Question

As per IUPAC nomenclature, the name of the complex $[Co{{({{H}_{2}}O)}_{4}}{{(N{{H}_{3}})}_{2}}]C{{l}_{3}}$ is
A. Tetraaqua Diamine Cobalt(III) chloride
B. Tetraaqua Diamine Cobalt(II) chloride
C. Diammine Tetraaqua Cobalt(II) chloride
D. Diammine Tetraaqua Cobalt(III) chloride

Answer 1

Hint: The IUPAC system of nomenclature is a set of rules which are mainly aimed to give an unambiguous name to an organic compound. By using this system, it is possible to give a systematic name to an organic compound just by looking at its structure and it is also possible to write the structure of an organic compound.

Step by step solution:
IUPAC stands for “International Union of Pure and Applied Chemistry” it gives us rules for naming the compound. The main rules of the system is as follows:
a) The ligands are named first as compared to metal.
b) The charge or oxidation state of metal indicated with the Roman numerals and enclosed in the parenthesis after metal name.
c) The ligands are named in alphabetical order before the metal ion.
d) Ligands that include a numerical prefix in the name use the prefixes bis for 2, tris for 3, tetra for 4 to indicate their number.
e) If the complex ion is an anion, we drop the ending of the metal name and add -ate
In the given coordination compound metal is named after the ligand here metal is $Co$ and firstly give name to ligand alphabetically here $N{{H}_{3}}$ termed as ammine and ${{H}_{2}}O$ termed as aqua so now there are 4 molecules of ${{H}_{2}}O$ so it can be written as tetraaqua and two molecules of \[N{{H}_{3}}\]it can be written as diammine now calculate the oxidation state of metal.
Aqua and ammine both are neutral and chlorine carries -1 charge.
$\therefore x+4(0)+2(0)=3$
$x=3$

Hence the oxidation state of metal is +3 and the name of the compound is Diammine Tetraaqua Cobalt(III) chloride, Option D is correct.

Note:
IUPAC names can sometimes be simpler than older names as with ethanol, instead of ethyl alcohol. For relatively simple molecules they can be more easily understood than non-systematic names, which must be learnt or looked over. However, the common or trivial name is often substantially shorter and clearer, and so preferred. These non-systematic names are often derived from an original source of the compound. In addition, very long names may be less clear than structural formulas.