Structure and Magnetic Properties of Solid Solutions of Molecular Magnetics Based on Ni(II) and Co(II) Complexes with Nitroxyl Radicals

Ni(II) and Co(II) complexes with deprotonated paramagnetic enaminoketones 4(3,3,3trifluorine2oxopropylidene) 2,2,5,5tetramethyl3imidazolidine1oxyl (L) and 4(3,3,3trifluorine1chlorine2oxopropylidene)2,2,5,5tetramethyl3imidazolidine1oxyl (L¹) and alcohols are shown to form continuous solid solutions Ni_xCo_1-xL₂(C₂H₅OH)₂ and Ni_xCo_1-xL₂ ¹(CH₃OH)₂. Single crystal Xray diffraction analysis showed that concentration variation practically does not affect the structural characteristics of the solid solutions. Distinguishing features if the magnetic behavior of Ni_xCo_1-xL₂ · (C₂H₅OH)₂ and Ni_xCo_1-xL₂ ¹(CH₃OH)₂ are the antiferromagnetic interaction of the moments of the nickel and cobalt sublattices inside the polymeric layers and the antiferromagnetic nature of interlayer interaction of the magnetic moments.     

Some aspects of mathematical statistics as applied to nonisothermal kinetics

Restrictions of the simplest use of correlation and regression analysis to obtain a single-valued solution to the inverse kinetic problem are considered. The Coats-Redfern method is suggested as a version of nonlinear regression analysis to increase the unambiguity of the solution.

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Zusammenfassung Die Beschränkungen der einfachsten Anwendung der Korrelations- und Regressionsanalyse zur eindeutigen Lösung des inversen kinetischen Problems werden erörtert. Die Coats-Redfern-Methode wird als eine Version der nichtlinearen Regressionsanalyse zur Erhöhung der Eindeutigkeit der Lösung vorgeschlagen.

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. - .

     

Energetic and kinetic investigation of thermally induced molecular rearrangements of esters of (hydroxymethyl) hydridosilanes by DSC

Silanes of the type R¹R²Si(H)CH₂OEl(O)_xR _y ³ [R=organyl; El=C (x=y=1), S (x=2,y=1), P (x=1y=2)] undergo a thermally induced rearrangement to give silanes of the type R¹R²Si (CH₃)OEl(O)_xR _y ³ . The energetic (reaction enthalpy) and kinetic data (reaction order, enthalpy and entropy of activation) of this reaction were determined by means of differential scanning calorimetry. The results obtained are discussed in terms of mechanistic aspects.

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Zusammenfassung Silane des Typs R¹R²Si(H)CH₂OE10_xR _y ³ mit R=organyl; E1=C (x=y=1), S(x=2, y=1) oder P (x=1,y=2) zeigen eine thermisch induzierte Umlagerung zu Silanen des Typs R¹R²Si(CH₃)OE10_xR _y ³ . Energetische (Reaktionsenthalpie) und kinetische Daten (Reaktionsordnung, Aktivierungsenthalpie und -entropie) dieser Umlagerungsreaktion wurden mittels DSC ermittelt. Die mechanistischen Aspekte der Ergebnisse werden diskutiert.

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R¹R²Si(H)OE1(O)_xR _y ³ , R= , E1=C (x=y=1), S (x=2,y=1), P (x=1,y=2), R¹R²Si(CH₃)OE1(O)_xR _y ³ . ( ) ( , ) . .

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Oxidation of naphthalene on olefin oxidation catalysts

Oxidation of naphthalene on Co–Mo–O, NiMoO₄ and Mg–Mo–O catalysts gives phthalic anhydride, its maximal yield being about 40% on nickel molybdate. On bismuth molybdates and the Sn–Sb–O system, naphthalene is mainly oxidized to carbon oxides.

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Co–Mo–O, NiMoO₄ Mg–Mo–O , ( 40%) . Sn–Sb–O .

     

Location of chromium and nickel cations in stabilized Y zeolites

The influence of the hydrothermal treatment of stabilized and nonstabilized Y zeolites on the location of Cr and Ni cations was tested. A significant influence of the above treatment was found.

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Cr Ni. .

     

Kinetic behavior of ethylene polymerization in the presence of highly active titanium-magnesium catalysts

The influence of the composition of highly active titanium-magnesium catalysts (TiCl₄ supported on MgCl₂ and a TiCl₃·nMgCl₂ catalyst), the nature and concentration of organoaluminium cocatalyst, the concentration of catalyst and monomer on the activity and the shape of the kinetic curves during ethylene polymerization has been studied.

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(TiCl₄, MgCl₂ TiCl₃·nMgCl₂), , .

     

Maximally inhibited gas phase elimination kinetics of methyl 3-bromopropionate

The gas phase elimination of methyl 3-bromopropionate has been studied in a static system and in vessels seasoned with allyl bromide. The reaction is autocatalyzed by HBr. However, under maximum inhibition with propene, the reaction obeys first order kinetics and is a homogeneous unimolecular elimination. The products are methyl acrylate and hydrogen bromide. The observed rate coefficients are represented by the Arrhenius equation: log k₁ (s^–1)=(12.94±0.46)–(214.5±6.0) kJ/mol/2.303 RT in the temperature range 400.1–449.9 °C and pressure range 49–98 Torr. The pyrolysis of methyl 3-bromopropionate is 3.5 times faster than that of ethyl bromide. This significant difference may be attributed to the greater acidity of the -hydrogen in 3-bromopropionate compared to that in ethyl bromide.

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3- , . HBr . . . , , : log k₁ (^–1)=(12,94±0,46)–(214,5±6,0) ·^–1/2,303 RT 400,1–449,9°C 49–98 . - 3,5 , . - - .

     

Free-radical addition reactions initiated by metal oxides, VI

CuO catalyzed additions of ethyl cyanoacetate, initiated thermally and by di-tert-butyl peroxide, to 1-decene and ethyl 10-undecylenoate were investigated. The CuO catalyzed reaction proceeds already at 80°C at a high rate, produces 11 adducts in high yields and represents the first example of catalysis in radical addition reactions of non-halogenated compounds.

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1- 10-, CuO, -.-. , CuO, 80°C, 11 . .

     

Influence of physically adsorbed oxygen on the separation of electron-hole pairs on anatase irradiated by visible light

ESR studies on the formation and properties of O ₂ ^– and [O^–·O₂] ion-radicals under photo-irradiation of oxidized anatase have been performed. The role of physically adsorbed oxygen in the separation of electrone-hole pairs is shown.

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- O ₂ ^– [O^–·O₂], . - .

     

Infrared and mass spectroscopic evidence for hydrocarbon formation on a supported cobalt catalyst

Interrupting the surface carbonyl development at 345 K on an aerosilsupported cobalt oxide catalyst in CO/H₂ atmosphere at maximum surface concentration of linear carbonyl species by heating to 475 K results in the formation of Fischer-Tropsch type products detectable by combined IR and MS measurements.

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345°K , , CO/H₂ , 475° -, .

     

Heterogeneous bulk nucleation and differential thermal analysis

The effect of the addition of Ag₂O on the mechanism of non-isothermal devitrification of Li₂O · 2 SiO₂ glass has been studied by differential thermal analysis. In both bulk and powdered samples, the presence of heterogeneous nuclei lowers the crystallization temperatures but not the value of the crystal growth activation energy.The influence of the catalyst on the crystallization mechanism is not affected by a pre vious heat treatment at the temperature of the maximum nucleation rate.

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Zusammenfassung Die Wirkung des Einflusses von Ag₂O auf den nicht-isothermen Entglasungsmechanismus von Li₂O · 2 SiO₂-Glas wurde durch Differentialthermoanalyse untersucht.Die Gegenwart heterogener Kerne setzt die Kristallisierungstemperaturen herab, jedoch nicht die Werte der Aktivierungsenergien des Kristallwachstums in grob- als auch in feinpulverisierten Proben.Die Wirkung des Katalysators auf den Kristallisationsmechanismus wird durch eine vorhergehende Wärmebehandlung bei der Temperatur der maximalen Keimbildungsgeschwindigkeit nicht beeinflusst.

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Résumé On a étudié, par analyse thermique différentielle, l'effet de l'addition d'Ag₂O sur le mécanisme de dévitrification non-isotherme du verre Li₂O · 2 SiO₂. La présence de noyaux hétérogènes abaisse les températures de cristallisation, mais pas la valeur de l'énergie d'activation de la croissance des cristaux, que les échantillons soient massifs ou pulvérisés.L'influence du catalyseur sur le mécanisme de la cristallisation n'est pas altérée par un traitement thermique préalable à la température de la vitesse maximale de nucléation.

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Li₂O·2SiO₂ , , . .

     

Quantitative thermal analysis,II

Some problems on adjustment of the equipment and on data evaluation, in view of the equations derived earlier for the calculation of specific heat and heat of transformation are discussed. It is shown that quantitative determinations are possible also if the adjustment is non-ideal and that both air and an inert material, respectively, may be used as reference material.

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Zusammenfassung Gewisse Probleme des Adjustierens der Ausrüstung und der Auswertung der Daten in Hinsicht auf die früher abgeleiteten Gleichungen zur Errechnung der spezifischen und Umwandlungswärmen wurden besprochen. Man bewies, daß quantitative Bestimmungen auch bei nichtidealem Adjustieren möglich sind bzw. daß Luft und Inertstoff gleichwie als Referenzstoffe dienen können.

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Résumé On discuté divers problèmes relatifs à la mise au point de l'appareillage et à l'évaluation des données, dans l'optique des équations déduites précédemment pour le calcul de la chaleur spécifique et de la chaleur de transformation. On montre qu'il est possible de faire des déterminations quantitatives même si la mise au point n'est pas idéale et que l'on peut utiliser comme substances de référence l'air aussi bien qu'un corps inerte.

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, . ë ë . , , « » , .

     

Quantum chemical study of the influence of the zeolite electrostatic field on the physical characteristics of ethylene

A modified CNDO/2 method whose Hamiltonian includes the terms describing the interaction of electrons with the electrostatic field of the zeolite crystal is employed for studying the influence of the faujasite electrostatic field on the physical characteristics of ethylene. It is shown that this field causes significant changes in the distribution of electron density in the ethylene molecule as a function of its orientation and localization in the large cavity of faujasites.

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/2, , , . , .

     

Synthesis,structural and spectroscopic characterization of the α and β forms of bis(imidazole)copper(II) dibenzoate, [Cu(im)2(OBz)2]

Two modifications of the and forms of bis(imidazole)copper(II) dibenzoate, [Cu(im)₂(OBz)₂], have been obtained by recrystallization from EtOH. X-ray analysis reveals that the two modifications have the same structure with different geometric parameters. The form crystallizes in the C2/c space group and the form, in the P2(1)/n space group. The crystal structures of both consist of centrosymmetric monomeric molecules of [Cu(im)₂(OBz)₂] with a distorted octahedral geometry for the CuN₂O₂O₂ chromophore. The e.s.r. spectra of the and forms exhibit a shf structure that consists of 9 lines, and these signals are also different from those of monomeric tetra(imidazole)copper(II) diacetate. Electronic and i.r. spectra are in agreement with the structural data.     

Pyrolysis of propane in the presence of hydrogen

The pyrolysis of propane in the presence of hydrogen, deuterium and argon was studied in the temperature range 890–1019 K. The acceleration of the reaction in the presence of hydrogen has been observed.

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, 890–1019 . .

     

Synthesis of Pd(II) nitro and nitrate complexes and studies of their reactivity towards oxidation of olefins in organic solvents

Complexes of the composition Pd(NO_n)_2–mCl_mL₂ (n=2, 3; m=0, 1, 2; L=CH₃CN) have been synthesized and their reactivity in ethylene and propylene oxidation has been examined. Data on the influence of the ligands, solvents and olefins on the composition of reaction products are reported.

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Pd(NO_n)_2–mCl_mL₂ (n=2, 3; m=0, 1, 2; L=CH₃CN) . , .

     

Natural flavours of wine: correlation between instrumental analysis and sensory perception

Summary The aroma of wine consists of 600 to 800 aroma compounds from which especially those, typical for the variety, are already present in the grapes. The aroma extracts — received by extraction with trichlorofluoromethane — are separated by gas chromatography. There are significant varietal differences between the aromagrams (fingerprint pattern). Thus the amount of some flavour compounds (key substances) shows typical dependence on the variety. Especially monoterpene compounds play an important role in the differentiation of wine varieties.The German white wines can be differentiated into three groups only by quantitative determination of 12 monoterpenes (terpene profile). These groups are: Riesling type, Muscat type and Silvaner-Weißburgunder type. Such terpene profiles are also useful for the separation of real Riesling wines from others called Riesling (e.g. Welschriesling, Kap Riesling, Emerald Riesling) but not produced from grapes of the variety Riesling. Including further components and by means of statistical methods as for example linear discriminant analysis even the different varieties within the mentioned groups (for instance the Riesling-group: Riesling, Kerner, Ehrenfelser, Bacchus, Müller-Thurgau) can be separated from each other.To identify compounds causing off-flavours the sniffing technique is the method of choice. The off-flavour is pinpointed during gas chromatography separation of the complex aroma mixture by effluent sniffing. Once allocated, the chemical nature of the off-flavours is elucidated by spectroscopic methods. Substances contributing to the green pepper taint, the strawberry note, mousiness, corkiness etc. in wine could be found in this way.     

Heterogeneous reactions of solid nickel(II) Complexes. XXII

The stoichiometry of thermal decomposition was studied for the following compounds: Ni(pyNO)Cl₂H₂O (I), (pyNO=pyridine N-oxide), Ni(2-MepyNO)Cl₂·2H₂O (II), Ni(3-MepyNo)Cl₂·2H₂O (III) and Ni(4-MepyNO)₂Cl₂·C₂H₅OH (IV). The heating of the compounds led first to the release of H₂O molecules (or C₂H₅OH molecules), with the formation of Ni(pyNO)Cl₂ (V), Ni(2-MepyNO)Cl₂(VI), Ni(3-MepyNO)Cl₂ (VII) and Ni(4-MepyNO)₂Cl₂ (VIII). In the next stage, decomposition of the heterocyclic liugands set in. The compositions and spectral and magnetic properties of these complexes indicate their dimeric (II, III, IV, VIII) of polymeric (I, V, VI, VII) structure with coordinated molecules of H₂O (or C₂H₅OH).

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Zusammenfassung Die Stöchiometrie der thermischen Zersetzung folgender Verbindungen wurde untersucht: Ni(pyNO)Cl₂·H₂O (I), (pyNO=Pyridin-N-oxid), Ni(2-MepyNO)Cl₂·2H₂O (II), Ni(3-MepyNO)Cl₂·2H₂O (III) und Ni(4-MepyNO)₂Cl₂·C₂H₂OH (IV). Beim Erhitzen erfolgt zunächst die Abspaltung von Wasser bzw. C₂H₅OH unter Bildung von Ni(pyNO)Cl₂ (V), Ni(2-MepyNO)Cl₂ (VI), Ni(3-MepyNO)Cl₂ (VII) und Ni(4-MepyNo)₂Cl₂ (VIII). Im nächsten Schritt setzt die Zersetzung der heterozyklischen Liganden ein. Aus den Zersetzungsreaktionen und den spektralen und magnetischen Eigenschaften dieser Komplexe folgt deren dimere (II, III, IV, VIII) oder polymere (I, V, VI, VII) Struktur mit koordinierten Wasser- bzw. C₂H₅OH-Molekülen.

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: Ni(pyNO)Cl₂-H₂O (I), (pyNO=H- ), Ni(2-MepyNO)Cl₂·2₂ (II), Ni(3-MepyNO)Cl₂-2H₂O (III) Ni(4-MepyNO)₂Cl₂-C₂H₅OH (IV). ( ) Ni(pyNO)Cl₂ (V), Ni(2-MepyNO)Cl₂ (VI), Ni(3-MepyNO)Cl₂ (VII) Ni(4-MepyNO)₂Cl₂ (VIII). . , (II, III, IV, VIII) (I, V, VI, VII) .

     

Thermoanalytical and thermogastitrimetric investigation of oil-shales

From thermoanalytical curves (DTG, TG) recorded in an oxygen atmosphere, the moisture and carbonate contents of oil-shales were determined with acceptable accuracy. The nature of the carbonates was predicted from the shape of the DTG curves above 550°C Dolomite (ankeritc) as found in Gérce oil-shale, and calcite in Pula-9 oil-shale. The clay content was determined from the signal of a water-detector recorded in a nitrogen atmosphere. The peaks at 80°C and 150°C for Gérce oil-shale were attributed to montmorillonite, and the sharp peak at 525°C for Pula-9 oil-shale to kaolinite.The volatile and fixed carbon contents of the oil-shales were calculated from the thermogastitrimetric curves.

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Zusammenfassung Feuchtigkeits- und Carbonatgehalt von Ölschiefern werden aus in Sauerstoffatmosphäre aufgenommenen thermoanalytischen Kurven (DTG, TG) mit annehmbarer Genauigkeit bestimmt. Die Natur der Carbonate wurde aus dem Verlauf der DTG-Kurve oberhalb 550 °C vorausgesagt. Dolomit (Ankerit) wurde im Gérce-Ölschiefer, Calcit im Pula-9-Ölschiefer gefunden. Der Gehalt an Tonen wurde aus dem in Stickstoffatmosphäre erhaltenen Signal eines Wasserdetektors bestimmt. Die Peaks bei 80 und 150 °C in der DTG-Kurve des Gérce-Ölschiefers werden Montmorillonit, der scharfe Peak bei 525 °C im Falle von Pula-9-ölschiefer Kaolinit zugeschrieben. Die Gehalte der Ölschiefer an flüchtigem und fixiertem Kohlenstoff werden aus gastitrimetrischen Kurven berechnet.

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(, ) , , . 550°. (), -9-. . , 80 150° , 525° -9 — . , .

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The authors are indebted to J. Kristóf (Dept. of Anal. Chem., Univ. of Veszprém) for carrying out the continuous water measurements; to K. Labdy (Central Laboratory, Univ. of Veszprém) for the elemental analysis results; to I. Vassányi (Dept. of Mineralogy, Univ. of Veszprém) for the diffractometric results; and to I. Koncz (Hydrocarbon Research and Development Institute, Nagykanizsa) for donating the oil-shale samples.     

Redox Properties of Rhodium(III) Oxo-Bridged Carboxylate Complexes

Chemical and electrochemical oxidation of rhodium (III) oxo-bridged carboxylate complexes was studied. The chemical [with O₃ and Ce(IV) salts] or electrochemical (at potentials of 1.00-1.20 V) oxidations of the binuclear complexes [Rh₂(-O)(-O₂CCH₃)₂(H₂O)₆]^{2 +} and [Rh₂(-O)(-O₂CCF₃)₂(H₂O)₆]^{2 +} leads to the superoxo complexes [Rh₂(-O)(O₂-)(-O₂CCH₃)₂(H₂O)₅]⁺ and [Rh₂(-O)(O₂ ^-)(-O₂CCF₃)₂(H₂O)₅]⁺ with terminal coordination of O₂-. The trinuclear acetate [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺, unlike its trifluoroacetate analog [Rh3(₃-O)(-O₂CCF₃)₆(H₂O)₃]⁺, is oxidized only electrochemically at a potential of 1.38 V. The oxidation of [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺ is reversible and involves formation of an unstable superoxo group O₂ ^- between two Rh₃III(₃-O) cores.