Which of the following statements is not true about the complex ion `[Pt(en)_2Cl_2]^(2+)`?

Options

A. It has two geometrical isomers - cis and trans
B. Both the cis and trans isomers display optical activity.
C. Only the cis isomer displays optical acitivity
D. Only the cis isomer has non-superimposable mirror image.

Answer

To determine which statement is not true about the complex ion \([Pt(en)_2Cl_2]^{2+}\), we will analyze the properties of the complex, particularly focusing on its isomerism and optical activity.

### Step-by-Step Solution:

1. **Identify the Isomers**:
The complex \([Pt(en)_2Cl_2]^{2+}\) can exist in two geometric isomer forms: cis and trans.
- **Cis Isomer**: The two ethylenediamine (en) ligands are adjacent to each other.
- **Trans Isomer**: The two ethylenediamine (en) ligands are opposite each other.

**Hint**: Remember that cis and trans isomers depend on the arrangement of ligands around the central metal atom.

2. **Determine Optical Activity**:
- **Optical Activity**: A complex is optically active if it lacks a plane of symmetry.
- **Trans Isomer**: The trans isomer has a plane of symmetry, making it optically inactive.
- **Cis Isomer**: The cis isomer lacks a plane of symmetry and is optically active, meaning it has non-superimposable mirror images (enantiomers).

**Hint**: Check for the presence of a plane of symmetry to determine optical activity.

3. **Evaluate the Statements**:
- **Statement 1**: Both cis and trans isomers display optical activity. (False, as the trans isomer is optically inactive)
- **Statement 2**: Only the cis isomer displays optical activity. (True)
- **Statement 3**: Only the cis isomer has non-superimposable mirror images. (True)

**Hint**: Compare each statement with the properties of the isomers you identified.

4. **Conclusion**:
The statement that is not true about the complex ion \([Pt(en)_2Cl_2]^{2+}\) is that both cis and trans isomers display optical activity. Therefore, the answer is the first statement.

### Final Answer:
The statement that is not true is: **Both cis and trans isomers display optical activity.**