Question

What is an ambidentate ligand?

Answer 1

Hint: It is a type of ligand that has two donor sites. The complexes that contain ambidentate ligands can show linkage isomerism.

Complete Step-by-Step answer:
Ambidentate ligand is a type of ligand that has the ability to bind with the central atom via two different atoms which are not the same elements.

$$M \leftarrow :AB:$$ $$:AB: \to M$$

Here is a molecule AB which has two different atoms A and B which both have the ability to make covalent coordinate bonds with the central metal atom M. This is a simple explanation of ambidentate ligand.
Thiocyanate ion ($$SC{N^ - }$$), Cyanide ligand ($$C{N^ - }$$) and nitrite ion ($$N{O_2}^ - $$) are examples of ambidentate ligand.

Let’s see the example.
$${\left[ {Ag{{\left( {CN} \right)}_2}} \right]^ - }$$
Here Ag can bind with Carbon atom or Nitrogen atom also but at a time, it binds via one atom only.

Additional Information:
a) Presence of ambidentate ligands makes linkage isomerism possible because linkage isomers are also the compounds that have different binding sites and same molecular formula.
b) The nomenclature of the same ligand also changes as it binds with different atoms. For example, if nitrite ion binds with central metal ion via N-atom, then it is called ‘nitro’ ligand and when it binds with O-atom, it is called ‘nitrito’ ligand.
c) Same way, when $$SC{N^ - }$$ binds with S-atom, the ligand is called ‘thiocyanate’ and when it uses N-atom to bind, the ligand is named as ‘isothiocyanate’.

Note: Ambidentate ligand and polydentate ligands, both are completely different terms and they do not have any similarity, do not get confused between them. Note that when a ligand has two donor sites but both of the atoms are same, then the ligand is not called ambidentate ligand.