Carbon monoxide acts as a donor and reacts with certain metals to give carbonyls. This is due to

Options

A. presence of one sigma and two pi bonds between C and O `( :C -= O: )`
B. presence of a lone pair on carbon atom in CO molecule
C. Presence of lone pair on oxygen atom in CO molecule
D. Poisonous nature of CO

Answer

To understand why carbon monoxide (CO) acts as a donor and reacts with certain metals to form carbonyls, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding the Structure of Carbon Monoxide (CO)**:
- Carbon monoxide consists of one carbon atom and one oxygen atom.
- The structure includes a triple bond between carbon and oxygen, which consists of one sigma bond and two pi bonds.
- Additionally, both carbon and oxygen have lone pairs of electrons.

2. **Lone Pairs and Bonding**:
- The presence of lone pairs on the carbon and oxygen atoms is crucial for the reactivity of CO.
- Specifically, the lone pair on the carbon atom can be donated to a metal.

3. **Formation of Metal Carbonyls**:
- When CO interacts with certain metals, the lone pair from the carbon atom can bond with vacant orbitals of the metal.
- This interaction leads to the formation of metal carbonyl complexes, where the metal atom is coordinated to the carbon atom of CO.

4. **Role of the Metal's Vacant Orbitals**:
- The ability of CO to act as a donor is primarily due to the availability of vacant orbitals in the metal that can accept the electron pair from carbon.
- This results in a stable metal-carbon bond, forming a carbonyl complex.

5. **Conclusion**:
- The key reason CO acts as a donor is due to the presence of a lone pair on the carbon atom, which allows it to bond with metals, leading to the formation of carbonyls.

### Final Answer:
The correct reason for carbon monoxide acting as a donor and forming carbonyls with certain metals is **the presence of a lone pair on the carbon atom in CO**.

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