(b) If cation is complex, then we first name ligand in alphabetical order and then central atom with oxidation state remain numeral in common brackets.
$\left[\mathrm{Cr}(\mathrm{en})_{2} \mathrm{Br}_{2}\right] \mathrm{Br}-$ is named as dibromidobis (ethylenediamine) chromium(III) bromide:
Ligands are : Br (two), ethyenediammine (two).
Central ion: $\mathrm{Cr}(\mathrm{III})$ or $\mathrm{Cr}^{3+}$
Counter ion: $\mathrm{Br}^{-}$