Despite the earth abundance and easy availability of silicon, only few examples of isolable neutral silicon centered Lewis superacids are precedent in the literature. To approach the general drawbacks of limited solubility and unselective deactivation pathways, we introduce a Lewis superacid, based on perfluorinated pinacol substituents. The compound is easily synthesized on a gram-scale as the corresponding acetonitrile mono-adduct 1•(MeCN) and was fully characterized, including single crystal X-ray diffraction analysis (SC-XRD) and state-of-the-art computations. Lewis acidity investigations by the Gutmann-Beckett method and fluoride abstraction experiments indicate a Lewis superacidic nature. The challenging SiÀF bond activation of Et 3 SiF is realized and promising catalytic properties are demonstrated, consolidating the potential applicability of silicon centered Lewis acids in synthetic catalysis.

By use of the ethylene-bridged bidentate bis-NHI (NHI = N-heterocyclic imine) ligand 1 toward the complexation of ECl2·(dioxane) (E = Ge, Sn) the synthesis of the first bis-NHI-stabilized chlorogermyliumylidene 2a[GeCl3] and chlorostannyliumylidene 2b[SnCl3] by Lewis base mediated autoionization was achieved. Using additional TMSOTf enabled the isolation of the corresponding triflate salts 2a[OTf] and 2b[OTf] in moderate yields. The obtained tetryliumylidene ions were fully characterized, including single-crystal X-ray diffraction analysis, and additionally investigated by density functional theory calculations. Reaction of 2a[OTf] with NaBH4 led to the formation of a push–pull-stabilized hydridogermyliumylidene complex by Cl/H exchange. The same reaction with the stannyliumylidene led to transmetalation, yielding the corresponding dihydroboronium complex. Also, reactions with LiAlH4 in both cases afforded the transmetalation product.

Obwohl Silicium ein einfach zugängliches und häufig vorkommendes Element der Erdkruste ist, gibt es bisher nur wenige Beispiele isolierbarer Lewis-Supersäuren auf der Basis von neutralen Siliciumverbindungen. Um Lçslichkeitsproblemen und unselektiven Deaktivierungsmechanismen entgegenzuwirken, stellen wir in dieser Arbeit eine Lewis-Supersäure mit perfluorierten Pinakolat-Substituenten vor. Die Titelverbindung wird auf einfachstem Weg im Gramm-Maßstab als das Acetonitril-Monoaddukt 1•(MeCN) synthetisiert und inklusive modernster Berechnungen vollständig charakterisiert. Untersuchungen der Lewis-Azidität mittels Gutmann-Beckett-Methode und weiterführende Experimente zur Fluorid-Abstraktion bestätigen den Charakter einer Lewis-Supersäure. Die Aktivierung der SiÀF-Bindung von Et 3 SiF sowie vielversprechende Katalyse-Experimente demonstrieren das hohe Potenzial Silicium-basierter Lewis-Säuren in der katalytischen Synthese.

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The exceptional catalytic activity of a neutral Si(IV) Lewis superacid was highlighted on the degradation of oligo‐ and polyethers via ring closing metathesis. Model reaction experiments with diglyme and 1,5‐dimethoxypentane outlined a significantly increased reactivity surpassing comparable Lewis acid catalyst presented in the literature. The high observed activity was explained by the kinetic effect of the bulky perfluorinated substituents, blocking a second coordination site that is responsible for catalyst deactivation by substrate chelation. Further experiments with aliphatic oligoethers outlined a gradual activity loss of the catalyst due to mechanistic disparities favoring side‐reactions when more than one internal product unit is present. The extraordinary affinity for the cleavage of etheric C−O bonds was ultimately demonstrated by the reaction with diethylether, producing a pentavalent silicate species that was fully characterized including SC‐XRD analysis.