Pentalene

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Pentalene
Pentalene.svg
Pentalene-3D-balls.png
Identifiers
CAS number 250-25-9 YesY
PubChem 5460726
ChemSpider 4574194 N
ChEBI CHEBI:33074 YesY
Jmol-3D images Image 1
Properties
Molecular formula C8H6
Molar mass 102.13 g mol−1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Pentalene is a polycyclic hydrocarbon composed of two fused cyclopentadiene rings.[1] 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.[2][3] The derivative 1,3,5-tri-tert-butylpentalene was synthesized in 1973.[4] 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.[1]

Dilithium pentalenide was isolated in 1962, long before pentalene itself in 1997.[5] 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 10 pi aromatic species and is thus a bicyclic analogue of the cyclooctatetraene (COT) dianion C8H82-.

Synthesis dilithium pentalenide

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.[6]

See also[edit]

References[edit]

  1. ^ a b Hopf, Henning (2013). "Pentalenes-From Highly Reactive Antiaromatics to Substrates for Material Science". Angewandte Chemie International Edition 52 (47): 12224. doi:10.1002/anie.201307162. 
  2. ^ Carey, Francis A.; Sundberg, Richard J. (1984). Advanced Organic Chemistry: Part A Structure and Mechanisms (2nd ed.). New York, NY: Plenum Press. ISBN 0-306-41198-9. 
  3. ^ Bally T., Chai S., Neuenschwander M., Zhu Z. (1997). "Pentalene: Formation, Electronic, and Vibrational Structure" (reprint). J. Am. Chem. Soc. 119 (8): 1869–1875(7). doi:10.1021/ja963439t. 
  4. ^ 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. doi:10.1002/anie.197305751
  5. ^ Katz, Thomas J.; Rosenberger, Michael. (1962). "The Pentalenyl Dianion". Journal of the American Chemical Society 84 (5): 865. doi:10.1021/ja00864a038. 
  6. ^ Summerscales, Owen T.; Cloke, F. Geoffrey N. (2006). "The organometallic chemistry of pentalene". Coordination Chemistry Reviews 250 (9–10): 1122. doi:10.1016/j.ccr.2005.11.020.