The Heavy Analogue of CpLi:  Lithium 1,2-Disila-3-germacyclopentadienide, a 6π-Electron Aromatic System

• Published in: Journal of the American Chemical Society 2005-09, Vol.127 (38), p.13142-13143
• Main Authors: Lee, Vladimir Ya, Kato, Risa, Ichinohe, Masaaki, Sekiguchi, Akira
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed matter: structure, mechanical and thermal properties; Coordination compounds; Exact sciences and technology; Inorganic chemistry and origins of life; Inorganic compounds; Metal complexes; Physics; Preparations and properties; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja054398g

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 η5-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.