Ab initio investigation of the electron structure in bis-Cu+ acetylene and vinylidene complexes

[Cu(-C₂H₂)₂]⁺, [Cu(-CCH₂)₂]⁺ and [Cu(-C₂H₂) (-CCH₂]⁺ complexes have been studied by the ab initio double-zeta basis set method. It has been established that all calculated compounds are stable to decomposition into two C₂H₂ molecules and Cu⁺ cation and into one C₂H₂ molecules and the respective monocomplex. Calculation results suggest the possibility of intramolecular acetylene-vinylidene rearrangement in the coordination sphere of Cu⁺.

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ab initio : [Cu(-C₂H₂)₂]⁺, [Cu(-CCH₂)₂]⁺, [Cu(-C₂H₂) (-CCH₂)]⁺. C₂H₂ Cu⁺ C₂H₂ . - Cu⁺.

     

Acid-base properties of supported vanadium oxide catalyst

Reduction of V₂O₅/Al₂O₃ and V₂O₅/silica-alumina produced Lewis acid sites which could strongly adsorb CO (heat of adsorption: 90 kJ/mol). Such strong acid sites were not formed in the cases of V₂O₅/SiO₂ and V₂O₅/MgO. V₂O₅ loaded on Al₂O₃ interacted with the basic sites of alumina but not with the acidic sites, while the V₂O₅ on silica-alumina interacted with the acidic sites of the silica-alumina and decreased its acidity.

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V₂O₅/Al₂O₃ V₂O₅/SiO₂–Al₂O₃ , CO ( 90 /). V₂O₅/SiO₂ V₂O₅/MgO . V₂O₅, Al₂O₃, , , V₂O₅ SiO₂–Al₂O₃ - .

     

Reaction of triphenyl phosphite ozonide with thioacetals

Kinetic regularities in the reaction of triphenyl phosphite ozonide with several thioacetals in CH₂Cl₂ solution at –15°C have been studied. The consumption rate of ozonides is described by the kinetic equation W=k₀[(C₆H₅O)₃P·O₃]+k₁[(C₆H₅O)₃P·O₃][R₁R₂C(SR₃)₂] Rate constants k₀ and k₁ for the thioacetals: (CH₃H₇S)₂CH₂, (C₆H₅S)₂CH₂, (C₆H₅CH₂S)₂CH, (n=C₁₂H₂₅–S)₂CH₂, (C₃H₇S)₂C(H)CH₃, (C₃H₇S)₂C(H)C₆H₅, (C₃H₇S)₂C(CH₃)C₆H₅ and (C₃H₇S)₂C(H)C₁₀H₉, increases with increasing the electron-donating power of subtituents R_i.

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CH₂Cl₂ –15°C. : W=k₀[(C₆H₅O)₃P·O₃]+k₁[(C₆H₅O)₃P·O₃][R₁R₂C(SR₃)₂] k₀ k₁ (C₃H₇S)₂CH₂, (C₆H₅S)₂CH₂, (C₆H₅CH₂S)₂CH₂, (n-C₁₂H₂₅S)₂CH₂, (C₃H₇S)₂C(H)CH₃, (C₃H₇S)₂C(H)C₆H₅, (C₃H₇S)₂C(CH₃)C₆H₅, (C₃H₇S)₂C(H)C₁₀H₉. .

     

Studies on double malonates. III. Thermal decomposition of sodium lanthanide malonates,Na5Ln(C3H2O4)4.7.5H2O,where Ln=Gd,Tb or Ho

The double malonates of gadolinium, terbium and holmium with sodium, of the type Na₅Ln(C₃H₂O₄)₄.7.5H₂O, have been studied by means of thermal analysis. A mechanism of thermal dehydration and decomposition has been proposed on the basis of the results obtained.

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Zusammenfassung Doppelmalonate von Gadolinium, Terbium und Holmium mit Natrium des Typs Na₅Ln(C₃H₂O₄)₄.7,5 H₂O wurden mittels thermischer Analyse untersucht. Für die thermische Dehydratisierung und Zersetzung wird ein auf den erhaltenen Ergebnissen basierender Mechanismus vorgeschlagen.

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, Na₅Ln(C₃H₂O₄)₄.7.5H₂O. .

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Part II. Communicated     

Thermische Zersetzung des Lithiumhexacyanoferrats(III)

Zusammenfassung Die thermische Zersetzung von Lithiumhexacyanoferrat (III) in Luft führt in drei Temperaturbereichen, d.h. zwischen 250 und 400°, 500 und 650° und 925 und 1000° zur Bildung ferromagnetischer Produkte. Durch Röntgendiffraktionsuntersuchung und magnetische Messungen wurde bewiesen, daß im ersten Temperaturbereich-Fe₂O₃ die für die ferromagnetischen Eigenschaften der Zersetzungsprodukte verantwortliche Phase ist, während in den anderen Bereichen diese Eigenschaften durch Lithiumferrit der Formel Li_0.5Fe_2.5O₄ verursacht werden.

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The thermal decomposition of lithium hexacyanoferrate (III) in air leads to the formation of ferromagnetic products in three temperature ranges, namely 250–400°, 500–650° and 925–1000°. By X-ray diffraction studies and magnetic measurements it has been proved that in the first temperature region-Fe₂O₃ is the phase responsible for the ferromagnetic properties of the decomposition products, whereas in the other regions these properties are due to the presence of the lithium ferrite Li_0.5Fe_2.5O₄.

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Résumé La décomposition thermique du ferricyanure de lithium dans l'air conduit à des produits ferromagnétiques dans trois intervalles de température: 250–400°, 500–650° et 925–1000°. Par diffraction des rayons X et mesures magnétiques, on montre que lors de la première étape de décomposition c'est l'oxyde-Fe₂O₃ qui est responsable des propriétés ferromagnétiques des produits de décomposition, tandis que pour les deux autres étapes, le ferromagnétisme est dû à la présence de ferrite de lithium de formule Li_0.5Fe_2.5O₄.

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-()- : 250–400°, 500–650° 925–1000°. - , , , , -Fe₂O₃. Li_0.5Fe_2.5O₄.

     

Ligand exchange between bis-acetylacetonato cobalt(II) and organotin compounds SnR2Cl2 (R=Ph, Et), II. Mechanism of ligand exchange between acetylacetonate complexes of Co(II)

Ligand exchange between the compounds Co(AA)₂Py₂ and Co(AA)Clpy_x (x=1 or 3) formed in the, system, CO(AA)₂–SnR₂Cl₂(R=Ph, Et) in chloroform with pyridine has been established to be catalyzed by SnR₂Cl₂. An interpretation of the catalytic action of SnR₂Cl₂ is suggested.

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, Co(AA₂py₂ Co(AA)Clpy_x (x=1 3) (Co(AA)₂–SnR₂Cl₂ (R=Ph, Et) , SnR₂Cl₂. SnR₂Cl₂.

     

Effect of heating rate on the thermal decomposition of lead dioxide

Experimental data are presented on the kinetics and mechanism of PbO₂ decomposition at heating rates varying from 0 to 2.5 · 10³ °/sec. The studies were carried out with a time-of-flight mass spectrometer MSKH-4, a Paulik-Paulik-Erdey derivatograph and an X-ray diffractometer DRON-0.5At low heating rates (0 to 0.2 °/s) oxygen is evolved in four stages: PbO₂ PbO_1.56 PbO_1.44 PbO. At extremely high heating rates (2 · 10²–2.5 · 10³ °/s) the number of stages is reduced to two: PbO₂ PbO_1.4 PbO. An attempt is made to connect the observed change in the decomposition mechanism of PbO₂ with the crystal structure formation of the lead oxides.

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Zusammenfassung Versuchsergebnisse bezüglich der Kinetik und des Mechanismus der Zersetzung von PbO₂ bei Aufheizgeschwindigkeiten zwischen 0 und 2.5 · 10³°/s werden mitgeteilt. Die Untersuchungen wurden mittels eines time-of-flight Massenspektrometers MSKH-4, eines Derivatographen des Typs Paulik-Paulik-Erdey und eines Röntgendiffraktometers DRON-0.5 durchgeführt.Bei niedrigen Aufheizgeschwindigkeiten (0 bis 0.2 °/sec) wird Sauerstoff in vier Stufen entwickelt: PbO₂ PbO_1.56 PbO_1.44 PbO. Bei extrem hohen Aufheizgeschwindigkeiten (2 · 10² – 2.5 · 10³°/s) wird die Zahl der Stufen auf zwei herabgesetzt: PbO₂ PbO_1.4 PbO. Es wird versucht die beobachtete Ánderung in dem Zersetzungsmechanismus von PbO₂ mit der Kristallstrukturbildung der Bleioxide in Verbindung zu bringen.

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Résumé On présente des résultats expérimentaux concernant la cinétique et le mécanisme de la décomposition de PbO₂ pour des vitesses de chauffage allant de 0 à 2.5 · 10³°/s. Les études ont été effectuées à l'aide d'un spectromètre de masse du type MSKH-4, d'un Dérivatograph du type Paulik-Paulik-Erdey et d'un diffractomètre des rayons X du type DRON-0,5.Aux faibles vitesses de chauffage (0 à 0.2°/s) l'oxygène se dégage en quatre étapes: PbO₂ PbO_1.56 PbO_1.44 PbO. Aux vitesses de chauffage très élevées (2 · 10² à 2.5 · 10³°/s) le nombre des étapes se réduit à deux: PbO₂ PbO_1.4 PbO. On essaye de relier le changement observé dans le mécanisme de décomposition de PbO₂à la structure cristalline des oxydes de plomb.

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PbO₂ 2.5 · 10³°/c. — — MCX — 4, — — — 0.5. (0–0.2°/c) : PbO₂ PbO_1.56. PbO_1.44 PbO. (2 · 10²–2.5 · 10³°/c) : PbO₂ PbO_1.4 PbO. PbO₂ .

     

Determination of the surface acidity of solid catalysts

A novel method has been developed for determining the surface acidity of white, as well as deeply colored porous solids. The method, which was tested on Al₂O₃, SiO₂–MgO–Al₂O₃ and Fe₂O₃ catalysts, is based on the adsorption of pyridine or benzylamine on acidic sites and subsequent displacement of the adsorbed bases by n-butylamine. A linear correlation was found between the concentration of acidic sites on Al₂O₃ and Fe₂O₃ catalysts and their activity in the dehydration oftert-butyl alcohol.

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, . , Al₂O₃, SiO₂–MgO–Al₂O₃ Fe₂O₃, -. Al₂O₃ Fe₂O₃ - .

     

Use of differential calorimetry for characterization of hydration processes in the system Ca4(Al6O12) (SO4)-CaSO4.2H2O-H2O

Differential calorimetry was used to determine the heat evolution and kinetics of hydration processes of the calciumsulphatealuminate phase Ca₄(Al₆O₁₂)(SO₄) with gypsum CaSO₄ · 2H₂O at room temperature with one mole of water added to the solid phase. An increasing content of sulphate ions in the sytem results in substitution of the monosulphate Ca₄(Al₂O₆)(SO₄) · 12H₂O in the reaction products by ettringite, Ca₆(Al₂O₆)(SO₄)₃ · 32H₂O. Higher contents of ettringite influence the rates of hydration reactions and the values of the evolved heat.

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Zusammenfassung Die Wärmeentwicklung und ihr zeitlicher Ablauf bei der Hydratation des Calciumsulfat-aluminats Ca₄(Al₆O₁₂)SO₄ mit Gips CaSO₄ · 2H₂O bei Zimmertemperatur und einem Wasser/Feststoff-Massenverhältnisw/s=1 wurde durch isotherme Differenzkalorimetrie untersucht. Bei erhöhtem Sulfatgehalt wird das Monosulfat Ca₄(Al₂O₆)SO₄ · 12H₂O im Reaktionsprodukt durch Ettringit Ca₆(Al₂O₆)(SO₄)₃ · 32H₂O ersetzt. Der erhöhte Ettringitgehalt beeinflusst die Beschleunigung der Hydration und die abgegebene Wärmemenge.

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₃( l₆₁₂) (SO₄) . - ₆(l₂₆)(S₄)₃·32₂, .

     

Decomposition of isopropanol on V2O5 of different grain morphology and its relation to o-xylene oxidation catalysts

Decompositon of isopropanol has been studied on V₂O₅ samples of different morphology. It has been shown that the selectivity to acetone increases with the increase in the fraction of (010) plane of V₂O₅ on the sample surface, whereas the selectivity to propene decreases. The results are compared with previous data of o-xylene oxidation on the same samples and discussed in terms of the model of V₂O₅ surface [7].

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V₂O₅ . , (010) V₂O₅ , . - V₂O₅.

     

Role of tin in a PtSb alloy and a Pt-Sn/Al2O3 reforming catalyst

The conversion of n-hexane was studied on a Pt-Sn/Al₂O₃ catalyst, a PtSn alloy and on the corresponding Pt catalysts. The results indicate the same catalytic effect of tin in supported and unsupported catalysts. It is concluded that the role of tin is connected with alloy formation.

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- Pt-Sn/Al₂O₃, PtSn Pt-. . , .

     

Influence of thermal treatment and rehydration of Al2O3 on the amount of Al3+ ions migrating into HCl solution

The amount of Al³⁺ ions migrating into HCl solution from unit surface of Al₂O₃ grows with increasing oxide calcination temperature up to 1123 K, remains unchanged up to 1373 K and then, after the formation of -Al₂O₃, rises sharply. Preliminary rehydration of the surface - and -Al₂O₃ relatively decreases their amount.

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Al³⁺, Al₂O₃, 1123 1373 , -Al₂O₃ . - -Al₂O₃ , .

     

Kinetics of thermal decomposition of pyrite in an inert atmosphere

The thermal decomposition of pyrite in an inert atmosphere was studied in order to obtain a detailed knowledge of the kinetics and mechanism of the reaction 2 FeS₂=2FeS+S₂, which is one of the methods of producing elementary sulphur. The process was studied under isothermal conditions at temperatures of 600, 660, 700, 750, 800 and 850 °C in a nitrogen atmosphere, by means of a thermobalance. The rate-controlling processes were determined and their kinetic parameters were calculated. The optimum temperature for the process was found to be 800 °C.

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Zusammenfassung Es wurde die thermische Zersetzung von Pyrit in inerter Atmosphäre bestimmt, um detaillierte Informationen über Kinetik und Mechanismus der Reaktion 2 FeS₂=2FeS+S₂, einer der Darstellungsreaktionen von elementarem Schwefel zu erlangen. Der Vorgang wurde mittels einer Thermowaage unter isothermen Bedingungen bei Temperaturen von 600, 660, 700, 750, 800 und 850 °C untersucht. Es wurden die geschwindigkeitsbestimmenden Schritte bestimmt und deren kinetische Parameter errechnet. Als Optimumtemperatur für diesen Prozeß erwies sich 800 °C.

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- 2FeS₂=2FeS + S₂, . 600, 660, 700, 750, 800 850 ° . , 800°.

     

Trends in the high-temperature heat capacities of ternary chalcopyrite semiconductors

The anharmonic contribution to the heat capacity of any chalcopyrite semiconductor A^IB^IIIC ₂ ^VI or A^IIB^IVC ₂ ^V is evaluated. It is shown that the degree of lattice anharmonicity decreases with increasing atomic weight of the constituent atoms of the compounds, and there is no essential difference in the degree of lattice anharmonicity of the two groups of compounds. Except for CdGeAs₂, the trend in the Grüneisen constants is the same.

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Zusammenfassung Der anharmonische Beitrag zur Wärmekapazität verschiedener Halbleiterverbindungen A^IB^IIIC ₂ ^VI und A^IIB^IVC ₂ ^V vom Chalkopyrit-Typ wird bestimmt. Es wird gezeigt, dass die Gitteranharmonizität mit steigender relativer Atommasse der Bestandteile der Verbindungen abnimmt und dass keine wesentlichen Unterschiede in der Gitteranharmonizität beider Gruppen von Verbindungen bestehen. Der Trend der Grüneisen-Konstanten ist der gleiche, ausgenommen bei CdGeAs₂.

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^IIII ₂ ^{VI IIIV} ₂ ^V . , , , . , CdGeAs₂.

     

Thermal conductivity measurements on samples with low cross-sections

A simple, low-cost apparatus has been designed and constructed for measurement of the thermal conductivities of samples with low cross-sections (10^–7 m²). This apparatus has been used to determine variations in the thermal conductivity of the metallic glass Fe₈₀B₂₀ (Metglas 2605) in the crystallization process induced by thermal treatment.In spite of the simplicity, the deviations from the real values of thermal conductivities measured have been lower than 8%, which has proved to be satisfactory for establishing the glass formation, temperature, T₈, from changes in thermal conductivity.

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Zusammenfassung Eine einfache, billige Apparatur zur Messung der Wärmeleitfähigkeit von Proben mit kleinen Querschnitten (10^–7 m²) wurde entworfen und gebaut. Die Apparatur wurde zur Bestimmung von Veränderungen der Wärmeleitfähigkeit des metallischen Glases Fe₈₀B₂₀ (Mctglass 2605) während des durch thermische Behandlung ausgelösten Kristallisationsprozesses benutzt. Trotz der Einfachkeit betrug die Abweichung von den gemessenen tatsächlichen Wärmeleitfähigkeitswerten weniger als 8%, was sich als ausreichend für die Ermittlung der Glasbildungstemperatur 7₉ aus Veränderungen der Wärmeleitfähigkeit erwiesen hat.

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( 10^–7 ₄). Fe₈₀B₂₀ 2605) , . , 8%, _g .

     

Relative reactivities of phosphites in reactions with hydrotrioxides

Studies of the interaction of hydrotrioxides ROOOH of ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1,1-dimetoxyethane, 1,1-diethoxyethane, benzaldehyde and tetrahydrofuran with trimethyl triisopropyl, tributyl, triallyl, triphenyl and tri-o-chresyl phosphites (RO)₃P have revealed that in mild conditions ROOOH rapidly and selectively oxidizes (RO)₃P to the corresponding phosphates. The reaction stoichiometry has been established. Aromatic phosphites are shown to be of inferior reactivity to ROOOH as compared with aliphatic phosphites.

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, 1-, 2-, 1-, 2-, 1,1-, 1,1-, -, -, -, -, -, -, -- (RO)₃P. ROOOH (RO)₃P . . , ROOOH .

     

Studies on catalytically active surface compounds, VIII. On the reaction of VCl4 with aerosil

The preparation and hydrolysis of silica supported vanadium catalysts have been investigated using VCl₄ as a paramagnetic probe. Chemical analysis shows the possibility of the VCl₄ molecule to react one, two, or three hydroxy groups of the surface. The type of reaction is influenced by the temperature of pretreatment of aerosil (TPA). ESR measurements show distortions of the tetrahedral coordination of the (SiO)_nVCl_4–n surface complex, which is strongest for the threefold attachment (n=3) of VCl₄ to the surface. Hydrolysis is accompanied by an increase of the coordination number and leads to highly mobile vanadium species.

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, VCl₄ . , VCl₄ , . . (SiO)_nVCl_4–n, VCl₄ (n=3). .

     

On the nature of surface sites for heterolytic dissociation of hydrogen on Al2O3

A quantum-chemical analysis of the models for geminal OH groups of Al₂O₃ and of the processes of their dehydroxylation with further dissociative chemisorption of hydrogen has been carried out. Calculations were performed by the SCF MO LCAO method using STO-3G basis set in terms of the cluster approach.

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OH- Al₂O₃ . , STO-3G .

     

Studies on catalytically active surface compounds, X. Alkali metal induced slow tumbling of vanadyl complexes on the surface of aerosil

The effect of alkali metal admixtures (Li, Na, K, Rb, and Cs) on V/SiO₂ catalysts was studied by ESR spectroscopy. Alkali metals strongly change the VO²⁺ spectra. Reduction leads to spectra showing a slow rotational motion of VO²⁺ species on the support surface. The proposed explanation includes former structural models and the formation of salts of polyvanadium acid.

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(Li, Na, K, Rb Cs) V/SiO₂ . VO²⁺. , VO²⁺ . .