Which of the following is not bidentate ligand?

Options

A. acac
B. ox
C. en
D. dien

Answer

To determine which of the following ligands is not a bidentate ligand, we need to analyze the donor sites of each ligand mentioned: Acetyl Acetonate (ACAC), Oxalate (OX), Ethylene Diamine (EN), and Diethylene Triamine (DYE).

### Step-by-Step Solution:

1. **Understanding Bidentate Ligands**:
- Bidentate ligands are those that have two donor atoms that can coordinate (bond) to a central metal atom. Each donor atom must have a lone pair of electrons available for bonding.

2. **Analyzing Acetyl Acetonate (ACAC)**:
- The structure of Acetyl Acetonate (CH3C(O)CH2C(O)CH3) has two oxygen atoms that can donate lone pairs to the metal center. Therefore, ACAC is a bidentate ligand.

3. **Analyzing Oxalate (OX)**:
- The oxalate ion (C2O4^2-) has two carboxylate groups, each containing an oxygen atom that can donate a lone pair. Thus, oxalate is also a bidentate ligand.

4. **Analyzing Ethylene Diamine (EN)**:
- Ethylene Diamine (NH2CH2CH2NH2) has two nitrogen atoms, each with a lone pair of electrons that can coordinate to a metal atom. Therefore, Ethylene Diamine is a bidentate ligand.

5. **Analyzing Diethylene Triamine (DYE)**:
- Diethylene Triamine (NH2CH2CH2NHCH2CH2NH2) contains three nitrogen atoms, each with a lone pair of electrons. However, it can coordinate through all three nitrogen atoms, making it a tridentate ligand, not a bidentate ligand.

### Conclusion:
The ligand that is **not** a bidentate ligand is **Diethylene Triamine (DYE)**, as it has three donor sites and can form three bonds with the central metal atom.