JEE Main 2006 — Coordination Compounds Question with Solution

The IUPAC name for the complex $[{\text{Co(NO}}_2)({\text{NH}}_3{)}_5]{\text{Cl}}_2$ is: Pentaammine(nitrito-$\text{N,O}$)cobalt(III) chloride

Here's how to arrive at the name:

The complex is a cobalt complex, and cobalt has a +3 charge in this compound (since it has one negatively charged NO${}_2$ ligand and one negatively charged Cl ion, for a total of -2, to balance the +3 charge on cobalt).

The ligands are NH${}_3$ (ammonia) and NO${}_2$ (nitrito).

Ammonia is a neutral ligand, so its name is just "ammine" and it is designated by the prefix "penta" because there are five of them.

Nitrito is a negatively charged ligand, so its name is "nitrito-$\text{N,O}$" (the "-$\text{N,O}$" indicates that the NO${}_2$ ligand is bound through both the nitrogen and oxygen atoms).

Finally, the compound has a chloride ion, so its name is "chloride" and it is designated by the prefix "di" because there are two of them.

Putting it all together, we get the name "pentaammine(nitrito-$\text{N,O}$)cobalt(III) chloride".