Coordination of N-Heterocyclic Carbene to H2SiX2 (X = Cl, OTf) and H3SiOTf (OTf = OSO2CF3): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms

Abstract

Abstract The reactivity of the N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)imidazol-2- ylidene towards dichlorosilane H2SiCl2, bis(trifluoromethanesulfonato)silane H2Si(OTf)2 (OTf = OSO2CF3), and silyl trifluoromethanesulfonate H3SiOTf has been investigated. It turned out that the coordination of the NHC ligand can occur stepwise to form the three neutral compounds (NHC)SiH2Cl2 (1), (NHC)2SiH2Cl2 (2), (NHC)SiH2(OTf)2 (3), as well as the two ion pairs [(NHC)SiH3]+(OTf-) (4) and [(NHC)2SiH3]+(OTf-) (5); the latter represent the first NHC adducts of the parent silylium cation (H3Si+). The multinuclear NMR and IR spectroscopic data of the products reflect the characteristics of four-, five-, and six-coordinate silane complexes. All new compounds were structurally characterized by single-crystal X-ray diffraction analyses