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  • Inorganic Chemistry  (2)
  • Exobiology
  • Surface physics, nanoscale physics, low-dimensional systems
  • peer-reviewed
  • 2010-2014  (2)
  • 1995-1999  (2)
  • 1
    ISSN: 0044-2313
    Keywords: 1,2-Diphospha-3,4-diboretanes ; 1,3-diphospha-2,4,5-triborolane derivative ; preparation ; molecular structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2-Diphospha-3,4-diboretanes and 1,3-Diphospha-2,4,5-triborolane: Synthesis and Structure as well as Calculations on the Molecular Structure On the Effect of Substituents on the Structure of 1,2-Diphospha-3,4-diboretane[2 + 2]-Cyclocondensation reactions led to the synthesis of the 1,2-diphospha-3,4-diboretanes [(t-BuP)2B2(NMe2)2], 1 a, and [(t-BuP)2B(NMe2)B(NiPr2)], 1 b. Their molecular structures have been determined by X-ray methods, and these are compared with the structure of [(t-Bu)P—BN(iPr2)]2, 2 a. Compounds 1 show a folded B2P2 four membered ring having tert.-butyl groups in anti-positions. Ab initio calculations on 1,2-diphospha-3,4-diboretanes demonstrate that two conformers with anti-orientation of the substituents at the phosphorus atoms can be expected. These differ by the relative orientation of the almost planar P2BR groups to the BP2 plane. The influence of substituents (H and NH2 at the B atoms, and H and Me at the P atoms) on the ring conformation has been studied. Finally, the first derivative of a 1,3-diphospha-2,4,5-triborolane, 3 a, is reported.
    Notes: Durch [2 + 2]-Cyclokondensationen wurden die 1,2-Diphospha-3,4-diboretane [(t-BuP)2B2(NMe2)2], 1 a, und [(t-BuP)2B(NMe2)B(NiPr2)], 1 b, dargestellt, ihre Molekülstrukturen mit Röntgenbeugungsmethoden bestimmt und mit der Struktur von [(t-Bu)P—B(NiPr2)]2, 2 a, verglichen. In den Verbindungen 1 liegen gefaltete B2P2-Vierringe vor mit anti-ständigen tert.-Butylgruppen, während das Ringsystem in 2 a planar gebaut ist, die tert.-Butylgruppen aber ebenfalls anti-Stellung einnehmen. Ab initio-Rechnungen an 1,2-Diphospha-3,4-diboretanen belegen, daß zwei unterschiedliche Konformere mit anti-Orientierung der Substituenten an den P-Atomen stabil sind, die sich durch die relative Orientierung der annähernd trigonal-planaren P2BR-Baugruppen zur BP2-Ebene voneinander unterscheiden. Der Einfluß von Substituenten (H und NH2 am B-Atom, H und CH3 am P-Atom) wird ermittelt. Beschrieben wird ferner das erste Derivat eines 1,3-Diphospha-2,4,5-triborolans, 3 a.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1945-1953 
    ISSN: 0044-2313
    Keywords: Bismutoxideiodides ; totale pressure measurements ; mass spectrometry ; thermodynamic data ; melting diagram ; barogram ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations on the System Bi2O3/BiI3The temperature functions of decomposition pressures of the ternary compounds on the quasibinary line Bi2O3/BiI3 were determined by total pressure measurements and mass spectrometry. The barogram of the system was constructed and the melting diagram precised. The enthalpies of formation and the standard entropies of the solid phases were derived from the decomposition functions: (Values see Inhaltsübersicht).
    Notes: Die Temperaturabhängigkeit der Zersetzungsdrücke der auf dem quasibinären Schnitt Bi2O3/BiI3 existierenden ternären Verbindungen wurde durch Gesamtdruckmessungen mit dem Membrannullmanometer und dem Massenspektrometer ermittelt. Das Zustandsbarogramm für das System wurde aufgestellt und das Zustandsdiagramm präzisiert. Unter Zugrundelegung der Zersetzungsgleichungen wurden die Standardbildungsenthalpien und Standardentropien der festen ternären Phasen hergeleitet: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} \Delta {\rm H}_{\rm B}^{\rm o} \,({\rm BiOI, f, 298) = - 268,1} \pm {\rm 6,3}\,{\rm kJ}\,{\rm mol}^{{\rm - 1}} \\ {\rm S}^ \circ \,({\rm BiOI, f, 298) = 116,9} \pm {\rm 7,1}\,{\rm J}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} \\ \Delta {\rm H}_{\rm B}^{\rm o} \,({\rm Bi}_{\rm 4} {\rm O}_{\rm 5} {\rm I}_{\rm 2} {\rm, f, 298) = - 1148,8} \pm 20{\rm,9}\,{\rm kJ}\,{\rm mol}^{{\rm - 1}} \\ {\rm S}^ \circ \,({\rm Bi}_{\rm 4} {\rm O}_{\rm 5} {\rm I}_{\rm 2} {\rm, f, 298) = 367,1} \pm 25{\rm,1}\,{\rm J}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} \\ \Delta {\rm H}_{\rm B}^{\rm o} \,({\rm Bi}_{\rm 7} {\rm O}_{\rm 9} {\rm I}_{\rm 3} {\rm, f, 298) = - 2022,5} \pm 34{\rm,3}\,{\rm kJ}\,{\rm mol}^{{\rm - 1}} \\ {\rm S}^ \circ \,({\rm Bi}_{\rm 7} {\rm O}_{\rm 9} {\rm I}_{\rm 3} {\rm, f, 298) = 619,8} \pm 41{\rm,0}\,\,{\rm J}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} \\ \Delta {\rm H}_{\rm B}^{\rm o} \,({\rm Bi}_{\rm 5} {\rm O}_{\rm 7} {\rm I, f, 298) = - 1471,2} \pm 20{\rm,1}\,{\rm kJ}\,{\rm mol}^{{\rm - 1}} \\ {\rm S}^ \circ \,({\rm Bi}_{\rm 5} {\rm O}_{\rm 7} {\rm I, f, 298) = 385,3} \pm 24{\rm,3}\,{\rm J}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} \\ \end{array} $$\end{document}.
    Additional Material: 6 Ill.
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  • 3
    Publication Date: 2011-09-15
    Description: Author(s): W. G. Schmidt, M. Babilon, C. Thierfelder, S. Sanna, and S. Wippermann Density functional theory calculations are performed to study the influence of Na adatoms on the electron transport and structural properties of the In-Si(111)( 4×1 )–( 8×2 ) nanowire array. It is found that there are several energetically nearly degenerate Na adsorption sites, the precise energetic ord... [Phys. Rev. B 84, 115416] Published Wed Sep 14, 2011
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 4
    Publication Date: 2019-07-13
    Description: Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.
    Keywords: Exobiology
    Type: GSFC-E-DAA-TN21724 , Science (ISSN 0036-8075) (e-ISSN 1095-9203); 343; 6169; 1244734
    Format: text
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