Which of the following will give a pair of enantiomorphs? (en = NH2CH2CH2NH2)
- [Cr(NH3)6][Co(CN)6]
- [Co(en)2Cl2]Cl
- [Pt(NH3)4][PtCl6]
- [Co(NH3)4Cl2]NO2
Answer
(2) [Co(en)2Cl2]Cl
Solution
Options (1) and (3) contain only [MA6] and [MA4] / [MB6] ions — no optical isomerism.
Option (4): [Co(NH3)4Cl2]+ ([MA4B2]) shows only cis–trans isomerism; both forms have a plane of symmetry.
Option (2): [Co(en)2Cl2]+ ([M(AA)2B2]). As per NCERT, its cis isomer has no plane of symmetry and exists as a pair of non-superimposable mirror images (d and l forms).
Answer: (2)