Question

IUPAC name of $N{a}_3\left[Co{\left(ONO\right)}_6\right]$ is:

• A. Sodium cobaltinitrite
• B. Sodium hexanitritocobaltate (III)
• C. Sodium hexanitrocobalt (III)
• D. Sodium hexanitritocobaltate (II)

Answer 1

Answer: (B)

Sodium hexanitritocobaltate (III)

The above complex ${Na}_3\left[Co\right(ONO{)}_6]$ has two ions: ${Na}^{+}$ and a complex ion which is negatively charged $\left[Co\right(ONO{)}_6{]}^{-}$

According to the rules, name of the positive ion comes first (i.e., sodium), do not mention the number of sodium as it is not present in a square bracket.

After naming the positive ion, next will be the negative ion, Now in this example,the negative ion is a complex compound, which contain's 'metal' and 'ligand'. While naming a complex, name of ligand comes first, also mention the number of ligand by using prefix (di, tri, tetra. etc..) and if a bidentate ligand is present then mention the atom which is attached to central metal (i.e., hexanitrito $-O-)$ followed by name of metal with the ending 'ate' (i.e., cobaltate, always use the word 'ate' if the complex is negatively charge) and than oxidation number of metal.

To show the oxidation state, we use Roman numerals inside parenthesis.

Option B is correct.