Question

What is the IUPAC name of ${\left[ {{\text{Ni}}{{\left( {{\text{CN}}} \right)}_{\text{4}}}} \right]^{2 - }}$?
A) Tetracyanonickelate (II)
B) Tetracyanonickelate (II)
C) Tetracyanonickelate (I)
D) None of these

Answer 1

First we have to determine the charge on the central metal atom. The charge on the cyanide ligand is - 1 and the total charge on the complex ion is - 2. According to the assigned set of rules we have to give the oxidation number to the given compound.

Complete step by step answer:
Determine the oxidation number (ON) of the central metal atom ${\text{Ni}}$ as follows:
${\text{Oxidation number of Ni + 4}} \times {\text{Oxidation number of C}}{{\text{N}}^ - } = {\text{Charge of the complex ion}}$
Substitute $\left( { - 1} \right)$ for the oxidation number of ${\text{C}}{{\text{N}}^ - }$, $- 2$ for the charge on the complex. Thus,
${\text{Oxidation number of Ni + 4}} \times \left( { - 1} \right) = - 2$
${\text{Oxidation number of Ni}} = - 2 + 4$
${\text{Oxidation number of Ni}} = + 2$
Thus, the oxidation number of the central metal atom ${\text{Ni}}$ is $+ 2$.
Write the IUPAC name of ${\left[ {{\text{Ni}}{{\left( {{\text{CN}}} \right)}_{\text{4}}}} \right]^{2 - }}$ as follows:
The charge on the complex ion is negative. Thus, ${\left[ {{\text{Ni}}{{\left( {{\text{CN}}} \right)}_{\text{4}}}} \right]^{2 - }}$ is a complex anion.
Write the name of the ligands. There are four cyanide ligands. Thus, tetracyano.
Write the name of the metal ending with suffix –ate. Thus, nickelate.
Write the charge on the nickel atom in a bracket. The charge on the nickel atom is $+ 2$.
Thus, the IUPAC name of ${\left[ {{\text{Ni}}{{\left( {{\text{CN}}} \right)}_{\text{4}}}} \right]^{2 - }}$ is tetracyanonickelate (II).

Thus, the correct option is (A) tetracyanonickelate (II).

Note: The rules for writing the IUPAC nomenclature of complex anions are as follows:
- Identify the ligand and name the ligand with the prefix mono-, di-, tri-, tetra-, etc. depending on the number of ligands.
- Identify the central metal atom and write the name of the central metal atom ending with suffix –ate.
- Determine the oxidation number of the central metal atom and write the charge in roman numeral in a bracket ( ) after writing the complete name.