Coordination Chemistry

To determine which complexes exhibit optical isomerism, we must understand the conditions under which a complex can display optical isomerism. Optical isomerism occurs in certain coordination compounds that lack a plane of symmetry, center of symmetry, or any improper axis of rotation. It is commonly exhibited in octahedral complexes, especially with bidentate ligands.

Let's analyze each option:

1. cis-[ : This complex has a 6-coordinate octahedral geometry with two bidentate ethylenediamine (en) ligands and one monodentate ammonia ligand. The presence of the bidentate ligands allows for chirality, as the arrangement can result in non-superimposable mirror images. Thus, it can exhibit optical isomerism.
2. cis-[ : This complex involves oxalate (ox) bidentate ligands. With the configuration, optical isomerism is possible due to the potential for non-superimposable mirror images derived from its arrangement.
3. cis-[ : Similar to the first complex, this also contains bidentate ligands in a configuration which allows for chirality, thereby enabling optical isomerism.
4. cis-[ : This complex is a 6-coordinate octahedral system with only monodentate and Cl ligands. It doesn't have bidentate ligands or suitable asymmetry within its arrangement to exhibit optical isomerism.

Thus, the complexes that show optical isomerism are:

• cis-[
• cis-[
• cis-[

The correct answer is: (i), (ii), (iii)

In coordination chemistry, isomerism can be classified into two main types: geometrical isomerism and structural isomerism. - Geometrical isomerism arises due to the different spatial arrangements of ligands around a metal center. This occurs only in coordination complexes where ligands are not identical, such as square planar and octahedral coordination compounds.

- Structural isomerism arises when the connectivity of ligands in the coordination complex is different, such as linkage isomerism (where a ligand can coordinate via different atoms) or coordination isomerism (where different combinations of ions coordinate to the central metal ion). For the given compounds:

1. A = : This compound can exhibit both geometrical isomerism (cis/trans) due to the two chloride ligands and structural isomerism because the nitrite can act as a nitrito ligand or a nitro ligand.
2. C = : This compound can exhibit geometrical isomerism due to the two nitrite ligands (cis/trans arrangement), and structural isomerism due to the different ways the ligands can bind to the metal (linkage isomerism).
3. B = : This compound shows no geometrical isomerism (only one possible arrangement of ligands) and does not exhibit structural isomerism because the ligand coordination does not change.
4. D = : This is an octahedral complex where the ligands are identical (water molecules), and it does not show either geometrical or structural isomerism. Thus, the compounds that exhibit both geometrical and structural isomerism are A and C.