Bis(cyclooctadiene)nickel(0) is the
organonickel compound with the formula Ni(C
8H
12)
2, also written Ni(cod)
2. It is a diamagnetic
coordination complex
A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...
featuring tetrahedral nickel(0) bound to the alkene groups in two
1,5-cyclooctadiene
1,5-Cyclooctadiene (also known as cycloocta-1,5-diene) is a cyclic compound, cyclic hydrocarbon with the chemical formula , specifically .
There are three configurational isomers with this structure, that differ by the arrangement of the four C†...
ligand
In coordination chemistry, a ligand is an ion or molecule with a 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 el ...
s. This highly air-sensitive yellow solid is a common source of Ni(0) in chemical synthesis.
Preparation and properties
The complex is prepared by reduction of anhydrous
nickel(II) acetylacetonate in the presence of the diolefin:
:Ni(acac)
2 + 2 cod + 2
AlEt3 → Ni(cod)
2 + 2 acacAlEt
2 + C
2H
6 + C
2H
4
Ni(cod)
2 is moderately soluble in several organic solvents.
If exposed to air, the solid oxidizes in a few minutes to
nickel(II) oxide
Nickel(II) oxide is the chemical compound with the formula . It is the principal oxide of nickel. It is classified as a basic metal oxide. Several million kilograms are produced annually of varying quality, mainly as an intermediate in the product ...
. As a result, this compound is generally handled in a
glovebox
A glovebox (or glove box) is a sealed container that is designed to allow one to manipulate objects where a separate atmosphere is desired. Built into the sides of the glovebox are gloves arranged in such a way that the user can place their hand ...
.
Reactions
The reactivity of Ni(cod)
2 has been extensively examined. One or both
1,5-cyclooctadiene
1,5-Cyclooctadiene (also known as cycloocta-1,5-diene) is a cyclic compound, cyclic hydrocarbon with the chemical formula , specifically .
There are three configurational isomers with this structure, that differ by the arrangement of the four C†...
ligands are readily displaced by phosphines, phosphites,
bipyridine, and
isocyanide
An isocyanide (also called isonitrile or carbylamine) is an organic compound with the functional group –. It is the isomer of the related nitrile (–C≡N), hence the prefix is ''isocyano''.IUPAC Goldboo''isocyanides''/ref> The organic fragme ...
s.
Oxidation gives the highly reactive monocation, which can be isolated when using
weakly coordinating anion
Anions that interact weakly with cations are termed non-coordinating anions, although a more accurate term is weakly coordinating anion. Non-coordinating anions are useful in studying the reactivity of electrophilic cations. They are commonly found ...
s:
:
Of its many catalytic reactions,
[ Ni(cod)2 in the presence of phosphine ligands catalyzes the demethoxylation of ]anisole
Anisole, or methoxybenzene, is an organic compound with the formula . It is a colorless liquid with a smell reminiscent of anise seed, and in fact many of its derivatives are found in natural and artificial fragrances. The compound is mainly ...
s by hydrosilane
Hydrosilanes are tetravalent silicon compounds containing one or more Si-H bond. The parent hydrosilane is silane (SiH4). Commonly, hydrosilane refers to organosilicon derivatives. Examples include phenylsilane (PhSiH3) and triethoxysilane ((C2H ...
s:
References
{{Nickel compounds
Organonickel compounds
Cyclooctadiene complexes