Which of the following complex has minimum magnitude of `Delta^(0)` ?

Options

A. `[Cr(CN)_6]^(3-)`
B. `[Co(NH_3)_6]^(3+)`
C. `[CoCl_6]^(3-)`
D. `[Cr(H_2O)_6]^(3+)`

Answer

To determine which complex has the minimum magnitude of Δ₀ (crystal field splitting energy), we need to analyze the ligands involved in the complexes. The strength of the ligands affects the magnitude of Δ₀, with weak field ligands resulting in lower Δ₀ values compared to strong field ligands.

### Step-by-Step Solution:

1. **Identify the Ligands:**
- The ligands mentioned in the question are cyanide (CN⁻), ammonia (NH₃), chloride (Cl⁻), and water (H₂O).

2. **Classify the Ligands:**
- **Cyanide (CN⁻)**: Strong field ligand
- **Ammonia (NH₃)**: Strong field ligand
- **Chloride (Cl⁻)**: Weak field ligand
- **Water (H₂O)**: Moderate field ligand

3. **Understand the Concept of Δ₀:**
- Δ₀ represents the energy difference between the higher energy and lower energy d-orbitals in a transition metal complex. The greater the splitting, the larger the Δ₀ value.

4. **Analyze the Ligands' Effects on Δ₀:**
- Strong field ligands (CN⁻ and NH₃) cause a larger splitting of the d-orbitals, resulting in a higher Δ₀.
- Weak field ligands (Cl⁻) cause a smaller splitting, resulting in a lower Δ₀.
- Water (H₂O) is a moderate field ligand and will have a Δ₀ value between that of weak and strong field ligands.

5. **Conclusion:**
- Since chloride (Cl⁻) is the weakest field ligand among the given options, the complex formed with chloride will have the minimum magnitude of Δ₀.

### Final Answer:
The complex with minimum magnitude of Δ₀ is the one that contains **chloride (Cl⁻)** as the ligand.