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1998 (1)
1995 (1)
1Author    Gerald Huber, Hubert SchmidbaurRequires cookie*
 Title    The Basicity of Silylamines and Alkylamines: An Equilibrium Study of the Competitive Borane Adduct Formation  
 Abstract    In order to investigate the Lewis acid/base chemistry of silylamines in solution, the equilib­ rium reactions of MeßSiNMea / Me3SiNMe2(BH3) and different amines NR3 / amineboranes NR3(BH3) were monitored by 'H NMR spectroscopy in CöDö and CDCI3 at 60 °C. For the equilibrium of the reference silylamine/-borane and Me3CNMe2 / Me3CNMe?(BH3) values K = 0.35 (A G = 3.1 kJ m o P ') in C6D6 and K = 0.50 (A G = 2.0 kJ m o r T) in CDC13 have been estimated, showing that both the silylamine and the C/Si-analogous organic amine have very similar donor properties. Small amines like NMe3 proved to be much more powerful donors than the silylamine Me3SiNMe2, whereas bulky amines are less efficient donors, indicating that steric effects play an important role. The formation of BH3 adducts of Me2NSiH3 and (H3Si)3N which could not be followed experimentally owing to the low stability of the products, has been studied by quantum chemical calculations. A comparison with data for Me3N(BH3) shows that the silylamines are poorer donors, but the reason for this remains unclear. 
  Reference    Z. Naturforsch. 53b, 1103—1108 (1998); received July 21 1998 
  Published    1998 
  Keywords    Silylamines, Alkylamines, Borane Adducts, Amineboranes, Basicity Studies 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-1103.pdf 
 Identifier    ZNB-1998-53b-1103 
 Volume    53 
2Author    Bernd Wrackmeyer, HeidiE. Maisel, Wolfgang MiliusRequires cookie*
 Title    2-Stannylpyridine-Borane Adducts -Multinuclear Magnetic Resonance Study and X-Ray Structure Determination of a l,4-Dihydro-4 a,l,4-azastannabora-naphthalene Derivative  
 Abstract    The adduct formation between 2-trimethylstannyl-pyridine (1) and triethylborane, leading to 2a, and 9-borabicyclo[3.3.1]nonane, leading to 2b, was studied by 'H, " B, 13C, 15N and 119Sn NMR in solution. Changes in the magnitude of the coupling constants 7(119Sn, 13C), with respect to the data for 1, were analysed. The absolute signs have been determined [all coupling constants " /(119Sn,13C) to methyl and pyridine carbon atoms in 1 to 3 possess a negative sign and the same is true for "y(119Sn,*H) of the pyridine hydrogen atoms] by various two-dimensional NMR experiments, and attributed to the influence of the lone pair of electrons at the nitrogen atom in 1. The NMR spectroscopic results for the 1,4-dihydro-4a,l,4-azastannabora-naphthalene derivative 3, in which structural fragments are present analogous to those in the borane adducts 2, correspond to those for 1 and 2a,b. The molecu­ lar structure of 3 has been determined by X-ray analysis [orthor' nombic; P 2 i2121; a = 713.9(2), b = 1566.0(2), c -1578.4(2) pm]. Solid-state 13C and 119Sn CP/MAS NM R spectra prove that the molecular structures of 3 in the solid state and in solution are very similar. 
  Reference    Z. Naturforsch. 50b, 809—815 (1995); received 
  Published    1995 
  Keywords    O ctober 28, 1994 2-Trimethylstannyl-pyridine, Borane Adducts, Heterobicycle, X-Ray, NM R Spectra 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-0809.pdf 
 Identifier    ZNB-1995-50b-0809 
 Volume    50