Question

Which one of the following has largest number of isomers?

(R=alkyl group;en=ethylenediamine)

• A. $\left[Ir\right(PP{h}_3{)}_{2}H\left(CO\right){]}^{2+}$
• B. $\left[Co\right(N{H}_3{)}_{5}Cl{]}^{2+}$
• C. $\left[Ru\right(N{H}_3{)}_{4}C{l}_2{]}^{+}$
• D. $\left[Co\right(en{)}_{2}C{l}_2{]}^{+}$

Answer 1

The correct option is D $\left[Co\right(en{)}_{2}C{l}_2{]}^{+}$

(a)
(b)(c)(d)
$\left[Co\right(en{)}_{2}C{l}_2{]}^{+}$ shows geometrical as well as optical isomerism. It has largest number of isomers which includes geometrical isomers (cis and trans isomers) as well as stereoisomers (d form, l form and optically inactive form). en is a bidentate ligand.

Optical isomers are the mirror images of the compounds that cannot be superimposed on each other. So, the cis isomer can form such two isomers (including itself) that are enentiomers. The optical isomers are named as dextro and laevo depending upon its characteristic to rotate the plane polarized light.
Here, one isomer is laevorotatory and one is dextrorotatory