Weakly coordinating anions, ideal

In the way it became clear that at least one or two of the criteria (1) - (6) had to be fulfilled to expect any success in the quest for free silylium cations in solution, one systematically started to use solvents with weak nucleophilic character as well as weakly coordinating counterions such as 33 or 35 shown in Scheme 5. The lead in this research was taken by Lambert, but Reed made also several important contributions and, therefore, one can say that both Lambert and Reed pushed forward the issue of silylium cations in solution despite scepticism and criticism on the usefulness of such work for general chemistry. Benzene and toluene were chosen as the ideal solvents and in 1993 Lambert and Zhang reported on trialkyl substituted silyl cations in aromatic solvents at the presence of TPFPB as a counterion. [7] From measured 29Si NMR chemical shifts (80 - 110 ppm), Lambert and Zhang concluded that they had obtained R3Si+ (R = Me, Et, Pr, Me3Si) ions with reduced electrophilic interactions with solvent or anion and, therefore, with nearly free cationic structure. 

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