Which of the following is a flexidentate ligand?

Options

A. `H_(2)O`
B. EDTA
C. `CI^(-)`
D. `NO_(2)^(-)`

Answer

To determine which of the given options is a flexidentate ligand, we need to understand the concept of denticity in ligands. Let's analyze each option step by step.

### Step 1: Understand the Definition of Flexidentate Ligands
A flexidentate ligand is a type of ligand that can coordinate to a metal ion through different numbers of donor atoms, depending on the coordination environment or the demands of the metal center. This means that a flexidentate ligand can act as a bidentate, tridentate, or even higher denticity ligand based on the situation.

### Step 2: Analyze Each Option
1. **Water (H2O)**:
- Water is a monodentate ligand because it can only donate one lone pair of electrons from the oxygen atom to the metal center.
- **Conclusion**: Not a flexidentate ligand.

2. **EDTA (Ethylenediaminetetraacetic acid)**:
- EDTA is a well-known hexadentate ligand, meaning it can coordinate through six donor atoms (four carboxylate groups and two amine groups).
- However, it can also act as a pentadentate ligand if fewer coordination sites are required.
- **Conclusion**: EDTA is a flexidentate ligand.

3. **Chloride ion (Cl-)**:
- The chloride ion is also a monodentate ligand, as it can only donate one lone pair of electrons.
- **Conclusion**: Not a flexidentate ligand.

4. **Nitrite ion (NO2-)**:
- The nitrite ion can act as a bidentate ligand by coordinating through either the nitrogen or one of the oxygen atoms. However, it does not have the flexibility to change its denticity in the same way as EDTA.
- **Conclusion**: Not a flexidentate ligand.

### Step 3: Final Conclusion
Based on the analysis, the only ligand that qualifies as a flexidentate ligand is **EDTA** (option 2).

### Summary of the Solution
- **Flexidentate Ligand**: A ligand that can coordinate through different numbers of donor atoms.
- **Options Analysis**:
- Water: Monodentate (not flexidentate)
- EDTA: Hexadentate (can also be pentadentate, thus flexidentate)
- Chloride ion: Monodentate (not flexidentate)
- Nitrite ion: Bidentate (not flexidentate)
- **Correct Answer**: EDTA (Option 2)