Scrambling-free synthesis of heteroleptic silylium ions by halide abstraction from halosilanes

Abstract

Abstract Heteroleptic silylium ions with different substituents at the silicon atom are generally not accessible using established tools for producing such reactive intermediates because substituent exchange reactions occur in acidic media, leading to homoleptic silylium ions with three identical alkyl and aryl substituents, respectively. Here we report a broadly applicable route to heteroleptic silylium ions using halosilanes as silylium ion precursors, which are less prone to that scrambling process. While this deceptively simple method has failed so far owing to the lack of a suitable halide-abstracting agent, superhalophilic halogen-substituted silylium ions enable smooth halide abstraction from a diverse set of halosilanes at ambient temperature without substituent redistribution. Accordingly, this approach provides access to essentially any heteroleptic acyclic as well as cyclic silylium-ion motif from common halosilanes, including trialkyl-, dialkyl(aryl)-, alkyldiaryl- and triaryl-substituted congeners. Computational calculations reveal the mechanism of heteroleptic silylium-ion formation and the origin of the suppressed substituent-scrambling process.