Indicate the types of isomerism exhibited by the following complexes anddraw the structures for these isomers:

Solution:

i. Both geometrical (cis-, trans-) isomers for $\mathrm{K}\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\right]$ can exist. Also, optical isomers for cis-isomer exist.

Trans-isomer is optically inactive. On the other hand, cis-isomer is optically active.

(ii) Two optical isomers for $\left[\mathrm{CO}(\mathrm{en})_{3}\right] \mathrm{Cl}_{3}$ exist.

Two optical isomers are possible for this structure.

(iii) $\left[\mathrm{CO}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{NO}_{2}\right)\right]\left(\mathrm{NO}_{3}\right)_{2}$

A pair of optical isomers:

It can also show linkage isomerism.

$\left[\mathrm{CO}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{NO}_{2}\right)\right]\left(\mathrm{NO}_{3}\right)_{2}$ and $\left[\mathrm{CO}\left(\mathrm{NH}_{3}\right)_{5}(\mathrm{ONO})\right]\left(\mathrm{NO}_{3}\right)_{2}$

It can also show ionization isomerism.

$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{NO}_{2}\right)\right]\left(\mathrm{NO}_{3}\right)_{2} \quad\left[\mathrm{CO}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{NO}_{3}\right)\right]\left(\mathrm{NO}_{3}\right)\left(\mathrm{NO}_{2}\right)$

(iv) Geometrical (cis-, trans-) isomers of $\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)\left(\mathrm{H}_{2} \mathrm{O}\right) \mathrm{Cl}_{2}\right]$ can exist.