The statements that are incorrect about the nickel(II) complex of dimethylglyoxime are:
A. It is red in colour.
B. It has a high solubility in water at pH =9.
C. The Ni ion has two unpaired d-electrons.
D. The N - Ni - N bond angle is almost close to 90°
E. The complex contains four five-membered metallacycles (metal containing rings).
Choose the correct answer from the options given below :

We need to identify the incorrect statements about the nickel(II) complex of dimethylglyoxime (DMG), which is $$[Ni(DMG)_2]$$.

Statement A: It is red in colour.

The nickel-DMG complex is indeed bright red (also called strawberry red). Statement A is CORRECT.

Statement B: It has high solubility in water at pH = 9.

The nickel-DMG complex is insoluble in water. It precipitates out at pH 5-9, which is actually how nickel is detected gravimetrically. Statement B is INCORRECT.

Statement C: The Ni ion has two unpaired d-electrons.

In the square planar nickel-DMG complex, $$Ni^{2+}$$ has a $$d^8$$ configuration. In a square planar field, all 8 electrons are paired ($$d_{xy}^2, d_{yz}^2, d_{xz}^2, d_{z^2}^2$$, empty $$d_{x^2-y^2}$$). So there are zero unpaired electrons. Statement C is INCORRECT.

Statement D: The N-Ni-N bond angle is almost close to 90 degrees.

In the square planar geometry of the complex, the N-Ni-N bond angle between adjacent nitrogen atoms is approximately 90 degrees. Statement D is CORRECT.

Statement E: The complex contains four five-membered metallacycles.

Each DMG molecule forms one five-membered chelate ring with Ni (Ni-N-C-C-N). With two DMG ligands, there are only two five-membered metallacycles, not four. Statement E is INCORRECT.

The incorrect statements are B, C, and E. The answer is Option D) B, C and E Only.