Match List I with List II

Choose the correct answer from the options given below:

A-IV, B-III, C-I, D-II

The correct answer is option 4. A-IV, B-III, C-I, D-II.

Let us delve into each type of isomerism and explain how they apply to the given complexes.

1. (A) \([Co(NH_3)_5SO_4]Br\): (IV) Ionization isomerism:

Ionization isomerism occurs when a complex can form different ions in solution due to the interchange of counterions. This complex consists of a coordination sphere with \([Co(NH_3)_5SO_4]^+\) and a bromide counter ion. This complex can form ionization isomers where the sulfate ion \((SO_4^{2-})\) and bromide ion \((Br^-)\) can switch places. For instance:

\([Co(NH_3)_5SO_4]Br\) in solution could potentially dissociate as \([Co(NH_3)_5SO_4]^+ \text{ and } Br^-\).

The ionization isomer \([Co(NH_3)_5Br]SO_4\) would dissociate as \([Co(NH_3)_5Br]^+ \text{ and } SO_4^{2-}\).

(B) \([Co(NH_3)_5(NO_2)]Cl_2\): (III) Linkage isomerism

Linkage isomerism occurs when a ligand can bind to the metal center through different atoms. This complex contains a nitrite ion \((NO_2^-)\) as one of the ligands. The nitrite ion \((NO_2^-)\) can coordinate to the metal center through either nitrogen or oxygen:

Nitro \((NO_2^-)\): Coordination through nitrogen.

Nitrito \((ON^-)\): Coordination through oxygen.

Therefore, you can have two isomers based on which atom of the nitrite ion is bonded to the cobalt center.

(C) \([Co(NH_3)_6][Cr(CN)_6]\): (I) Coordination isomerism

Coordination isomerism occurs when there is a difference in the coordination sphere of the metal centers in a complex. It typically involves the interchange of ligands between different metal centers in a coordination compound. This complex involves two metal centers: cobalt and chromium, each with its own coordination sphere.

Coordination Isomers: The coordination spheres of cobalt and chromium can be interchanged. For instance:

\([Co(NH_3)_6][Cr(CN)_6]\) can be a coordination isomer with \([Cr(NH_3)_6][Co(CN)_6]\).

(D) \([CoCl_2(en)_2]\): (II) Geometrical isomerism

Geometrical isomerism (or cis-trans isomerism) occurs in coordination complexes where the arrangement of ligands around the metal center leads to different spatial configurations. This type of isomerism is typically seen in octahedral and square planar complexes. This complex involves a cobalt center with two ethylenediamine (en) ligands and two chloride ligands.

Geometrical Isomers: In an octahedral arrangement:

Cis Isomer: The two chloride ions are adjacent to each other.

Trans Isomer: The two chloride ions are opposite each other.

Summary

(A) \([Co(NH_3)_5SO_4]Br\) shows Ionization Isomerism (IV) because of the possible interchange between sulfate and bromide ions in solution.

(B) \([Co(NH_3)_5(NO_2)]Cl_2\) exhibits Linkage Isomerism (III) due to the ability of the nitrite ion to bind through either nitrogen or oxygen.

(C) \([Co(NH_3)_6][Cr(CN)_6]\) demonstrates Coordination Isomerism (I) where the ligands in the coordination spheres of cobalt and chromium can be exchanged.

(D) \([CoCl_2(en)_2]\) displays Geometrical Isomerism (II) because of the possible different spatial arrangements of the ligands around the cobalt center.

So, the correct matches are 4. A-IV, B-III, C-I, D-II.