Transition metal alkene complex

In organometallic chemistry, a transition metal alkene complex is a coordination compound containing one or more alkene ligands. Such compounds are intermediates in many catalytic reactions that convert alkesnes to other organic products, e.g. hydrogenation, hydroformylation, and polymerization.^[1]

• Metal alkene complexes.
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  Bis(cyclooctadiene)nickel(0).

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  Zeise's Salt, the first alkene complex.

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  Crabtree's catalyst.

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  The complex Rh₂(COD)₂Cl₂.

The bonding between alkenes and transition metals is described by the Dewar-Chatt-Duncanson model, which involves donation of electrons in the pi-orbital on the alkene to empty orbitals on the metal. This interaction is reinforced by back bonding that entails sharing of electrons in other metal orbitals into the otherwise empty pi-antibonding level on the alkene. Mono- and diolefins are often used as ligands in stable complexes. Cyclooctadiene and norbornadiene are popular chelating agents, and ethylene itself is sometimes used as a ligand, for example, in Zeise's salt. In addition, metal–alkene complexes are intermediates in many metal-catalyzed reactions including hydrogenation, hydroformylation, and polymerization.

References

1. ↑ Elschenbroich, C. ”Organometallics” (2006) Wiley-VCH: Weinheim. ISBN 3-527-29390-6