Chelating Agents

In coordination compounds, the ligand attaches to the central metal ion through the donor atom. A bidentate ligand attaches to the metal ion in two places (two donor atoms), and a polydentate ligand attaches to the central atom in three or more locations. A ligand that has two or more donor atoms is called a chelating agent.

Examples:

1. Ethylenediamine



In this example the ligand can attach to the metal ion at the site of both N atoms.

2. Terpyridyl



In this polydentate ligand, the molecule can have three donor atoms.