Which is not a `pi`-bonded complex ?

Options

A. Zeise's salt
B. Ferrocene
C. bis(benzene) chromium
D. Tetraethyl lead

Explanation

To determine which complex is not a pi-bonded complex, we need to understand the characteristics of pi-bonded complexes and identify the nature of bonding in the given options.

### Step-by-Step Solution:

1. **Understanding Pi-Bonded Complexes**:
- Pi-bonded complexes involve ligands that can donate electron pairs to the metal while the metal can also donate electron pairs back to the ligands. This type of bonding is known as synergic bonding.
- Ligands that participate in this type of bonding are referred to as pi ligands.

2. **Analyzing the Given Options**:
- **Option 1: G's Salt (K[PtCl3(C2H4)])**:
- C2H4 (ethylene) acts as a pi ligand. Therefore, G's salt is a pi-bonded complex.

- **Option 2: Ferrocene (Fe(C5H5)2)**:
- Cyclopentadienyl (C5H5) is also a pi ligand. Hence, ferrocene is a pi-bonded complex.

- **Option 3: Bisbenzene Chromium (Cr(C6H6)2)**:
- Benzene (C6H6) is a pi ligand as well. Thus, bisbenzene chromium is a pi-bonded complex.

- **Option 4: Tetraethyl Lead (Pb(C2H5)4)**:
- In tetraethyl lead, the bonding occurs through sigma bonds with the ethyl groups (C2H5). There are no pi ligands involved, making this a sigma-bonded complex.

3. **Conclusion**:
- The complex that is not a pi-bonded complex is **Tetraethyl Lead (Pb(C2H5)4)**, as it forms only sigma bonds with the ethyl groups.

### Final Answer:
Tetraethyl Lead (Pb(C2H5)4) is not a pi-bonded complex.