Structure and bonding in the metal complexes of ethylenediaminetetra-acetic acid

The metal-ion complexes of ethylenediaminetetra-acetic acid (EDTA) find widespread use not only in analysis, but also in foodstuffs, pharmacy, and medicine. A review of the structures of the solid complexes illustrates the considerable variation in co-ordination number of the metal-ion, and the possible denticities of EDTA. These data are relevant to the solid-state properties and also to the structures of the complexes in solution, which cannot be directly determined.