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|Section2= |Section7= }} Pentalene is a polycyclic hydrocarbon composed of two fused cyclopentadiene rings. It has chemical formula C8H6. It is antiaromatic, because it has 4n π electrons where n is any integer. For this reason it dimerizes even at temperatures as low as -100 °C. The derivative 1,3,5-tri-''tert''-butylpentalene was synthesized in 1973.〔Hafner, K. and Süss, H. U. (1973), ''1,3,5-Tri-tert-Butylpentalene. A Stabilized Planar 8π-Electron System''. Angew. Chem. Int. Ed. Engl., 12: 575–577. 〕 Because of the ''tert''-butyl substituents this compound is thermally stable. Pentalenes can also be stabilized by benzannulation for example in the compounds benzopentalene and dibenzopentalene.〔 Dilithium pentalenide was isolated in 1962, long before pentalene itself in 1997. It is prepared from reaction of dihydropentalene (pyrolysis of an isomer of dicyclopentadiene) with ''n''-butyllithium in solution and forms a stable salt. In accordance with its structure proton NMR shows 2 signals in a 2 to 1 ratio. The addition of two electrons removes the antiaromaticity; it becomes a planar 10π-electron aromatic species and is thus a bicyclic analogue of the cyclooctatetraene (COT) dianion C8H82−. : The dianion can also be considered as two fused cyclopentadienyl rings, and has been used as a ligand in organometallic chemistry to stabilise many types of mono- and bimetallic complexes, including those containing multiple metal-metal bonds, and ''anti''-bimetallics with extremely high levels of electronic communication between the centers. == See also == * Cyclooctatetraene * Benzocyclobutadiene * Acepentalene 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pentalene」の詳細全文を読む スポンサード リンク
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