Which of the following does not show optical isomerism? (en =...

Which of the following does not show optical isomerism? (en = ethylenediamine)

Options

A $\left[\mathrm{Co}(\mathrm{en})_2 \mathrm{Cl}_2\right]^{+}$
B $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_3 \mathrm{Cl}_3\right]^0$
C\left[\mathrm{Co}(\mathrm{en}) \mathrm{Cl}_2 $\left(\mathrm{NH}_3\right)_2\right]^{+}$
D $\left[\operatorname{Co}(\mathrm{en})_3\right]^{3+}$

B. $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_3 \mathrm{Cl}_3\right]^0$

Optical isomerism is exhibited by only those complexes in which elements of symmetry are absent. Octahedral complexes of the types

\left[\mathrm{M}(\mathrm{aa})_3\right],

\left[\mathrm{M}(\mathrm{aa}) \mathrm{x}_2, \mathrm{y}_2\right]

and

\left[\mathrm{M}(\mathrm{aa})_2 \mathrm{x}_2\right]

have absence of elements of symmetry, thus exhibit optical isomerism. Here,

a a

represents bidentate ligand,

or

represents monodentate ligand and

represents central metal ion. Hence,

\left[\mathrm{Co}

\left(\mathrm{NH}_3\right)_3 \mathrm{Cl}_3\right]^0

due to presence of symmetry elements does not exhibit optical isomerism.