Question

IUPAC nomenclature of;
(i) $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}ONO \right]C{{l}_{2}}$
(ii) $\left[ Pt{{\left( N{{H}_{3}} \right)}_{4}} \right]\left[ PtC{{l}_{4}} \right]$

Answer 1

The IUPAC name for the complex compounds has a specific pattern and contains the word root of all the elements comprising the complex compound.

Complete Solution :
Let us first understand about the coordination complex and the procedure to name any complex before we move towards the given data.

Coordination complex –
- Coordination compounds are any class of substances with chemical structures which have a central metal atom surrounded by ligands (nonmetal atoms or groups of atoms) joined by chemical bonds.
- The central atom is called the coordination centre.
- Ligands or complexing agents are an array of bound molecules or ions.
Coordination complexes are mostly metal containing compounds, those are transition metals.
The basic procedure for naming a complex is as follows:
1. While naming a complex ion, the ligands are named prior to the metal ion.
2. The ligands’ names are given in alphabetical order. Numerical prefixes do not affect the order.
- Monodentate ligands receive di-, tri-, tetra-, penta-, or hexa- as prefix according to their number of occurrences.
- Multiple occurring polydentate ligands receive bis-, tris-, tetrakis-, etc.
- Anions end in o. this replaces the final ‘e’ when the anion ends with ‘-ide’, ‘-ate’ or ‘-ite’, example- chloride becomes chlorido and sulphate becomes suphato.
- Neutral ligands are given their common name, with some exceptions: $N{{H}_{3}}$becomes amine, ${{H}_{2}}O$ becomes aqua or aqu, CO becomes carbonyl, NO becomes nitrosyl.
3. Write the name of the central atom/ion. The central atom’s name will end in ‘-ate’, if the central atom is an anion. Except for mercury, other atoms will get their respective Latin name.
4. The oxidation state of the central atom is to be specified enclosed in parentheses. Those should be in roman numerals.
5. Name of the cation should be preceded by the name of anion.

Illustration-
(i) $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}ONO \right]C{{l}_{2}}$
As, the ligands are named in an alphabetical order and here Co has oxidation number of +3 [oxidation number of Co turns out to be +3 as, oxidation number of chlorine and nitrito group is -1 each],
The name of the above given compound will be pentaamminenitritocobalt (III) chloride.

(ii) $\left[ Pt{{\left( N{{H}_{3}} \right)}_{4}} \right]\left[ PtC{{l}_{4}} \right]$
Here, $N{{H}_{3}}$ is the neutral ligand which makes the first complex positively charged. Whereas, Cl has -1 charge which is responsible to make the next complex as anion. So, according to the rules;
The IUPAC name for the above given compound will be tetraamine platinum (II) tetrachloroplatinate (II).

Note: Students may get confused between $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}ONO \right]C{{l}_{2}}$ and $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}N{{O}_{2}} \right]C{{l}_{2}}$ . These two compounds show the linkage isomerism for the coordination compound. The IUPAC name of $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}N{{O}_{2}} \right]C{{l}_{2}}$ is pentaamminenitro cobalt (III) chloride.