`pi` bonding is not involved in

Options

A. Ferrocene
B. Dibenzene chromium
C. Zeise's slat
D. Grignard reagent

Answer

To determine which complex does not involve π bonding, we can analyze the given options step by step.

### Step 1: Analyze Ferrocene
- **Description**: Ferrocene is an organometallic compound where a cyclopentadienyl anion (C5H5-) forms a sandwich complex with iron (Fe).
- **Bonding**: In ferrocene, the cyclopentadienyl rings donate π electrons to the iron center, resulting in π bonding.
- **Conclusion**: Ferrocene involves π bonding.

### Step 2: Analyze Dibenzene Chromium
- **Description**: Dibenzene chromium is a complex where chromium is sandwiched between two benzene rings.
- **Bonding**: Similar to ferrocene, the benzene rings donate π electrons to the chromium center, leading to π bonding.
- **Conclusion**: Dibenzene chromium involves π bonding.

### Step 3: Analyze G Salt
- **Description**: G salt refers to a complex that typically involves a metal and a ligand that can participate in π bonding.
- **Bonding**: Like the previous examples, G salt also involves π bonding due to the interaction between the metal and the π electrons of the ligands.
- **Conclusion**: G salt involves π bonding.

### Step 4: Analyze Grignard Reagent
- **Description**: A Grignard reagent has the general formula R-Mg-X, where R is an organic group, Mg is magnesium, and X is a halogen.
- **Bonding**: The bond between the magnesium and the carbon (R) is a single σ bond. There is no π bonding involved in this interaction.
- **Conclusion**: Grignard reagent does not involve π bonding.

### Final Conclusion
The complex that does not involve π bonding is the **Grignard reagent (R-Mg-X)**.

---