Si-B Functional Group Exchange Reaction Enabled by a Catalytic Amount of BH₃: Scope, Mechanism, and Application

Functional group exchanges based on single-bond transformationare rare and challenging. In this regard, functional group exchangereactions of hydrosilanes proved to be more problematic. This is becausethis exchange requires the cleavage of the C-Si bond, whilethe Si-H bond is relatively easily activated for hydrosilanes.Herein, we report the first Si-B functional group exchangereactions of hydrosilanes with hydroboranes simply enabled by BH3 as a catalyst. Our methodology works for various aryl andalkyl hydrosilanes and different hydroboranes with the tolerance ofgeneral functional groups (up to 115 examples). Control experimentsand density functional theory (DFT) studies reveal a distinct reactionpathway that involves consecutive C-Si/B-H and C-B/B-H & sigma;-bond metathesis. Further investigations of using more readilyavailable chlorosilanes, siloxane, fluorosilane, and silylborane forSi-B functional group exchanges, Ge-B functional groupexchanges, and depolymerizative Si-B exchanges of polysilanesare also demonstrated. Moreover, the regeneration of MeSiH3 from polymethylhydrosiloxane (PMHS) is achieved. Notably, the formalhydrosilylation of a wide range of alkenes with SiH4 andMeSiH(3) to selectively produce (chiral)trihydrosilanes and(methyl)dihydrosilanes is realized using inexpensive and readily availablePhSiH(3) and PhSiH2Me as gaseous SiH4 and MeSiH3 surrogates.