Difference between didentate & ambidentate with example.

Bidentate ligand

 

A bidentate ligand has two points at which it can attach to the central atom. One example of such a ligand is:

oxalate ion

258-1592_oxalate.gif

The two single-bonded oxygen atoms can each donate electrons to a central atom.

Three oxalate ions can coordinate a single central atom, giving an octahedral complex.

 

Ambidentate ligand

Ligands with more than one potential donor atom are known as ambidentate, such as the thiocyanate ion, NCS-, which can bind to the metal center with either the nitrogen or sulphur atoms. Examples of ambidentate ligands include NO2-/ONO- (O and N), and SO32-/OSO22- (O and S), where the first named atom refers to that which is bonded to the metal center.

 

The existence of ambidentate ligands means that there can be linkage isomerism: [Co(NO2)(NH3)5]2+ exists in a red form and a yellow form. The red form has the NO2- group bound by oxygen, when the ligand is known as the nitrito group, and the yellow form has the NO2- group bound by nitrogen, when the ligand is known as the nitro group.