Cleavage of Unactivated Si-C(sp 3 ) Bonds with Reed's Carborane Acids: Formation of Known and Unknown Silylium Ions.

An efficient method for the benzenium-ion-mediated cleavage of inert Si-C(sp3 ) bonds is reported. Various tetraalkylsilanes can thus be converted into the corresponding counteranion-stabilized silylium ions. The reaction is chemoselective in the case of hexamethyldisilane. Computations reveal a mechanism with backside attack of the proton at one of the alkyl groups. Several activated Si-C(spn ) bonds (n=3-1) react equally well, and the procedure can be extended to the generation of stannylium ions.