The optically active co-ordination complex ion among the following is

Options

A. trans `[Co(en)_(2)Cl_(2)]^(+)`
B. cis `[Co(en)(NH_(3))_(2)Cl_(2)]^(+)`
C. `[Co(NH_(3))_(6)]^(3+)`
D. `[Fe(CN)_(6)]^(3-)`

Answer

B

Explanation

Octahedral complexes of the type `[M ( A A)_(2)b_(2)]^(n+-)` and `[ M( A A)a_(2)b_(2)]^(n+-)` exhibit geometrical isomerism.
Option(a) , i.e., trans - `[Co(en)_(2)Cl_(2)]^(+)` which belongs to the `1^(st)` category is optically inactive owing to presence of an element of symmetry . However (b), cis- `[Co(en)(NH_(3))_(2)Cl_(2)]^(+)` exists is optically active forms.

Options (c ) and (d) are optically inactive as all the ligands are same.