Question

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

• 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.

Answer 1

The Correct Option is B

The question describes the reaction between an ethanol solution of dimethylglyoxime (DMG) and ammoniacal Ni(II), resulting in a red precipitate. This precipitation is a well-known reaction in coordination chemistry where dimethylglyoxime acts as a ligand to form a complex with nickel ions (Ni²⁺).

Let's analyze each statement given in the options:

1. The complex has symmetrical H-bonding:

   This statement is true as the nickel-dimethylglyoxime complex (also known as Ni-DMG complex) has symmetrical hydrogen bonding. In the complex, each glyoxime molecule forms two intramolecular hydrogen bonds, giving this symmetry.

2. Red complex has a tetrahedral geometry:

   This statement is not true. The red complex formed between Ni²⁺ and dimethylglyoxime is a planar structure, specifically a square planar geometry, which is characteristic of this complex.

3. Dimethylglyoxime functions as a bidentate ligand:

   This statement is true. Dimethylglyoxime functions as a bidentate ligand through two nitrogen atoms, each donating a pair of electrons to form coordinate covalent bonds with the nickel ion.

4. Red complex has a square planar geometry:

   This statement is true. The geometry of the nickel-dimethylglyoxime complex is square planar, which is typical for many nickel complexes where the metal is in the +2 oxidation state.

Given these analyses, the statement that is not true is: Red complex has a tetrahedral geometry. This confirms the correct answer, as the geometry of this particular complex is square planar, not tetrahedral.