The octahedral complexes of the type [M(AA)2Q2]±, in which two symmetrical bidentate chelating ligands like AA and two monodentate ligands like a are coordinated to the central metal atom or ion exhibit optical isomerism and two optical isomers d and l can be resolved.
For example,
[Pt Cl2(en)2]2.
The cis-form is unsymmetrical and optically active while the trans-form is symmetrical and hence optically inactive.
The optical isomers of cis-form (d and ) of this complex along with trans-form are shown below,
