Question

The IUPAC name of the complex \([ \text{Co(NH}_3 )_5(\text{NO}_2)]\text{Cl}_2\) is:

• A. Pentaamminenitrito-O-cobalt(III) chloride
• B. Pentaamminenitrito-N-cobalt(III) chloride
• C. Pentaamminenitro-cobalt(III) chloride
• D. Pentaamminenitroso-cobalt(II) chloride

Hint:

Ambidentate ligands like NO\(_2^-\) must specify donor atom as nitrito-N or nitrito-O. Check ligand attachment carefully.

Answer 1

The Correct Option is B

- The complex has 5 NH\(_3\) and one NO\(_2^-\) ligand. - NO\(_2^-\) can bind via N (–NO\(_2\)) or O (–ONO), so it must be specified. - Oxidation state of Co: \[ x + 5(0) + (-1) = +2 \Rightarrow x = +3 \Rightarrow \text{Cobalt(III)} \] Since NO\(_2^-\) is written as NO\(_2\) (not ONO), it is nitrito-N. Hence the IUPAC name is: \[ \boxed{\text{Pentaamminenitrito-N-cobalt(III) chloride}} \]