On Silylated Oxonium and Sulfonium Ions and Their Interaction with Weakly Coordinating Borate Anions

Attempts have been made to prepare salts with the labile tris(trimethylsilyl)chalconium ions, [(Me(3)Si)(3)E](+) (E=O, S), by reacting [Me(3)Si‐H‐SiMe(3)][B(C(6)F(5))(4)] and Me(3)Si[CB] (CB(−)=carborate=[CHB(11)H(5)Cl(6)](−), [CHB(11)Cl(11)](−)) with Me(3)Si‐E‐SiMe(3). In the reaction of Me(3)Si‐O‐SiMe(3) with [Me(3)Si‐H‐SiMe(3)][B(C(6)F(5))(4)], a ligand exchange was observed in the [Me(3)Si‐H‐SiMe(3)](+) cation leading to the surprising formation of the persilylated [(Me(3)Si)(2)(Me(2)(H)Si)O](+) oxonium ion in a formal [Me(2)(H)Si](+) instead of the desired [Me(3)Si](+) transfer reaction. In contrast, the expected homoleptic persilylated [(Me(3)Si)(3)S](+) ion was formed and isolated as [B(C(6)F(5))(4)](−) and [CB](−) salt, when Me(3)Si‐S‐SiMe(3) was treated with either [Me(3)Si‐H‐SiMe(3)][B(C(6)F(5))(4)] or Me(3)Si[CB]. However, the addition of Me(3)Si[CB] to Me(3)Si‐O‐SiMe(3) unexpectedly led to the release of Me(4)Si with simultaneous formation of a cyclic dioxonium dication of the type [Me(3)Si‐μO‐SiMe(2)](2)[CB](2) in an anion‐mediated reaction. DFT studies on structure, bonding and thermodynamics of the [(Me(3)Si)(3)E](+) and [(Me(3)Si)(2)(Me(2)(H)Si)E](+) ion formation are presented as well as mechanistic investigations on the template‐driven transformation of the [(Me(3)Si)(3)E](+) ion into a cyclic dichalconium dication [Me(3)Si‐μE‐SiMe(2)](2) (2+).