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)(3)NSi(H)Me-2](+), in the reaction of (Me3Si)(3)N 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 pbelpbeiaug-cc-pVDZ level, indicating alkyl substituent exchange equilibria at the silane and preference of the formation of [(Me3Si3NSi(H)Me-2](+) over [(Me(3)Si(4)Nr](+).