ESR study of NiIII complexes with nitrosonaphthols and dithio acids

Mixed-ligand Ni^III complexes with -nitroso--naphthol, -nitroso--naphthol,o-ethylxanthate, andN,N-diethyldithiocarbamate as ligands have been studied by ESR in liquid and frozen solutions. The degrees of symmetry distortion for the first coordination sphere of these complexes have been determined. It is shown that the transition from planar square Ni^IIL₂ complexes to more stable octahedral Ni^IIIL₂L and Ni^IIILL₂ complexes occursvia the radical addition mechanism. A method for trapping short-lived radicals is suggested on the basis of the complex formation scheme.Translted fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1513–1515, August, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-5050)     

Molecular-beam mass spectrometry of van der Waals clusters. Mass spectrum of hydrogen sulfide dimer

Hydrogen sulfide clusters generated by ultrasonic expansion of an H₂S-Ar mixture into a vacuum were detected by electron impact mass spectrometry. The mass spectrum of the dimer, (H₂S)₂, was obtained under conditions of predominant dimerization. A mechanism of the formation of ions that involves intracluster reactions between the fragment ions of the monomer and the monomer molecule has been suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 839–844, May, 1995.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-4933). The authors are also grateful to the European Environmental Research Organisation (EERO) for support.     

Mechanism of Formation of Bi4Ti3O12

The mechanism of solid-phase reaction of Bi₄Ti₃O₁₂ formation was studied. Formation of the layered perovskite-like bismuth titanate occurs via intermediates with sequential changes in the coordination polyhedron of bismuth. A correlation is analyzed between the temperature of the onset of activation of the solid-phase reaction and the melting point of the surface (intergrain) phase based on bismuth oxide.     

NMR and X-ray diffraction studies of the influence of adsorbed molecule nature on phase transitions in a ZSM-5 silicalite

Pulsed NMR and X-ray diffraction analysis are employed to study the influence of adsorbed toluene, p-xylene, acetone, and di(ethylene glycol) (DEG) molecules on phase transitions in a ZSM-5 silicalite. In the region of phase transitions, times T₁ and T₂ of longitudinal and transverse magnetic relaxation of apolar molecules adsorbed in silicalite micropores increase and decrease in a jumpwise manner, respectively, with a rise in the total content of the liquid. Such changes in T₁ and T₂ occur for hexane, decane, toluene, and p-xylene molecules. Qualitatively different concentration dependences of T₁ and T₂ are observed for polar acetone and DEG molecules, because these liquids do not cause a earrangement in the crystal lattice of silicalite; this is confirmed by the X-ray diffraction data.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 802–806.Original Russian Text Copyright © 2004 by Pimenov, Skirda, Maksimenko, Morozov, Opanasyuk.     

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 .

     

Synthesis and reactions of metallocycles. 6. Stereoselective synthesis of 3,4-dialkyl-substituted aluminocyclopentanes by cyclometallation of α-olefins using trialkylalanes in the presence of Cp2ZrCl2

An efficient method has been developed for the synthesis of a new class of organoaluminum compounds, trans-3,4-dialkyl-substituted aluminocyclopentanes, via the cyclometallation of -olefins using R₃A1 in the presence of catalytic amounts of Cp₂ZrCl₂. Hydrolysis, deuterolysis, and oxidation of the resulting aluminocy-clopentanes generate the corresponding transformation products having exclusively the threo-configuration.For previous communication see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1141–1144, May, 1991.     

Synthesis and transformations of metallocycles. 9. Regioselective and stereoselective synthesis of al-substitutedtrans-3,4-dialkylaluminocyclopentanes catalyzed by (η5-C5H5)2ZrCl2

A new stereoselective method is developed for the synthesis of 1-chloro-, 1-alkoxy-, and 1-N,N-dialkylaminoalumino-cyclopentanes from -olefins, metallic magnesium, and aluminum halides (AlCl₃, RO-AlCl₂, R₂N-AlCl₂) in the presence of catalytic amounts of Cp₂ZrCl₂ (Cp=⁵-C₅H₅). The products from hydrolysis and deuterolysis of the Al-substituted 3,4-dialkylaluminocyclopentanes (ACP) have the threo configuration.For Communication 8, see [1].Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 450054 Ufa. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1393–1397, June, 1992.     

Behavior of copper in gallium arsenide with a high tellurium concentration

The electrophysical properties and cathode luminescence spectra of gallium arsenide with a high tellurium concentration (n = 2·10¹⁸ cm^–3) alloyed with copper are investigated under different diffusion conditions. Centers are determined from measurements of the Hall effect with an ionization energy of 0.190 ± 0.006 eV whose concentration does not depend on the arsenic vapor pressure (0.1 and 1 atm) and the cooling rate of the samples from the diffusion temperature. A band with h_m = 1.30–1.32 eV whose intensity depends on the cooling conditions of the samples was observed in the cathode luminescence spectra of these samples. The nature of the observed defects is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 93–99, July, 1979.In conclusion of this article the authors express their gratitude to L. K. Tarasova for preparation of the samples.