Which of the following ligands is expected to bidentates?

Options

A. `CH_(3)NH_(2)`
B. `CH_(3)CequivN`
C. `Br`
D. `C_(2)O_(4)^(2-)`

Explanation

To determine which of the given ligands is expected to be bidentate, we need to analyze each ligand's ability to donate electron pairs to a central metal atom. A bidentate ligand can form two coordinate bonds with a metal ion due to the presence of two donor atoms.

### Step-by-Step Solution:

1. **Understanding Bidentate Ligands**:
- A bidentate ligand has two donor atoms that can coordinate to a metal center. This means it can form two bonds with the metal ion.

2. **Analyzing Each Ligand**:
- **Option 1: CH3NH2 (Methylamine)**:
- This ligand has one nitrogen atom with a lone pair that can donate. Therefore, it can only form one bond with a metal ion.
- **Conclusion**: Monodentate.

- **Option 2: CH3C≡N (Acetonitrile)**:
- In this case, the nitrogen atom has a lone pair that can donate to the metal. Similar to the first option, it can only form one bond.
- **Conclusion**: Monodentate.

- **Option 3: Br⁻ (Bromide ion)**:
- Bromide is a negatively charged ion and has one lone pair available for donation. It can only form one bond with a metal ion.
- **Conclusion**: Monodentate.

- **Option 4: Oxalate (C2O4²⁻)**:
- The oxalate ion has two oxygen atoms that can each donate a lone pair of electrons. This allows it to form two bonds with a metal ion.
- **Structure**: The oxalate ion can be represented as:
```
O=C-C=O
| |
O⁻ O⁻
```
- **Conclusion**: Bidentate.

3. **Final Answer**:
- The ligand that is expected to be bidentate is **Option 4: Oxalate (C2O4²⁻)**.