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Chemistry · Glossary

What is Dewar–Chatt–Duncanson model?

Also known as: Dewar--Chatt--Duncanson model · metallacyclopropane

Definition 20.8 University Chemistry — Year 3 · Chapter 20 — Organometallic Chemistry: Bonding and Ligands

The Dewar–Chatt–Duncanson model of the bonding of an alkene to a metal combines σ\sigma donation from the C=C π\pi orbital to an empty metal orbital with back-donation from a filled metal dd orbital into the C=C π∗\pi^* orbital. Its limit of strong back-donation is a metallacyclopropane, a three-membered ring with two M–C σ\sigma bonds and a C–C single bond.

The Dewar–Chatt–Duncanson model of an alkene bound side-on (C=C vertical, the metal on the left). Left: the filled π orbital (two p orbitals in phase) donates into an empty metal orbital. Right: a filled metal d orbital of matching phases donates into the empty π* orbital (the two p orbitals out of phase).
The Dewar–Chatt–Duncanson model of an alkene bound side-on (C=C vertical, the metal on the left). Left: the filled π\pi orbital (two pp orbitals in phase) donates into an empty metal orbital. Right: a filled metal dd orbital of matching phases donates into the empty π∗\pi^* orbital (the two pp orbitals out of phase).
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