The number of geometrical isomers for octahedral ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_2{\mathrm{Cl}}_4\right]}^{-}$and square planar ${\left[{\mathrm{AuCl}}_2{\mathrm{Br}}_2\right]}^{-}$ respectively are :

There are two geometric isomers for the square planar [$[AuC{l}_{2}B{r}_2{]}^{-}$ and the octahedral $\left[Co\right(N{H}_3{)}_{2}C{l}_4{]}^{-}$ respectively.$M_{{\mathit{a}}_{\mathit{2}}{\mathit{b}}_{\mathit{2}}}$ and $M_{a_4{b}_{\mathit{2}}}$illustrate these isomers.