E(SiMe3)4+ Ions (E=P, As): Persilylated Phosphonium and Arsonium Ions

Only strong Lewis acidic, arene-solvated Me3Si+ ions react with E(SiMe3)3 compounds (E=P, As) to give the crystallographically characterized E(SiMe3)4+ onium ions 1 (left hand picture), which contain highly negative polarized P and As atoms, respectively. The masked Me3Si+ ions in 1 can be easily transferred to Et2O, to give the first structurally characterized planar silyloxonium ion [Et2(Me3Si)O]+ 2 (right hand picture).