[Co(NH3)3Cl3] shows two geometrical isomers and both can't show optical isomerism due to presence of plane of symmetry.

cis[Co(en)2Cl2]Cl shows optical isomerism

trans[Co(en)2Cl2]Cl forms identical mirror image due to presence of plane of symmetry.

[Co(NH3)4Cl2] shows geometrical isomerism.
