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1988 (1)
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 
2Author    M. Veith, J. PöhlmannRequires cookie*
 Title    Nitrogen Compounds of Elements of the Third Main Group with Intra-and Intermolecular Donor Acceptor Bonds, V [1] Special Gallium and Indium Amides with Alkoxo Groups  
 Abstract    The lithium alkoxoamidosilane (Me2Si(O r Bu)(N r Bu)Li)2 (4) and its trimethyltin derivative Me2Si(0'Bu)(N'Bu)SnMe3 (7) have been used, to introduce the ligand Me2Si(0'Bu)(N'Bu) = L into molecular compounds of gallium and indium. The following molecules were synthesized: L—M(Me)Cl (M = Ga (5), In (6)), L-InMe2 (8), L-InX2 (X = Cl (9), Br (10)), L2InX (X = Cl (11), Br (12)) and L2Ga2Cl2 (22). The ligand L is assumed to chelate the metal atom on the basis of temperature dependent 'H NMR spectra. The chelating effect is more pronounced in the gallium derivatives than in the indium analogues. Equilibria between L2InX/InX, and LInX: have been observed in diethylether solutions. No metal(I) derivatives LGa or Lin could be isolated. L2Ga2Cl2 (22), formally containing gallium(ll), can be sublimed without decomposition at 110 °C in vacuo. 
  Reference    Z. Naturforsch. 43b, 505—512 (1988); eingegangen am 28. Dezember 1987 
  Published    1988 
  Keywords    Synthesis, Chelated Metal Atoms, Intramolecular Rearrangements, Equilibria Followed by 'H NMR 
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 TEI-XML for    default:Reihe_B/43/ZNB-1988-43b-0505.pdf 
 Identifier    ZNB-1988-43b-0505 
 Volume    43