The complex that exists as a pair of enantiomers is

Coen33+, where, en = NH2CH2CH2NH2The complex shows optical isomerism. Optical isomers are mirror image that cannot be superimposed on one another. These are called enantiomers. The molecules or ions that cannot be superimposed are called chiral.Optical isomers (d and l) of [Co(en)3]3+