Given below are two statements: Statement (I): Dimethyl glyoxime forms a six membered covalent chelate when treated…

🧠 One Statement Correct, One Not

• Statement I says DMG forms a six-membered covalent chelate with $\mathrm{NiCl_2}$. The actual chelate ring is five-membered (Ni–N=C–C=N–Ni cycle counts five atoms, including Ni). So I is false.
• Statement II says Prussian blue contains Fe in both +2 and +3. True — Prussian blue is $\mathrm{Fe_4^{III}[Fe^{II}(CN)_6]_3 \cdot xH_2O}$, a mixed-valence complex. So II is true.

Combination: I false, II true → option (1).

🗺️ Verify the DMG Chelate Ring Size

The DMG ligand is $\mathrm{HON{=}C(CH_3){-}C(CH_3){=}NOH}$ (deprotonated to give $\mathrm{HON{=}C(CH_3){-}C(CH_3){=}NO^-}$ as the binding form). Each DMG⁻ binds Ni²⁺ through the two N atoms. The ring goes:

Ni → N=C → C=N → Ni

Five atoms in the ring: Ni, N, C, C, N → 5-membered. Two DMG ligands per Ni²⁺, plus stabilising O–H···O hydrogen bonds connecting the two ligand units. Final geometry: square planar.

⚡ Anchor: DMG-Ni Ring Size

DMG–Ni complex → 5-membered chelate ring × 2 → square planar → bright rosy red precipitate. JEE asks variants of this annually. Always 5.

⚠️ The "6-Membered" Common Slip

Some students count the ring as six (including a hydrogen of the H-bonded bridge). H-bonds are not counted as ring members; only formal coordinate bonds and single covalent C–C, C=N etc count. Ring size for the chelate alone = 5.

$\boxed{\text{Answer: (1) Statement I is false but Statement II is true}}$