Which of the following can exhibit geometrical isomerism ?
`[Co(NH_(3))_(4)Cl_(2))]`
`[Co(en)_(3)]Cl_(2)`
`[Co(en)_(2)(NO_(2))aCl]SCN`
`[Co(NH_(3)_(6)][Cr(CN)_(6)]`

Options

A. (i) , (ii) , (iii)
B. (i) , (ii)
C. (ii) , (iv)
D. (i) , (ii) , (iv)

Explanation

To determine which of the given complexes can exhibit geometrical isomerism, we need to analyze each complex based on the rules for geometrical isomerism.

### Step-by-Step Solution:

1. **Understanding Geometrical Isomerism**:
- Geometrical isomerism occurs when there are different spatial arrangements of ligands around a central metal atom. This typically happens in coordination complexes where there are two or more different types of ligands.

2. **Analyzing Each Complex**:
- **Complex 1: `[Co(NH₃)₄Cl₂]`**:
- This complex has 4 identical NH₃ ligands and 2 identical Cl ligands. It can exhibit geometrical isomerism as it can exist in two forms:
- **Cis**: where the two Cl ligands are adjacent to each other.
- **Trans**: where the two Cl ligands are opposite each other.
- **Conclusion**: This complex can exhibit geometrical isomerism.

- **Complex 2: `[Co(en)₃]Cl₂`**:
- Here, all three ligands are ethylenediamine (en), which is a bidentate ligand. Since all the ligands are identical, this complex cannot exhibit geometrical isomerism.
- **Conclusion**: This complex cannot exhibit geometrical isomerism.

- **Complex 3: `[Co(en)₂(NO₂)Cl]SCN`**:
- This complex has 2 identical en ligands and 2 different ligands (NO₂ and Cl). The two en ligands can be arranged in different ways relative to the NO₂ and Cl ligands:
- **Cis**: where NO₂ and Cl are adjacent to each other.
- **Trans**: where NO₂ and Cl are opposite each other.
- **Conclusion**: This complex can exhibit geometrical isomerism.

- **Complex 4: `[Co(NH₃)₆][Cr(CN)₆]`**:
- In this complex, all ligands around Co are identical (NH₃), and all ligands around Cr are also identical (CN). Since all ligands are the same, this complex cannot exhibit geometrical isomerism.
- **Conclusion**: This complex cannot exhibit geometrical isomerism.

3. **Final Conclusion**:
- The complexes that can exhibit geometrical isomerism are:
- Complex 1: `[Co(NH₃)₄Cl₂]`
- Complex 3: `[Co(en)₂(NO₂)Cl]SCN`

### Answer:
The complexes that can exhibit geometrical isomerism are **Option 1 and Option 3**.

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