Evidence of the Lewis‐Amphoteric Character of Tris(pentafluoroethyl)silanide, [Si(C(2)F(5))(3)](−)

According to a first view on the geometrical and electronic structure of the tris(pentafluoroethyl)silanide, this anion appears as a Lewis base. Quantum chemical calculations on perfluoroalkylated silanides show significantly lower HOMO and LUMO energy levels in comparison to their non‐fluorinated counterparts, which implies reduced Lewis basicity and increased Lewis acidity of the [Si(C(2)F(5))(3)](−) ion. With these findings and a HOMO–LUMO gap of 4.80 eV similar to N‐heterocyclic silylenes (NHSis), perfluoroalkyl silanides are predestined to exhibit Lewis‐amphoteric character similar to silylenes. Deprotonation of Si(C(2)F(5))(3)H with sterically demanding phosphazene bases afforded thermally stable phosphazenium salts of the [Si(C(2)F(5))(3)](−) anion, which add to benzaldehyde, benzophenone, CS(2), and CO(2) in various manners. This behavior also mirrors the reactivity of silylenes towards ketones as well as heterocumulenes and is rationalized by Lewis amphotericity being inherent in these silanides.