The possible stereoisomers of the [Co(ox)2(Br)(NH3)]2− complex is given below.
The isomers with no plane of symmetry or centre of symmetry is optically active. Hence, it will have a non-superimposable mirror image.
Isomer at the bottom has plane of symmetry hence it is a meso form.
\( 7^{2-} \)
Optically active
Mirror
Optically active
Optically inactive
Total stereoisomer = 2 (O.A) (pair of enantiomers) + 1 meso = 3