Tuning the Lewis Acidity of Neutral Silanes Using Perfluorinated Aryl- and Alkoxy Substituents

The emerging field of Lewis acidic silanes demonstrates the versability of molecular silicon compounds for catalytic applications. Nevertheless, when compared to the multifunctional boron Lewis acid B(C6F5)3, silicon derivatives still lack in terms of reactivity. In this regard, we demonstrate the installation of perfluorotolyl groups (TolF) on neutral silicon atoms to obtain the respective tetra- and trisubstituted silanes Si(TolF)4 and HSi(TolF)3. These compounds were fully characterized including SC-XRD analysis but unexpectedly showed no significant Lewis acidity. By using strongly electron-withdrawing perfluorocresolato groups (OTolF) the tetrasubstituted silane Si(OTolF)4 was obtained, bearing an 8 % increased & UDelta;& delta;(31P) shift when applying the Gutmann-Beckett method, compared to literature-known Si(OPhF)4. Ultimately the heteroleptic Si(PhF)2pinF was successfully synthesized and fully characterized including SC-XRD analysis, introducing a highly Lewis acidic silicon atom holding two silicon-carbon bonds. A set of Lewis acids was synthesized by installing perfluorotolyl- and perfluorocresolato ligands on neutral Si(IV) atoms. Additionally, a heteroleptic silane was synthesized using perfluoropinacolato and perfluorophenyl substituents. The obtained silanes were fully characterized and a Lewis acidity assessment was conducted by the Gutmann-Beckett and Childs method.image

Automated summary

The emerging field of Lewis acidic silanes demonstrates the versability of molecular silicon compounds for catalytic applications. Nevertheless, silicon derivatives still lack in terms of reactivity when compared to boron Lewis acid B(C6F5)3. This study successfully installed perfluorotolyl and perfluorocresolato groups on neutral Si(IV) atoms, and synthesized tetra- and trisubstituted silanes with different acidity levels.