Question

The type of isomerism present in nitropentamine chromium (III) chloride is
A . Optical
B . Linkage
C . Ionisation
D . Polymerisation

Answer 1

Hint: In this question we have used the concept of isomerism of coordinate compounds. Isomers are substances with the same chemical formula but distinct structural configurations. There are many different types of isomerism because many coordination compounds have complex formulae, a wide range of bond types, and a wide range of potential geometries.

Complete answer:Optical Isomerism: The two compounds with the same chemical formula that cannot be superimposed on one another's mirror images are said to be optical isomers. We have two types of optical isomers, depending on the way the polarimeter rotates the plane of polarised light. As follows:
The dextro isomer rotates to the right and the Laevo Isomer spins to the left.

Linkage Isomerism: Linkage isomers are two or more coordination compounds in which at least one of the ligands has a different donor atom from the others (i.e., the connectivity between atoms is different). Only a molecule with a ligand that can form two (or more) distinct bonds with the metal atom can exhibit this kind of isomerism.

Ionisation Isomerism: Except for the fact that a ligand has switched places with an anion or neutral molecule that was once outside the coordination complex, ionisation isomers are identical. The other ligands and the core ion are the same.
The complex ion and the ions around it swap groups, which results in this kind of isomerism.

Polymerisation: It happens between molecules that have the same empirical formula but different molecular weights, hence it is not a true isomer

Due to the presence of NO2, nitropentamine chromium (III) chloride exhibits linkage isomerism. The nitro group can bond to metal through either oxygen or nitrogen as nitrito (-NO2) (–ONO).
The isomers are [CO(NH3)5NO2]2+ and [CO(NH3)5ONO]2+.

The correct answer is B.

Note:Some ligands have many atoms that have the potential to give an electron pair. Either N or O atoms could serve as the electron pair donor in the NO2- ion. Isomerism is therefore a possibility.
Theoretically, it is also feasible for the NO2 and one of the Cl- to switch places; as a result, ionisation isomerism might also be seen.