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1987 (1)
1Author    M. Veith, A. BeloRequires cookie*
 Title    Stickstoffverbindungen von Elementen der dritten Hauptgruppe mit intra-und intermolekularen Donor-Akzeptor-Bindungen, III [1]. Dynamische Phänomene und Lewis-Säure-Stärke Nitrogen Compounds of Elements of the Third Main Group with Intra-and Intermolecular Donor Acceptor Bonds, III [1]. Dynamic Phenomena and Lewis Acidity  
 Abstract    Compounds of the general formula f BuN(H)-SiMe 2 -N(r Bu)ElX 2 (El = B, X = Me (lm), F (If), Cl (lc); El = AI, X = Me (2m), Cl (2c), Br (2b); El -Ga, X -Me (3m), Cl (3c), Br (3b); El -In, X -Me (4m), Cl (4c), Br (4b); El -Tl, X -Me (5m)) and r BuN(D)-SiMe 2 -N(r Bu)ElMe 2 (El = Al (2d), Ga (3d), In (4d)) have been characterized by IR and temperature dependent ! H NMR techniques with respect to their structural changes in solution. A reversible, dynamic, intramolecular equilibrium between two enantiomeric four-membered rings has been established to be responsible for the changes in the spectra. The cyclic form Bl, which arises from Lewis acid base interaction of the rerr-butyl-amino with the E1X 2 group, transforms to the mirror-image B2 via an acyclic intermediate, in which reorien-tation of the groups by rotation or inversion can take place. In the boron derivatives (lm, lc, and If) no comparable N—B interaction can be detected. The Lewis acidity of the E1X 2 group deduced from NH wave numbers increases within the following series: TlMe 2 <GaMe 2 ~InMe 2 <AlMe 2 <GaBr 2 =InBr 2 <GaCl 2 ~AlBr 2 ~InCl 2 <AlCl 2 . Intramolecular hydrogen transfer from one nitrogen atom to the other can be excluded by comparison of the rate constant k H vs. k D . The free enthalpy of activation A G* depends on the acidity of E1X 2 , the steric requirements and the relative masses of X. The syntheses and characterisation of If, 2b, 3b, 4b, 2d, 3d, and 4d are described. 
  Reference    Z. Naturforsch. 42b, 525—535 (1987); eingegangen am 6. November 1986 
  Published    1987 
  Keywords    Temperature Dependent NMR, Synthesis, Intramolecular Rearrangements, Donor Acceptor Bonds 
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 TEI-XML for    default:Reihe_B/42/ZNB-1987-42b-0525.pdf 
 Identifier    ZNB-1987-42b-0525 
 Volume    42