8-Hydroxyquinolates of trivalent metals as new catalysts for the reaction of CO2 with epoxides

Tris-(8-hydroxyquinolates) of aluminum(iii), chromium(iii), and iron(iii) in the presence of triphenylphosphine oxide efficiently catalyze the formation of alkylenecarbonates by the reaction of CO₂ with oxiranes, viz., propylene oxide, but-2-ene oxides, and isobutylene oxide. The catalytic system is active at 140—170 °C and a CO₂ pressure of 15—100 atm.     

Synthesis of trialkylaluminum derivatives by the reaction of non-solvated aluminum hydride with α-olefins

Hydroalumination of -olefins by non-solvated polymeric aluminum hydride (AlH₃) _n occurs at 120—140 °C. Mechanochemical activation accelerates this reaction. The addition of catalytic amounts of the prepared R₃Al forms to the reaction system decreases the temperature of the process to 90—100 °C. The greatest initiation effect is observed when ate-complexes of the MAlR₄ type (M = Li, Na) are used: the reaction occurs with a higher rate already at 60—90 °C affording R₃Al free of admixtures of carbalumination products and dimers of -olefins.     

Metal–thiosemicarbazone interactions. Synthesis of an iodo-bridged dinuclear [diiodobis(pyrrole-2-carbaldehydethiosemicarbazone)dicopper(I)] complex

Reaction of copper(I) iodide with pyrrole-2-carbaldehydethiosemicarbazone (Hptsc) in a 1:1 mole ratio in MeCN, followed by addition of one mole of Ph₃P, yielded a complex of empirical formula, CuI(Hptsc)(Ph₃P), whose X-ray structure determination has shown that it exists as an iodo-bridged dinuclear copper(I) complex, [Cu₂(-I)₂( ¹-S-Hptsc)₂(PPh₃)₂](1). The central kernel, Cu(-I)₂Cu forms a parallelogram with unequal Cu—I distances {Cu—I, 2.644(2), 2.707(2)Å} and bond angles {Cu—I—Cu, 70.72(7), I—Cu—I, 109.28(7)°}. Each Cu atom is further bonded to one S atom of Hptsc and one P atom of Ph₃P, thus completing tetracoordination. The Cu...Cu separation of 3.097(4)Å is close to the sum of the van der Waals radius of the Cu atom, 2.80 Å. Compound (1) involves relatively strong inter-dimer hydrogen bonding via hydrazinic and pyrrole ring hydrogens with sulfur and iodine atoms respectively of the adjacent dimer {N(1)H...S^#2, 2.50 Å; N(4)H...I^#3, 2.91 Å}. The complex represents the first report of a copper(I) dimer with a thiosemicarbazone.     

Structural Aspect of a Thermal Activation Effect in the MnO x /γ-Al2O3 System

Solid-phase reactions in the aluminum–manganese oxide system, including the structural mechanism of the thermal activation of catalysts, were studied at temperatures up to 1100°C. It was found that the solid-phase reaction at 900–1000°C occurred via two pathways because of the diffusion of manganese ions to aluminum oxide and aluminum ions to manganese oxide. Nanoheterogeneous state of the active component, which was observed in the range 25–600°C, is the product of incomplete decomposition of the high-temperature aluminum–manganese phase Mn_{2.1 – x} Al_{0.9 + x} O₄ (0 x 0.6) with a cubic spinel structure; this phase was equilibrium at the synthesis temperature but metastable below 650°C.     

Sorption of carbon dioxide by the composite sorbent “potassium carbonate in porous matrix”

Sorption of CO₂ in the presence of water vapor by the K₂CO₃—-Al₂O₃ composite sorbent was studied by IR spectroscopy in situ, X-ray diffraction analysis, and the differentiating dissolution method and reasons for a decrease in its dynamic capacity are given. The samples containing K₂CO₃·1.5H₂O in pores are characterized by the maximal dynamic capacity. A mechanism for CO₂ sorption was proposed, which qualitatively explains the obtained dependence of the capacity on the water content in the composite sorbent. A high dynamic capacity can be maintained by regeneration of the sorbents by water vapor at 170 °N. The capacity of the sorbents decreases during the first 10 sorption—regeneration cycles due to the formation of an inactive phase of potassium aluminum carbonate.     

Effects of gamma-irradiation and Li2O-doping on surface and catalytic properties of unloaded Co3O4 solid

The effects of -irradiation (20–160 Mrad) and lithium oxide doping (0.75–6 mol%) on the surface and catalytic properties of unloaded Co₃O₄ solid have been investigated. The surface characteristics of various solids were determined from nitrogen adsorption isothems taken at –196 °C and their catalytic activities were measured by following the kinetics of CO-oxidation by O₂ at 100–150 °C using a static method. The results showed that -rays brough about a decrease of 21% inS _BET of Co₃O₄ due to widening of its pores and led also to a considerable increase in its catalytic activity. A maximum increase of 91% was observed upon exposure to a dose of 80 Mrad. Lithium oxide-doping at at 500 °C resulted in an increase of 150% inS _BET of treated solid without changing its mean pore radius. This treatment was also accompanied by an increase of about 50% in its catalytic activity measured at 150 °C. Gamma-irradiation and Li₂O-doping of unloaded Co₃O₄ did not change the magnitude of apparent activation energy of catalysis of CO-oxidation by O₂ but increased the concentration of catalytically active sites contributing in the catalytic process. In other words, -rays and lithium oxide doping did not alter the mechanism of catalytic oxidation of CO by O₂ over unloaded cobaltic oxide solid.     

Die Systeme Nickel—Selen und Kobalt—Nickel-Selen

Zusammenfassung Das System Ni–Se wurde thermisch und röntgenographisch untersucht und aus den Resultaten und aus Literaturangaben das Phasendiagramm aufgestellt. Die Hochtemperaturphase -Ni₃Se₂ zersetzt sich peritektisch bei 785 °C, die Verbindung Ni₆Se₅ peritektoidisch bei 647,5 °C. Die B8-(NiAs-)Phase Ni_1–x Se hat einen kongruenten Schmelzpunkt bei 53,5 At% Se und 959 °C und eine maximale Phasenbreite von 50,5 At% Se (785 °C) bis 56,8 At% Se (856 °C). NiSe₂ zerfällt peritektisch bei 853 °C in Ni_1–x Se und eine Se-reiche Schmelze. In Schmelzen mit mehr als 68,0 At% Se tritt oberhalb 856 °C eine Mischungslücke auf. Röntgenographisch konnte die Existenz der vier Verbindungen -Ni₃Se₂, Ni₆Se₅, Ni_1–x Se und NiSe₂ bestätigt werden.Im Dreistoffsystem Co–Ni–Se wurden drei Schnitte untersucht. In den quasibinären Schnitten zwischen den B8-Phasen Ni_1–x Se und Co_1–x Se und zwischen den C2-Phasen NiSe₂ und CoSe₂ sind die Legierungen sowohl im flüssigen als auch im festen Zustand vollkommen mischbar. In beiden Schnitten fallen die Liquidus- und Solidustemperaturen kontinuierlich von der Co-zur Ni-Seite ab. Die ternäre Phase (Co_1–y Ni _y )₁₁Se₈ ist bei 400 °C zwischen 0,9>y>0,5 stabil.

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The systems nickel—selenium and cobalt—nickel—selenium. Transition metal-chalcogen systems, II Übergangsmetall-Chalkogensysteme, 2. Mitt.

The Ni–Se system was investigated by X-ray and thermal analyses and from the results and from published data the Ni–Se phase diagram was constructed. The high temperature phase -Ni₃Se₂ decomposes peritectically at 785°C, the compound Ni₆Se₅ peritectoidically at 647.5°C. The B8 (NiAs) phase Ni_1–x Se has a congruent melting point at 53.5 at% Se and 959°C and a maximum range of homogeneity between 50.5 at% Se (785 °C) and 56.8 at% Se (856 °C). NiSe₂ decomposes peritectically at 853 °C into Ni_1–x Se and a Se-rich melt. Melts with more than 68.0 at% Se exhibit above 856 °C a miscibility gap. X-ray investigations confirmed the existence of the four compounds -Ni₃Se₂, Ni₆Se₅, Ni1– xSe, and NiSe₂.Three sections of the ternary system Co–Ni–Se were investigated. Alloys of the quasibinary sections between the B8 phases Ni_1–x Se and Co_1–x Se and between the C2 phases NiSe₂ and CoSe₂ are completely miscible in the liquid as well as in the solid state. The liquidus and the solidus temperatures in these sections drop continuously from the Co-to the Ni-side of the diagram. The ternary phase (Co_1–y Ni _y )₁₁Se₈ is stable at 400 °C between 0.9<y<0.5.

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Mit 5 Abbildungen     

Peri Interactions in Naphthalene Diketones: A Preference for (Z,Z) Conformations

The crystal structures of 1,8-dibenzoylnaphthalene (9), 1,4,5,8-tetrabenzoylnaphthalene (10), and 1,8-diacetylnaphthalene (11) have been determined by X-ray diffraction. Diketone 9 crystallizes in triclinic space group P ^—1 with a = 7.924(2), b = 14.068(3), c = 7.876(1) Å, = 99.47(2), = 90.58(1), = 91.43(2)°. Tetraketone 10 crystallizes in monoclinic space group P2₁/c a = 7.374(4), b = 11.960(5), c = 15.524(5) Å, = 93.15(5)°. Diketone 11 crystallizes in orthorhombic space group Pbca a = 6.986(3), b = 15.946(4), c = 8.257(1) Å. Each of these naphthalene ketones adopt a (Z,Z) conformation, with torsion angles O—C—C¹—C^8a/O—C—C⁸—C^8a of 49.8°/44.5° (9), 52.1°/46.6° (10), and 44.8°/42.4° (11). The structures 9–11 are overcrowded with the distances between two neighboring carbonyl carbon atoms being significantly shorter than the sum of the van der Waals radii of two carbon atoms (342 pm): 293.4 pm (9), 281.6 pm (10), and 293.0 pm (11).     

Chromatographische Enantiomerentrennung,chiroptische Eigenschaften und absolute Chiralität von Pentacyclo [7.4.1.12,7 .01,9 .02,7]pentadeca-3,5,10,12-tetraen-8-on,einem pentacyclischen Cyclopentanonderivat mitC 2-Symmetrie

The title compound1 was resolved into enantiomers by medium-pressure liquid chromatography on microcrystalline triacetylcellulose in ethanol. After four cycles pure enantiomers were obtained ([] _D ²⁰ + and — 330°, resp., in ethanol) and their circular dichroism spectra recorded. From optical comparison with structurally related thujane derivatives and by applying the octant rule, for (—)-1 the chirality (7R, 9R) was deduced.

     

Enantioselective reduction of C=O and C=N bonds by TADDOL-containing aluminum hydride reagents based on NaAlH4 and AlH3

Prochiral substrates (alkyl aryl ketones, cyclopropyl methyl ketone, 1-indanone, 1-tetralone, ethyl 2-oxo-4-phenylbutyrate, and N-(diphenylphosphinyl)acetophenoneimine) were subjected to asymmetric reduction with aluminum hydride reagents, which were prepared by modifications of NaAlH₄ or AlH₃ with chiral ,,","-tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOL). The effects of the nature of the substituents in TADDOL, the structure of the prochiral substrate, and the reaction conditions on the stereochemistry of reduction were investigated. The highest enantioselectivity (70—90% ee) was achieved upon reduction of alkyl aryl ketones and N-(diphenylphosphinyl)acetophenoneimine with NaAl(TADDOLate)H₂ in THF or diglyme at a temperature from –70 to –20 °C. The mechanism of asymmetric induction in the reduction reactions of ketones with aluminum hydride reagents is discussed. The stereochemical results of reduction were explained by comparing three-dimensional models of the most probable transition states.     

Stereoselective hydrogenation of 2-hexyne on Cu/γ-Al2O3 catalysts

The stereoselective hydrogenation of 2-hexyne in ethanol on Cu/-Al₂O₃ catalysts (1–40 % Cu) at 4–10 atm and 80–120 °C has been studied. The reaction affordscis-2-hexene as the only reaction product in 100 % yield at [Cu] 30 %. For samples with 20 % Cu, hydrogenation proceeds in parallel with absorption of H₂ by the catalyst.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1314–1315, July, 1993.     

Sol-Gel Synthesis and Pyrolysis Study of Oxyfluoride Silica Gels

Silicon oxyfluoride materials are synthesized by the sol-gel method using triethoxyfluorosilane as precursor, bearing the Si—F bond. SiO_(2–0.5x) F _x gel preparation requires peculiar experimental control of hydrolysis and condensation reactions. Maintenance of the Si—F bond during gelling, heating and aging was studied in the case of processes carried out under an argon atmosphere or in air. Fluorine contents in resulting samples were quantified by FT-IR and X-ray photoelectron spectroscopy (XPS); specific surface area and porosity of powdered samples were determined by N₂ adsorption. The thermal stability of oxyfluoride gels was studied by thermogravimetric-mass spectrometric (TG-MS) coupled analyses during heat treatment, under He flow. Mass spectra recorded during principal weight losses indicate the release of variously fluorinated silicon species resulting from Si—F/Si—O exchange reactions. The evolution of these species was observed at different temperatures, depending on gelling conditions. In particular, degradation of Si—F moieties was prominent for gels aged in air, whereas samples processed under an argon atmosphere preserve the Si—F bond up to 300°C.     

Intramolecular Nonbonded Interactions Between Oxygen and Group VIA Elements: An Ab Initio Molecular Orbital and Density Functional Theory Investigation of the Structures of HX—CH2—COOH (X=S,Se, and Te)

Ab initio molecular orbital and density functional methods have been used to study the potential energy surfaces of the substituted acetic acids HX—CH₂—COOH, where X is one of the Group VIA Chalcophiles S, Se, or Te. The various conformers adopted by these compounds provide information regarding the energetic importance of nonbonded and hydrogen bonding interactions involving oxygen atoms with different hybridizations. Density functional and ab initio molecular orbital methods yield similar structural and energetic trends for these compounds. Calculations show that the structure of the lowest-energy conformer of each of these acids has the X—C—C—O backbone substantially twisted from planarity, similar to that previously observed for the corresponding aldehydes, HX—CH₂—CHO. In the twisted acid structures the shortest distance is within about 0.1 Å of the sum of the X and O van der Waals radii, which reduces overcrowding of the lone pairs of electrons on these atoms. In conformers where the heavy atom backbone is planar, one of the distances is significantly shorter than the sum of the van der Waals radii, and the total molecular energy of these conformers is higher than that of the twisted forms. The variation of X—H vibrational frequencies among conformers reflects the extent of X—H hydrogen bonding, and indicates that formation of this hydrogen bond is not the dominant factor in determining the lowest-energy conformation. When X is oxygen (HO—CH₂—COOH), the lowest-energy conformer is also nonplanar, whereas for the corresponding aldehyde, HO—CH₂—CHO, the lowest-energy conformer is a planar structure with C_S symmetry. The conformational preferences of these simple species provide reference points for inter- and intramolecular interactions in more complex systems of biological interest.     

Tetracarbonyliron adducts of Cp2Cr2(CO)4(μ-η2-P2). Syntheses and crystal structures of Cp2Cr2(CO)4P2[Fe(CO)4] m (m=1 and 2)

Cp₂Cr₂(CO)₄( - ² - P₂), 1, reacts with one molar equivalent of Fe₂(CO)₉ in THF to yield the mono- and di-iron complexes, Cp₂Cr₂(CO)₄P₂[Fe(CO)₄], 2, (16.5% yield) and Cp₂Cr₂(CO)₄P₂[Fe(CO)₄]₂, 3, (16.9% yield), as dark magenta brown and dark greenish brown crystals, respectively. Both complexes were characterized by single-crystal X-ray diffraction analysis. Crystal data –2: space group =P2₁/c,a=17.024(1) Å,b=8.180(1) Å,c=30.891(2) Å, =100.953(5)°,V=4223.4(7)ų,Z=8, 3743 observed reflections,R _F=0.033; 3: space group P1,a=10.209(2) Å,b=10.212(2) Å,c=15.989(3) Å, =106.93(1)°, =91.87(1)°, =119.50(1)°,V=1356.5(4) ų,Z=2, 3489 observed reflections,R _F=0.029.     

Die Kristallstruktur von Tetrachloräthylencarbonat—Antimon(V)-chlorid,C2Cl4O2CO·SbCl5

Zusammenfassung Die Kristallstruktur des Adduktes Tetrachloräthylencarbonat—Antimon(V)-chlorid, C₂Cl₄O₂CO·SbCl₅ wurde mit Hilfe der Schweratom-Methode aus dreidimensionalen Röntgendaten bestimmt und nach der Methode der kleinsten Quadrate bis zu einemR-Wert von 13,1% verfeinert (Raumgruppe P2₁/n — Nr. 14;a=10,13,b=12,15 undc=12,55 Å, =108°40). Die Elementarzelle enthält 4 Moleküle C₂Cl₄O₂CO· SbCl₅. Das Antimonatom ist oktaedrisch von 5 Chloratomen und dem Carbonylsauerstoffatom des Tetrachloräthylencarbonats umgeben (Sb–Cl 2,28–2,33 und Sb–O 2,40 Å).

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The crystal structure of tetrachloroethylene carbonate antimony(V) chloride, C₂Cl₄O₂CO·SbCl₅

The crystal structure of the adduct tetrachloroethylene carbonate antimony(V)-chloride, C₂Cl₄O₂CO·SbCl₅, has been determined by the heavy-atom method from three-dimensional X-ray data. The refinement of the parameters was carried out by least-squares resulting anR-value of 13.1% (space group P2₁/n — No. 14;a=10.13,b=12.15 andc=12.55 Å, =108°40). The unit cell contains 4 discrete molecules C₂Cl₄O₂CO·SbCl₅. The antimony atom is coordinated octahedrally by 5 chlorine atoms and the carbonyl oxygen atom of tetrachloroethylene carbonate (Sb–Cl 2.28–2.33 and Sb–O 2.40 Å).

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Mit 2 Abbildungen     

Selective Hydrogenation of Diethyl Disulfide to Ethanethiol in the Presence of Sulfide Catalysts

The gas-phase reaction of diethyl disulfide hydrogenation at atmospheric pressure in the presence of supported transition metal sulfides was studied. The reaction of diethyl disulfide with hydrogen at T = 200°C resulted in ethanethiol, and the selectivity to ethanethiol was no lower than 94%. The selectivity decreased at a higher temperature because of diethyl disulfide decomposition to ethylene and hydrogen sulfide. The reaction of diethyl disulfide in the presence of hydrogen occurred at a higher rate and selectivity than that in an atmosphere of helium. The activity of metal sulfides supported on aluminum oxide was higher than on the other studied supports—aluminosilicate, silica gel, and a carbon support. Metal sulfides supported on Al₂O₃ were arranged in the following order according to their activity: Rh > Ru > Mo Pd > Ni > W. Bimetallic catalysts were less active than monometallic catalysts. The activity of catalysts increased with the sulfide sulfur content; the partial reduction of metal sulfides also increased the catalytic activity.     

Thermodynamic properties of crystalline polymeric C60 phases in the temperature region from O → 0 to 340 E

The temperature dependences of the heat capacity C _p° = f(T) were studied in an adiabatic vacuum calorimeter for the orthorhombic, tetragonal, and rhombohedral polymeric C₆₀ phases in the 7—340 K temperature interval with an error of 0.2%. Comparative analysis of C _p° of these phases formed by stacking of one-dimensional and two types of two-dimensional polyfullerenes C₆₀, was performed, and their fractal dimensionalities D were determined for temperatures below 50 K. The thermodynamic functions of the crystalline polymeric C₆₀ phases were calculated in the temperature region from O 0 to 340 K: C _p°(T), H°(T) — H°(0), S°(T) — S°(0), and G°(T) — H°(0). Assuming that S°(0) = 0, the standard entropies of formation _f S° of these phases from graphite at T = 298.15 K and standard pressure were calculated. In addition, the entropies of transformation of the initial face-centered cubic phase of fullerite C₆₀ in the crystalline polymeric C₆₀ phases and entropies of their interconversions under the same conditions were estimated. The thermodynamic characteristics of the polymeric C₆₀ phases were reviewed.     

Alkaloids ofRhinopetalum bucharicum. The structure of rhinolinine

The combined alkaloids of the epigeal part ofRhinopetalum bucharicum have yielded solanidine, rhinoline, imperialine, a base with mp 272–274°C, and the new alkaloid rhinolinine with mp 301–302°C (methanol), []_D — 36.5° (c 1.7, ethanol), C₄₀H₆₇NO₁₂. On the basis of a study of IR and NMR spectra, and also passage to the known alkaloids rhinoline and rhinolidine, the structure of rhinolidine 3-O-[O--D-glucopyranosyl-(14)--D-glucopyranoside] has been established for rhinolinine.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 350–353, May–June, 1979.     

Synthesis,crystal structure and magnetic properties of a two-dimensional mixed-valence assembly [Fe(salen)]2[Fe(CN)5NO]

A cyanide-bridged Fe^III–Fe^II mixed-valence assembly, [Fe^III(salen)]₂[Fe^II(CN)₅NO] [salen = N,N-ethylenebis(salicylideneiminato)dianion], prepared by slow diffusion of an aqueous solution of Na₂[Fe(CN)₅NO] · 2H₂O and a MeOH solution of [Fe(salen)NO₃] in an H tube, has been characterized by X-ray structure analysis, i.r. spectra and magnetic measurements. The product assumes a two-dimensional network structure consisting of pillow-like octanuclear [—Fe^II—CN—Fe^III—NC—]₄ units with dimensions: Fe^II—C = 1.942(7) Å, C—N = 1.139(9) Å, Fe^III—N = 2.173(6) Å, Fe^II—C—N = 178.0(6)°, Fe^III—N—C = 163.4(6)°. The Fe^II—N—O bond angle is linear (180.0°). The variable temperature magnetic susceptibility, measured in the 4.8–300 K range, indicates the presence of a weak intralayer antiferromagnetic interaction and gives an Fe^III–Fe^III exchange integral of –0.033 cm^–1.