When a ligand can bind through two donor atoms as in
H2NCH2CH2NH2 (ethane-1,2-diamine) or C2O4
2– (oxalate), the
ligand is said to be didentate and when several donor atoms are
present in a single ligand as in N(CH2CH2NH2)3, the ligand is said
to be polydentate Ethylenediaminetetraacetate ion (EDTA
4–) is
an important hexadentate ligand It can bind through two
nitrogen and four oxygen atoms to a central metal ion When a di- or polydentate ligand uses its two or more donor
atoms simultaneously to bind a single metal ion, it is said to be a
chelate ligand