Clarification of the nature of the "first chiral and highly Lewis acidic silyl cationic catalyst". Concerning the question of siliconium ions vs silyl cations

Density functional theory (DFT)/IGLO NMR studies show that the "first chira l and highly Lewis acidic silyl cationic catalyst" (Jorgensen et al. J. Am. Chem. Sec. 1998, 120, 7637) is not a free tertiary alkylsilicenium ion or a somewhat coordinatively stabilized silyl cation but a de facto silylated acetonitrilium ion 4 which possesses some chirality and thus is capable of catalyzing reported reactions, however, with very low enantioselectivity. A ttempts to find a minimum energy structure for the free silicenium ion 1 ca lculationally at the B3LYP/6-31G* level were unsuccessful and resulted inst ead in showing the stability of the derived intramolecularly silylated spir osilacyclopropylarenium ion 2 (a Cram-type aronium ion). In benzene solutio n a silylated benzenium ion 5 (Wheland intermediate) is obtained.