Coordination compound that would exhibit optical isomerism is:

Optical isomerism is exhibited by coordination compounds that lack any plane or centre of symmetry (i.e., chiral complexes) .

1. Diamminedichloroplatinum(II), $[Pt(NH_3)_2Cl_2]$, is a square planar complex and possesses a plane of symmetry, making it optically inactive.
2. Trans-dicyanobis(ethylenediamine)chromium(III) chloride, $trans-[Cr(en)_2(CN)_2]Cl$, has a plane of symmetry cutting through the metal and the symmetrical ligands, making it optically inactive. (Note: Its cis-isomer is optically active) .
3. Tris-(ethylenediamine)cobalt(III) chloride, $[Co(en)_3]Cl_3$, is an octahedral complex of the type $[M(AA)_3]^{n+}$ containing didentate ligands. It lacks a plane of symmetry and therefore exhibits optical isomerism, existing as non-superimposable dextro ($d$) and laevo ($l$) enantiomers .
4. Pentaamminenitrocobalt(III) iodide, $[Co(NH_3)_5(NO_2)]I_2$, is of the type $[Ma_5b]^{n+}$ and has a plane of symmetry, making it optically inactive.