Organonickel compound
Organonickel chemistry is a branch of organometallic chemistry that deals with organic compounds feature nickel-carbon bonds. They are used as a catalyst, as a building block in organic chemistry and in chemical vapor deposition. Organonickel compounds are also short-lived intermediates in organic reactions. The first organonickel compound was nickel tetracarbonyl Ni(CO)4, reported in 1890 and quickly applied in the Mond process for nickel purification. Organonickel complexes are prominent in numerous industrial processes including carbonylations, hydrocyanation, and the Shell higher olefin process.
Organonickel compounds adopts oxidation state 0 or +2. The resemblance to organopalladium compounds is not strong, although both metals undergo reactions that involve sequences of reductive elimination and oxidative addition reactions.
Many complexes exist of nickel coordinated to an alkene. In these compounds nickel is formally zerovalent Ni0 and the bonding is described with the Dewar-Chatt-Duncanson model. One common representative is Bis(cyclooctadiene)nickel(0) (Ni(COD)2), which contains two cyclooctadiene ligands. It is a 18VE compound with 10 electrons provided by nickel itself and 4x2 electrons more by the double bonds. This solid, which melts at 60 °C, is used as a catalyst and as a precursor for many other nickel compounds.
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