Synthesis of the First Persilylated Ammonium Ion, [(Me₃Si)₃NSi(H)Me₂]⁺, by Silylium-Catalyzed Methyl/Hydrogen Exchange Reactions

This work describes the unexpected synthesis and characterization of the first persilylated ammonium ion, [(Me₃Si)₃NSi­(H)­Me₂]⁺, in the reaction of (Me₃Si)₃N with [Me₃Si–H–SiMe₃]­[B­(C₆F₅)₄]. NMR and Raman studies revealed a transition-metal-free silylium ion catalyzed substituent redistribution process when [Me₃Si–H–SiMe₃]⁺ was used as the silylating reagent. These observations were affirmed in the reaction with [Et₃Si–H–SiEt₃]­[B­(C₆F₅)₄]. A Lewis acid catalyzed scrambling process always occurs if an excess of silanes is present in the formation of silylium cations while employing the standard Bartlett–Schneider–Condon type reaction. Additionally, the thermodynamics of this process was accessed by DFT computations at the pbe1pbe/aug-cc-pVDZ level, indicating alkyl substituent exchange equilibria at the silane and preference of the formation of [(Me₃Si)₃NSi­(H)­Me₂]⁺ over [(Me₃Si)₄N]⁺.