Select correct statement :

Options

A. Geometrical isomers of complexes may differ in dipole moment
and visible / UV spectra
B. Complexes of the type `[Ma_3b_3]` can also have facial (fac) and meridional (mer) isomer
C. No optical isomer exists for the complex trans - `[Co(en)_2Cl_2]^(+)`
D. All are correct

Answer

To solve the question, we need to evaluate the correctness of each of the three statements provided about geometrical isomers and complexes.

### Step-by-Step Solution:

1. **Evaluate the First Statement:**
- The first statement claims that geometrical isomers of complexes may differ in dipole moment and visible and UV spectra.
- **Analysis:**
- Geometrical isomers, such as cis and trans isomers, can indeed have different dipole moments due to the arrangement of polar bonds. For example, in a cis isomer, the dipole moments do not cancel out, leading to a net dipole moment, while in a trans isomer, the dipole moments can cancel each other out, resulting in a net dipole moment of zero.
- Additionally, these isomers can exhibit different spectra due to variations in electronic transitions.
- **Conclusion:** The first statement is correct.

2. **Evaluate the Second Statement:**
- The second statement asserts that complexes of the type MA3B3 can have facial and meridional isomers.
- **Analysis:**
- In a complex of the type MA3B3, where M is the central metal atom, A represents one type of ligand, and B represents another type, it is possible to arrange the ligands in two distinct ways:
- **Facial (FAC) Isomer:** All three A ligands are on one face of the octahedron.
- **Meridional (MER) Isomer:** The A ligands are arranged in a plane that includes the metal and two of the B ligands.
- **Conclusion:** The second statement is also correct.

3. **Evaluate the Third Statement:**
- The third statement claims that no optical isomer exists for the complex trans [Co(en)2Cl2].
- **Analysis:**
- The complex trans [Co(en)2Cl2] is symmetrical. Optical isomers exist when a molecule can exist in two forms that are non-superimposable mirror images. However, due to the symmetry of this complex, it does not have such non-superimposable forms.
- **Conclusion:** The third statement is correct.

4. **Final Conclusion:**
- Since all three statements are correct, the answer to the question is that all options are correct.

### Final Answer:
All statements are correct.

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