An inorganic complex in which a ligand is coordinated to a metal ion at two (or more) points, so that there is a ring of atoms including the metal. The process is known as chelation. Chelating agents are classified according to the number of points at which they can coordinate. A ligand such as diaminoethane (H2N(CH2)2NH2), which can coordinate at two points, is said to be bidentate. The angle made between two bonds coordinating to a metal atom is the bite angle of the ligand. See also sequestration.
Chelate
A chemical substance formed from the bonding of compounds to metallic ions. Intense podzolization in humic-iron podzols is linked to mineral chelation (Dearing et al. (2001) Geophys. J. Int. 144). See Siebner-Freibach et al. (2004) Soil Sci. Soc. Am. J. 68 on the interaction of iron chelating agents with clay minerals. The leaching out of chelates is cheluviation. Chelation, the formation of chelates, is a process whereby relatively insoluble materials may become soluble, and be released into the soil, increasing nutrient availability to plants.