Question

The ionization isomer of $[Cr{{({{H}_{2}}O)}_{4}}Cl({{O}_{2}}N)]Cl$ is:
(A) $[Cr{{({{H}_{2}}O)}_{4}}({{O}_{2}}N)]C{{l}_{2}}$
(B) $[Cr{{({{H}_{2}}O)}_{4}}C{{l}_{2}}]({{O}_{2}}N)$
(C) $[Cr{{({{H}_{2}}O)}_{4}}Cl(ONO)]Cl$
(D) $[Cr{{({{H}_{2}}O)}_{3}}C{{l}_{2}}(N{{O}_{2}})]({{H}_{2}}O)]$

Answer 1

Hint: The geometry of the central metal ion and the identity of other ligands are identical in ionization isomerism. Isomers do not necessarily share similar chemical or physical properties. Isomers are molecules or polyatomic ions with identical molecular formulas, that is, the same number of atoms of each element,but distinct arrangements of atoms in space. Isomerism is the existence or possibility of isomers.

Complete step by step answer:
Two main forms of isomerism are structural or constitutional isomerism, in which bonds between the atoms differ;and stereoisomerism or spatial isomerism, in which the bonds are the same but the relative positions of the atoms differ.
For inorganic complexes, there are three types of structural isomers: ionization, coordination and linkage. When determining a structural isomer, you look at (1) the ligands that are bonded to the central metal and (2) which atom of the ligands attach to the central metal.
Ionization isomers occur when a ligand that is bound to the metal center exchanges places with an anion or neutral molecule that is outside the coordination complex.
In the compound given, $[Cr{{({{H}_{2}}O)}_{4}}Cl({{O}_{2}}N)]Cl$, one chloride anion is outside, therefore, Option B having compound $[Cr{{({{H}_{2}}O)}_{4}}C{{l}_{2}}]({{O}_{2}}N)$, will be its ionisation isomer, as it has nitro group outside the coordination sphere, and rest of the compound is same.
So, the correct answer is “Option B”.

Note: Coordination isomerism occurs in compounds containing complex anionic and cationic parts and can be thought of as occurring by interchange of some ligands from the anionic part to the cationic part. Hence, there are two complex compounds bound together, one having negative charge and the other having positive charge.