In complexes more stability is shown by:-

Options

A. `[Fe(H_(2)O)_(6)]^(3+)`
B. `[Fe(CN)_(6)]^(3-)`
C. `[Fe(C_(2)O_(4))_(3)]^(3-)`
D. `[FeCl_(6)]^(3-)`

Answer

To determine which complex shows more stability among the given options, we will analyze the ligands and their binding characteristics with the central metal ion, which in this case is Fe³⁺.

### Step-by-Step Solution:

1. **Identify the Complexes:**
- The complexes given are:
- A: [Fe(H₂O)₆]³⁺
- B: [Fe(CN)₆]³⁻
- C: [Fe(C₂O₄)₃]³⁻
- D: [FeCl₆]³⁻

2. **Analyze the Ligands:**
- **A: [Fe(H₂O)₆]³⁺**
- Ligand: H₂O (a monodentate ligand)
- Type: Sigma donor
- **B: [Fe(CN)₆]³⁻**
- Ligand: CN⁻ (a monodentate ligand)
- Type: Pi acceptor
- **C: [Fe(C₂O₄)₃]³⁻**
- Ligand: C₂O₄²⁻ (a bidentate ligand)
- Type: Chelate ring formation
- **D: [FeCl₆]³⁻**
- Ligand: Cl⁻ (a monodentate ligand)
- Type: Sigma donor

3. **Stability Considerations:**
- Bidentate ligands (like C₂O₄²⁻) form chelate rings, which generally provide greater stability to the complex due to the chelate effect.
- Monodentate ligands (like H₂O, CN⁻, and Cl⁻) do not form such stable structures as they bind through a single site.

4. **Comparison of Stability:**
- Among the ligands:
- H₂O and Cl⁻ are weak field ligands and provide less stability.
- CN⁻ is a strong field ligand but is still monodentate.
- C₂O₄²⁻ is a bidentate ligand, which typically results in a more stable complex due to the chelate effect.

5. **Conclusion:**
- The complex with the bidentate ligand C₂O₄²⁻ ([Fe(C₂O₄)₃]³⁻) is expected to be the most stable due to the formation of chelate rings.
- Therefore, the answer is **C: [Fe(C₂O₄)₃]³⁻**.