Question

Identify the correct naming for $\left[Co\right(ONO\left)\right(N{H}_3{)}_5{]}^{2+}$.

• A. Pentaamminenitrocobalt(III)
• B. Pentaamminenitrito-O cobalt (III)
• C. Pentaamminenitritocobaltate(III)
• D. Pentaamminenitrito-N cobalt(III)

Answer 1

The correct option is B Pentaamminenitrito-O cobalt (III)

The names of coordination compounds are derived by the following principles of nomenclature,
1. The cation is named first in both positively and negatively charged coordination entities.
2. The ligands are named in an alphabetical order before the name of the central atom/ion.

$\left[Co\right(ONO\left)\right(N{H}_3{)}_5{]}^{2+}$
By rule (1), cationic complex is named first.

Ligands:
$N{H}_3\to \text{Neutral monodentate ligand and it named as 'ammine'}$
It will have prefix 'penta'.

$ONO\to \text{Negative ambidentate ligand and it named as 'O-nitrito'}$
Oxidation state of $Co$ is
$x+(-1)+\left(0\right)=+2x=+3$

Hence, the IUPAC name is Pentaamminenitrito-O cobalt(III) ion.