Tris(pentafluoroethyl)silanol Derivatives and the Lewis Amphoteric Tris(pentafluoroethyl)silanolate Anion, [Si(C2F5)3O]-

While alkyl-substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C2F5)(3)](-), which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron-withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C2F5)(3)O](-). In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C2F5)(3)OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C2F5)(3)SiOSi(C2F5)(3). Deprotonation of Si(C2F5)(3)OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C2F5)(3)O}(2)](2-), implies Lewis amphoteric character of the monomeric [Si(C2F5)(3)O](-) anion.

Automated summary

This study focused on investigating the Lewis amphoteric behavior of perfluoroalkyl siloxanes and their congener species, revealing the strong electron-withdrawing properties of pentafluoroethyl substituents. The synthesis of corresponding silanol and characterization of dimeric triorganosilanolate provided evidence for the Lewis amphoteric character of the monomeric anion.