Question

The IUPAC name of $\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_6}} \right]{\text{C}}{{\text{l}}_3}$ is:

Answer 1

For naming of coordination compound, IUPAC rules are to be followed. Positive part is to be written first, followed by the anionic part. Ligands are named before central metal atoms. Oxidation number of metal ions is to be named in Roman numbers.

Complete answer:
The main rules of naming complexes are:
-Like simple salts, the positive part of the coordination compound is named first.
-Then ligands of the coordination sphere are to be named.
-The ligands can be neutral, anionic or cationic. The neutral ligands are named as the molecule. Example ethylene diamine, pyridine ${{\text{C}}_5}{{\text{H}}_5}{\text{N}}$ . The neutral ligands which are not named as the molecule are carbonyl ${\text{CO}}$ , nitrosyl ${\text{NO}}$ , aqua ${{\text{H}}_2}{\text{O}}$ , amine ${\text{N}}{{\text{H}}_3}$ . Anionic ligands ending with ‘ide’ are named by replacing the ‘ide’ with suffix ‘O’. example of anionic ligand are chloro ${\text{C}}{{\text{l}}^ - }$ , bromo ${\text{B}}{{\text{r}}^ - }$ , oxo ${{\text{O}}^{ - 2}}$ , hydroxo ${\text{O}}{{\text{H}}^ - }$ , hydrido ${{\text{H}}^ - }$ . Ligands whose names end in ‘ite’ or ‘ate’ become ‘ito’. For example carbonato ${\text{CO}}_3^{ - 2}$ , sulphato ${\text{SO}}_4^{ - 2}$ , thiosulphato ${{\text{S}}_2}{{\text{O}}_3}^{ - 2}$ . -Positive ligands naming ends in ‘ium’. Example of cationic ligand are Hydrazinium ${\text{N}}{{\text{H}}_2}{\text{NH}}_3^ +$ , nitronium ${\text{NO}}_2^ +$ .
-If ligands are present more than once, then their repetition is indicated by prefixes like di, tri, tetra, etc. when more than one type of ligand is present in the complex, then the ligands are named in the alphabetical order.
-After naming ligands the central metal ion is to be named followed by its oxidation number state in Roman number in brackets.
-After naming the central metal ion, anion which is in the outer sphere is to be named.
The naming of some of the complexes is done as follows:

Complex compounds	IUPAC name
${{\text{K}}_4}\left[ {{\text{Fe}}{{\left( {{\text{CN}}} \right)}_6}} \right]$ , an anionic complex	Potassium hexacyanoferrate $\left( {{\text{II}}} \right)$
$\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_6}} \right]{\text{C}}{{\text{l}}_3}$ , an cationic complex	Hexammine cobalt $\left( {{\text{III}}} \right)$ chloride
$\left[ {{\text{Co}}\left( {{\text{N}}{{\text{H}}_3}} \right){\text{C}}{{\text{l}}_3}} \right]$ , a neutral complex	Triammine trichloro cobalt $\left( {{\text{III}}} \right)$

Note:
If a complex ion has two metal atoms then it is termed as polynuclear. The ligand which connects the two metal ions is called the Bridging ligand or Bridge group.