Which of the following molecules or ions may act as a bidenatate ligand ?

Options

A. `CO_3^(2-)`
B. `NO_3^(-)`
C. `CH_3C=N`
D. `C_2O_4^(2-)`

Explanation

To determine which of the given molecules or ions can act as bidentate ligands, we need to identify those that can donate two pairs of electrons from two different donor atoms. Let's analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Bidentate Ligands**:
- A bidentate ligand is a molecule or ion that can form two bonds with a metal ion by donating two pairs of electrons from two different atoms.

2. **Analyzing Each Option**:
- **Option 1: CO₃²⁻ (Carbonate Ion)**:
- The carbonate ion has three oxygen atoms, two of which have lone pairs that can donate electrons. Therefore, it can act as a bidentate ligand by coordinating through two oxygen atoms.
- **Conclusion**: CO₃²⁻ is a bidentate ligand.

- **Option 2: NO₃⁻ (Nitrate Ion)**:
- The nitrate ion has one nitrogen and three oxygen atoms. It can coordinate through the nitrogen atom and one of the oxygen atoms, allowing it to act as a bidentate ligand.
- **Conclusion**: NO₃⁻ is a bidentate ligand.

- **Option 3: CS₃C≡N (Acetonitrile)**:
- In this molecule, the nitrogen atom has a lone pair but can only donate from one site. Therefore, it acts as a monodentate ligand.
- **Conclusion**: CS₃C≡N is not a bidentate ligand.

- **Option 4: C₂O₄²⁻ (Oxalate Ion)**:
- The oxalate ion has two carboxylate groups (C=O and O⁻). It can donate electrons from both oxygen atoms, allowing it to act as a bidentate ligand.
- **Conclusion**: C₂O₄²⁻ is a bidentate ligand.

3. **Final Answer**:
- The molecules/ions that can act as bidentate ligands are:
- CO₃²⁻
- NO₃⁻
- C₂O₄²⁻
- The only molecule that does not act as a bidentate ligand is CS₃C≡N.

### Summary of Correct Options:
- **Correct Bidentate Ligands**: CO₃²⁻, NO₃⁻, C₂O₄²⁻
- **Incorrect Bidentate Ligand**: CS₃C≡N