Fulvalene

Fulvalene (bicyclopentadienylidene) is the member of the fulvalene family with the molecular formula C10H8. It is of theoretical interest as one of the simplest non-benzenoid conjugated hydrocarbons. Fulvalene is an unstable isomer of the more common benzenoid aromatic compounds naphthalene and azulene. Fulvalene consists of two 5-membered rings, each with two double bonds, joined by yet a fifth double bond. It has D2h symmetry.

Biferrocene is a complex of the fulvalene dianion.
Fulvalene
Names
Other names
Bicyclopentyliden-2,4,2',4'-tetraene
1,1'-Bi[cylopentadienylidene]
Pentafulvalene
Bicyclopentadienylidene
[5,5']Bicyclopentadienylidene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
Properties
C10H8
Molar mass 128.174 g·mol−1
Density 1.129 g/ml
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

History

An earlier attempt at synthesis of fulvalene in 1951 by Pauson and Kealy resulted in the accidental discovery of ferrocene.[1] Its synthesis was first reported in 1958 by E. A. Matzner, working under William von Eggers Doering.[2] In this method, cyclopentadienyl anion is coupled with iodine to the dihydrofulvalene. Double deprotonation of dihydrofulvalene with n-butyllithium gives the dilithio derivative, which oxidizes with oxygen. Fulvalene was spectroscopically observed at 77 K from photolysis of diazocyclopentadiene, which induces dimerization of cyclopentadiene-derived carbenes.[3] The compound was isolated in 1986.[4] It was found to be nonaromatic. Above −50 °C it dimerizes by a Diels-Alder reaction.

Derivatives

Perchlorofulvalene (C4Cl4C)2 is quite stable in contrast to fulvalene itself.[5]

See also

References
  1. T. J. Kealy, P. L. Pauson (1951). "A New Type of Organo-Iron Compound". Nature. 168 (4285): 1039–1040. Bibcode:1951Natur.168.1039K. doi:10.1038/1681039b0. S2CID 4181383.
  2. Dissertation Abstracts Int'l 26-06 page 3270 6411876.
  3. Demore, William B.; Pritchard, H. O.; Davidson, Norman (1959). "Photochemical Experiments in Rigid Media at Low Temperatures. II. The Reactions of Methylene, Cyclopentadienylene and Diphenylmethylene". Journal of the American Chemical Society. 81 (22): 5874–5879. doi:10.1021/ja01531a008.
  4. Escher, André; Rutsch, Werner; Neuenschwander, Markus (1986). "Synthese von Pentafulvalen durch oxidative Kupplung von Cyclopentadienid mittels Kupfer(II)-chlorid". Helvetica Chimica Acta. 69 (7): 1644 - 1654. doi:10.1002/hlca.19860690719.
  5. Mark, V. (1966). "Perchlorofulvalene". Organic Syntheses. 46: 93. doi:10.15227/orgsyn.046.0093.
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