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1990 (1)
1Author    MarcoL H Gruwel, RoderickE. WasylishenRequires cookie*
 Title    A Deuterium NMR Study of some Ammonium Tetraphenylborates  
 Abstract    Deuterium nmr has been used to study the rotational dynamics of the ammonium ion in ammo-nium tetraphenylborate and of the cation in a series of methylammonium tetraphenylborates. The results of variable temperature 2 H relaxation measurements (T 1Z and T 1Q) on the parent compound, ND 4 B(C 6 H 5) 4 , lead to a low activation energy for reorientation of the ND 4 ion, 5.0 ± 0.5 kJ mol -1 , indicative of weak cation-anion interactions. Related studies of the tetramethyl-d 12 ammonium salt indicate rapid jumps of the whole cation (T <|10 -5 S) over the complete temperature range investi-gated, 137 to 385 K, with an activation energy of 14.1 + 0.5 kJ mol" 1 . Deuterium nmr lineshape studies of the methylammonium salt indicate rapid reorientation of the CD 3 and ND 3 groups about their C 3 axes; however, the motion of the C-N axis is restricted to large amplitude librations. Similar studies of the dimethylammonium salt indicate methyl group jumps at 245 K; at temperatures above 320 K the cation also undergoes two-site jumps about the C 2 axis. In the case of the trimethylam-monium salt, the nmr lineshapes indicate methyl group jumps superimposed on C 3 rotations of the complete cation about the N-H bond axis over the temperature interval 185-348 K. In all the tetraphenylborate salts studied, the 2 H nmr lineshapes indicate substantial librational motion of the cation at room temperature. 
  Reference    Z. Naturforsch. 45a, 55—66 (1990); received August 31 1989 
  Published    1990 
  Keywords    2 H nmr, rotation, ammonium derivatives, tetraphenylborates 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0055.pdf 
 Identifier    ZNA-1990-45a-0055 
 Volume    45