Which of the following is not an ambidentate ligand ?

Options

A. `CN^(-)`
B. `SCN^(-)`
C. `CO`
D. `NO_(2)^(-)`

Explanation

To determine which of the given options is not an ambidentate ligand, we need to understand the definition and characteristics of ambidentate ligands.

### Step-by-Step Solution:

1. **Understand Ambidentate Ligands**:
- Ambidentate ligands are ligands that have more than one donor atom but can only coordinate to the metal center through one of these donor atoms at a time.

2. **Identify Examples of Ambidentate Ligands**:
- Common examples include:
- **Cyanide (CN⁻)**: Can donate through carbon or nitrogen, but only one at a time.
- **Thiocyanate (NCS⁻)**: Can coordinate through either sulfur or nitrogen.
- **Nitrite (NO₂⁻)**: Can coordinate through nitrogen or oxygen.

3. **Analyze the Given Options**:
- We need to analyze each ligand provided in the options to see if they can coordinate through multiple donor atoms.
- For instance:
- **CN⁻**: Ambidentate (can coordinate through C or N).
- **NCS⁻**: Ambidentate (can coordinate through S or N).
- **NO₂⁻**: Ambidentate (can coordinate through N or O).
- **CO**: This ligand has only one donor atom (the carbon atom), which can only donate its electron pair to the metal center.

4. **Conclusion**:
- Based on the analysis, **CO** is the ligand that is not ambidentate because it has only one donor site.

### Final Answer:
The ligand that is not an ambidentate ligand is **CO**.

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