Question

Which of the following statement is not true about the complex ion $\left[CrCl\right(N{O}_2\left)\right(en{)}_2{]}^{+}$ (en = ethylenediamine) ?

• A. It has two geometrical isomers - cis and trans
• B. cis and trans forms are not diastereomers to each other
• C. Only the cis isomer displays optical activity
• D. It has three optically active isomers

Answer 1

Answer: (B), (D)

The correct options are
B cis and trans forms are not diastereomers to each other
D It has three optically active isomers


In trans form both the (en) ligands are opposite to each and the plane passing through the axis contaning $N{O}_2,Cr$ and $Cl$ bisects the compound into two equal halves. Hence, it is optically inactive.

In cis, the (en) ligands are located at different planes, hence, there is no plane of symmetry so it shows optical activity. Hence, cis form will have a enatiomeric form (mirror image).
Thus, statement (a) and (c) are true.
The compound has only two optically active isomers, hence, statement (d) is false.

Geometrical isomers are diastereomeric to each other. Hence, statement (b) is not true.