Question

The IUPAC name for the complex $\left[Co\right(N{H}_3{)}_5\left(N{O}_2\right)]C{l}_2$ is:

• A. nitrito-N-pentaamminecobalt(III) chloride
• B. nitrito-N-pentamminecobalt(II) chloride
• C. pentaamminenitrito-N-cobalt(II) chloride
  
• D. pentaamminenitrito-N-cobalt(III) chloride

Answer 1

The correct option is D pentaamminenitrito-N-cobalt(III) chloride

First of all, the compound has complex positive part therefore, according to IUPAC convention positive part will be named first Secondly in written name of complex, ligands are named first in alphabetical order, irrespective of its charge, hence ''ammine'' will be written prior to "nitrito-N or nitro''.
Oxidation state of Co be "x"
$x+5\times 0+1\times (-1)=+2$
$x=+3$
Therefore, IUPAC is pentaamminenitrito-N-cobalt(III) chloride.
Hence, option (d) is correct.