Which of the following molecule has weakest `(ppi-dpi)` back bonding?

Options

A. `OCl_(2)`
B. `N(SiH_(3))_(3)`
C. `SiF_(3)`
D. `O(SiH_(3))_(2)`

Answer

To determine which molecule has the weakest p-pi d-pi back bonding, we need to analyze the bonding characteristics of the given molecules. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand Back Bonding
Back bonding occurs when a ligand donates electron density to a metal center, and the metal, in turn, donates some electron density back to the ligand. In the case of p-pi d-pi back bonding, p orbitals from the ligand interact with d orbitals of the metal.

**Hint:** Recall that back bonding involves the donation of electrons from both the ligand and the metal.

### Step 2: Identify the Molecules
The molecules in question are likely to involve combinations of elements such as oxygen, nitrogen, silicon, and chlorine. We need to identify which of these can participate in p-pi d-pi back bonding.

**Hint:** List the elements and their respective orbitals (p or d) to understand their bonding capabilities.

### Step 3: Analyze the Electronegativity
Electronegativity plays a crucial role in back bonding. More electronegative atoms tend to hold onto their electrons more tightly, making them less likely to participate in back bonding.

**Hint:** Consider the electronegativity of the elements involved. Higher electronegativity means weaker back bonding.

### Step 4: Evaluate Each Molecule
- **OCl2**: Oxygen has a high electronegativity and is less likely to donate electrons to chlorine, which has d orbitals. This results in weak p-pi d-pi back bonding.
- **Other molecules**: Analyze other combinations (like SiO2, N2O, etc.) to see if they exhibit stronger back bonding due to lower electronegativity or better orbital overlap.

**Hint:** Compare the bonding characteristics of each molecule to see which one shows the least effective back bonding.

### Step 5: Conclusion
After evaluating the bonding characteristics and electronegativities, we conclude that **OCl2** has the weakest p-pi d-pi back bonding due to the high electronegativity of oxygen, which prevents effective electron donation to chlorine.

**Final Answer:** OCl2 has the weakest p-pi d-pi back bonding.