The heavy analogue of CpLi: lithium 1,2-disila-3-germacyclopentadienide, a 6pi-electron aromatic system.
Lithium 1,2-disila-3-germacyclopentadienide 2-.Li+ was synthesized by the reduction of 1,2-disila-3-germacyclopenta-2,4-diene 1 with potassium graphite followed by treatment with an excess amount of LiBr. The X-ray analysis of 2-.[Li+(THF)] revealed a delocalized aromatic cyclopentadienide-type structure with the diagnostic eta5-coordination of the Li+ cation to the five-membered ring. Aromaticity of this compound was verified and confirmed by theoretical calculations. The solution behavior of the 2-.Li+ is different in nonpolar and polar solvents; in nonpolar toluene, 2-.Li+ maintained the properties of a delocalized aromatic compound with the characteristically shielded 7Li NMR resonance at -5.4 ppm, whereas in polar THF, 2-.Li+ exhibited the properties of a localized nonaromatic compound with the negative charge situated on the Ge atom.
Lee
Vladimir Ya
VY
Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Kato
Risa
R
Ichinohe
Masaaki
M
Sekiguchi
Akira
A
D018360:Crystallography, X-Ray; D003517:Cyclopentanes / Q000737:chemistry*; D004583:Electrons; D008094:Lithium / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*
D003517:Cyclopentanes; D009942:Organometallic Compounds; C505701:lithium 1,2-disila-3-germacyclopentadienide; D008094:Lithium; D012825:Silicon