Fulvenes are the class of

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

obtained by formally cross-conjugating one

ring Ring may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell :(hence) to initiate a telephone connection Arts, entertainment and media Film and ...

and

methylidene Methylene (systematically named methylidene and dihydridocarbon; also called carbene) is an organic compound with the chemical formula (also written ). It is a colourless gas that fluoresces in the mid-infrared range, and only persists in dilut ...

through a common

exocyclic In organic chemistry, an alicyclic compound contains one or more all-carbon rings which may be either saturated or unsaturated, but do not have aromatic character. Alicyclic compounds may have one or more aliphatic side chains attached. The s ...

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

. The name is derived from

fulvene Fulvene (pentafulvene) is a hydrocarbon with the formula (CH=CH)2C=CH2. It is a prototype of a cross-conjugated hydrocarbon. Fulvene is rarely encountered, but substituted derivatives ( fulvenes) are numerous. They are mainly of interest as ligand ...

, which has one pentagonal ring. Other examples include

methylenecyclopropene 3-Methylenecyclopropene, also called methylenecyclopropene or triafulvene, is a hydrocarbon with chemical formula . It is a colourless gas that polymerizes readily as a liquid or in solution but is stable as a gas.W. E. Billups , Long Jin Lin , Ed ...

(triafulvene) and heptafulvene.

Subclasses

Several types of fulvenes are defined. They are: *pentafulvene * triafulvene *heptafulvene *nonafulvene

Preparation

Fulvenes are readily prepared by the condensation of

cyclopentadiene Cyclopentadiene is an organic compound with the chemical formula, formula C5H6.LeRoy H. Scharpen and Victor W. Laurie (1965): "Structure of cyclopentadiene". ''The Journal of Chemical Physics'', volume 43, issue 8, pages 2765-2766. It is often ab ...

and

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

s and

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...

s: :C₅H₆ + R₂C=O → C₄H₄C=CR₂ + H₂O Thiele is credited with discovering this reaction. Modern synthesis of fulvenes employ buffer systems.

Ligand in organometallic chemistry

Fulvenes are common ligands and ligand precursors in

organometallic chemistry 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 ...

. 2,3,4,5-Tetramethylfulvene, abbreviated Me₄Fv, results from the deprotonation of cationic

pentamethylcyclopentadienyl 1,2,3,4,5-Pentamethylcyclopentadiene is a cyclic diene with the formula C5Me5H (Me = CH3). 1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ligand ''1,2,3,4,5-pentamethylcyclopentadienyl'', which is often denoted Cp* (C5Me5) and read ...

complexes. Some Me₄Fv complexes are called

tuck-in complex In organometallic chemistry, a tuck-in complex usually refers to derivatives of Cp* ligands wherein a methyl group is deprotonated and the resulting methylene attaches to the metal. The C5–CH2–M angle is acute. The term "tucked in" was coined t ...

es.

References

{{Authority control Hydrocarbons Cycloalkenes