Question

$\left[Co\right(en{)}_3{]}^{3+}$ ion is expected to show :

• A. Two optically active isomers ; d and $l$ forms.
• B. Three optically active isomers ; d, $l$ and meso forms.
• C. Four optically active isomers ; cis- d and $l$ isomers and trans- d and $l$ isomers.
• D. None of these

Answer 1

The correct option is A Two optically active isomers ; d and $l$ forms.

$\left[Co\right(en{)}_3{]}^{+}$
It is a octahedral complex and the ligand (en) is symmetrical bidentate ligand. In this complex, all the three (en) ligands are not in the same plane so it lacks plane of symmtery and the compound is optically active.
It does not show geometrical isomers since all ligands are same.
Hence, it has only two optical isomers namely d and l.
d-isomer rotate non-polarised light clockwise and l-isomer rotate non-polarised light anticlockwise.