The optically active co-ordination complex ion among the following is

Options

A. `Trans-[Co(en)_2Cl_2]^+`
B. `Cis-[Co(en)(NH_3)_2Cl_2]^+`
C. `[Co(NH_3)_6]^(3+)`
D. `[Co(NH_3)_4 Cl_2]^+`

Answer

To determine which coordination complex ion is optically active among the given options, we need to analyze the symmetry properties of each complex. An optically active complex is one that does not have a center of symmetry or a plane of symmetry, allowing it to rotate plane-polarized light.

### Step-by-Step Solution:

1. **Understand Optical Activity**:
- Optical activity in coordination complexes arises when the complex lacks a center of symmetry and a plane of symmetry. Such complexes can rotate plane-polarized light.

2. **Identify the Complexes**:
- The question provides multiple coordination complexes. We will analyze each one for symmetry.

3. **Analyze the First Complex (trans-CO(NH2CH2CH2NH2)2Cl2)**:
- This complex has a trans configuration, meaning that the two identical ligands (Cl) are positioned 180 degrees apart.
- In this configuration, a plane can be drawn that bisects the complex, reflecting the two Cl atoms.
- **Conclusion**: This complex has a plane of symmetry, making it optically inactive.

4. **Analyze the Second Complex (cis-CO(NH2CH2CH2NH2)Cl2)**:
- This complex has a cis configuration, meaning that the two Cl ligands are positioned at 90 degrees to each other.
- No plane can bisect this complex into two identical halves, and it also lacks a center of symmetry.
- **Conclusion**: This complex does not have a plane of symmetry or a center of symmetry, making it optically active.

5. **Analyze the Third Complex (CO(NH3)6)**:
- This complex has all identical ligands (NH3) arranged octahedrally.
- A plane can be drawn that bisects the complex, reflecting all ligands.
- **Conclusion**: This complex has both a plane of symmetry and a center of symmetry, making it optically inactive.

6. **Analyze the Fourth Complex (CO(NH3)4Cl2)**:
- Similar to the third complex, this complex has a symmetrical arrangement of ligands.
- A plane can be drawn that bisects the complex, reflecting the NH3 and Cl ligands.
- **Conclusion**: This complex also has both a plane of symmetry and a center of symmetry, making it optically inactive.

7. **Final Conclusion**:
- Among the complexes analyzed, the only optically active complex is the **cis-CO(NH2CH2CH2NH2)Cl2**.

### Answer:
The optically active coordination complex ion among the following is **cis-CO(NH2CH2CH2NH2)Cl2**.