Question

The IUPAC name of $[Co{(N{H_3})_4}Cl(N{O_2})]Cl$ is:
A) tetraamminechloridonitrito-N-cobalt(III) chloride
B) tetraamminechloridonitritocobalt(II) chloride
C) tetraaminechloridonitrocobalt(I) chloride
D) tetraaminechloridonitritocobalt(II) chloride

Answer 1

Given complex, $[Co{(N{H_3})_4}Cl(N{O_2})]Cl$, is a coordination complex.The formulas and names adopted for the coordination complexes are based on the recommendations of the IUPAC. Recall the rules used for naming coordination complexes given by IUPAC. Ligand $N{O_2}$ is an ambidentate ligand and here, in the given complex, the N- side of the ligand $N{O_2}$ is linked to the metal ion.

Complete step by step solution:
Inside the coordination complex, $[Co{(N{H_3})_4}Cl(N{O_2})]Cl$, there are four $N{H_3}$ ligands, one $Cl$ ligand, one $N{O_2}$ ligand, and one $Cl$ is outside the coordination sphere. $Cl$ is the counter ion in the complex and it has -1 charge , therefore, charge on the complex must be +1, that is, ${[Co{(N{H_3})_4}Cl(N{O_2})]^{ + 1}}$.
Now, let oxidation state of metal ions in the complex i.e., $Co$ is $x$. $N{H_3}$ is a neutral ligand, so charge on $N{H_3}$ is zero. Charge on $Cl$ is -1 and charge on $N{O_2}$ is also -1.
So, calculating the oxidation state of $Co$ in the complex ion ${[Co{(N{H_3})_4}Cl(N{O_2})]^{ + 1}}$ :
$x + 4(0) + ( - 1) + ( - 1) = + 1$
$\Rightarrow x = + 3$ .
Therefore, the oxidation state of $Co$ in the complex ion is +3 and in the IUPAC naming it will be written as (III) with the metal ion name.
Since the charge on the ionisation or coordination sphere is positive, central metal ion cobalt,$Co$ would be named as cobalt only according to the IUPAC naming. If there will be a negative charge on the coordination sphere, then cobalt would be named as cobaltate. While writing the IUPAC naming of coordination complexes, we first write the name of ligands and they are written alphabetically. $N{H_3}$ is named as ammine, $Cl$ is named as chlorido, and $N{O_2}$ is named as nitrito-N (since N-side of the $N{O_2}$ is linked to the metal ion $Co$ in the complex).
On summarising above explanation, the IUPAC name of the coordination complex, $[Co{(N{H_3})_4}Cl(N{O_2})]Cl$ will be: tetraamminechloridonitrito-N-cobalt(III) chloride.

Thus, option A is the correct answer.

Note: There should be no space while writing the IUPAC naming of the ligands and the metal ion within a coordination sphere. Names of the anionic ligands end in –o, and those of neutral and cationic ligands are the same except aqua for ${H_2}O$, ammine for $N{H_3}$, carbonyl for $CO$ and nitrosyl for $NO$.