Red precipitate is obtained when ethanol solution of dimethylglyoxime is added to ammoniacal Ni(II). Which of the following statements is not true ?

Options

A. Complex has symmetrical H-bonding
B. Red complex has a tetrahedral geometry
C. Dimethylglyoxime functions as bidentate ligand
D. Red complex has a square planar geometry.

Explanation

To solve the question regarding the red precipitate obtained when ethanol solution of dimethylglyoxime is added to ammoniacal Ni(II), we need to analyze the statements provided and determine which one is not true.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- When dimethylglyoxime (DMG) is added to an ammoniacal solution of nickel(II) ions (Ni²⁺), a red precipitate is formed. This precipitate is a complex of nickel with dimethylglyoxime.

2. **Identifying the Complex**:
- The complex formed is known as nickel dimethylglyoxime (Ni(DMG)₂). The structure of this complex involves nickel at the center, coordinated by two dimethylglyoxime molecules.

3. **Analyzing the Geometry**:
- The geometry of the Ni(DMG)₂ complex is square planar, not tetrahedral. This is important to note because it helps us evaluate the statements provided.

4. **Evaluating the Statements**:
- **Statement A**: "The complex has symmetrical H bonding."
- This statement is true because the hydrogen bonding in the complex is symmetrical.
- **Statement B**: "The complex has tetrahedral geometry."
- This statement is false because the complex actually has square planar geometry.
- **Statement C**: "The DMG functions as a bidentate ligand."
- This statement is true because DMG can coordinate to the nickel through two donor sites.

5. **Conclusion**:
- The statement that is not true is Statement B: "The complex has tetrahedral geometry."

### Final Answer:
The statement that is not true is: **"The complex has tetrahedral geometry."**