chelation

Complex formation involving a metal ion (cation) & 2 or more polar groups of a single molecule (chelating agent), such as EDTA. Examples: 1) chelation of Fe⁺² by a porphyrin ring to form heme 2) chelation of Pb+2 by EDTA

References

Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999