Bis(cyclooctadiene)nickel(0) is the organonickel compound with the formula Ni(C<sub>8</sub>H<sub>12</sub>)<sub>2</sub>, also written Ni(cod)<sub>2</sub>. It is a diamagnetic coordination complex featuring tetrahedral nickel(0) bound to the alkene groups in two 1,5-cyclooctadiene ligands. This highly air-sensitive yellow solid is a common source of Ni(0) in chemical synthesis.
The complex is prepared by reduction of anhydrous nickel(II) acetylacetonate in the presence of the diolefin:
Ni(cod)<sub>2</sub> is moderately soluble in several organic solvents.
If exposed to air, the solid oxidizes in a few minutes to nickel(II) oxide. As a result, this compound is generally handled in a glovebox.
The reactivity of Ni(cod)<sub>2</sub> has been extensively examined. One or both 1,5-cyclooctadiene ligands are readily displaced by phosphines, phosphites, bipyridine, and isocyanides.
Oxidation gives the highly reactive monocation, which can be isolated when using weakly coordinating anions:
Of its many catalytic reactions, Ni(cod)<sub>2</sub> in the presence of phosphine ligands catalyzes the demethoxylation of anisoles by hydrosilanes: