Question

Types of isomerism shown by $[Cr{{(N{{H}_{3}})}_{5}}N{{O}_{2}}]C{{l}_{2}}$ is [DCE 2002]
(A) Optical
(B) Ionisation
(C) Geometrical
(D) Linkage

Answer 1

Hint: Stereoisomers interconnected by non-superimposable mirror images of one another are known as optical isomers. The interchange of ions inside and outside the coordination sphere is a characteristic of ionization isomerism. Geometric isomers are two or more coordination compounds that have the same quantity, kind, and type of atoms as well as bonds but differ in the atoms' spatial configurations. When a compound has a ligand that has the ability to form two (or more) different bonds with the metal atom, linkage isomers are formed.

Complete answer:The coordination compound $[Cr{{(N{{H}_{3}})}_{5}}N{{O}_{2}}]C{{l}_{2}}$is an octahedral complex, with five $N{{H}_{3}}$ groups and one $N{{O}_{2}}$ group. The $N{{O}_{2}}$is an ambidentate ligand. It can link through the N-side as (−$N{{O}_{2}}$), called the nitro group, as well as through the O-side as (−$ONO$), called the nitrito group. So, $[Cr{{(N{{H}_{3}})}_{5}}N{{O}_{2}}]C{{l}_{2}}$can show two isomers, one with a nitro group and another with a nitrito group. Despite having identical molecular structures, linkage isomerism differs in how molecules attach to metals.
Hence, the type of isomerism shown by $[Cr{{(N{{H}_{3}})}_{5}}N{{O}_{2}}]C{{l}_{2}}$ is linkage isomerism.

Correct Option: D) Linkage

Additional Information: A ligand known as an ambidentate ligand can bind to the central metal atom using atoms from two distinct elements. Other than nitro groups, some of the ambidentate ligands are-
1. Thiocynate ligand ($SC{{N}^{-}}$), which can bind through both sulphur ($-SCN$) and nitrogen ($-NCS$).
2. Cyanide ligand ($C{{N}^{-}}$), which can bind through both carbon ($-CN$) and nitrogen ($-NC$) etc.

Note: The two linkage isomers also show two different colours. The compound $[Cr{{(N{{H}_{3}})}_{5}}N{{O}_{2}}]C{{l}_{2}}$ shows red-coloured crystals, whereas $[Cr{{(N{{H}_{3}})}_{5}}ONO]C{{l}_{2}}$shows yellow-coloured crystals.