Novel dioximato-bridged chromium(III)-copper(II)-chromium(III) trinuclear complexes with ferromagnetic exchange interactions

Summary Two new dioximato-bridged trinuclear Cr^II-Cu^II-Cr^III complexes, [Cr(salen)-Cu(-BD)₂-Cr(salen)] (1) and [Cr(salen)-Cu(-FD)₂-Cr(salen)]-H₂O (2), have been prepared and characterized [salen^2– = N,N-ethylene- bis (salicylideneiminate), (-BD)^2– = -benzyldioximato and (-FD)^2– = -furildioximato]. Magnetic susceptibility measurements in the 4.2–300 K range demonstrated the operation of a ferromagnetic interaction between the adjacent Cr^III and Cu^II ions through oximato bridges in both (1) and (2). Based on spin Hamiltonians =–2J(₁₂+₂₃)(S₁=S₃=3/2,S₂=1/2) the exchange integrals (J) were evaluated as 3.19 and 5.38 cm^–1 for (1) and (2), respectively.     

Dehydration of lithium triphosphate pentahydrate,Li5P3O10· 5H2O

The kinetics of isothermal-isobaric dehydration of Li₅P₃O₁₀·5H₂O in vacuum (p=10^–1 hPa) and in water vapour atmosphere ( =23·hPa) was investigated by TG in the temperature range 40–140°. It was shown that the initial non-degradation removal of 1/10 of the crystal water, the rate of which is sensitive to , proceeds according to the laws of reversible topochemical reactions. In the next, irreversible degradation stage, where the bulk of the crystal water is removed, the kinetic characteristics of the process and the DSC effects exhibit a low sensitivity to the water vapour pressure. The peculiarities of Li₅P₃O₁₀·5H₂O dehydration were considered in comparison with the thermal behaviour of Na₅P₃O₁₀·6H₂O and K₅P₃O₁₀·4H₂O.

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Zusammenfassung Die Kinetik der isotherm-isobaren Dehydratisierung von Li₅P₃O₁₀·5H₂O in Vakuum (p=10^–4 hPa) und in Wasserdampfatmosphäre ( =23 hPa) wurde durch TG im Temperaturbereich von 40–140° untersucht. Es wurde gezeigt, daß die anfängliche, noch keine Zersetzung zur Folge habende Eliminierung von 1/10 des Kristallwassers, deren Geschwindigkeit von abhängt, nach den Gesetzen der reversiblen topochemischen Reaktionen abläuft. Im nächsten irreversiblen Zersetzungsschritt, in dem die Hauptmenge des Kristallwassers austritt, sind die kinetischen Kennwerte des Prozesses und die DSC-Effekte nur wenig vom Wasserdampfdruck abhängig. Die Besonderheiten der Dehydratisierung von Li₅P₃O₁₀·5H₂O werden im Vergleich mit dem thermischen Verhalten von Na₅P₃O₁₀·6H₂O und K₅P₃O₁₀·4H₂O erörtert.

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40–140° - Li₅P₃O₁₀ · 5₂ (=10^–4 ) (=23 ). , 1/10 , . , - . L₅₃₁₀·5₂ Na₅P₃O₁₀·6H₂O K₅₃₁₀·4₂.

     

Interaction of tribenzyltitanium with butadiene

It has been established that the interaction of (C₆H₅CH₂)₃Ti with butadiene does not change the parameters of ESR spectra. Only the hydrodynamic radius of this complex increases.

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, (C₆H₅CH₂)₃Ti . .

     

m-Xylene conversion over dealuminated Y zeolites studied by the pulse method

m-Xylene conversion was studied over dealuminated Y type zeolites in hydrogen forms, SiO₂ to Al₂O₃ ratios were varied from 4.86 to 12.95.

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- . SiO₂/Al₂O₃ 4,86 12,95.

     

Effect of acid-base properties of oxide catalysts in the oxidative dehydrodimerization of olefins

The dependence of the activity of tin-containing oxide catalysts on their basicity and acidity has been examined. The rate of oxidative dehydrodimerization of olefins is shown to be determined by the mobility of allyl compounds depending on the catalyst acid properties.

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. , , .

     

Synthesis and magnetic properties of copper(II)-MII-copper(II) trinuclear complexes with N,N′-bis(2-aminoethyl)oxamidocopper(II) [M = Co and Ni]

Summary Two novel trinuclear complexes were prepared, namely [Cu₂(oxae)₂(H₂O)₂M] (ClO₄)₂, [oxae = N,N-bis(2-aminoethyl) oxamido dianion; M = Co and Ni]. Based on elemental analyses, conductivity measurements and i.r. spectra, the complexes are proposed to have extended oxamidobridged structures. The magnetic susceptibility of [Cu₂-(oxae) ₂(H₂O)₂Co](ClO₄)₂ were measured over the 4–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian, =–2J(₁·₂·₂·₃). The exchange integral, J, was found to be equal to –29.2 cm^–1, indicating an antiferromagnetic spin-exchange interaction between the adjacent metal ions.     

Glass transition and crystallization effects demonstrated by thermal analysis of liquid-quenched ternary glasses Te80Ge20−xA x V (AV=Sb,Bi)

In DSC studies of liquid-quenched ternary chalcogenide glasses Te₈₀Ge_20–xA _x ^V (A^V=Sb, Bi), the characteristic temperatures (glass transition and crystallization temperatures) were determined. Changes in the thermal stabilities of these glasses, depending on the element A (Sb, Bi) from group V of the periodic table and on its content in the alloy were evaluated. Moreover, the effect of changes in the glass composition on the glass formation ability expressed by the parameter K_g1 was determined.

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Zusammenfassung In DSC-Untersuchungen abgeschreckter ternärer Chalkogenidgläser des Typs Te₈₀Ge_20–xA _x ^v (A^x=Sb, Bi) wurden die charakteristischen Temperaturen (die GlasÜbergangs- und Kristallisationstemperaturen) bestimmt. Die Änderungen der Thermostabilität dieser Gläser wurden in Abhängigkeit von dem Element A (=Sb, Bi) aus der V Gruppe der Periodensystems und von seinem Gehalt in der Legierung ausgewertet. Ausserdem wurde der Einfluß der Änderungen in der Glaszusammensetzung auf die Glasbildungsfähigkeit, ausgedrückt durch den Parameter K_g1, bestimmt.

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Résumé On a déterminé par analyse calorimétrique différentielle (DSC) les températures caractéristiques (températures de transition vitreuse et de cristallisation), des verres ternaires à chalcogénures formés par trempe à partir du liquide, du type Te₈₀Ge_20–xA _x ^v (A^v=Sb, Bi). On a évalué la variation de la stabilité thermique de ces verres en fonction de l'élément A (=Sb, Bi) du Vème groupe du tableau périodique et de sa teneur dans l'alliage. De plus, on a déterminé l'effet des variations de la composition du verre sur la capacité de formation du verre qui s'exprime par le paramètreK _g1.

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Te₈₀Ge_20–xA _x ^v (A^v=Sb, Bi), , . A(=Sb,Bi) . , K _gl, .

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Research supported by the U. S. National Science Foundation under Grant No. GF 421 76     

Effect of vanadium content on the character of acidic sites on V2O5/Al2O3 catalysts

By IR spectroscopy and TPD the effect of vanadium content on the relative proportion of strongly acidic sites of V₂O₅/Al₂O₃ catalyst was studied.

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- - V₂O₅/Al₂O₃.

     

Synthesis of dimethyl sulfide in the presence of zeolites

In the presence of zeolites, dimethyl sulfide is produced either through CH₃OH interaction with H₂S or via CH₃SH decomposition. In accordance with their activities, in both reactions, zeolites arrange in the same sequence: HZSMHNaY>NaXNaY. Realization of the reaction CH₃OH+H₂S is more difficult compared to methanethiol decomposition.

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CH₃OH H₂S CH₃SH. : HZSMHNaY>NaXNaY. CH₃OH+H₂S , .

     

Magnetic properties of new copper(II) and [copper(II)]3-manganese(II) complexes of [14]N4 macrocyclic oxamides

Four new complexes of [14]N4 macrocyclic oxamides, namely [CuL1], [CuL2], [(CuL1)3Mn](ClO4)3 and [(CuL2)3 Mn](ClO4)3 [L1 and L2 are the dianions of 2,3-dioxo-5,6: 3,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene (H2L1) and 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclo-tetradeca-7,11-diene (H2L2), respectively], have been prepared and characterized. The observed magnetic susceptibilities of the [(CuL1)3Mn] (ClO4)3 complex over the ca. 2–300 K range have been fitted to theoretical equations based on the Heisenberg spin Hamiltonian =–2JMn(Cu1+ Cu2+Cu3) and molecular field approximation. The results indicated that both the intramolecular and intermolecular magnetic interactions are antiferromagnetic with JCuMn= –19.8cm–1 and zJ=–1.41cm–1.     

Mechanism of isotope exchange of dihydrogen with liquid water catalyzed by hydroxide ions

In the analysis of the reaction between dissolving hydrogen and aqueous alkali hydroxide solutions the interaction of hydrogen with the molecular ion (H₃O₂)^– should be studied. This interaction is analyzed by the interacting bonds method. The activation energy (E_a) is estimated.

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, (H₃O₂)^–. . (E_a).

     

Analysis of thermal desorption spectra of oxygen desorbed from rhodium

Thermal desorption spectra of oxygen desorbed from rhodium have been analyzed in terms of models accounting for the effect of lateral interactions between adsorbed particles and of their diffusion into the bulk of metal on the desorption kinetics of O₂. Complex configuration of these spectra is ascribed to the processes of formation/decomposition of surface Rh oxides and the diffusion of particles into the near-surface layers of metal and back to the surface.

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- , O₂ . - O₂ Rh - .

     

Hydrocarbon hydrogenolysis on nickel-tin catalysts

Hydrogenolysis of ethane, n-hexane and cyclohexane has been studied on nickel-kieselguhr catalysts modified by organic and inorganic compounds of tin. Tin additives decrease nickel reactivity with respect to C–C dissociation, which is ascribed to the formation of surface intermetallides on the catalyst.

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, - - , . . C–C .

     

Catalytic desulfurization of ethanethiol over zinc-forms of NaX zeolites

Zinc exchanged zeolite X was found to catalyze effectively the dehydrosulfurization of ethanethiol. The catalytic activity correlated linearly with the degree of ion exchange and increased with the reaction temperature. The role of zinc cations in the reaction examined is discussed and suggestions concerning the reaction mechanism are put forward.

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X, Zn, . . .

     

Interaction between peroxyl radicals of polyatomic esters and aromatic nitrons

Reactivity and rate constants in reactions between peroxyl radicals of ethylene glycol diacetate and aromatic nitrons have been investigated.

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.

     

Molybdenum hexacarbonyl catalyzed photooxygenation of cyclohexane by air dioxygen in acetonitrile solution

ESR and XPS investigations on Cu/–Al₂O₃ catalysts with various amounts of Cu loading are reported. Experimental data are related to the surface structure and dispersed state of catalysts. The results show that ESR can be used as a means of charaterizing monolayer dispersed state for paramagnetic supported catalysts.

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Cu/–Al₂O₃ . . .

     

Kinetics of triphenylphosphite ozonide consumption in reaction with triphenylphosphite

Kinetic regularities of triphenylphosphite ozonide reaction with triphenylphosphite have been studied at T=–75°C to –40°C. The rate of ozonide consumption is estimated as W=k₁[(C₆H₅O)₃P·O₃]+k₂[(C₆H₅O)₃P·O₃][(C₆H₅O)₃P], where k₁=(2.03±0.39)×10^–5s^–1(–50°C), 1gk₂=(3.82±0.33)–(6.61±0.32)/gq dm³/mol s and =2.303RT kcal/mol.

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–75°C –40°C . : W=k₁[(C₆H₅O)₃P·O₃]+k₂[(C₆H₅O)₃P·O₃][(C₆H₅O)₃P], k₁=(2,03±0,39)·10^–5–1(–50°C); 1g k₂=(3,82±0,33)–(6,61±0,32)/ /·, =2,303·RT /

     

Effect of medium composition on the monooxygenase activity of immobilized hemin in aniline oxidation

The effect of the composition of the reaction medium on the rate of aniline oxidation to p-aminophenol by hydrogen peroxide on hemin immobilized on -propylimidazole-modified silica has been studied. Organic solvent additives (alcohols, esters and nitriles) are shown to increase the reaction rate. The observed effect is attributed to the decrease of the medium dielectric constant.

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- , , --. , (, , ) . .