Why can octahedral complexes with three didentate ethylenediamine ligands form enantiomers?

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Structural diagram of the vitamin B12 coenzyme molecule, highlighting its organometallic core with five nitrogen-cobalt bonds and one cobalt-carbon bond at the center, surrounded by complex organic groups. — coordination compound Coordination compounds contain a central metal atom surrounded by nonmetal atoms or groups of atoms, called ligands. For example, vitamin B₁₂ is made up of a central metallic cobalt ion bound to multiple nitrogen-containing ligands.

Octahedral complexes containing three didentate ethylenediamine ligands can form enantiomers due to an asymmetric arrangement of the ligands around the central metal ion.1

In these coordination compounds, the three didentate ligands create a structure that lacks a plane of symmetry. Consequently, the complex exists in two distinct forms that are mirror images of each other but are not superimposable, a property known as chirality. These enantiomers are characterized by their ability to rotate plane-polarized light in opposite directions.1