Given below are two statements.
Statement I The identification of Ni2+ is carried out by dimethyl gl

Q: Why do we need $\text{NH}_4\text{OH}$ for this reaction?

$\text{NH}_4\text{OH}$ provides a basic medium. This is crucial because it helps remove a proton from the neutral DMG molecule, converting it into the $\text{DMG}^-$ anion, which then strongly coordinates with the $\text{Ni}^{2+}$ ion.

Q: Is DMG really a neutral ligand?

As a standalone molecule, Dimethyl glyoxime is completely neutral. However, when it acts as a ligand in this specific complex, it loses a proton and acts as a monoanionic ligand ($\text{DMG}^-$). The statement refers to the molecule itself, which is why it's considered true.

Q: What is the geometry of the $\text{Ni}(\text{DMG})_2$ complex?

The complex has a square planar geometry. The $\text{Ni}^{2+}$ ion is $dsp^2$ hybridized, and the four nitrogen atoms from the two DMG ligands occupy the four corners of a square.

Q: Why is the $\text{Ni}(\text{DMG})_2$ complex so exceptionally stable?

Its high stability comes from the chelate effect. Not only do the DMG ligands form five-membered rings with the Nickel ion, but the intramolecular hydrogen bonds between the oxygen atoms form two additional six-membered rings!

Q: Can DMG act as a ligand without losing a proton?

Yes, in some rare complexes, DMG can coordinate as a neutral ligand. But in the classic analytical test for Nickel, it always coordinates as the $\text{DMG}^-$ anion.

Question

Given below are two statements.
Statement I The identification of $	ext{Ni}^{2+}$ is carried out by dimethyl glyoxime in the presence of $	ext{NH}_4	ext{OH}$.
Statement II The dimethyl glyoxime is a bidentate neutral ligand.
In the light of the above statements, choose the correct answer from the options given below.

Options:

(A) Both statements I and II are true.

(B) Both statements I and II are false.

(C) Statement I is true but statement II is false.

(D) Statement I is false but statement II is true.

Sigma Percentile · Accepted Answer

### The Magic of Dimethyl Glyoxime

Welcome to one of the most beautiful and classic reactions in coordination chemistry! We are looking at the famous test for identifying **Nickel ions** in a solution.

This test is not just a dry fact to memorize; it is a visually stunning reaction that produces a brilliant rosy red precipitate. Let's break down the chemistry behind this magic.

### Analyzing Statement I: The Classic Nickel Test

Statement I claims that the identification of $	ext{Ni}^{2+}$ is carried out by dimethyl glyoxime (DMG) in the presence of $	ext{NH}_4	ext{OH}$.

This is absolutely correct. When we add DMG to a solution containing $	ext{Ni}^{2+}$ ions, we need a basic medium to facilitate the reaction. Ammonium hydroxide ($	ext{NH}_4	ext{OH}$) provides this perfect basic environment.

The reaction yields a highly insoluble, rosy red precipitate of the $	ext{Ni}(	ext{DMG})_2$ complex.

$$ 	ext{Ni}^{2+} + 2	ext{DMG} \xrightarrow{	ext{NH}_4	ext{OH}} 	ext{Ni}(	ext{DMG})_2 \downarrow $$

Because this test is so reliable and visually distinct, Statement I is undeniably true.

### Analyzing Statement II: The Nature of DMG

Now, let's examine Statement II, which states that dimethyl glyoxime is a bidentate neutral ligand.

If we look at the standalone structure of the DMG molecule, it is indeed completely neutral. It contains two nitrogen atoms, each possessing a lone pair of electrons ready to be donated to a metal center.

Because it can coordinate through these two nitrogen atoms simultaneously, it is classified as a **bidentate ligand**. Therefore, describing the DMG molecule as a "bidentate neutral ligand" is factually true.

### The Secret to Stability: Hydrogen Bonding

Here is where the chemistry gets incredibly fascinating. While DMG is a neutral molecule, the basic medium ($	ext{NH}_4	ext{OH}$) plays a crucial role. It removes one proton ($	ext{H}^+$) from each DMG molecule, converting it into the monoanionic $	ext{DMG}^-$ ligand.

When two of these $	ext{DMG}^-$ ligands coordinate with the $	ext{Ni}^{2+}$ ion, they form a **square planar geometry**. But the stability of this complex doesn't just come from the metal-ligand bonds.

Look closely at the top and bottom of the complex structure. The oxygen atoms from the adjacent ligands engage in **intramolecular hydrogen bonding**.

This hydrogen bonding creates two additional six-membered chelate rings! This massive chelate effect is the secret behind the exceptional stability and the striking color of the rosy red precipitate.

### Final Conclusion

To wrap up our analysis, both statements hold their ground.

Statement I correctly describes the standard laboratory test for Nickel. Statement II correctly describes the intrinsic nature of the DMG molecule as a neutral, bidentate species.

Therefore, the correct option is **(a) Both statements I and II are true.**

Select Answer:

Visualized Solution

Identification of $Ni^{2 +}$

Reaction of $Ni^{2 +}$ with DMG

Structure of Dimethyl Glyoxime

Formation of the Complex

The $Ni (DMG)_{2}$ Complex

Conclusion

The Sigma Insight: Nomenclature, Isomerism, Importance and Werner's Theory

The Magic of Dimethyl Glyoxime

Analyzing Statement I

Analyzing Statement II

The Secret to Stability

Final Conclusion

Similar Questions

In the coordination compound, $K_{4} [N i (C N)_{4}]$ the oxidation state of nickel is

The correct option(s) regarding the complex $[C o (e n) (N H_{3})_{3} (H_{2} O)]^{3 +}$ :- $(e n = H_{2} N C H_{2} C H_{2} N H_{2})$ is (are)

The one that is not expected to show isomerism is

The coordination number and the oxidation state of the element 'E' in the complex $[E (en)_{2} (C_{2} O_{4})] N O_{2}$ (where (en) is ethylene diamine) are, respectively

The correct structures of trans-[NiBr_2(PPh_3)_2] and meridonial-[Co(NH_3)_3(NO_2)_3], respectively are

The equation which is balanced and represents the correct product(s) is

Match each coordination compound in List-I with an appropriate pair of characteristics from List-II and select the correct answer using the code given below the lists. ${en = H_{2} NCH_{2} CH_{2} NH_{2}; atomic numbers ; Ti = 22; Cr = 24; Co = 27; Pt = 78}$

List-I

List-II

Consider the complex ions, trans-[Co(en)2Cl2]+ (A) and cis-[Co(en)2Cl2]+ (B). The correct statement regarding them is