Generation and Aromaticity of 2-Silaimidazo-lium Ion, a New π-Conjugated Silylium Ion

silaimidazolium ion - aromaticity -

Significance

The 2-silaimidazolium ion, a new kind of heterocylic aromatic cation has been generated from the corresponding chlorosilane by a chloride abstraction using Et₃Si(benzene) tetrakis(pentafluorophenyl)borate. The silaimidazolium ion is stable at temperatures below -10 °C and was fully characterized by ¹H, ¹³C and ²⁹Si NMR parameters which were compared with theoretical calculations [²⁹Si NMR 53.0 (CD₂Cl₂) and 53.2 (C₇D₈) for the 2-silaimidazolium compared to the chlorosilane (-17.7 in CD₂Cl₂)].

Comment

Silylene compounds have been a focus of structural interest for the last ten years (B. Tumanskii, P. Pine, Y. Apeloig, N. Hill, R. West J. Am. Chem. Soc. 2004, 126, 7786-7787). However, this represents the first synthesis and full characterization of a silaimidazolium ion which will undoubtedly trigger studies on scope and limitation of the synthetic route and reactivity, as well as efforts to derive new silanimine systems. For simple Si=N derivatives, see N. Wiberg, K. Schurz J. Organomet. Chem. 1988, 341, 145-164.