Question

Is ammonia a bidentate ligand?

Answer 1

Hint: Ligands are bidentate, monodentate, or polydentate based upon the number of atoms that can donate their electron pairs. Look into the formula of ammonia. In the structure all the hydrogens are bonded to nitrogen, they don’t have any electron pair left for bonding to the central atom and so ammonia forms a single bond with the central atom. Only ammonia donates its electron pairs.

Complete answer:
Ligands are the ions or molecules that are bonded to the central metal atom to form coordination complexes. They are electron pair donors. By donating their electrons they form bonds with central metal ions. And so ligands are considered as Lewis bases and central metal ions are considered as Lewis acids. Ligands can be cations, anions as well as neutral. Cation ligands are Nitrosonium\[(N{O^ + })\], Hydrazinium $({N_2}{H_5}^ + )$ etc. Anionic ligands are Cyanide$\left( {C{N^ - }} \right)$, Nitrite$\left( {N{O_2}^ - } \right)$, Chloride $\left( {C{l^ - }} \right)$ etc. and Neutral ligands are Carbon monoxide $\left( {CO} \right)$, water $\left( {{H_2}O} \right)$, ammonia $\left( {N{H_3}} \right)$ etc.
Ligands can be classified into three different types based on the number of sites for attachment. These are monodentate, bidentate, and polydentate ligands.
Monodentate ligands are those which coordinate through only one atom and to only one side of a metal ion. They donate only one pair of electrons to form a bond with the central atom.
Bidentate ligands are those which coordinate through two atoms and occupy two sites of the central atom. They have two atoms that donate their electron pairs to form a bond with the central metal atom.
Polydentate ligands are those which coordinate through more than two atoms to form a bond with the central metal atom.
Now to know whether ammonia is bidentate or not we will look into its formula.
The formula of ammonia is $N{H_3}$.
We see here that ammonia has only one atom which can donate its electron pairs, that is $N$ and so by this, we can say that ammonia is a monodentate ligand and not a bidentate ligand.

Note:
Coordination compound consists of a central metal atom and a ligand bonded to each other. Coordination compounds are different from double salts. When dissolved in water double salts dissociate into simpler ions whereas coordination compounds do not dissociate. Coordination compounds have a wide range of applications. They are used in extraction processes of gold and silver, hemoglobin in blood is a coordination compound of iron, EDTA in lead poisoning and many more.