N2O decomposition over Fe/ZSM-5: reversible generation of highly active cationic Fe species

Fe-oxide species in Fe/ZSM-5 (prepared by chemical vapor deposition of FeCl3)--active in N2O decomposition--react with zeolite protons during high temperature calcination to give highly active cationic Fe species, this transformation being reversible upon exposure to water vapor at lower temperature.     

Palladium hydrogenation catalysts modified with aluminum-and phosphorus-containing compounds and with alcohols: Effect of modifiers

The catalytic properties of nanosize catalysts derived from Pd(acac)₂ and triethylaluminum in hydrogenation of organic substrates were studied, and the optimal conditions for the catalyst preparation were found. The maximum observed on the plot of the catalyst specific activity vs. Al/Pd ratio was explained by experiments.     

Molecular and crystal structures of hemigossypolone and gossypolone

The results are given of an x-ray structural investigation of hemigossypolone isolated from the stems of a wiltinfected cotton plant and of gossypolone obtained by oxidizing gossypol.     

Syntheses and structures of structurally diverse potassium beta-diketiminates derived from the ligand [(N(SiMe3)C(Ph))2CH

The compounds [K((mu-N(SiMe3)C(Ph))2CH)(thf)2]infinity 1, [K(mu-N(SiMe3)C(Ph)C(H)C(Ph)NH)L]2 [L = (thf)2 2, tmen 3], [K(mu-NSi(Me)2C(Ph)C(H)C(Ph)N)(thf)3]2 4 and [K(N(H)C(Ph))2CH](thf)0.5 5 have been prepared from K[(N(SiMe3)C(Ph))2CH] and the X-ray structures of 1-4 are reported.     

Cure kinetics of a cobalt catalysed dicyanate ester monomer in air and argon atmospheres from DSC data

A kinetic analysis of the cyclotrimerisation reaction of a dicyanate ester monomer catalysed by cobalt(II) acetylacetonate and nonylphenol in air and argon atmospheres has been carried out by differential scanning calorimetry (DSC). Dynamic and isothermal DSC scans as well as the glass transition temperature are the experimental data obtained. From isothermal scans a higher cyanate conversion in air than in argon was obtained. The cyanate conversions are satisfactorily described with a second-order kinetic equation in the kinetically controlled region, and by m-order (m<1) equation after vitrification is reached. Activation energies determined by different procedures agree among them, showing slightly higher values in argon than in air.     

Coordination of N-Substituted Porphyrins with Simple and Chelate Zinc Salts in DMSO

The effect of peripheral substitution in the porphyrin macrocycle (₂OEtP, H₂TPP) of the nature of the N-substituent (X = Me, Ph) and of the anion in the salt solvate (A = ^–, NO₃ ^–, ^–) on the complexation of the N-substituted porphyrins with zinc salts in DMSO is studied. The positions of the bands in the electronic absorption spectrum of the (A)M(N-X)P metal complex were found to depend only slightly on the nature of the A anion in the composition of the coordination sphere of the complex. An inhibition of coordination of the N-substituted ₂TPP derivatives by zinc nitrate was discovered that is not typical of porphyrins proper. The type of hybridization of the substituted nitrogen atom in the porphyrin molecule is discussed. A mixed type of hybridization is suggested: the sp ²- and p ³-forms in the ligands and an almost complete transition to the p ³ form in the N-substituted metal complexes.     

A methodology for synthesis of primary o-phenylenebisphosphines and o-chlorophenylphosphines

On the basis of the reaction of ethynediylbisphosphonates and chloroethynylphosphonates with classical donor alka-1,3-dienes, a general strategy for synthesis of o-bisphosphanylbenzenes and o-chlorophosphanylbenzenes, which includes two consecutive steps: Diels-Alder condensation → aromatization of the carbocyclic phosphonate (bisphosphonate) formed → reduction of the phosphonate groups, was developed. Convenient procedures are devised for aromatization of phosphorus-containing cyclohexa-1,4-dienes and for reduction of o-phenylenebisphosphonates and o-clorophenylphosphonates to primary phosphines. A series of new alkylsubstituted phosphonic chlorides were prepared, and a possibility of functionalization of methylsubstituted o-phenylenebisphosphonates and o-clorophenylphosphonates by the methyl groups is demonstrated.     

Phytoecdysteroids of plants of the genusSilene XIV. Brahuisterone fromSilene brahuica

A new ecdysteroid with the composition C₂₇H₄₄O₆ which has been called brahuisterone has been isolated from the epigeal part of the plantSilene brahuica Boiss. Its chemical and complete spatial structures have been established by spectral studies and the x-ray structural method (diffractometer, Cu-K radiations, 996 reflections, direct method, R=0.119).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbekistan Republic, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 553–558, July–August, 1993.     

Structure and reactivity of benzothiazole-2-thione polysulfides

A quantum-chemical study was made of the possibility of the formation of polysulfides from benzothiazole-2-thione and their structure. The reactivity indices of the benzothiazole-2-thione molecule and of the small sulfur fragments were calculated. It was shown that as the fragments approach each other the formation of polysulfide structures with increased reactivity becomes possible.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 1, pp. 73–78, January–February, 1990.