Find the number of ligand (s) which is//are polydentate ligand
`en, C_(2)O_(4)^(2-)` acac, `DMG` gly,ph .

Explanation

To determine the number of polydentate ligands from the given list (en, C2O4^(2-), acac, DMG, and phen), we need to analyze each ligand and identify how many donor atoms they possess. A polydentate ligand is one that has multiple donor atoms, allowing it to bind to a metal ion at multiple points.

### Step-by-Step Solution:

1. **Identify Ethylenediamine (en)**:
- Ethylenediamine (en) has the structure: NH2-CH2-CH2-NH2.
- It has two nitrogen atoms that can donate electrons to a metal ion.
- **Conclusion**: en is a bidentate ligand (2 donor sites).

2. **Identify Oxalate Ion (C2O4^(2-))**:
- The oxalate ion has the structure: O=C(COO^-)C(=O)O^-.
- It has two carboxylate groups, each capable of donating one pair of electrons.
- **Conclusion**: C2O4^(2-) is a bidentate ligand (2 donor sites).

3. **Identify Acetylacetone (acac)**:
- Acetylacetone (acac) has the structure: CH3C(=O)CH2C(=O)CH3.
- It can donate two pairs of electrons from the two carbonyl oxygen atoms.
- **Conclusion**: acac is a bidentate ligand (2 donor sites).

4. **Identify Dimethylglyoxime (DMG)**:
- Dimethylglyoxime (DMG) has the structure: CH3C(=O)C(=O)CH3 with two nitrogen atoms.
- Each nitrogen can donate a pair of electrons, making it capable of binding at two points.
- **Conclusion**: DMG is a bidentate ligand (2 donor sites).

5. **Identify Phenanthroline (phen)**:
- Phenanthroline (phen) consists of three fused rings with two nitrogen atoms.
- The two nitrogen atoms can donate electrons, allowing it to bind to a metal ion at two points.
- **Conclusion**: phen is a bidentate ligand (2 donor sites).

### Final Count of Polydentate Ligands:
- All the ligands listed (en, C2O4^(2-), acac, DMG, and phen) are bidentate ligands.
- Since each ligand has more than one donor site, they are all considered polydentate ligands.

**Total Number of Polydentate Ligands = 5**