Which of the following involves synergic bonding?

Options

A. `[Fe(C_(5)H_(5))_(2))]`
B. `(CH_(3))_(2)Zn`
C. `[Fe(CO)_(5)]`
D. `CH_(3)MgBr`

Answer

To determine which of the given options involves synergic bonding, we need to understand the concept of synergic bonding and analyze the options provided.

### Step-by-Step Solution:

1. **Understanding Synergic Bonding**:
- Synergic bonding occurs when both sigma (σ) and pi (π) bonds are formed between a metal and a ligand. In this type of bonding, the ligand donates electron density to the metal through its lone pair (σ donation), and simultaneously, the metal can donate electron density back to the ligand through its empty π* (pi star) orbital (π back-donation).
- This dual interaction strengthens the overall bond between the metal and the ligand.

2. **Identifying the Ligands**:
- Review the ligands mentioned in the options. Common ligands that exhibit synergic bonding include carbon monoxide (CO), which is a strong π-acceptor, and certain organometallic compounds.

3. **Analyzing Each Option**:
- **Option 1: CO (Carbon Monoxide)**:
- CO is a well-known example of a ligand that exhibits synergic bonding. It can donate electron density through its lone pair (σ donation) and accept electron density back from the metal into its π* orbital (π back-donation).
- **Option 2: Cyclopentadienyl (C5H5)**:
- Cyclopentadienyl ligands typically form π bonds with metals but do not exhibit significant σ donation. Thus, they do not involve synergic bonding.
- **Option 3: CH3MgBr (Methylmagnesium Bromide)**:
- This compound primarily forms σ bonds and does not involve π bonding, so it cannot exhibit synergic bonding.
- **Option 4: Other Ligands**:
- If there are other ligands provided in the options, analyze them similarly to determine their bonding characteristics.

4. **Conclusion**:
- Based on the analysis, the ligand that involves synergic bonding is **CO**. It participates in both σ donation and π back-donation, making it a classic example of synergic bonding.

### Final Answer:
The ligand that involves synergic bonding is **Carbon Monoxide (CO)**.

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