Optical isomerism is shown by :
(i) Complexes of the type
[M(AA)X2Y2]i.e.,
[Co(en)Cl2(NH3)2]+ containing one symmetrical bidentate ligand.
(ii) complexes of the type
[M(AA)3],i.e.,
[Co(en)3]3+ containing a symmetrical bidentate ligand.
(iii) complexes of the type
[M(AA)2X2] i.e.,
[Co(en2)Cl2]+However complexes of the type
[MA3B3] show geometrical isomerism,know as fac-mer isomerism.
∴
[Co(NH3)3Cl3] exhibit fac-mer isomerism