Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. Engl. 6/1997)
The cover picture shows the calculated structure of a 2-silanorbornyl cation and its synthesis by a hydride transfer reaction, both of which show similarities to the structure and synthesis of the carbon analog, the 2-norbornyl cation. The depicted structure emphasizes the intramolecular π complexation of the “siliconium ion”. Electron transfer from the double bond to the positively charged silicon is corroborated by the characteristic, low-field shift of the vinylic 13C signals of the cation (red) relative to those of the starting silane (blue). Efficient intramolecular stabilization of the siliconium ion reduces the tendency to form complexes with solvent molecules or counterions. More details on the synthesis and properties of this novel silyl cation are reported by N. Auner and P. von R. Schleyer et al. on pages 626ff.