NiCOD2

NiCOD2, or bis(1,5-cyclooctadiene)nickel, is a nickel(0) organometallic complex commonly used as a practical source of Ni(0) in laboratory chemistry. The two COD ligands, 1,5-cyclooctadiene, are neutral, bidentate dienes that coordinate to nickel in an η2 fashion, giving a relatively reactive, low-coordinate complex. The compound is typically a air- and moisture-sensitive solid that dissolves in nonpolar to moderately polar solvents to give reactive solutions.

In terms of structure and reactivity, NiCOD2 is a two-ligand complex that imparts 18 electrons to the metal center, contributing to its status as a versatile Ni(0) precatalyst. The COD ligands are comparatively labile, so they can be displaced by other ligands such as phosphines, amines, or N-heterocyclic carbenes. This displacement allows NiCOD2 to generate a range of active nickel species that participate in catalytic cycles, notably in nickel-catalyzed cross-coupling reactions, including Negishi, Kumada, and Suzuki–Miyaura couplings, as well as various polymerization and hydrofunctionalization processes.

Preparation and handling vary by protocol, but NiCOD2 is generally prepared by reducing a nickel(II) precursor in the presence of COD under inert atmosphere, or it is purchased from chemical suppliers. It is stored under inert gas, typically at low temperature, to minimize decomposition. Due to the covalent Ni(0)–COD bonding and air sensitivity, standard Schlenk techniques or glovebox methods are used for handling.

Safety and environmental notes: nickel compounds can be toxic and sensitizing; NiCOD2 should be handled with appropriate protective equipment and waste managed according to institutional and regulatory guidelines.