According to af irst view on the geometrical and electronic structure of the tris(pentafluoroethyl)silanide,t his anion appears as aLewis base.Quantum chemical calculations on perfluoroalkylated silanides show significantly lower HO-MO and LUMO energy levels in comparison to their nonfluorinated counterparts,whichimplies reduced Lewis basicity and increased Lewis acidity of the [Si(C 2 F 5 ) 3 ] À ion. With these findings and aH OMO-LUMO gap of 4.80 eV similar to Nheterocyclic silylenes (NHSis), perfluoroalkyl silanides are predestined to exhibit Lewis-amphoteric character similar to silylenes.Deprotonation of Si(C 2 F 5 ) 3 Hwith sterically demanding phosphazene bases afforded thermally stable phosphazenium salts of the [Si(C 2 F 5 ) 3 ] À anion, which add to benzaldehyde,b enzophenone,C S 2 ,a nd CO 2 in various manners.T his behavior also mirrors the reactivity of silylenes towards ketones as well as heterocumulenes and is rationalized by Lewis amphotericity being inherent in these silanides.

While perfluorinated aryl, aryloxy and alkoxy aluminum species are well‐established as weakly coordinating anions (WCAs), corresponding perfluoroalkyl aluminum derivatives are virtually unknown. Reaction of Si(C2F5)3CH3 with Li[AlH4] afforded the tetrakis(pentafluoroethyl)aluminate, [Al(C2F5)4]−. Several salts of the [Al(C2F5)4]− ion were synthesized and characterized by NMR spectroscopic methods, mass spectrometry, X‐ray diffraction studies and elemental analysis.

Bei Betrachtung der geometrischen und elektronischen Struktur des Tris(pentafluorethyl)silanids erscheint das Anion auf den ersten Blick als Lewis‐Base. Quantenmechanischen Rechnungen zufolge liegen die HOMO‐ und LUMO‐Energien von Perfluoralkylsilaniden deutlich niedriger als die nicht fluorierter Derivate. Dies hat eine geringere Lewis‐Basizität und zugleich eine erhöhte Lewis‐Acidität des [Si(C2F5)3]−‐Ions zur Folge. Mit diesen Erkenntnissen und einer der N‐heterocyclischen Silylenen (NHSis) ähnlichen HOMO‐LUMO‐Lücke von 4.80 eV sind Perfluoralkylsilanide dazu prädestiniert, Lewis‐amphoteres Verhalten ähnlich dem der Silylene aufzuweisen. Die Deprotonierung von Si(C2F5)3H mit sterisch anspruchsvollen Phosphazenbasen liefert thermisch stabile Phosphazenium‐Salze des [Si(C2F5)3]−‐Anions, welche in unterschiedlicher Weise an Benzaldehyd, Benzophenon, CS2 und CO2 addieren. Dieses Verhalten spiegelt die Reaktivität von Silylenen gegenüber Ketonen sowie Heterocumulenen wider und wird durch die Lewis‐Amphoterie des Silanids begründet.

Compounds exhibiting main group elements in low oxidation states were found to mimic the reactivity of transition metal complexes. Like the latter, such main group species show a proclivity of changing their oxidation state as well as their coordination number by + 2, therefore fulfilling the requirements for oxidative additions. Prominent examples of such main group compounds that undergo oxidative additions with organohalides RÀ X (R = alkyl, aryl, X = F, Cl, Br, I) are carbenes and their higher congeners. Aluminyl anions, which like carbenes and silylenes oxidatively add to strong σ-bonds in RÀ X species, have been recently discovered. We present the first anion based upon a Group 14 element, namely the tris(pentafluoroethyl)silanide anion, [Si(C 2 F 5 ) 3 ] À , which is capable of oxidative additions towards CÀ F bonds. This enables the isolation of non-chelated tetraorganofluorosilicate salts, which to the best of our knowledge had only been observed as reactive intermediates before.

Das Tris(pentafluorethyl)silanid‐Anion addiert an Carbonylverbindungen Ph(R)CO (R=Ph, H), CS2 und CO2, was die Isolierung neuartiger negativ geladener Spezies wie [Si(C2F5)3(η2‐OC(R)Ph)]− (R=Ph, H), [Si(C2F5)3(η2‐CS2)]− und [Si(C2F5)3(η2‐CO3)]− ermöglicht. Details zu den Reaktionen werden im Forschungsartikel von Berthold Hoge et al. auf S. 12231 beschrieben.