Bis(cyclooctadiene)nickel(0) is the organonickel compound with the formula Ni(C8H12)2, also written Ni(cod)2. 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.
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 acacAlEt2 + C2H6 + C2H4Ni(cod)2 is moderately soluble in several organic solvents.23
If exposed to air, the solid oxidizes in a few minutes to nickel(II) oxide.4 As a result, this compound is generally handled in a glovebox.5
Reactions
The reactivity of Ni(cod)2 has been extensively examined. One or both 1,5-cyclooctadiene ligands are readily displaced by phosphines, phosphites, bipyridine, and isocyanides. 6
Oxidation gives the highly reactive monocation, which can be isolated when using weakly coordinating anions:7
Ni(cod)2 + Ag[Al(OCH(CF3)2)4] → [Ni(cod)2][Al(OCH(CF3)2)4] + AgOf its many catalytic reactions,8 Ni(cod)2 in the presence of phosphine ligands catalyzes the demethoxylation of anisoles by hydrosilanes:9
2 C6H5OCH3 + [(CH3)2HSi]2O → 2 C6H6 + [(CH3)2(CH3O)Si]2OReferences
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"Ni(COD)2 60+ Years – Still an Effective Source of Ni(0) in Organometallic Chemistry". Strem Chemical. https://www.strem.com/catalog/product_blog/328/5/ni_cod_2_60_years-still_an_effective_source_of_ni_0_in_organometallic_chemistry ↩
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