Synthesis and thermal decomposition of cobalt-containing oligosilanes

Oligo(phenylcobaltcarbonylsilane) was prepared from oligo(phenylsilane) and dicobalt octacarbonyl. The reaction proceeds with elimination of H₂ and CO and insertion of cobalt carbonyl fragments into the silicone backbone of oligosilane. Oligosilane containing cobalt carbonyl groups in side organic substituents was obtained from oligolmethyl(phenylethynyl)Isilane and CO₂(CO)₈. The reaction of 1,2-bis(phenylethyny1)tetramethyldisilane with Co₂(CO)₈ proceeds with the sequential attachment of cobalt carbonyl fragments to ethynyl groups to form disilane derivatives [²-CCPhCo₂(CO)₆] Thermal decomposition of cobalt-containing oligosilanes affords a mixture of paramagnets and ferromagnets.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 10, pp. 2561–2567, October, 1996.     

Triterpene saponins fromThalictrum minus. V. Structure of thalicoside B

The epigeal part ofThalictrum minus L. has yielded a new bidesmoside — thalicoside B — which has the structure of oleanolic acid 28-O-β-D-glucopyranoside 3-O-[O-α-L-rhamnopyranosyl-(1 → 2)-O-β-D-glucopyranosyl-(1 → 3)-α-L-arabinopyranoside].     

Extraction of Aromatic Hydrocarbons from Hydrofined Diesel Fraction with 2-Methoxyethanol in the Presence of Pentane

Five-step countercurrent extraction of aromatic hydrocarbons from hydrofined diesel fraction with the 2-methoxyethanol-water-pentane extraction system was studied. The process was performed on a rotary-disk extractor.     

Observation of the decaya 2 − (1320)→π − η′

The reaction ^– C ^– C has been studied at 36 GeV/c. A clear signal for the decaya ₂ ^– (1320) ^– · is observed in the ^– mass spectrum. The measured ratio of branchings is BR (a ₂ ^{– –} )/BR(a ₂ ^{– –} );(3.4±0.8±0.5)·10^–2.     

Organosilicon Amidophosphates and Their Eu and Er Complexes in Solutions and Films: Spectral and Luminescence Properties

Fluorescence and fluorescence excitation spectra of phosphorus-containing organosilicon ligands O = PX₂NHR (X = NMe₂, OPh; R = CH₂CH₂CH₂Si(Oet)₃ and their Eu(III) complexes in acetonitrile solutions and in films are studied. In UV region (285–420 nm), bis(dimethylamido)triethoxysilylpropylamidophosphate (X = NMe₂) and diphenyltriethoxysilylpropylamidophosphate (X = OPh) exhibit two emission bands, whose position and intensity depend on the nature of substituents at the phosphorus atom. The Eu complexes show the ligand and the cation luminescence. The emission bands of coordinated ligands are shifted to long-wave region. The cation luminescence appears as three or four bands due to f-f transitions from the excited ⁵ D ₀ level to the lower ⁷ F _1–4 levels. The most intense transition is ⁵ D ₀ → ⁷ F ₂. The emission band in a region of 420 nm appears in solutions and films prepared from both pure ligands and their Eu(III) complexes. This band is due to luminescence of spatially crosslinked nanoparticles of sesquioxane structure. The intensity ratio of the Eu³⁺ emission bands changes when going from solutions to films, the emission intensity increases in a range of 420 nm. Films containing incorporated Er complexes with amidophosphates show intense luminescence of a matrix at 430 nm and a series of weak narrow bands due to the Er³⁺ cation at 550–700 nm.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 550–558.Original Russian Text Copyright © 2005 by Semenov, Cherepennikova, Klapshina, B. Bushuk, S. Bushuk, Douglas.     

Structural features of diastereomeric oxazolidin-2-ones

Model diastereomeric oxazolidinones containing various substituents at positions 3 and 5 were synthesized. Several individual diastereomers bearing methyl groups at positions 4 and 5 in cis-and trans orientations were isolated. The TLC and ¹H NMR spectroscopic data suggest that diastereomers, particularly those containing the aryl substituent at position 5, are substantially different in the physical and spectral properties. The configurations of some diastereomers were established by X-ray diffraction and NOESY spectroscopy. For these compounds, the reliable assignment of the characteristic ¹H NMR signals of individual groups was made, which provided evidence for the cis or trans orientation of the methyl groups at positions 4 and 5. The scope of the method as applied to the determination of the cis and trans isomers from their ¹H NMR spectra is discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 133–139, January, 2007.     

Forms of iron occurrence in a series of binary tellurides Fe<Subscript>x</Subscript>Ti<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>1.45</Subscript>

Nonstoichiometric tellurides Fe_xTi_1–x Te_1.45 synthesized at 850°C were studied by X-ray phase and X-ray fluorescence analysis and by ⁵⁷Fe Mössbauer spectroscopy. The mutual iron-titanium substitution is limited in this series. The system contains four individual phases in which iron is in three different states: Fe²⁺ in an asymmetric environment, Fe²⁺ in a symmetric environment, and Fe⁰. The distribution of various iron states in the system depends not only on the Fe : Ti ratio, but also on the structure of phases.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1761–1764.Original Russian Text Copyright © 2004 by Pankratova, Zabolotnaya, Panchuk, Semenov, Zvinchuk, Suvorov.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis and thermal transformations of polyphosphosiloxane based on trimethyl phosphate and (3-aminopropyl)triethoxysilane

A method for the synthesis of polyphosphosiloxane by the thermal condensation of an equimolar mixture of trimethyl phosphate and (3-aminopropyl)triethoxysilane at 200 °C was developed. The reaction affords ethanol and polyphosphosiloxane-{Si(OEt)[(CH₂)₃NR¹R²]-O-P(O)(OMe)-O}_n-(R¹ = H, Me; R² = Me), whose composition and structure were confirmed by ¹H, ¹³C, and ³¹P NMR spectroscopy, IR spectroscopy, and elemental analysis. The scheme of polymerization involving the intermediate formation of methyl-and dimethylphosphoric acids and their condensation with ethoxysilanes was proposed. The calcination of the obtained polyphosphosiloxane in vacuo at 350 °C results in the elimination of the amino groups and alkoxide substituents, and a spatially cross-linked polymer is formed as an amorphous powder. Its further thermolysis at 600 and 1000 °C gives crystalline phosphosilicates Si₅O(PO₄)₆ or SiP₂O₇. Their amorphous and crystalline samples were characterized by IR spectroscopy, X-ray diffraction analysis, and solid-state ¹³C and ³¹P spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2138–2148, November, 2007.     

Chemical structure characteristics of lignins and their sorption capacity towards 4,15-diacetoxy-8-(3-methylbutyryloxy)-12,13-epoxytrichothecen-3-ol

Russian Chemical Bulletin - Chemical structure aspects of the lignins derived from various plants were investigated, and their adsorption capacity towards...