Silylnitrilium ions

The oxidation of sterically hindered disilanes by trityl cation in pivaloyl nitrile was shown to yield silylium ions which form with the solvent silylnitrilium ions, e.g., 38 (Scheme 14) [53]. The generatitMi of silyl cations was, however, only observed for sterically overloaded disilanes, such as hexa-tcrt.-butyldisilane. Hexaethyldisilane for example was found to be inert under the applied reaction conditions [53], In view of the problems with bulky silanes in the standard hydride-transfer reaction, the oxidation of disilanes is a complementary addendum to the synthetic methodology. The very limited preparative access to stable radicals restricts the oxidation of silyl radicals to give silylium ions to only a few selected examples. The most prominent example is the oxidation of the stable radical 39 to the homoaromatic silylium ion 40 by trityl cation (Scheme 15) [23]. 

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