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  • 204-1244C; 204-1245B; 204-1247B; 204-1248C; 204-1249C; 204-1249F; 204-1250C; 204-1250D; DRILL; Drilling/drill rig; Joides Resolution; Leg204; North Pacific Ocean; Ocean Drilling Program; ODP  (1)
  • Pentacoordinate silicon
  • Fluorosilicates, zwitterionic
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  • 1
    ISSN: 0009-2940
    Keywords: Fluorosilicates, zwitterionic ; Pentacoordinate silicon ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Existence of Zwitterionic λ5-(Ammonioorganyl)tetrafluorosilicates: Synthesis and Crystal and Molecular Structure of Tetrafluoro(pyrrolidiniomethyl)silicateThe zwitterionic tetrafluoro(pyrrolidiniomethyl)silicate (6) was synthesized by the reaction of trimethoxy(pyrrolidinomethyl)silane (7) with hydrogen fluoride in ethanol/hydro-fluoric acid (yield 83%). 6 crystallizes in the space group P1/c with two crystallographically distinct molecules in the asymmetric unit. In both molecules the pentacoordinate silicon atom is surrounded by four fluorine atoms and one carbon atom, the latter being in an equatorial position. The coordination polyhedron of the silicon atoms can be described as a slightly distorted trigonal bipyramid. The zwitterionic structure was also proved for dissolved 6 (solution in CD3CN, NMR-spectroscopic studies).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
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    PANGAEA
    In:  Supplement to: Bohrmann, Gerhard; Kuhs, Werner F; Klapp, Stephan A; Techmer, Kirsten S; Klein, Helmut; Murshed, Mangir M; Abegg, Friedrich (2007): Appearance and preservation of natural gas hydrate from Hydrate Ridge sampled during ODP Leg 204 drilling. Marine Geology, 244(1-4), 1-14, https://doi.org/10.1016/j.margeo.2007.05.003
    Publication Date: 2024-01-09
    Description: The state of preservation of natural gas hydrate samples, recovered from 6 sites drilled during ODP Leg 204 at southern summit of Hydrate Ridge, Oregon Margin, has been investigated by X-ray diffraction (XRD) and cryo-scanning-electron-microscopy (cryo-SEM) techniques. A detailed characterization of the state of decomposition of gas hydrates is necessary since no pressurized autoclave tools were used for sampling and partial dissociation must have occurred during recovery prior to the quench and storage in liquid nitrogen. Samples from 16 distinct horizons have been investigated by synchrotron X-ray diffraction measurements at HASYLAB/ Hamburg. A full profile fitting analysis (“Rietveld method”) of synchrotron XRD data provides quantitative phase determinations of the major sample constituents such as gas hydrate structure I (sI), hexagonal ice (Ih) and quartz. The ice content (Ih) in each sample is related to frozen water composed of both original existing pore water and the water from decomposed hydrates. Hydrate contents as measured by diffraction vary between 0 and 68 wt.% in the samples we measured. Samples with low hydrate content usually show micro-structural features in cryo-SEM ascribed to extensive decomposition. Comparing the appearance of hydrates at different scales, the grade of preservation seems to be primarily correlated with the contiguous volume of the original existing hydrate; the dissociation front appears to be indicated by micrometer-sized pores in a dense ice matrix.
    Keywords: 204-1244C; 204-1245B; 204-1247B; 204-1248C; 204-1249C; 204-1249F; 204-1250C; 204-1250D; DRILL; Drilling/drill rig; Joides Resolution; Leg204; North Pacific Ocean; Ocean Drilling Program; ODP
    Type: Dataset
    Format: application/zip, 8 datasets
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