Question

Write the IUPAC name of $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$.

Answer 1

IUPAC rules:

• The name of the cation is formed first followed by the name of the anion.
• A complex cation by naming the ligands and then metal ion.
• A complex anion is named by writing ligands followed by name of the metal ending with the suffix- ate.
• Ligand names typically end in "o" if the ligand is neutral or unaltered if the ligand is negative (e.g. "chlorido" , "cyanido" or “hydro”). The special ligand names for water, ammonia, carbonyl, and nitrosyl are aqua, ammine, carbonyl, and nitrosyl, respectively.
• Each ligand's number is denoted by a Greek prefix (mono, di, tri, tetra, penta, hexa, etc). (mono is usually omitted for a single ligand of a given type). The name of the ligand is contained in parenthesis and its number is instead given with the alternative prefixes bis, tris, and tetrakis if the ligand's name itself contains the phrases mono, di, or tri, such as triphenylphosphine.
• The oxidation number of the central metal atom is denoted by a Roman numeral or a zero in parenthesis.
• Regardless of the number of each ligand, if the species contains more than one, the ligands are named in alphabetical order.

The IUPAC name of this compound can be done as follows:

Step 1. Naming the ligand

• First, the name of the ligand should be there.
• Here, one ligand- ammine is present, and the number of ammines is $6$ so the name will be Hexaammine.
• If more than one ligand is present it should be named alphabetically.
• The given compound is a cation complex thus, the name of the metal will be the same as the name of the element
• Here, the metal ion is a chloride ion, thus the name will be chloride.

Step 2: Naming the cation:

• Here the metal ion is Cobalt with an oxidation state $3$ so it will be Cobalt $\left(\mathrm{III}\right)$

Thus the name of the compound with respect to the above rules will be Hexaamminecobalt $\left(\mathrm{III}\right)$ chloride.