Question

Both geometrical and optical isomerism is shown by which of these coordination compounds?
A. \[[{\text{Pt(N}}{{\text{H}}_3}{{\text{)}}_2}{\text{C}}{{\text{l}}_2}]\]
B. $[{\text{Pt(N}}{{\text{H}}_3}{{\text{)}}_4}{\text{C}}{{\text{l}}_2}]$
C. $[{\text{Pt(en}}{{\text{)}}_2}{\text{C}}{{\text{l}}_2}]$
D. $[{\text{Pt(en}}{{\text{)}}_3}{\text{C}}{{\text{l}}_2}]$

Answer 1

Hint:Isomers are two different chemical compounds having the same chemical formula but different arrangements of atoms. Coordination compounds primarily show two types of isomerism stereoisomerism and Structural isomerism, optical and geometric isomerism both are subcategories of stereoisomerism.


Complete solution:
Optical isomerism can also be shown by compounds having a chiral centre, a chiral centre is an atom which has all different atoms/ or molecules bonded it in such a manner that its mirror image is non-superimposable.We know now that both optical and geometrical isomerism are subcategories of stereoisomerism, but what is stereoisomerism?
Stereoisomerism is the property shown by stereoisomers, these isomers have different spatial arrangements of atoms. And as mentioned Stereoisomerism can be further divided into two groups;
i. Optical – non-superimposable mirror images.
ii. Geometrical – Cis /trans or facial/ meridional isomers
Now, if look at the option ‘A’ i.e., \[[{\text{Pt(N}}{{\text{H}}_3}{{\text{)}}_2}{\text{C}}{{\text{l}}_2}]\] we can see that it is a square planer geometry and can show both of the geometrical isomerism i.e., cis / and trans.Also, both cis and trans isomer of \[[{\text{Pt(N}}{{\text{H}}_3}{{\text{)}}_2}{\text{C}}{{\text{l}}_2}]\] has a non-superimposable mirror image.Therefore, \[[{\text{Pt(N}}{{\text{H}}_3}{{\text{)}}_2}{\text{C}}{{\text{l}}_2}]\] can show both isomerism i.e., Optical and Geometrical
Therefore, from the above explanation we can say that the correct option is (A).


Note:Geometrical isomerism can also be shown by all the other option, and $[{\text{Pt(en}}{{\text{)}}_2}{\text{C}}{{\text{l}}_2}]$ even shows optical isomerism, but with only its trans- isomer, since cis- isomer can not show optical isomer as the mirror image of the cis isomer is superimposable. Hence, we have chosen an option whose cis/trans isomers both can show optical isomerism.