In basic medium the amount of $\mathrm{Ni}^{2+}$ in a solution can be estimated with the dimethylglyoxime reagent. The correct statement(s) about the reaction and the product is (are)

• Correct answer
  A

  in a ammoniacal solution $\mathrm{Ni}^{2+}$ salts give cherry-red precipitate of nickel(il) dimethylglyoximate
• Correct answer
  B

  two dimethylglyoximate units are bound to one $\mathrm{Ni}^{2 *}$
• Correct answer
  C

  in the complex two dimethylglyoximate units are hydrogen bonded to each other
• Correct answer
  D

  each dimethylglyoximate unit forms a six membered chelate ring with $\mathrm{Ni}^{2+}$

Solution

Estimation of $\mathrm{Ni}^{2+}$ is carried out as. Filtrate of group III $+\mathrm{NH}_{4} \mathrm{OH}+\mathrm{NH}_{4} \mathrm{Cl} \longrightarrow$ passing $\mathrm{H}_{2} \mathrm{S}$ gas $\rightarrow$ black pPt of NiS. This black ppt of NiS is soluble in conc. HCl in presence of oxidising agent like $\mathrm{KClO}_{3}$ $\mathrm{NiS}+\underset{\mathrm{COnc}}{2 \mathrm{HCl}}+\mathrm{O} \longrightarrow \mathrm{NiCl}_{2}+\mathrm{H}_{2} \mathrm{O}+\mathrm{S}$ Now this $\mathrm{NiCl}_{2}$, in basic medium, treated with dimethyl glyoxime, cherry red ppt of nickel (II) dimethyl glyoximate is obtained, in which two dimethyl glyoximate units are hydrogen bonded to each other and each unit forms a six-membered chelate ring with $\mathrm{Ni}^{2+}$

Hence, the correct answer is options: 'A', 'B', 'C', 'D'.