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]+.

本研究描述了首例噻吩基化铵离子[(Me3Si)3NSi(H)Me2]+的意外合成与表征。该离子是在(Me3Si)3N与[Me3Si–H–SiMe3]­[B(C6F5)4]的反应中生成的。核磁共振(NMR)和拉曼光谱研究揭示了，当使用[Me3Si–H–SiMe3]+作为硅基化试剂时，发生了一种无过渡金属催化的取代基重排过程。在[Et3Si–H–SiEt3]­[B(C6F5)4]的反应中也得到了相同的观察结果。在采用标准的Bartlett–Schneider–Condon型反应并存在过量硅烷的情况下，总会有一个路易斯酸催化的重排过程发生。此外，通过在pbe1pbe/aug-cc-pVDZ水平上进行的DFT计算，探讨了该过程的动力学，表明在硅烷中存在烷基取代基交换的平衡，并且[(Me3Si)3NSi(H)Me2]+的形成比[(Me3Si)4N]+更优。