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'Halogenohydrohexaborates' in keywords
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1988 (2)
1987 (1)
1Author    J. Fritze, W. PreetzRequires cookie*
 Title    c/osö-Halogenohydrohexaborate, III Schwingungsspektren der c/oso-Halogenohydrohexaborate X"B  
 Abstract    ~, n = 1-5; X = Cl, Br, I c/oso-Halogenohydrohexaborate, III Vibrational Spectra of the c/oso-Halogenohydrohexaborates X"B 6 H 6 _" 2_ , n = 1-5; X = Cl, Br, I The IR and Raman spectra of 20 different halogenohydrohexaborates, including pairs of geometric isomers of the series X"B 6 H 6 _ n :_ , X = Cl, Br, I; n = 1—5, have been assigned according to their point groups D 4h , C 4v , C 3v and C 2v determined previously by NMR studies. Due to weak coupling, the vibrations are treated separately to a first approximation in terms of internal B 6 -cage modes on one hand and modes of the substituents against the cage entity on the other hand. Disregarding the splitting by lowered symmetry, depending on the degree of halogenation, all internal modes of the B 6 cluster are observed at nearly unchanged positions in the range of 450—1250 cm -1 . The B 6 —X stretching vibrations, however, exhibit significant shifts to lower energy with increasing mass of substituents. 
  Reference    Z. Naturforsch. 42b, 293—300 (1987); eingegangen am 21. November 1986 
  Published    1987 
  Keywords    Halogenohydrohexaborates, IR Spectra, Raman Spectra 
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 TEI-XML for    default:Reihe_B/42/ZNB-1987-42b-0293.pdf 
 Identifier    ZNB-1987-42b-0293 
 Volume    42 
2Author    W. Preetz, A. Heinrich, J. ThesingRequires cookie*
 Title    c/oso-Halogenohydrohexaborate, IV Protonierung, Deuterierung und Schwingungsspektren von c/aso-Hexaboraten c/oso-Halogenohydrohexaborate, IV Protonation, Deuteration and Vibrational Spectra of c/oso-Hexaborates  
 Abstract    The weak Brönsted acids B 6 H 7 ~ and XB^H,", X = Cl, Br, I; pk a : 7-4,75, are formed by protonation of B 6 H h 2 ~ and XB 6 H 5 2 respectively. The deuteration rates, evaluated from inte-grated IR band intensities of the BH and BD stretching vibrations, are linearly dependent on the mole fractions of the protonated species, and decrease with increasing degree of halogenation in the series Cl>Br>I. H atoms trans-positioned to halogens are exchanged 100 times more rapidly than the remaining ones. The activation energy for the H/D exchange amounts to 76 ± 1,5 kJ/mol for B 6 H 7 ". The lower symmetry of the protonated borates is evident from additional IR and Raman bands. They are distinguished from the corresponding Brönsted bases by a high frequency shift of the BH stretching vibrations in the order of 100 cm '. Due to the pH dependent equilib-rium B h H (S 2 ~/B (,H 7 " and different solubilities of the tetrabutylammonium salts, the separation of BF,H 6 2 "/B 12 H| 2 2 " mixtures is achievable. In alkaline solutions the very soluble B ft H 6 2 ~ is present, whereas (TBA) 2 B, : HI : precipitates quantitatively. By subsequent cautious acidification of the supernatant, insoluble (TBA)B 6 H 7 is obtained. 
  Reference    Z. Naturforsch. 43b, 1319—1326 (1988); eingegangen am 16. Juni 1988 
  Published    1988 
  Keywords    Halogenohydrohexaborates, Protonation Deuteration, IR Spectra, Raman Spectra 
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 TEI-XML for    default:Reihe_B/43/ZNB-1988-43b-1319.pdf 
 Identifier    ZNB-1988-43b-1319 
 Volume    43 
3Author    A. Heinrich, W. Preetz, H. C. MarsmannRequires cookie*
 Title    n B-NMR-Spektren von Alkyl-, Halogeno-und Rhodanohydrohexaboraten "B NMR Spectra of Alkyl-, Halogeno-and Rhodanohydrohexaborates  
 Abstract    The temperature dependence of the "B NMR spectra of the monosubstituted and protonated c/oso-hexaborates RB 6 H 6 ", R -CH 3 , C : H 5 , C,H 7 , QH,,, C 8 H 17 , (SCN)B h H 6 -. and XB h H h . X = Cl. Br. I, has been determined in the range 180—300 K. The extra proton migrates at higher temperatures intramolecularly, probably across the edges of the B fl core. The extra proton is fixed to a facet of the octahedron below the coalescence temperatures 240 K (RB h H 6 ~) and 210 K (XB(,H 6 ") as recognized by the splitting of the signal of the equatorial B atoms due to the lowering of the symmetry from C 4v to C s . From the spin-spin coupling it can be deduced that the proton prefers with the softer Brönsted acids RB 6 H 6 " facets adjacent to the substituent, while with the stronger Brönsted acids XB h H 6 facets including the antipodal B atom are occupied. 
  Reference    Z. Naturforsch. 43b, 1647—1652 (1988); eingegangen am 23. August 1988 
  Published    1988 
  Keywords    Alkylhydrohexaborates, Halogenohydrohexaborates, Rhodanohydrohexaborate, "B and "B{'H} NMR Spectra 
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 TEI-XML for    default:Reihe_B/43/ZNB-1988-43b-1647.pdf 
 Identifier    ZNB-1988-43b-1647 
 Volume    43