Question

Consider the following statements for [Ni(dmg)$_2$]: (A) It is a red coloured compound.
(B) It is readily soluble in water at pH = 9.
(C) Central metal ion has two unpaired electrons.
(D) It has four, 5-membered metal containing rings.

• A. A and D are correct
• B. B, C and D are incorrect
• C. A, C and D are correct
• D. A, B, C, D are incorrect

Hint:

When analyzing metal-ligand complexes, be aware of their solubility and color based on the coordination environment and the oxidation state of the metal ion.

Answer 1

The Correct Option is B

Let's analyze each statement for the compound [Ni(dmg)₂], where dmg stands for dimethylglyoxime:

1. Statement A: It is a red coloured compound.
   • [Ni(dmg)₂] is known to form a red-colored complex. This is a characteristic feature of nickel complexes with dimethylglyoxime. Hence, statement A is correct.
2. Statement B: It is readily soluble in water at pH = 9.
   • The complex [Ni(dmg)₂] is not water-soluble. It is known for its low solubility which is utilized in a gravimetric analysis to precipitate nickel. Hence, statement B is incorrect.
3. Statement C: Central metal ion has two unpaired electrons.
   • Nickel in [Ni(dmg)₂] is in the +2 oxidation state. The electronic configuration of Ni²⁺ is [Ar] 3d⁸. Upon complexation with dimethylglyoxime, it forms a square planar complex that is diamagnetic. Thus, it has no unpaired electrons. Therefore, statement C is incorrect.
4. Statement D: It has four, 5-membered metal containing rings.
   • The complex [Ni(dmg)₂] contains two 5-membered rings, not four. These rings are formed due to the chelation of dimethylglyoxime around the nickel ion. Hence, statement D is incorrect.

Based on the analysis above, the correct answer is that statements B, C, and D are incorrect.