Which of the following octahedral complexes do not show geometrical isomerism?

Options

A. `[Co(NH_(3))_(3)CI_(3)]`
B. `[PtCI_(2)(NH_(3))_(4)]`
C. `[Pt(NH_(3))_(4)CI_(2)]`
D. `[Co_(2)(en)_(3)]^(3+)`

Answer

To determine which octahedral complexes do not show geometrical isomerism, we need to analyze the given complexes based on their ligand arrangements. Geometrical isomerism occurs in octahedral complexes when there are different spatial arrangements of ligands around the central metal atom.

**Step-by-Step Solution:**

1. **Identify the Complexes:**
Let's consider the complexes mentioned in the video transcript:
- [Co(NH3)3Cl3]
- [PtCl2(NH3)4]
- [Co(en)3]

2. **Analyze [Co(NH3)3Cl3]:**
- This complex has three NH3 ligands and three Cl ligands.
- The possible arrangements can lead to two geometrical isomers:
- Facial (fac) where two NH3 ligands are adjacent to each other.
- Meridional (mer) where the NH3 ligands are arranged in a plane with Cl ligands.
- Therefore, [Co(NH3)3Cl3] shows geometrical isomerism.

3. **Analyze [PtCl2(NH3)4]:**
- This complex has four NH3 ligands and two Cl ligands.
- The Cl ligands can be positioned either opposite each other (trans) or adjacent (cis).
- Hence, [PtCl2(NH3)4] also shows geometrical isomerism.

4. **Analyze [Co(en)3]:**
- Ethylenediamine (en) is a bidentate ligand, meaning each en can attach to the metal at two points.
- Since there are three en ligands, they will always occupy the octahedral positions in a way that does not allow for different spatial arrangements.
- Therefore, [Co(en)3] does not show geometrical isomerism.

5. **Conclusion:**
- Among the complexes analyzed, only [Co(en)3] does not exhibit geometrical isomerism.

**Final Answer:**
The octahedral complex that does not show geometrical isomerism is [Co(en)3].

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