Chelate
A cyclic complex formed when a multidentate ligand grips a metal ion through two or more donor atoms.
Unit
Dimensionless
In depth
The name comes from the Greek for claw. Chelate rings of five or six members are the most stable, and their formation greatly increases both the thermodynamic stability and the kinetic inertness of the complex. Chelation is used to sequester unwanted metal ions.
Examples in the real world
EDTA chelating calcium in water softening; deferoxamine chelating iron in overload therapy.