Dinuclear chelates of acyclic and cyclic tridentate Schiff bases derived from sterically hindered o-aminophenols. A new type of reactivity of tridentate ligands under electrosynthesis conditions

The chemical and electrochemical synthesis of cobalt(II), nickel(II), and copper(II) complexes based on sterically hindered tridentate Schiff bases obtained by the coupling of 2-amino-4,6-di-tert-butylphenol with salicylaldehyde derivatives (H₂L, H₂L’) was performed. The resulting dinuclear complexes were characterized by elemental analysis, IR spectroscopy, and magnetochemical measurements in the 300–2 K temperature range. The structures of the dinuclear nickel(II) and copper(II) complexes with the composition Ni₂L₂·2AcOH·2MeOH and Cu₂L₂, respectively, were established by X-ray diffraction. The copper chelates are characterized by the presence of antiferromagnetic exchange interactions. The mononuclear copper(II) complexes (DMSO)bis[2-(5,7-di-tert-butyl-4-hydroxybenzoxazol-2-yl)phenolato]copper(II) and (DMF)₂bis[2-(5,7-di-tert-butyl-4-hydroxybenzoxazol-2-yl)phenolato]copper(II) were isolated upon electrochemical dissolution of copper(0) and were structurally characterized.     

Interval estimation of system reliability using a conditional distribution function of the number of failures

Interval estimators of the no-failure probability of a system are constructed from tests of system elements. The estimators are obtained using the conditional distribution function of the number of failures during the tests.Translated from Statisticheskie Metody Otsenivaniya i Proverki Gipotez, pp. 58–64, 1986.     

Formation of molecular π-complexes upon the mechanochemical reaction of the freshly formed surface of alkali halide crystals with some organic compounds

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, p. 2646, November, 1988.     

Analysis of Niobium–Rare-Earth Ores by Inductively Coupled Plasma Mass Spectrometry

To determine the composition of niobium–rare-earth ores by atomic emission spectrometry and inductively coupled plasma mass spectrometry, two procedures are developed for sample preparation based on autoclave decomposition and flux fusion. Autoclave decomposition is carried out in a mixture of HF and HNO₃ at a temperature of up to 220°C and a pressure of up to 160 atm using a developed system with resistive heating. Subsequent evaporation to dry salts ensures the removal of F^– ions and silicon as SiF₄. The residue is dissolved in a mixture of HCl and H₂O₂ at 160°C under elevated pressure. The resulting solutions (10% with respect to HCl with the addition of H₂O₂) are diluted before measurements. The dissolution process is monitored for each sample using stable highly enriched isotopes of ⁹¹Zr, ¹⁰⁰Mo, ¹⁴⁹Sm, and ¹⁷⁸Hf. The second procedure is based on fusing samples with a mixture of Na₂CO₃ and Na₂B₄O₇ at 1050°C in a muffle furnace and dissolving the resulting melt in a mixture of HCl and H₂O₂. The procedures were tested using the national (NFS-23) and foreign standard samples of composition (OREAS-462, 463, 464, 465, Australia) and real samples of niobium–rare-earth ores.     

Selective catalytic oxidation of ammonia to nitrogen

The activity of catalysts of different nature in ammonia partial oxidation has been studied. Vanadium-titanium, copper-titanium catalysts and copper-substituted zeolites are the most active in the reaction. These catalysts are promising if used as honeycomb monoliths.     

Gas chromatographic analysis of gas emissions containing impurities of hydrocyanic acid and carbon oxysulfide

Gas chromatography was used for studying the retention of HCN, COS, H₂S, H₂O, CO₂, CO, and H₂ on organic porous polymer sorbents Chromosorb-104 and Hayesep C either unmodified or modified with different amounts of H₃PO₄. The effect of water on the signal of the thermionic detector was studied, and the conditions of the determination of 6–23 ppm HCN in aqueous solutions were found: column (3 m × 2 mm) with Hayesep C containing 15 wt % H₃PO₄. A procedure was developed for the determination of 15–1000 ppm COS in the presence of high concentrations (up to 1 vol %) of H₂S on a column (3 m × 2 mm) packed with Chromosorb-104 modified with 0.5 wt % H₃PO₄ with a flame photometric detector (396 nm). A basic scheme was proposed for the gas chromatographic analysis of the products of the catalytic detoxication of gas emissions in the process of coal gasification.     

Synthesis of N-(indol-3-yl)-N′,N′-dialkylamidines by the vilsmeier reaction with 3-aminoindoles

3-Aminoindoles substituted at C-2 and C-5 of the indole ring are converted by the action of Vilsmeier complexes into N-(indol-3-yl)-N,N-dialkylamidines. When C-2 is unsubstituted, the formylation proceeds but not the acetylation of this position. N-(Indol-3-yl)-N,N-dimethylacetamidine reacts with the complex obtained from DMF and POCl₃ to give 2-dimethylamino-3-formyl--carboline. The optimal conditions were found for the conversion of amidines to amides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 76–81, January, 1985.     

Kinetic regulaties in oxidative dehydrogenation of butene-1 over V?Mg catalyst at various temperatures

Kinetic studies of nonsteady-state steps in oxidative dehydrogenation of butene-1 over a supported V-Mg catalyst were carried out at temperatures of 573–748 K. The kinetic data were used to perform a numerical simulation of changes in the catalyst activity under stepwise variation of the reaction temperature.

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-1 573–748 . .

     

Tautomerism and Stereodynamics of Indophenols,Amidines, and Their Derivatives and Analogs: XVI. Synthesis of Tetrahydroquinoxalines Having Spiro-Fused Oxoindole and Cyclohepta[c]furan Fragments

Alkylation of o-(N-sulfonylamino)phenylimino derivatives of indol-2-one and cyclohepta[c]furan with phenacyl bromides is accompanied by cyclization to previously unknown tetrahydroquinoxalines having spiro-fused oxoindole and cyclohepta[c]furan fragments. The structure of the latter includes a nitrogen-oxygen triangular system typical of most natural cytotoxic compounds.     

Zirconium sorption by chelating polymer sorbents with an <Emphasis Type="Italic">o</Emphasis>,<Emphasis Type="Italic">o</Emphasis>′-dihydroxyazo analytical functional group

The complexing properties of new chelating polymer sorbents (CPSs) with an o, o′-dihydroxyazo functionality and zirconium sorption on these sorbents were studied. Quantitative correlations were found between pK′_OH of the analytical functional groups (AFGs) of sorbents and the stability of chelates (logβ) in order to understand the lows governing the effect of the structural features and acid-base properties of the AFGs on zirconium chemisorption parameters. These correlations make it possible to quantitatively predict the physicochemical parameters of sorbents and their chelates, synthesize them, and use CPSs for zirconium preconcentration in analyses of natural and industrial objects.