Match the complex species in Column-I with possible isomerism given in Column-II and select the correct answer using the codes given below : Column-I (Complex Species) – Column-II (Isomerism) A. $[Co(NH_{3})_{4}Cl_{2}]^{+}$ – 1. Optical B. $Cis[Co(en)_{2}{Cl_{2}]}^{+}$ – 2. Ionisation C. $[Co(NH_{3})_{5}SO_{4}]Br$ – 3. Coordination D. $[Co(NH_{3})_{6}][Cr(CN)_{6}]$ – 4. Geometric

Q: Match the complex species in Column-I with possible isomerism given in Column-II and select the correct answer using the codes given below : Column-I (Complex Species) – Column-II (Isomerism) A. $[Co(NH_{3})_{4}Cl_{2}]^{+}$ – 1. Optical B. $Cis[Co(en)_{2}{Cl_{2}]}^{+}$ – 2. Ionisation C. $[Co(NH_{3})_{5}SO_{4}]Br$ – 3. Coordination D. $[Co(NH_{3})_{6}][Cr(CN)_{6}]$ – 4. Geometric

Match the complex species in Column-I with possible isomerism given in Column-II and select the correct answer using the codes given below : Column-I (Complex Species) – Column-II (Isomerism) A. $[Co(NH_{3})_{4}Cl_{2}]^{+}$ – 1. Optical B. $Cis[Co(en)_{2}{Cl_{2}]}^{+}$ – 2. Ionisation C. $[Co(NH_{3})_{5}SO_{4}]Br$ – 3. Coordination D. $[Co(NH_{3})_{6}][Cr(CN)_{6}]$ – 4. Geometric

Question

Accepted Answer

To justify why Option 3 is the correct answer, let's analyze each complex species in Column-I and match them with the appropriate type of isomerism from Column-II.

**A. $[Co(NH_{3})_{4}Cl_{2}]^{+}$ – Geometric Isomerism (4):**

- The complex $[Co(NH_{3})_{4}Cl_{2}]^{+}$ is a coordination compound with a coordination number of 6, forming an octahedral geometry. In such complexes, geometric isomerism is possible due to the different spatial arrangements of ligands. Specifically, the two chloride ions can be adjacent to each other (cis) or opposite each other (trans), leading to geometric isomerism. Therefore, it matches with option 4 (Geometric).

**B. $Cis[Co(en)_{2}{Cl_{2}]}^{+}$ – Optical Isomerism (1):**

- The complex $Cis[Co(en)_{2}{Cl_{2}]}^{+}$ contains ethylenediamine (en), a bidentate ligand, and is in a cis configuration. Such complexes can exhibit optical isomerism because the arrangement of ligands can lead to non-superimposable mirror images, known as enantiomers. Therefore, it matches with option 1 (Optical).

**C. $[Co(NH_{3})_{5}SO_{4}]Br$ – Ionisation Isomerism (2):**

- The complex $[Co(NH_{3})_{5}SO_{4}]Br$ can exhibit ionisation isomerism. This type of isomerism occurs when the counter ion in the complex can exchange places with a ligand within the coordination sphere. In this case, the sulfate ion (SO₄²⁻) can exchange with the bromide ion (Br⁻), leading to different isomers such as $[Co(NH_{3})_{5}Br]SO_{4}$. Therefore, it matches with option 2 (Ionisation).

**D. $[Co(NH_{3})_{6}][Cr(CN)_{6}]$ – Coordination Isomerism (3):**

- The complex $[Co(NH_{3})_{6}][Cr(CN)_{6}]$ can exhibit coordination isomerism, which occurs when there is an exchange of ligands between the cationic and anionic parts of the complex. In this case, the ligands coordinated to Co and Cr can be exchanged, leading to different coordination isomers. Therefore, it matches with option 3 (Coordination).

Now, let's explain why the other options are incorrect:

- **Option 1:** Incorrect because it mismatches the types of isomerism for each complex. For example, it assigns optical isomerism to $[Co(NH_{3})_{4}Cl_{2}]^{+}$, which is incorrect as this complex exhibits geometric isomerism.

- **Option 2:** Incorrect because it assigns coordination isomerism to $Cis[Co(en)_{2}{Cl_{2}]}^{+}$, which is incorrect as this complex exhibits optical isomerism.

- **Option 4:** Incorrect because it assigns ionisation isomerism to $Cis[Co(en)_{2}{Cl_{2}]}^{+}$, which is incorrect as this complex exhibits optical isomerism.

In conclusion, Option 3 correctly matches each complex species with the appropriate type of isomerism, making it the correct answer.