Compound (A) on reduction with `LiAIH_4` gives a hydribe (P) containing 21.72% hydrogen along with other products.The one mole of hydride (P) and 2 moles of ammonia at higher temperature gives a compound (Q) which is known as inorganic benzene. (A) hydrolyses incompletely and forms a compound (R) and `H_3BO_2`
Which of the following statement is incorrect for the compound (A) ?

Options

A. It has trigonal planar geometry
B. The bond length between the central atom and the substituent atoms is shorter than the sum of the covalent radii.
C. The coordination geometry around central atom of compound (A) and N atom in 1:1 complex of (A) and `NH_3` is same.
D. In compound (A) , there is `ppi-dpi` bonding

Explanation

To solve the question step-by-step, we need to analyze the information given about compound (A) and its reactions.

### Step 1: Identify Compound (A)
The problem states that compound (A) on reduction with lithium aluminum hydride (LiAlH4) gives a hydride (P) containing 21.72% hydrogen. The hydride (P) is likely diborane (B2H6) because it is a common product formed from the reduction of boron compounds.

**Hint:** Look for common boron compounds that can be reduced to form hydrides.

### Step 2: Analyze the Composition of Hydride (P)
Given that hydride (P) contains 21.72% hydrogen, we can calculate its empirical formula. The molar mass of B2H6 can be calculated as follows:
- Boron (B) = 10.81 g/mol
- Hydrogen (H) = 1.008 g/mol
- Molar mass of B2H6 = (2 × 10.81) + (6 × 1.008) = 21.62 + 6.048 = 27.668 g/mol

Calculating the percentage of hydrogen:
\[ \text{Percentage of H} = \left( \frac{6 \times 1.008}{27.668} \right) \times 100 = 21.72\% \]

**Hint:** Use the molar mass to verify the percentage composition of hydrogen.

### Step 3: Reaction of Hydride (P) with Ammonia
One mole of hydride (P) reacts with two moles of ammonia (NH3) at higher temperatures to form compound (Q), known as inorganic benzene, which is B3N3H6 (borazine).

**Hint:** Recognize the reaction between boron hydrides and ammonia that leads to the formation of borazine.

### Step 4: Hydrolysis of Compound (A)
Compound (A) hydrolyzes incompletely to form compound (R) and H3BO3 (boric acid). The incomplete hydrolysis of BF3 leads to the formation of HBF4 (tetrafluoroboric acid) and H3BO3.

**Hint:** Understand the hydrolysis reactions of boron compounds.

### Step 5: Analyze the Statements About Compound (A)
Now we need to evaluate the statements given about compound (A) (BF3):

1. **Statement A:** It has triangular planar symmetry.
- This is true as BF3 has a trigonal planar structure.

2. **Statement B:** The bond length between the central atom and the subsequent atom is shorter than the sum of the covalent radii.
- This is also true due to p-pi p-pi back bonding.

3. **Statement C:** The coordination geometry around the central atom of compound (A) and the nitrogen atom in a 1:1 complex of A and NH3 is the same.
- This is true, as both will exhibit sp3 hybridization in the complex.

4. **Statement D:** In compound (A), there is p-pi d-pi bonding.
- This is incorrect. BF3 exhibits p-pi p-pi bonding, not p-pi d-pi bonding.

**Final Conclusion:** The incorrect statement about compound (A) is **Statement D**.

### Summary of Steps:
1. Identify compound (A) as BF3.
2. Calculate the percentage of hydrogen in hydride (P).
3. Understand the reaction of hydride (P) with ammonia to form inorganic benzene (Q).
4. Analyze the incomplete hydrolysis of compound (A).
5. Evaluate the statements to find the incorrect one.