Chelate: Definition and Examples

A chelate is an organic compound formed when a polydentate ligand bonds to a central metal atom. Chelation, according to the IUPAC, involves the formation of two or more separate coordinate bonds between the ligand and central atom. The ligands are terms of chelating agents, chelants, chelators, or sequestering agents.

Uses of Chelates

Chelation therapy is used to remove toxic metals, as in heavy metal poisoning. Chelation is used to formulate nutritional supplements. Chelating agents are using in fertilizers, to prepare homogeneous catalysts, and as contrast agents in MRI scans.

Chelate Examples

• Most biochemical molecules can dissolve metal cations to form chelate complexes. Polynucleic acids, proteins, amino acids, polypeptides, and polysaccharides all act as polydentate ligands.
• The bidentate ligand ethylenediamine forms a chelate complex with the copper ion to form a five-membered CuC₂N₂ ring.
• Almost all metalloenzymes involve chelated metals, typically to cofactors, peptides, or prosthetic groups.
• Hot chemical weathering is typically due to organic chelants extracting metal ions from rocks and minerals.
• Many nutritional supplements are prepared by chelating metal ions to help protect the metal from forming complexes with insoluble salts in the stomach. These supplements thus provide a higher capacity for absorption.
• Homogeneous catalysts, such as ruthenium(II) chloride chelated with a bidentate phosphine, frequently are chelated complexes.
• EDTA and phosphonates are common chelating agents used to soften water.