Which one of the following is expected to exhibit optical isomerism? (en = ethylenediamine)
- cis-[Pt(NH3)2Cl2]
- trans-[Pt(NH3)2Cl2]
- cis-[Co(en)2Cl2]+
- trans-[Co(en)2Cl2]+
Answer
(3) cis-[Co(en)2Cl2]+
Solution
cis- and trans-[Pt(NH3)2Cl2] are square planar; the molecular plane is a plane of symmetry optically inactive.
trans-[Co(en)2Cl2]+ has a plane of symmetry (through Co and the two en rings) optically inactive.
cis-[Co(en)2Cl2]+ has no plane of symmetry its mirror image is non-superimposable.
As per NCERT, only the cis isomer of [Co(en)2Cl2]+ shows optical isomerism.
Answer: (3)