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  • 1
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3-Dithienium and 1,3-Dithiolenium Salts. IX. Reactions of 1,3-Dithiane-2-ylium Tetrafluoroborates with C-Nucleophiles1,3-Dithian-2-ylium tetrafluoroborates (1), which can be easily obtained by variable methods, react in good to excellent yields with variable C-nucleophiles to new geminal disubstituted 1,3-dithianes. The latter compounds are potential precursors of interesting synthetic building blocks. Reactions are described with 2-lithio-1,3-dithianes 2, sodium cyanide 4, sodium salts of the nitro alkanes 7 and CH-acids of the type of the 1,3-dicarbonyl compounds 9. The reduction of 3-oxo-2-(2-phenyl-1,3-dithian-2-yl)-ethoxybutanoat-following a diastereoselective pathway - leads to the Cram product 11. Further presented is the crystal structure of 2-phenyl-1,3-dithiane-2-ylium tetrafluoroborate (1b).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Crystal structure ; hydrates of ternary alkali/lanthanide(III) chlorides ; preparation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Rb3LnCl6 · 2 H2O (Ln = La—Nd): Preparation, Crystal Structure, and Thermal BehaviourThe compounds Rb3LnCl6 · 2 H2O (Ln = La—Nd) were prepared from acetic acid as powders. The preparation from aqueous solutions does not yield the pure products because RbCl precipitates as first compound. The structure of Rb3LaCl6 · 2 H2O was determined by X-ray analysis of a single crystal obtained from aqueous solution. The compounds with Ln = La—Nd are isotypic. They crystallize hexagonally in the space group P63/m (Rb3LaCl6 · 2 H2O: a = 1 220.4(2) pm, c = 1 688.6(3) (pm) with Z = 6. Anionic trimeric units [Ln3Cl12(H2O)6]3- are stacked along the c-axis over the corners of the unit cell. In the stacking frequency the units are rotated by 60° with respect to each other around the c-axis. The coordination number (C. N.) of Ln3+ is 8, which is satisfied by four bridging and two terminal chloride ions and two water molecules. The coordination spheres of the three rubidium ions in the different atomic positions are composed differently, their C.N. are 9, 8(+1) and 6(+6). The thermal dehydration of the compounds occurs in one step. The hydrates decompose at ca. 100°C to form the anhydrous compounds Rb2LnCl5 und RbCl since the anhydrous chlorides Rb3LnCl6 are thermodynamically stable above ca. 400°C only.
    Notes: Verbindungen Rb3LnCl6 · 2 H2O (Ln = La—Nd) lassen sich feinkristallin aus Eisessig als Lösungsmittel darstellen. Aus wäßriger Lösung lassen sich Einkristalle im Gemisch mit RbCl erhalten. An einem Einkristall von Rb3LaCl6 · 2 H2O wurde eine Strukturanalyse durchgeführt: Raumgruppe P63/m. a = 1 220,4(2) pm, c = 1 688,6(3) pm, Z = 6). Als anionische Teilstruktur liegen trimere Einheiten [Ln3Cl12(H2O)6]3- vor, die entlang der c-Achse über den Ecken der hexagonalen Elementarzelle gestapelt sind. In der Stapelfolge sind die Einheiten um jeweils 60° zueinander verdreht. Die Koordinationszahl (C. N.) des Ln3+ ist 8 und setzt sich aus vier verbrückenden und zwei terminalen Chloridionen sowie zwei Wassermolekülen zusammen. Die C.N. der drei Rubidiumionen auf nicht symmetrieäquivalenten Lagen betragen 9, 8(+1) und 6(+6). Die thermische Entwässerung der Verbindungen erfolgt in einem Schritt bei ca. 100°C unter Zerfall in Rb2LnCl5 und RbCl, da die wasserfreien 3:1 Verbindungen Rb3LnCl6 erst ab ca. 400°C stabil sind.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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