Silicon Tetrakis(trifluoromethanesulfonate): A Simple Neutral Silane Acting as a Soft and Hard Lewis Superacid

Abstract

A facile synthesis and isolation of pristine silicon tetrakis(trifluoromethanesulfonate), Si(OTf) 4 , is reported, acting as the first neutral silicon-based Lewis superacid suitable towards soft and hard Lewis bases. Its OTf groups have a dual function: they are excellent leaving groups and modulate the degree of reactivity towards soft and hard Lewis bases. Exposed to soft Lewis donors, Si(OTf) 4 leads to [L 2 Si(OTf) 4 ] complexes (L = isocyanide, thioether and carbonyl compounds) with retention of all SiÀOTf bonds. In contrast, it can cleave CÀX bonds (X = F, Cl) of hard organic Lewis bases with a high tendency to form SiX 4 (X = F, Cl) after halide/triflate exchange. Most notable, Si(OTf) 4 allows a gentle oxydefluorination of mono-and bis(trifluoromethyl)benzenes, resulting in the formation of the corresponding benzoylium species, which are stabilized by the weakly coordinating [Si(OTf) 6 ] dianion.

Bis(perfluoropinacolato)silane: A Neutral Silane Lewis Superacid Activates Si−F Bonds

“…O1-Si1-O4) and 133.11(11)8 (O2-Si1-O3) in the trans position, respectively.The addition of Ph 3 CCl to a CD 2 Cl 2 solution of 1•(MeCN) immediately led to the formation of a triphenyl carbenium ion, which was indicated by rapid color change yielding a luminous yellow solution 19. F and 29 Si NMR spectroscopic analyses of the reaction mixture after 24 hours revealed the quantitative formation of the pentavalent [1-Cl] À species,…”

“…In this regard, we present the straight-forward synthesis and characterization of a novel and easy to handle, neutral silicon-centered Lewis superacid, its exceptional catalytic activity, and its ability to Figure 1. Literature known neutral, silicon-centered Lewis superacids (left) [9,11] and the catalytically active Lewis superacid 1•(MeCN), presented in this work.…”

“…This result is in good agreement with literature-known electron deficient silanes like Si(cat F ) 2 (Dd = 36.1 ppm) and even the Lewis superacidic Si(cat Cl ) 2 (Dd = 36.7 ppm). [9b] In contrast to related silanes holding halogenated catechol derivatives or triflate substituents, no bis-adduct formation was observed in case of 1•(MeCN), [9,11] even when surplus Et 3 PO amounts were added (up to 3.0 equiv. ).…”

Bis(perfluoropinacolato)silan: Eine neutrale Lewis‐Supersäure aktiviert Si−F‐Bindungen

“…keine Bildung des Bis-Addukts festgestellt. [9,11] Für eine weiterführende Strukturanalyse von 1•(MeCN) wurden Einkristalle aus Toluol kristallisiert und mittels SC-XRD-Analyse untersucht. [13] Die erhaltene Struktur zeigt eine pentavalente, quadratisch-pyramidale Koordination des Siliciums durch zwei Pinakolat-Gruppen und einem terminal gebundenen Acetonitril-Molekül.…”

Siliciumtetrakis(trifluormethansulfonat): Ein einfaches, neutrales Silan als weiche und harte Lewis‐Supersäure

“…10 % m-(COOTf)(CF 2 OTf)C 6 H 4 basierend auf 1 H-NMR-Integralen). [33] [34] 1807 (C=O) und 2250 cm À1 (CO) wurde in 62 % Ausbeute ausgehend von m-(COOTf) 2 C 6 H 4 und Si(OTf) 4 erhalten. [30] In…”