Question

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 :

• A. C and E Only
• B. B, C and E Only
• C. A, D and B Only
• D. C and D Only

Hint:

Work out the hybridization and geometry of the nickel complex first. That single structure, square planar, diamagnetic, two chelate rings per ligand, settles most of the statements at once, rather than checking each one from memory.

Answer 1

The Correct Option is B

Let's evaluate the given statements about the nickel(II) complex of dimethylglyoxime to determine their correctness:

1. The statement A. It is red in colour. is correct. The nickel(II) complex with dimethylglyoxime forms a red precipitate, which is a known characteristic of the Ni(dmg)₂ complex.
2. The statement B. It has a high solubility in water at pH = 9. is incorrect. The Ni(dmg)₂ complex is known to be relatively insoluble in water, particularly under neutral and basic conditions like pH = 9, where it forms a precipitate instead.
3. The statement C. The Ni ion has two unpaired d-electrons. is incorrect. In the nickel(II) complex with dimethylglyoxime, Ni²⁺ is in a square planar geometry. In this geometry, due to strong ligand field and electron pairing, the nickel ion typically has no unpaired electrons.
4. The statement D. The N – Ni – N bond angle is almost close to 90°. is correct. In a square planar geometry, the N – Ni – N angle is approximately 90°.
5. The statement E. The complex contains four five-membered metallacycles (metal containing rings). is incorrect. The complex actually consists of two five-membered metallacycles, not four.

Based on the evaluation:

• Statement B is incorrect as the complex is insoluble in water at pH = 9.
• Statement C is incorrect as the nickel ion does not have unpaired d-electrons in the complex.
• Statement E is incorrect as the complex forms two, not four, five-membered metallacycles.

Thus, the incorrect statements are B, C, and E. The correct answer is B, C and E Only.