Eingegangen a m 25. Marz 1974 In den NQR-Spektren von polykristallinem (CH3)3SiOReq und (CH,)jGeOReO, wurden alle erwarteten Frequenzubergange q(+ fund *87Re aufgefunden und zur Bestimmung der Quadrupol-Kopplungskonstanten und des Asymmetrieparameters ausgewertet. Die erhaltenen g r o k n Werte fur eZqQ/h und q weisen eine direkte kovalente Bindung der metallorganischen Reste mit dem Perrhenat-Ion nach. Die Elementarzellen der Kristalle enthalten alle Re-Atome in iiquivalenten Positionen.
IESRe-and 187Re-NQR-Investigations of Trimethylsilyl and Trimethjrlgermanyl PerrbenateAll transitions YI (& t f ) and v2 (* f G? f 5 ) required by theory have been detected in the NQR spectra of (CH3)3SiOReO, and (CHj),GeOReO3 for l*5Re and I87Renuclei. These results have been evaluated to yield quadrupole coupling constants and asymmetry parameters q. The data obtained are evidence for true covalent bonding between the organometallic groups and the perrhenate anion. The unit cells of the crystals contain all Re nuclei at equivalent sites.
Die physikalischen und chemischen Eigenschaften von hochtemperaturhydrolytisch hergestellten Kieselsauren und Metalloxiden (A1,0, C und TiO, P25) werden beschrieben, soweit sie fur den Katalysator-Hersteller von Interesse sein konnten. Eine Literaturiibersicht aus jiingster Zeit 1aBt Schwerpunkte auf dem Gebiet der Forschung und praktischen Anwendung erkennen. Der experimentelle Teil hat die Herstellung von Katalysator-Tragern aus hochdispersen Kieselsaure-Produkten zum Inhalt. Eine TabeIIe gibt Auskunft iiber deren Charakteristika.
Catalytic properties of silicic acids and metal oxidesprepared hydrolytically at high temperatures. The physical and chemical properties of silicic acids and metal oxides (A1,0, and TiO, P25) prepared hydrolytically at high temperatures are described, insofar as they might be of interest to catalyst producers. A highly topical literature survey reveals areas of interest in the fields of research and practical applications. The experimental section deals with the preparation of catalyst supports made of highly dispersed silica gel products. Their characteristics are tabulated.
The four 185Re, 187Re—NQR-transitions of RbReO4 were measured. From the NQR-coupling constants, asymmetry-parameter and normal temperature-coefficient in the range of 77-300°K one can conclude, that the anomalons temperature dependence of the NQR-frequencies of NH4ReO4 is not caused by the absolute values of certain lattice parameters.An experimental correlation of the Re—NQR-coupling constants of scheelite-structured perrhenates with the length of the elementar cell was found and discussed.
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