Question

Which of the following will have two stereoisomeric forms only?
(I) $\left[Cr\right(N{O}_2{)}_3\left(N{H}_3{)}_3\right]$
(II) $K_3\left[Fe\right(C_2{O}_4{)}_3]$
(III) $\left[CoC{l}_2\right(en{)}_2{]}^{+}$
(IV) $\left[CoBrCl\right(ox{)}_2{]}^{3-}$

• A. I only
• B. I and II
• C. III and IV
• D. All of these

Answer 1

The correct option is B I and II

Answer : B
Two geometrical isomers are possible for complex of the type $M{A}_3{B}_3$. They are facial and meridonial isomers.
In facial isomer the ligands of one type will form an equilateral triangle on one of the faces. In meridional isomers, two ligands are opposite or trans to each other.

Complex of type $\left[M\right(AA{)}_3]$ will form optical isomers 'd' and 'l' because it does not have plane of symmetry or centre of symmetry.
In (III), we have 3 stereoisomers where cis form has two non-superimposible mirror image and trans form is meso since it has a plane of symmetry.
In (IV), we have 3 stereoisomers where cis form has two non-superimposible mirror image and trans form is meso since it has a plane of symmetry.