Question

Write the IUPAC names for the following compounds:
(i) [Co(NH${}_3$)${}_5$ONO]Cl${}_2$
(ii) K${}_3$[Cr(CN)${}_6$]

• A. (i) Pentammonianitritocobalt (III) chloride
  (ii) Potassiumhexacyanochromate (II)
• B. (i) Pentammonianitratocobalt (II) chloride
  (ii) Potassiumhexacyanidechromate (III)
• C. (i) Pentamminenitritocobalt (III) chloride
  (ii) Potassiumhexacyanochromate (III)
• D. (i) Pentamminenitrocobalt (II) chloride
  (ii) Potassiumhexacyanchromate (III)

Answer 1

Answer: (C)

(i) Pentamminenitritocobalt (III) chloride

(ii) Potassiumhexacyanochromate (III)

Option (C) is correct.

IUPAC name $\left[Co\right(N{H}_3{)}_{5}ONO]C{l}_2$ is pentamminenitritocobalt (III) chloride. In this complex, ammonia is a neutral ligand,$N{O}_2$ and Cl has -1 charge.The oxidation state of cobalt is this complex is +3 so the word 'cobalt' is used. Oxidation state is written in roman letters within the brackets. Chloride ion is present outside the sphere so it will be named after naming the complex.

IUPAC name of $K_3\left[Cr\right(CN{)}_6]$ is potassiumhexacyanochromate (III). In this complex, cyanide is an anionic ligand and has -1 charge and potassium carries +1 charge. The oxidation state of cobalt is this complex is -3 so word 'alt' is used. Oxidation state is written in roman letters within the brackets.