Silicon Tetrakis(trifluoromethanesulfonate): A Simple Neutral Silane Acting as a Soft and Hard Lewis Superacid
André Hermannsdorfer, Matthias Drieß
Abstract
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 Si−OTf bonds. In contrast, it can cleave C−X 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.