IPr3 Si3 Cl5 (+) : A Highly Reactive Cation with Silanide Character.

The reaction of a metastable SiCl2 solution with the sterically less-demanding carbene N,N-diisopropylimidazo-2-ylidene (IPr) yields the salt [(IPr3 Si3 Cl5 )(+) ]Cl(-) (1-Cl), containing a silyl cation with a Si3 backbone. Salt 1 is highly reactive, but it can be used as a reagent in deuterated dichloromethane, whereby dehalogenation with Me3 SiOTf (OTf=O3 SCF3 ) gives the dicationic silyl halide [(IPr3 Si3 Cl4 )](2+) 2. Quantum chemical calculations show that the HOMO is localized at the negatively charged central silicon atom of 1 and 2, and thus although both compounds are cations they are better described as silanides, which was also corroborated by NMR investigations.