Norbornadiene

Norbornadiene is an organic compound and a bicyclic hydrocarbon. 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 alkenes). Norbornadiene is also a useful dienophile in Diels-Alder reactions.

Norbornadiene

Names
Preferred IUPAC name Bicyclo[2.2.1]hepta-2,5-diene
Other names 2,5-Norbornadiene
Identifiers
CAS Number	121-46-0 Y
3D model (JSmol)	Interactive image
ChemSpider	8160
ECHA InfoCard	100.004.066
EC Number	204-472-0
PubChem CID	8473
UNII	W9ZTQ75ZUS Y
UN number	2251
CompTox Dashboard (EPA)	DTXSID1059523
InChI InChI=1S/C7H8/c1-2-7-4-3-6(1)5-7/h1-4,6-7H,5H2 Key: SJYNFBVQFBRSIB-UHFFFAOYSA-N
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
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225
Precautionary statements	P210, P233, P240, P241, P242, P243, P280, P303+P361+P353, P370+P378, P403+P235, P501
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

Synthesis

Norbornadiene can be formed by a Diels-Alder reaction between cyclopentadiene and acetylene^[1]

Norbornadiene synthesis

Reactions

Quadricyclane, a valence isomer, can be obtained from norbornadiene by a photochemical reaction when assisted by a sensitizer such as acetophenone:^[2]

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.^[3]

Norbornadiene is reactive in cycloaddition reactions. Norbornadiene is also the starting material for the synthesis of diamantane^[4] 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.^[5]

As a ligand

Norbornadiene is a versatile ligand in organometallic chemistry, where it serves as a two-electron or four-electron donor. (Norbornadiene)molybdenum tetracarbonyl is used as a source of "Mo(CO)₄", exploiting the lability of the diene ligand in this case.^[6] which is a useful source of "chromium tetracarbonyl," e.g. in reactions with phosphine ligands.

The norbornadiene analogue of cyclooctadiene rhodium chloride dimer has been used in homogeneous catalysis. Chiral, C₂-symmetric dienes derived from norbornadiene have also been described.^[7][8]

See also

• Norbornane a saturated compound with the same carbon skeleton.
• Norbornene a compound with the same carbon skeleton, but with one less double bond.