 kJ mol^?1), and (iii) additional strain energy due to peri-oxygen interaction in 4 (?34.2 ± 7.6 kJ mol^?1). A computational study of these species, at the B3LYP/6-311++G(3df,2p) level, sheds light on structural, aromatic, intrinsic strain, or hydrogen bond effects and further confirmed the consistency of the experimental results.     

Thermochemical properties of lithium cobaltate

Samples of low- and high-temperature modifications of LiCoO₂ were produced and described. The heat capacity was measured by DSC in the temperature ranges of 140–570 and 180–570 K, respectively. The enthalpy and entropy of the cobaltates with respect to temperature were calculated from the data of heat capacity.     

Synthesis, structure and VUV luminescent properties of rubidium rare-earth fluorides

RbF-LnF₃ (Ln=rare earth) systems were synthesized by hydrothermal technique. Under the hydrothermal condition, the light rare-earth elements form LnF₃ (Ln=La-Nd), while the heavy ones form RbLn₂F₇ (Ln=Y, Er, Yb and Lu) with the RbEr₂F₇ structure type. RbLn₃F₁₀ compounds were found for the in-between rare-earth cations (Ln=Eu-Tm and Y), which crystallize exclusively in the cubic γ-KYb₃F₁₀-type structure. The luminescent properties under vacuum ultraviolet light were studied for the Eu³⁺-doped RbLn₃F₁₀ (Ln=Y, Gd) and a high quantum efficiency of about 150% was observed for RbGd₃F₁₀:Eu³⁺.     

Thermochemical reactivity of manganese(IV) oxides in reducing atmosphere

The thermochemical reduction of a series of structurally and morphologically different natural and synthetic manganese(IV) oxides has been investigated. Measurements have been performed by means of combined thermogravimetry/mass spectrometry, X-ray diffraction and analytical scanning electron microscopy. The mechanisms of the degradation of these materials have been characterized in order to establish standardized procedures for their reactivity as function of structure, morphology and experimental conditions. The corresponding results are the fundament with respect to a reproducible technical application.The authors would like to thank Dr. R. Lenck for compositional analyses of the investigated compounds. The financial support of the Chemetall GmbH, Frankfurt, Germany as well as the Fond der Chemischen Industrie is also acknowledged.