Assertion (A) : `N (SiH_3)_3` is a weaker based than`N (CH_3)_3`
Reason (R) : Due to ` p pi - d pi` back bonding imn `N (SiH_3)_3` the availvbaility of electrons on the (B) atom in `(SiH_3) N` decrease .

Options

A. If both (A) and (R) are correct and (R) is correct explanation of (A)
B. If both (A) and (R) are correct and (R) is NOT correct explanation of (A)
C. If (A) is correct , but (R) is incorrect
D. If (A) is incorrect but (R) is correct

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understanding the Assertion
The assertion states that \( N(SiH_3)_3 \) is a weaker base than \( N(CH_3)_3 \).

- **Base Strength**: The basicity of a compound is determined by the availability of the lone pair of electrons on the nitrogen atom to donate to protons (H⁺ ions).
- In \( N(CH_3)_3 \), there is no possibility of back bonding because carbon does not have vacant d orbitals. Thus, the lone pair on nitrogen is readily available for donation, making it a stronger base.
- In contrast, \( N(SiH_3)_3 \) can engage in pπ-dπ back bonding due to the presence of silicon, which has vacant d orbitals. This back bonding reduces the availability of the lone pair on nitrogen, making it a weaker base.

### Step 2: Understanding the Reason
The reason states that due to pπ-dπ back bonding in \( N(SiH_3)_3 \), the availability of electrons on the nitrogen atom decreases.

- **pπ-dπ Back Bonding**: This occurs when the lone pair of electrons on nitrogen can overlap with the empty d orbitals of silicon. This overlap stabilizes the molecule but decreases the availability of the lone pair for protonation.
- Therefore, the reason correctly explains why \( N(SiH_3)_3 \) is a weaker base than \( N(CH_3)_3 \).

### Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion. Thus, the correct answer is that both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

### Final Answer
Both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

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