A fulvalene is a
hydrocarbon obtained by formally
cross-conjugating two
rings through a common
exocyclic double bond. The name is derived from the similarly structured
fulvenes
Fulvenes are the class of hydrocarbon obtained by formally cross-conjugating one ring and methylidene through a common exocyclic double bond.
The name is derived from fulvene, which has one pentagonal ring. Other examples include methylenecyclopr ...
which lack one ring. Pentafulvalene (2) is also called simply
fulvalene, the parent structure of this class. Triapentafulvalene (3) is also known as
calicene from the words ''calix'' or ''
chalice'' because of its wine-glass appearance.
In general, the parent fulvalenes are very unstable; for instance, the parent
triafulvalene
Triafulvalene or cyclopropenylidenecyclopropene is a fulvalene hydrocarbon with chemical formula C6H4, composed of two linked cyclopropene rings. Triafulvalene has never been isolated, since it can decompose via an isodesmic reaction. However, ...
(1) has never been synthesized. On the other hand, stable fulvalenes can be obtained by proper
substitution
Substitution may refer to:
Arts and media
*Chord substitution, in music, swapping one chord for a related one within a chord progression
* Substitution (poetry), a variation in poetic scansion
* "Substitution" (song), a 2009 song by Silversun Pi ...
or
benzannulation. Several members should be stabilized taking into account a dipolar
mesomeric form with for instance
sesquifulvalene 4, which can be thought of as a
tropylium cation joined to a
cyclopentadienyl Cyclopentadienyl can refer to
*Cyclopentadienyl anion, or cyclopentadienide,
**Cyclopentadienyl ligand
*Cyclopentadienyl radical, •
*Cyclopentadienyl cation,
See also
*Pentadienyl
In organic chemistry, pentadienyl refers to the organic radic ...
anion (both stable and
aromatic). In this compound the dipolar structure is calculated to contribute 23% to the total structure.
Fulvalenes as a ligand
:
Tungsten fulvalene complex
Fulvalenes forms stable
organometallic
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
complexes that can be formally considered derivatives of the dianion C
10H
82−, akin to two bonded
cyclopentadienyl anions.
Ferrocene
Ferrocene is an organometallic compound with the formula . The molecule is a complex consisting of two cyclopentadienyl rings bound to a central iron atom. It is an orange solid with a camphor-like odor, that sublimes above room temperature, a ...
was isolated from an attempted synthesis of pentafulvalene. Many compounds are known, especially for the early transition metals. The bond joining the two rings in some fulvalene complexes can break reversibly.
[Boese, R. J.; Cammack, K.; Matzger, A. J.; Pflug, K.; Tolman,W. B.; Vollhardt, K. P. C.; Weidman, T. W. "Photochemistry of (Fulvalene)tetracarbonyldiruthenium and Its Derivatives: Efficient Light Energy Storage Devices" Journal of the American Chemistry Society 1997, volume 119, p. 6757-6773. ]
References
{{Reflist
Fulvalenes
