The IUPAC name of the complex [Co(NH3)4(H2O)Cl]Br2 is

The correct answer is Option (2) → Tetraammineaquachloridocobalt(III) bromide

IUPAC rules for naming a coordination compound:

• The cation is named first, then the anion (here the complex ion is the cation and bromide is the anion).

• Inside the complex, ligands are named in alphabetical order, ignoring numerical prefixes such as di-, tetra-. Neutral \( \ce{H2O} \) is aqua, \( \ce{NH3} \) is ammine, \( \ce{Cl^{-}} \) is chlorido.

• The metal follows, with its oxidation state in Roman numerals.

Alphabetical order: ammine comes before aqua (m before q), and both before chlorido. So the ligand part is tetraammine-aqua-chlorido.

Oxidation state of Co: the complex ion carries +2, balanced by two \( \ce{Br^{-}} \). \( \ce{NH3} \) and \( \ce{H2O} \) are neutral and Cl is −1:

    x + 4(0) + 0 + (−1) = +2, so x = +3

So the name is tetraammineaquachloridocobalt(III) bromide.

NCERT (2026-27 edition):
Naming of Mononuclear Coordination Compounds – …