Dynamic molecular motions resulting from the folding of a flexible macrocyclic component in a Cu(I)-complexed pseudorotaxane have been evidenced by variable temperature NMR experiments. The proposed conformational changes are also supported by the X-ray crystal structures of the compounds and computational studies.
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View Article and Find Full Text PDFDynamic topomerization of Cu(I)-complexed pseudorotaxanes.
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Laboratoire de Chimie des Matériaux Moléculaires, Université de Strasbourg et CNRS (UMR 7509), Ecole Européenne de Chimie, Polyméres et Matériaux, 25 rue Becquerel, 67087 Strasbourg Cedex 2, France.
Dynamic molecular motions resulting from the folding of a flexible macrocyclic component in a Cu(I)-complexed pseudorotaxane have been evidenced by variable temperature NMR experiments. The proposed conformational changes are also supported by the X-ray crystal structures of the compounds and computational studies.
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Variable-temperature (1)H and (13)C NMR spectroscopy of the sulfonimidoyl-substituted allyltitanium(IV) complexes E-1a-c and Z-1a-c, which carry diethylamino groups at the Ti atom, revealed a fast 1,3-C,N-shift of the Ti atom, leading to an equilibrium between the epimeric Calpha-titanium allyl complexes A and C and the N-titanium allyl aminosulfoxonium ylide B. Based on these findings a model for the reactions of E-1a-c and Z-1a-c with aldehydes is proposed, which features regio- and diastereoselective reactions of the N-titanium ylide B at the alpha-position and the Calpha-titanium complex A at the gamma-position. Model ab initio calculations of the methylene and allyl (dimethylamino)sulfoxonium ylides 10 and 14, respectively, revealed short Calpha-S bonds, a stabilization by both electrostatic interaction and negative hyperconjugation, and a low Calpha-S rotational barrier.
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