The heavy analogue of CpLi: lithium 1,2-disila-3-germacyclopentadienide, a 6pi-electron aromatic system |
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Authors: | Lee Vladimir Ya Kato Risa Ichinohe Masaaki Sekiguchi Akira |
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Institution: | Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan. |
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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. |
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