Please use this identifier to cite or link to this item: doi:10.22028/D291-22556
Title: Stickstoffverbindungen von Elementen der dritten Hauptgruppe mit intra- und intermolekularen Donor-Akzeptor-Bindungen. - III : Dynamische Phänomene und Lewis-Säure-Stärke
Author(s): Veith, Michael
Belo, Andreas
Language: German
Year of Publication: 1987
OPUS Source: Zeitschrift für Naturforschung / B. - 42. 1987, S. 525-535
SWD key words: Stickstoffverbindungen
DDC notations: 540 Chemistry
Publikation type: Journal Article
Abstract: Compounds of the general formula tBuN(H)-SiMe2-N(tBu)ElX2 (El=B, X=Me (1m), F (1f), Cl (1c); El=Al, 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 tBuN(D)-SiMe2-N(tBu)ElMe2 (El=Al (2d), Ga (3d), In (4d)) have been characterized by IR and temperature dependent 1H NMR techniques with respect to their structural changes in solution. A reversible, dynamic, intromolecular equilibrium between two enantiomeric four-membered rings has been establisehd to be responsible for the changes in the spectra. The cyclic form B1, which arises from Lewis acid base interaction of the tert-butyl-amino with the ElX2 group, transforms to the mirror-image B2 via an acyclic intermediate, in which reorientation of the groups by rotation or inversion can take place. In the boron derivatives (1m, 1c, and 1f) no comparable N-B interaction can be detected. The Lewis acidity of the ElX2 group deduced from NH wave numbers increases within the following series: TlMe2<GaMe2?InMe2<AlMe2<GaBr2 (approximately-equal) InBr2<GaCl2 (approximately-equal) AlBr2 (approximately-equal) InCl2<AlCl2. Intramolecular hydrogen transfer from one nitrogen atom to the other can be excluded by comparison of the rate constant kH vs. kD. The free enthalpy of activation delta G (unequal) depends on the acidity of ElX2, the steric requirements and the relative masses of X. The synthesis and characterisation of 1f, 2b, 3b, 4b, 2d, 3d, 4d are described.
Link to this record: urn:nbn:de:bsz:291-scidok-20230
Date of registration: 2-Feb-2009
Faculty: NT - Naturwissenschaftlich- Technische Fakultät
Department: NT - Chemie
SE - INM Leibniz-Institut für Neue Materialien
Collections:SciDok - Der Wissenschaftsserver der Universität des Saarlandes

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