Question

The IUPAC name of \[{K_2}\left[ {Ni{{\left( {CN} \right)}_4}} \right]\] is:
A. potassium tetracyanonickelate \[\left( {II} \right)\]
B. potassium tetracyanonickelate \[\left( {III} \right)\]
C. potassium tetracyanonickelate \[\left( {II} \right)\]
D. potassium tetracyanonickelate \[\left( {III} \right)\]

Answer 1

Hint: The IUPAC naming of coordination compounds is different from other covalent and ionic compounds. For IUPAC naming of compounds we follow certain rules. We have to mention the oxidation state of the central metal atom while writing the IUPAC name of the coordination compound.

Complete answer: In the given coordination compound we will first find the counter ion. Counter ion is that ion which is present outside the coordination entity. Here potassium is the counter ion. Now we will write the name of the complex ion or the structure which is present inside the coordination entity. Firstly nickel atoms are present as \[Ni\left( {II} \right)\]. Since the coordination entity is an anion part of the whole compound, it will be called nickelate\[\left( {II} \right)\]. We can also find the oxidation state of the nickel atom. It contains four cyano groups \[\left( {CN} \right)\]. Therefore it will be named as tetracyano for containing four cyano groups. These cyano groups also behave like ligands for the central metal atom, nickel. Therefore we can write the name of a complex ion as tetracyanonickelate\[\left( {II} \right)\]. But from the beginning it also contains potassium ions. Thus The IUPAC name of the whole compound will be potassium tetracyanonickelate\[\left( {II} \right)\].
Hence the correct option is A.

Note:
If the complex ion is a cation then the name of the central metal atom will be the same as the common name. The oxidation state of nickel in the above compound is two. We name the cationic and anionic part of the coordination compound separately. If there are more than one ligand attached to a central metal atom, then we will write them alphabetically.