Question

What is the IUPAC name of $K[Cr{(N{H_3})_2}C{l_4}]$ ?
(A) Potassium diammine tetra chlorochromate(III)
(B) Potassium diammine tetrachloro chromium(III)
(C) Potassium diammine tetra chlorochromate(II)
(D) None of these

Answer 1

At first, the cation of the salt is named. Then ligands are named in alphabetical order .Then the metal in coordination sphere is named. We should follow the rules when naming a compound.

Complete step by step answer
According to the IUPAC rule of naming of coordination compounds, the cation of the salt is named first. Here, the cation is potassium .Then there will be a space. Potassium has a charge $+ 1$ . That means, the coordination sphere has a negative charge. This is because the whole compound is neutral. Then the ligands are named alphabetically. The anionic ligands which end with “-ide” are replaced with”-o”. Here, chloride ions ( $- C{l^ - }$ ) are anionic ligands. That’s why, chloride ions will be written as chloro. Neutral ligands carry their own name. Here, $- N{H_3}$ ligands are neutral ligands. They keep their normal name “amine”. The number of ligands present in the coordination complex is denoted by prefixes .Here, four chloride ions are there. It will be named as “tetrachloro”.Two ammine ligands are there. They will be written as “diammine”. Here, the central metal atom is Chromium. As the whole coordination sphere has a negative charge, It will change its name to “chromate” while writing the compound’s name. Its oxidation state will be written in roman in a bracket after its name.
Let’s assume Cr has the oxidation state $x$
x + (2*0) + [4*( - 1)] = - 1 \\\ x = + 3 \\\
Hence, the name of the compound is Potassium diammine tetra chlorochromate (III)
Hence, option (A) is the correct answer.

Note
The coordination complexes are named using the naming conventions. We should consider all the rules while giving a name to any compound. Their salt name, ligands and the metals names should be kept in according to the rules.