Which of the following complex species is not expected to exhibit optical isomerism?

Options

A. `[Co(en)_(2)CI_(2)]^(o+)`
B. `[Co(NH_(3))_(3)CI_(3)]`
C. `[Co(en)(NH_(3))_(2)CI_(2)]^(o+)`
D. `[Co(en)_(3)]^(3+)`

Answer

b

Explanation

`[Co(NH_(3))_(3)CI_(3)]` I .e `Ma_(3)b_(3)` type exists in two geometrical forms (facial and meridional)
Both of these are achiral. Hence (b) does not show optical isomerism
Note `M(aa)_(2)_(2)b_(2), M(aa)b_(2)c_(2)` and `M(aa)_(3)` types show optical isomerism
But `Ma_(2)` or `Ma_(2)b_(4)` type shows only geometrical isomers
.