Preparation of the first tricoordinate silyl cation

The preparation of the first tricoordinate silyl cation was made possible by a sequence of discoveries over a 20 year period. The extremely high electrophilicity of the material required protection from all manner of nucleophiles. Only arenes had sufficiently low nucleophilicity to serve as solvent. Tetrakis(pentafluorophenyl) berate provided the least nucleophilic anion. Ah manipulations had to be carried out in an inert atmosphere, primarily as protection from moisture. Sterically bulky substituents such as mesityl were needed to protect the cation even from the optimized solvent and anion. The trimesitylsilylium ion was produced from allyltrimesitylsilane by reaction of electrophiles with the allyl double bond and extrusion of the allyl adduct. Copyright (C) 2001 John Wiley & Sons, Ltd.