Fulvalene

Fulvalene

Names
Preferred IUPAC name [1,1′-Bi(cyclopentylidene)]-2,2′,4,4′-tetraene
Other names Bicyclopentyliden-2,4,2′,4′-tetraene 1,1′-Bi[cyclopentadienylidene] Pentafulvalene Bicyclopentadienylidene [5,5′]Bicyclopentadienylidene
Identifiers
CAS Number	91-12-3  Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:51994  Y
ChemSpider	9083553  Y
PubChem CID	10908294
UNII	V2K3QQS6YW  Y
CompTox Dashboard (EPA)	DTXSID10447902
InChI InChI=1S/C10H8/c1-2-6-9(5-1)10-7-3-4-8-10/h1-8H Y Key: XEOSBIMHSUFHQH-UHFFFAOYSA-N Y InChI=1/C10H8/c1-2-6-9(5-1)10-7-3-4-8-10/h1-8H Key: XEOSBIMHSUFHQH-UHFFFAOYAP
SMILES C=1\C=C/C(/C=1)=C2\C=C/C=C2
Properties
Chemical formula	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). Y  verify  (what is  YN ?) Infobox references

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 D_2h symmetry.

History

Biferrocene and bis(fulvalene)diiron (not shown) are complexes of the fulvalene dianion.

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, the cyclopentadienyl anion is coupled with iodine to the dihydrofulvalene. Double deprotonation of the dihydrofulvalene with n-butyllithium gives the dilithio derivative, which is oxidized by oxygen. Fulvalene was spectroscopically observed at −196 °C (77 K) from photolysis of diazocyclopentadiene, which induces dimerization of cyclopentadiene-derived carbenes. ^[3] The compound was isolated in 1986 ^[4] and was found to be nonaromatic. Above −50 °C (223 K) it dimerizes by a Diels–Alder reaction.

Derivatives

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

See also

• Fulvenes, (CH=CH)₂C=CH₂ and substituted derivatives
• Tetrathiafulvalene, C₂H₂S₂C=CS₂C₂H₂

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.