Synthesis of 1,1-Bis(n-butyl, t-butyl)-2,3,4,5-Tetraphenyl-1-Silacyclopentadiene and NMR Study of Their 2,5-Carbodianions

Abstract

1,1-Bis(n-butyl)-2,3,4,5-tetraphenyl-1-silacyclopentadiene (3) and 1,1-bis(t-butyl)-2,3,4,5-tetraphenyl-1-silacyclopentadiene (4) are synthesized from the reaction of the versatile silole dianion (2) with n-butyl bromide and t-butyl bromide. Reduction of (3) and (4) with an excess of lithium to give 1,1-bis(n-butyl)-2,5-dilithio-2,3,4,5-tetraphenyl-1-silacyclopenta-3-enide (6) and 1,1-bis(t-butyl)-2,5-dilithio-2,3,4,5-tetraphenyl-1-silacyclopenta-3-enide (7). 13C-NMR study of two 2,5-carbodianions (6 and 7) shows tert-carbanion at 73.18 and 78.12 ppm respectively. Two bulky tert-butyl groups in (7) increase the inversion barrier at the tert-carbanion, line broadenings of tert-butyl groups in 1 H and 13 C-NMR spectrum are observed.

Recent progress in the chemistry of heavy aromatics

“…Since then, silole dianion 27 38 ) and germole dianions 28 39 , 40 ) and 29 41 ) were synthesized and characterized by NMR spectroscopic and X-ray crystallographic analyses. Furthermore, other ionic aromatic compounds containing heavier Group 14 elements, such as cyclotrisilenium cation 30 , 42 ) cyclotrigermenium cation 31 , 43 ) sila- and germafluorene dianions 32 and 33 , 44 ) and 1,2-disila-3-germacyclopentadienide 34 , 45 ) were successfully synthesized and characterized (Fig.…”