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Norbornadiene is an
organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
and a bicyclic
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 ...
. Norbornadiene is of interest as a metal-binding
ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elect ...
, whose complexes are useful for
homogeneous catalysis In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysi ...
. It has been intensively studied owing to its high reactivity and distinctive structural property of being a
diene In organic chemistry a diene ( ) (diolefin ( ) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alk''ene'' units, with the standard prefix ''di'' of systematic nomenclature. ...
that cannot isomerize (isomers would be
anti-Bredt Bredt's rule is an empirical observation in organic chemistry that states that a double bond cannot be placed at the bridgehead of a bridged ring system, unless the rings are large enough. The rule is named after Julius Bredt, who first discussed ...
alkenes In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, a ...
). Norbornadiene is also a useful dienophile in Diels-Alder reactions.


Synthesis

Norbornadiene can be formed by a Diels-Alder reaction between
cyclopentadiene Cyclopentadiene is an organic compound with the 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 abbreviated CpH beca ...
and
acetylene Acetylene ( systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
:


Reactions

Quadricyclane, a valence
isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Is ...
, can be obtained from norbornadiene by a
photochemical reaction Organic photochemistry encompasses organic reactions that are induced by the action of light. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ...
when assisted by a sensitizer such as acetophenone: : The norbornadiene-quadricyclane couple is of potential interest for
solar energy Solar energy is radiant light and heat from the Sun that is harnessed using a range of technologies such as solar power to generate electricity, solar thermal energy (including solar water heating), and solar architecture. It is an essen ...
storage when controlled release of the strain energy stored in quadricyclane back to norbornadiene is made possible. Norbornadiene is reactive in
cycloaddition In organic chemistry, a cycloaddition is a chemical reaction in which "two or more unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity" ...
reactions. Norbornadiene is also the starting material for the synthesis of diamantane and sumanene and it is used as an
acetylene Acetylene ( systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
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 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 s ...
, where it serves as a two-electron or four-electron donor. The norbornadiene analogue of
cyclooctadiene rhodium chloride dimer Cyclooctadiene rhodium chloride dimer is the organorhodium compound with the formula Rh2Cl2(C8H12)2, commonly abbreviated hCl(COD)sub>2 or Rh2Cl2(COD)2. This yellow-orange, air-stable compound is a widely used precursor to homogeneous catalyst ...
is widely used in
homogeneous catalysis In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysi ...
. (Norbornadiene)molybdenum tetracarbonyl is used as a source of "Mo(CO)4", exploiting the lability of the diene ligand in this case. Chiral, ''C''2-symmetric dienes derived from norbornadiene have also been described. One example is tetracarbonyl(norbornadiene)chromium(0),{{cite journal , title = High yield synthesis and structures of some achiral and chiral (diphosphine)tetracarbonylchromium(0) chelate complexes with tetracarbonyl(norbornadiene)chromium(0) as complexation reagent , author1=Markus Strotmann , author2=Rudolf Wartchow , author3=Holger Butenschön , name-list-style=amp , journal = Arkivoc , pages = KK–1112F , year = 2004 , url = http://www.arkat-usa.org/ark/journal/2004/I13_Krohn/1112/KK-1112F.asp which is a useful source of " chromium tetracarbonyl," e.g. in reactions with phosphine
ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elect ...
s.


See also

*
Norbornane Norbornane (also known as bicyclo .2.1eptane) is an organic compound and a saturated hydrocarbon with chemical formula C7H12. It is a crystalline compound with a melting point of 88 °C. The carbon skeleton is derived from cyclohexane ring with ...
a saturated compound with the same carbon skeleton. *
Norbornene Norbornene or norbornylene or norcamphene is a highly strained bridged cyclic hydrocarbon. It is a white solid with a pungent sour odor. The molecule consists of a cyclohexene ring with a methylene bridge between carbons 1 and 4. The molecule car ...
a compound with the carbon same skeleton, but with one less double bond.


References

Dienes Bicyclic compounds Cyclopentenes