NMR studies of heteropolyanion [P(2)W(20)O(70)(H2O)2](-10) complexes with metal cations

We have used multinuclear NMR and IR spectroscopy to study the interaction of a number of metal cations with monovacant heteropolyanion [P(2)W(20)O(7)(0)(H(2)O)(2)](10)(-) (P(2)W(20)) in aqueous solutions starting from its K salt. We have also prepared and studied P(2)W(20) in an Na-only medium. The observed differences in the NMR spectra of NaP(2)W(20)and KP(2)W(20)solutions and the importance of K(+) and Na(+) for the formation of P(2)W(20) suggest that this polyanion exists only as a complex with the alkaline cations. When both cations were simultaneously present in solution, we observed the broadening of the NMR signals of P(2)W(20)due to the Na-K exchange. Li(+) does not replace K(+) or Na(+) in such complexes, and in an Li-only medium P(2)W(20) does not form. Of all the M(n)(+) cations studied (Pd(2+), Bi(3+), Sn(4+), Zr(4+), Ce(4+), Ti(4+), V(5+), and Mo(6+)) only Bi(3+), Sn(4+), and Ce(4+) form complexes with P(2)W(20) in strongly acidic solutions. The (183)W and (119)Sn NMR data suggest that Sn(4+) forms in solution two mutually interconvertable P(2)W(20)Sn complexes of the composition P(2)W(20)O(70)(H(2)O)(3)SnOH(7)(-) and (P(2)W(20)O(70)(H(2)O)(3)Sn)(2)O(14)(-) while Bi(3+) forms one complex of the proposed composition P(2)W(20)O(70)(H(2)O)(2)Bi.(7)(-) We obtained complexes with Bi and Sn as free heteropoly acids and studied their thermostability in the solid state.     

Influence of silica on the properties of evaporated V?Mo oxide catalysts

According to⁵¹V-NMR studies of the state of vanadium ions in parent solutions and in catalysts, evaporated V–Mo oxide catalysts are shown to be more active and selective in acrolein oxidation to acrylic acid than unsupported samples.

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Novel azetidinones for carbapenems and fragmentation in the allylamine precursor analogue

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Titanium-Substituted Heteropolytungstates as Model Catalysts for Studying the Mechanisms of Selective Oxidation by Hydrogen Peroxide

The ³¹P NMR method shows that four forms of titanium(IV)-monosubstituted Keggin-type heteropolytungstate (Ti–HPA) exist in MeCN: the dimer (Bu₄N)₇[{PTiW₁₁O₃₉}₂OH] (in the abbreviated form, (PW₁₁Ti)₂OH or H1), its conjugate base (PW₁₁Ti)₂O (1), and two monomers, PW₁₁TiO (2) and PW₁₁TiOH (H2). The ratio between the forms depends on the concentrations of H⁺and H₂O. Dimer H1is produced from 2in MeCN when H⁺(1.5 mol) is added, and monomer H2is the key intermediate in this process. The catalytic activity of Ti–HPA in the oxidation of thioethers by H₂O₂correlates with their activity in peroxo complex formation and decreases in the order H2> H1> 2. The reaction of 2with H₂O₂in MeCN occurs slowly to form the inactive peroxo complex PW₁₁TiO₂(A). The addition of H₂O₂to H1and H2most likely results in the formation of the active hydroperoxo complex PW₁₁TiOOH (B). Complexes Aand Btransform into each other when H⁺or OH^–(1 mol) is added per 1 mol of Aor B, respectively. The activity of Btoward thioethers in the stoichiometric reaction is proven by ³¹PNMR and optical spectroscopy.     

Rheology behavior of nematic side-chain polymers in blends with thermoplasts

Peculiarities of the rheological behavior of blends composed of thermoplasts and side-chain nematic polymers have been studied. The strong role of interface interactions associated with the polymer chemical structure on the effect of rheology is shown. The influence of the nematic ordering is shown to be effective in the mechanical characteristics of blend extrudates whereas the rheology effect does not depend on the liquid crystal ordering.     

Activity of tungstate catalysts in the synthesis of metylmercaptane from methanol and hydrogen sulfide

Catalysis obtained by impregnation of Al₂O₃ with solutions of hepta-, dodeca-, meta- and normal alkaline metal tungstates showed approximately the same activity. Most selective towards methylmercaptane were catalysts with an alkaline metal to tungsten atomic ratio equal to 21.

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, Al₂O₃ -, -, -, . , : 21.

     

The heat capacities and thermodynamic functions of some derivatives of ferrocene

The heat capacities of benzoylferrocene (BOF), C₅H₅FeC₅H₄COC₆H₅, and benzylferrocene (BF), C₅H₅FeC₅H₄CH₂C₆H₅, have been measured by the low-temperature adiabatic calorimetry in the temperature range from 6 K to 372 K. The purity benzylferrocene and thermodynamic properties – the triple point temperature and the enthalpy of fusion have been obtained. The ideal gas thermodynamic functions (changes of the entropy, enthalpy, and Gibbs free energy) of BOF and BF were derived at T = 298.15 K using the heat capacities and previously determined data on the saturation vapours pressures and the enthalpies of sublimation. The ideal gas enthalpy of formation and absolute entropy of BOF at T = 298.15 K have been obtained from quantum chemical calculations, where as the thermodynamic properties of BF have been estimated by empirical method of group equations. A good agreement between experimental and theoretical values provides an additional check of the reliability of the experimental data.     

Direct EPR Detection of Nitric Oxide in Mice Infected with the Pathogenic Mycobacterium Mycobacterium tuberculosis

It has been shown that treatment of mice preinfected with Mycobacterium tuberculosis with spin NO traps (iron complexes with diethyldithiocarbamate) enables detection of large amounts of NO in internal organs 2 and 4 weeks after infection (up to 55–57 μmol/kg of wet lung tissue accumulated with spin NO traps during 30 min). The animals were infected with the drug-sensitive laboratory strain H37Rv and a clinical isolate nonrespondent to antituberculous drugs (the multidrug-resistant strain of M. tuberculosis) obtained from a patient with an active form of tuberculosis. Two weeks after infection with the multidrug-resistant strain, the NO level in the lungs, spleen, liver and kidney increased sharply concurrently with slight lesions of lung tissue. A reverse correlation, i.e., low level of NO in the lungs and other internal organs and extensive injury of lung tissue, was established for H37Rv-infected mice. Four weeks after infection, NO production in the lungs increased dramatically for both M. tuberculosis strains resulting in 80–84% damage of lung tissue. The lesion is suggested to be due to the development of defense mechanisms in M. tuberculosis counteracting NO effects.     

A new method for the synthesis of trifluoromethylating agents—Diaryltrifluoromethylsulfonium salts

A new synthetic method has been developed to prepare diaryltrifluoromethylsulfonium salts from diaryldifluorosulfuranes by the action of Me₃SiCF₃/F⁻. This reaction is the transformation of nucleophilic trifluoro-methylating reagent into electrophilic one.     

Acylation of Phosphorus Substituted Ch-Acids Under Phase Transfer Catalysis Conditions

Abstract.

Acylation of phosphoryl- and thiophosphoryl acetonitriles under phase transfer catalysis (PTC) conditions leads in high yields to C-acylated products existing as Z-isomers of the corresponding enol forms. They are stabilized by strong intramolecular H-bonds. On the contrary, acylation of phosphorylacetone proceeds mainly at the oxygene atom and gives Z and E enolacetate. Phosphorus trichloride was used as an acylating agent under PTC conditions. S-Alkyldichlorophosphites were obtained by the reaction with mercaptanes. Alcohols react with PCl₃ in the presence of sodium carbonate to result in dialkylphosphites.