Amongst the following, the most stable complex is

Options

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

Explanation

To determine the most stable complex among the given options, we need to analyze the ligands and the coordination environment around the metal ion in each complex. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Ligands and Their Denticity
- **Complex A**: Contains water (H2O) as a monodentate ligand.
- **Complex B**: Contains ammonia (NH3) as a monodentate ligand.
- **Complex C**: Contains oxalate ion (C2O4^2-) as a bidentate ligand.
- **Complex D**: Contains chloride ions (Cl-) as monodentate ligands.

### Step 2: Analyze the Coordination Number and Geometry
- **Complex A**: Coordination number is 6 (due to 6 water molecules).
- **Complex B**: Coordination number is also 6 (due to 6 ammonia molecules).
- **Complex C**: Coordination number is 6 (due to 3 oxalate ions, each binding through 2 sites).
- **Complex D**: Coordination number is 6 (due to 6 chloride ions).

### Step 3: Evaluate Stability Factors
- **Monodentate Ligands**: Water, ammonia, and chloride are all monodentate ligands. While they can form stable complexes, they do not provide the same level of stability as bidentate ligands.
- **Bidentate Ligands**: The oxalate ion in Complex C is a bidentate ligand, which means it can form two bonds with the metal ion. This leads to the formation of chelate rings.

### Step 4: Consider Chelation Effect
- The chelation effect significantly increases the stability of a complex. Complex C, with its bidentate oxalate ligands, forms stable chelate rings, which enhance the overall stability of the complex.

### Step 5: Conclusion
Based on the analysis of ligands, coordination numbers, and the chelation effect, the most stable complex is **Complex C** (Fe(C2O4)3).

### Final Answer
The most stable complex is **Complex C**.

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