Assertion (A) : `B_(2)H_(6),Si2H_(6)` are said to have similar structure .
Reason (R) : They have same number of `sigma` and `pi` bonds.

Options

A. If both A and R are true and R is the correct explanation of A.
B. If both A and R are true but R is not the correct explanation of A.
C. If A is true but R is false
D. If A is false but R is true.

Explanation

To solve the assertion and reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step 1: Understanding the Assertion
The assertion states that \( B_2H_6 \) (diborane) and \( Si_2H_6 \) (disilane) have similar structures.

- **Diborane Structure**:
- Diborane consists of two boron atoms and six hydrogen atoms. Each boron atom undergoes \( sp^3 \) hybridization, resulting in four orbitals.
- In diborane, there are four sigma bonds formed: three \( B-H \) bonds and one \( B-B \) bond, which involves a three-center two-electron bond (banana bond).

- **Disilane Structure**:
- Disilane consists of two silicon atoms and six hydrogen atoms. Each silicon atom also undergoes \( sp^3 \) hybridization.
- In disilane, there are four sigma bonds formed: three \( Si-H \) bonds and one \( Si-Si \) bond.

### Step 2: Analyzing the Reason
The reason states that \( B_2H_6 \) and \( Si_2H_6 \) have the same number of sigma and pi bonds.

- **Sigma Bonds**:
- In \( B_2H_6 \), there are 4 sigma bonds (3 \( B-H \) and 1 \( B-B \)).
- In \( Si_2H_6 \), there are also 4 sigma bonds (3 \( Si-H \) and 1 \( Si-Si \)).

- **Pi Bonds**:
- Neither diborane nor disilane has pi bonds in their structures. Therefore, both have 0 pi bonds.

### Conclusion
- The assertion is **true** because both compounds have similar structures due to \( sp^3 \) hybridization.
- The reason is **false** because while they have the same number of sigma bonds, they do not have the same number of pi bonds (both have 0, but the reason implies a comparison that is not valid).

Thus, the correct conclusion is that the assertion is true, but the reason is false.

### Final Answer
- Assertion (A) is true.
- Reason (R) is false.