Which of the following can exhibit geometrical isomerism ?
(i) `[Co(NH_(3))_(4)Cl_(2)]` (ii) `[Co("en")_(3)]Cl_(2)` (iii) `[Co("en")_(2)(NO_(2))Cl] SCN` (iv) `[Co(NH_(3))_(6)][Cr(CN)_(6)]`

Options

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

Explanation

To determine which of the given coordination complexes can exhibit geometrical isomerism, we need to analyze each compound based on its structure and the nature of its ligands.

### Step-by-step Solution:

1. **Understanding Geometrical Isomerism**:
- Geometrical isomerism (cis-trans isomerism) occurs in coordination compounds when ligands can occupy different spatial arrangements around the central metal ion. This typically happens in octahedral and square planar complexes, but not in tetrahedral complexes or complexes with symmetrical ligands.

2. **Analyzing Each Compound**:
- **(i) `[Co(NH₃)₄Cl₂]`**:
- This complex has four ammonia (NH₃) ligands and two chloride (Cl) ligands. It is an octahedral complex. The two Cl ligands can be arranged either adjacent to each other (cis) or opposite each other (trans).
- **Conclusion**: This complex can exhibit geometrical isomerism.

- **(ii) `[Co(en)₃]Cl₂`**:
- Here, "en" stands for ethylenediamine, which is a bidentate ligand (it binds through two donor atoms). Since all three ligands are the same (en), the arrangement does not allow for cis-trans isomerism.
- **Conclusion**: This complex cannot exhibit geometrical isomerism.

- **(iii) `[Co(en)₂(NO₂)Cl]SCN`**:
- In this complex, there are two bidentate ligands (en) and two monodentate ligands (NO₂ and Cl). The arrangement of the ligands can lead to different spatial configurations (cis and trans) for the NO₂ and Cl ligands.
- **Conclusion**: This complex can exhibit geometrical isomerism.

- **(iv) `[Co(NH₃)₆][Cr(CN)₆]`**:
- This complex has six ammonia ligands around cobalt and six cyanide ligands around chromium. Since both metal centers have symmetrical arrangements of identical ligands, there is no possibility for cis-trans isomerism.
- **Conclusion**: This complex cannot exhibit geometrical isomerism.

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