title: The heavy analogue of CpLi: lithium 1,2-disila-3-germacyclopentadienide, a 6pi-electron aromatic system.
abstract: 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.
authors.affiliation: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Vladimir Ya
authors.initials: VY
authors.lastname: Lee
authors.forename: Risa
authors.initials: R
authors.lastname: Kato
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ichinohe
authors.forename: Akira
authors.initials: A
authors.lastname: Sekiguchi
mesh_terms: 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*
chemical_list: D003517:Cyclopentanes; D009942:Organometallic Compounds; C505701:lithium 1,2-disila-3-germacyclopentadienide; D008094:Lithium; D012825:Silicon