Question

Which one of the following complexes shows optical isomerism? (en = ethylenediamine)

• A. $cis\left[Co\right(en{)}_{2}C{l}_2]Cl$
  
• B. $trans\left[Co\right(en{)}_{2}C{l}_2]Cl$
• C. $\left[Co\right(N{H}_3{)}_{4}C{l}_2]Cl$
• D. $\left[Co\right(N{H}_3{)}_{3}C{l}_3]$

Answer 1

The correct option is A $cis\left[Co\right(en{)}_{2}C{l}_2]Cl$


(a) $cis\left[Co\right(en{)}_{2}C{l}_2]Cl$ is optically active.


(b) $trans\left[Co\right(en{)}_{2}C{l}_2]Cl$ has plane of symmetry hence is optically inactive.

(c) Both cis and trans isomers of $\left[Co\right(N{H}_3{)}_{4}C{l}_2]Cl$ have a plane of symmetry and hence are optically inactive.

(d) Complexes of the type $\left[M{A}_3{B}_3\right]$ show geometrical isomerism known as fac-mer isomerism. They have a plane of symmetry.