Norbornadiene

Norbornadiene

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Names
IUPAC name Bicyclo[2.2.1]hepta-2,5-diene
Other names 2,5-Norbornadiene
Identifiers
CAS Number	121-46-0 Y
EC Number	204-472-0
Jmol 3D model	Interactive image
PubChem	8473
SMILES C1C2C=CC1C=C2
Properties
Chemical formula	C7H8
Molar mass	92.14 g/mol
Density	0.906 g/cm3
Melting point	−19 °C (−2 °F; 254 K)
Boiling point	89 °C (192 °F; 362 K)
Solubility in water	Insoluble
Vapor pressure	{{{value}}}
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

Norbornadiene is a bicyclic, hydrocarbon and an organic compound. Norbornadiene is of interest as a metal-binding ligand, whose complexes are useful for homogeneous catalysis. It has been intensively studied owing to its high reactivity and distinctive structural property of being a diene that cannot isomerize (isomers would be anti-Bredt olefins). Norbornadiene is also a useful dienophile in Diels-Alder reactions.

Synthesis

Norbornadiene can be formed by a Diels-Alder reaction between cyclopentadiene and acetylene.

Norbornadiene synthesis

Reactions

Quadricyclane, a valence isomer, can be obtained from norbornadiene by a photochemical reaction when assisted by a sensitizer such as acetophenone:

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The norbornadiene-quadricyclane couple is of potential interest for solar energy storage when controlled release of the strain energy stored in quadricyclane back to norbornadiene is made possible.

Norbornadiene is reactive in cycloaddition reactions. Norbornadiene is also the starting material for the synthesis of diamantane and sumanene and it is used as an acetylene transfer agent for instance in reaction with 3,6-di-2-pyridyl-1,2,4,5-tetrazine.

As a ligand

Norbornadiene is a versatile ligand in organometallic chemistry, where it serves as a two-electron or four-electron donor. The norbornadiene analogue of cyclooctadiene rhodium chloride dimer is widely used in homogeneous catalysis. Chiral, C₂-symmetric dienes derived from norbornadiene have also been described.

One example is tetracarbonyl(norbornadiene)chromium(0), which is a useful source of "chromium tetracarbonyl," e.g. in reactions with phosphine ligands.