The Weakly Coordinating Tris(trichlorosilyl)silyl Anion

Abstract

Abstract Closely following the procedure for the preparation of the base‐stabilized dichlorosilylene complex NHC Dipp ⋅SiCl 2 reported by Roesky, Stalke, and co‐workers ( Angew. Chem. Int. Ed . 2009 , 48 , 5683–5686), a few crystals of the salt [NHC Dipp −H⋅⋅⋅Cl⋅⋅⋅H−NHC Dipp ]Si(SiCl 3 ) 3 were isolated, aside from the reported byproduct [NHC Dipp −H + ⋅⋅⋅Cl − ], and characterized by X‐ray crystallography (NHC Dipp =N,N‐di(2,6‐diisopropylphenyl)imidazo‐2‐ylidene). They contain the weakly coordinating anion Si(SiCl 3 ) 3 − , which was also obtained in high yields upon deprotonation of the conjugate Brønsted acid HSi(SiCl 3 ) 3 with NHC Dipp or PMP (PMP=1,2,2,6,6‐pentamethylpiperidine). The acidity of HSi(SiCl 3 ) 3 was estimated by DFT calculations to be substantially higher than those of other H‐silanes. Further DFT studies on the electronic structure of Si(SiCl 3 ) 3 − , including the electrostatic potential and the electron localizability, confirmed its low basicity and nucleophilicity compared with other silyl anions.