Synthesis and NMR-Study of the 2,3,4,5-Tetraethylsilole Dianion [SiC₄Et₄]²⁻•2[Li]⁺

Abstract: The previously unknown silole dianion [SiC₄Et₄]²⁻•2[Li]⁺ (3) was prepared by the sonication of 1,1-dichloro-2,3,4,5-tetraethyl-1-silacyclopentadiene [Cl₂SiC₄Et₄, 2] with more than four equivalent of lithium in THF. ¹H-, ¹³C-, and ²⁹Si-NMR data of 3 are compared with those of the reported silole dianion [SiC₄Ph₄]²⁻. Trapping of 3 with trimethylchlorosilane gave 1,1-bis(trimethylsilyl)-2,3,4,5-tetraethyl-1-silacyclopentadiene [(Me₃Si)₂SiC₄Et₄, 4] in high yield. The silole of 2 was synthesized in high yield in three steps by a modified procedure using Cp₂ZrCl₂ via Cp₂ZrC₄Et₄ and 1,4-dibromo-1,2,3,4-tetraethyl-1,3-butadiene.