title: NHC→SiCl4 : an ambivalent carbene-transfer reagent.
abstract: The addition of BCl3 to the carbene-transfer reagent NHC→SiCl4 (NHC=1,3-dimethylimidazolidin-2-ylidene) gave the tetra- and pentacoordinate trichlorosilicon(IV) cations [(NHC)SiCl3 ](+) and [(NHC)2 SiCl3 ](+) with tetrachloroborate as counterion. This is in contrast to previous reactions, in which NHC→SiCl4 served as a transfer reagent for the NHC ligand. The addition of BF3 ⋅OEt2 , on the other hand, gave NHC→BF3 as the product of NHC transfer. In addition, the highly Lewis acidic bis(pentafluoroethyl)silane (C2 F5 )2 SiCl2 was treated with NHC→SiCl4 . In acetonitrile, the cationic silicon(IV) complexes [(NHC)SiCl3 ](+) and [(NHC)2 SiCl3 ](+) were detected with [(C2 F5 )SiCl3 ](-) as counterion. A similar result was already reported for the reaction of NHC→SiCl4 with (C2 F5 )2 SiH2 , which gave [(NHC)2 SiCl2 H][(C2 F5 )SiCl3 ]. If the reaction medium was changed to dichloromethane, the products of carbene transfer, NHC→Si(C2 F5 )2 Cl2 and NHC→Si(C2 F5 )2 ClH, respectively, were obtained instead. The formation of the latter species is a result of chloride/hydride metathesis. These compounds may serve as valuable precursors for electron-poor silylenes. Furthermore, the reactivity of NHC→SiCl4 towards phosphines is discussed. The carbene complex NHC→PCl3 shows similar reactivity to NHC→SiCl4 , and may even serve as a carbene-transfer reagent as well.
authors.affiliation: Fakultät für Chemie, Universität Bielefeld, Anorganische Chemie II, Universitätsstrasse 25, 33615 Bielefeld (Germany). tboettcher@jacobs-alumni.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Böttcher
authors.forename: Simon
authors.initials: S
authors.lastname: Steinhauer
authors.forename: Lesley C
authors.initials: LC
authors.lastname: Lewis-Alleyne
authors.forename: Beate
authors.initials: B
authors.lastname: Neumann
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Stammler
authors.forename: Bassem S
authors.initials: BS
authors.lastname: Bassil
authors.forename: Gerd-Volker
authors.initials: GV
authors.lastname: Röschenthaler
authors.forename: Berthold
authors.initials: B
authors.lastname: Hoge
keywords: boron; carbene ligands; main group elements; phosphorus; silicon