Coordination Compounds Part 4

Concept:Nickel(II) dimethylglyoxime complex has $\mathrm{Ni}^{2+}$ with $3d^8$ configuration.It undergoes $\mathrm{dsp}^2$ hybridization forming a square planar geometry.This leads to zero unpaired electrons and a characteristic red precipitate.Chemical Equation / Formula:The complex is $\mathrm{Ni}(\mathrm{DMG})_2$ (DMG = dimethylglyoxime anion).Each bidentate DMG ligand forms one five‑membered chelate ring with Ni.Explanation:Statement A: The complex is rose‑red in colour – correct.Statement B: The complex precipitates at $\mathrm{pH}=9$ but is sparingly soluble in water – incorrect (not highly soluble).Statement C: $\mathrm{Ni}^{2+}$ ($3d^8$) in square planar $\mathrm{dsp}^2$ complex has all electrons paired; zero unpaired $d$‑electrons – incorrect.Statement D: In square planar geometry, adjacent $\mathrm{N}-\mathrm{Ni}-\mathrm{N}$ bond angles are about $90^\circ$ – correct.Statement E: Two DMG ligands give only two five‑membered metallacycles, not four – incorrect.Shortcut:$\mathrm{Ni}^{2+}$ square planar is diamagnetic (0 unpaired $e^-$).Number of chelate rings = number of bidentate ligands = 2.Answer:Incorrect statements are B, C, and E. Correct option: C. B, C and E Only.