A: Coordination number of `Fe^(2+)` in ferrocene is 10.
R: Ferrocene is `pi` bonded complex 

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. ) If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question regarding the assertion and reason related to ferrocene, we will follow these steps:

### Step 1: Understand the Assertion
The assertion states that the coordination number of \( \text{Fe}^{2+} \) in ferrocene is 10.

### Step 2: Analyze Ferrocene Structure
Ferrocene is an organometallic compound with the formula \( \text{Fe}(\text{C}_5\text{H}_5)_2 \). It consists of an iron (Fe) atom sandwiched between two cyclopentadienyl anions (\( \text{C}_5\text{H}_5^{-} \)). Each cyclopentadienyl anion has 5 carbon atoms.

### Step 3: Determine Coordination Number
In ferrocene, the iron atom is bonded to two cyclopentadienyl rings. Each ring contributes 5 coordination sites (the 5 carbon atoms). Therefore, the total coordination number is:
\[ \text{Coordination Number} = 5 \text{ (from one ring)} + 5 \text{ (from the other ring)} = 10 \]
This confirms that the assertion is true.

### Step 4: Understand the Reason
The reason states that ferrocene is a pi-bonded complex.

### Step 5: Analyze Pi Bonding in Ferrocene
In ferrocene, the cyclopentadienyl anions have delocalized pi electrons that can interact with the iron atom. This interaction is characteristic of pi bonding, as the pi electrons from the cyclopentadienyl rings are shared with the iron atom.

### Step 6: Determine the Truth of the Reason
Since the pi electrons are indeed shared with the iron, the reason is also true.

### Step 7: Evaluate the Relationship Between Assertion and Reason
While both the assertion and reason are true, the reason does not explain why the coordination number of \( \text{Fe}^{2+} \) is 10. The coordination number is based on the number of bonding sites from the cyclopentadienyl rings, while the reason discusses the nature of bonding (pi bonding).

### Conclusion
Both the assertion and reason are true, but the reason does not correctly explain the assertion. Therefore, the correct option is that both are true, but the reason is not the correct explanation of the assertion.

### Final Answer
The correct option is **Option 2**: Both assertion and reason are true, but reason is not the correct explanation of assertion.

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