The questions given below consist of Assertion (A) and Reason (R ) . Use the following key to select the correct answer.
Assertion : `Ni("dmg")_2` is a square planar complex.
Reason : Chelation effect is present in `Ni("dmg")_2`.

Options

A. Statement-1 is True , Statement-2 is True , Statement-2 is a correct explanation for Statement-1
B. Statement-1 is True , Statement-2 is True , Statement-2 is NOT a correct explanation for Statement-1
C. Statement-1 is True , Statement-2 is False
D. Statement-1 is False , Statement-2 is True

Answer

To analyze the given Assertion (A) and Reason (R), we will break down the concepts involved step by step.

### Step 1: Understanding the Assertion
**Assertion (A):** `Ni(dmg)₂` is a square planar complex.

- **Explanation:** Nickel (Ni) in the complex `Ni(dmg)₂` has a coordination number of 4. This is because the ligand dimethylglyoxime (dmg) acts as a bidentate ligand, meaning it can form two bonds with the metal center. In coordination chemistry, when a metal has a coordination number of 4, it can adopt different geometries, including tetrahedral and square planar. However, for nickel(II), the square planar geometry is more common due to the specific electronic configuration and steric factors.

### Step 2: Understanding the Reason
**Reason (R):** Chelation effect is present in `Ni(dmg)₂`.

- **Explanation:** The chelation effect refers to the enhanced stability of a complex formed by a chelating ligand, which can bind to a metal ion at multiple sites, forming a ring structure. In `Ni(dmg)₂`, the dimethylglyoxime ligand is bidentate, meaning it can attach to the nickel ion at two points, leading to the formation of a five-membered ring. This ring formation is a characteristic of chelating ligands and contributes to the stability of the complex.

### Step 3: Evaluating the Relationship Between Assertion and Reason
- Both the assertion and the reason are true statements.
- However, the reason provided does not explain why `Ni(dmg)₂` is a square planar complex. The square planar geometry is primarily due to the coordination number and the electronic configuration of nickel, rather than the chelation effect itself.

### Conclusion
- **Assertion (A) is true.**
- **Reason (R) is true.**
- **However, (R) is not the correct explanation for (A).**

Thus, the correct answer is that both statements are true, but the reason is not the correct explanation for the assertion.

### Final Answer
The correct option is:
- Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion. (Option B)

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