Synthesis and NMR-Study of 1-Trimethylsilyl Substituted Silole Anion [Ph4C4Si(SiMe3)]−•[Li]+ and 3-Silolenide 2,5-carbodianions {[Ph4C4Si(n-Bu)2]−2•2[Li]+, [Ph4C4Si(t-Bu)2]−2•2[Li]+} via Silole Dianion [Ph4C4Si]−2•2[Li]+

Abstract

1-Trimethylsilyl, 1-R (R = Me, Et, i-Bu)-2,3,4,5-tetraphenyl-1-silacyclopentadiene [Ph4C4Si(SiMe3)R] are synthesized from the reaction of 1-trimethylsilyl,1-lithio-2,3,4,5-tetraphenyl-1-silacyclopentadienide anion [Ph4C4SiMe3]−•[Li]+ (3) with methyl iodide, ethyl iodide, and i-butyl bromide. The versatile intermediate 3 is prepared by hemisilylation of the silole dianion [Ph4C4Si]−2•2[Li]+ (2) with trimethylsilyl chloride and characterized by 1H-, 13C-, and 29Si-NMR spectroscopy. 1,1-bis(R)-2,3,4,5-tetraphenyl-1-silacyclopentadiene [Ph4C4SiR2] {R = n-Bu (7); t-Bu (8)} are synthesized from the reaction of 2 with n-butyl bromide and t-butyl bromide. Reduction of 7 and 8 with lithium under sonication gives the respective 3-silolenide 2,5-carbodianions {[Ph4C4Si(n-Bu)2]−2•2[Li]+ (10) and [Ph4C4Si(t-Bu)2]−2•2[Li]+ (11)}, which are characterized by 1H-, 13C-, and 29Si-NMR spectroscopy. Polarization of phenyl groups in 3 is compared with those of silole anion/dianion, germole anion/dianion, and 3-silolenide 2,5-carbodianions 10 and 11.

Keywords

• silacyclopentadiene
• silole
• anion
• dianion
• silyation
• 3-silolenide
• aromaticity
• NMR