Question

The name of complex ion, ${[Fe{(CN)_6}]^{3 - }}$ is:
(A) Tricyanoferrate (III) ion
(B) Hexacyanidoferrate (III) ion
(C) Hexacyanoiron (III) ion
(D) Hexacyanitoferrate (III) ion

Answer 1

If the complex ion is a cation, then the metal is named the same as the element. We write the prefixes like di-, tri-, tetra-, etc to show the number of ligands present in the complex. Here, iron is in (+3) oxidation state.

Complete step by step solution:
We will name this compound in a step by step manner.
- We can see that there is only one type of ligand which is $C{N^ - }$ (cyanide) is present. There are six cyanide ligands there. We can see that there is (-1) charge on this ligand. So, it is an anionic ligand. Thus, anionic ligands name in the nomenclature should and by –o. So, we will call this ligand cyanido. As there are six of such ligands there, we will call it hexacyanido.
- The oxidation state of the metal atoms is indicated in Roman numerals in parentheses after the name of them metal.
- If the complex ion is an anion, then the suffix –ate is added after the name of the metal. Here, metal is iron. Thus, we will call it ferrate (III).
- Now, in naming, we first write the name of ligands and then we describe the metal atom present in it. So, the name of the compound is hexacyanidoferrate (III) ion.

Therefore, the correct answer is (B).

Note: If both positively and negatively charged ions are present, then positively charged ions are named first. If more than one ligand is present, then they are named in an alphabetical order. If a complex is a cation, then the metal atom's name is the same as the element.