Ligands which can be coordinated to a metal or metal ion through either of the sides are called ambidentate. Such ligands contain two or more donor atoms. During complex formation, only one atom is attached to the metal.
For example, NO−2 group is an ambidentate ligand. It contains N and O donor atoms. It can form complexes M−NO2 or M−ONO in which either N or O atom is linked to metal.
Other examples of ambidentate ligands include SCN− and CN− ions.