Question

Optical isomerism is shown by octahedral complexes having:
A.Two trans bidentate ligands
B.All monodentate ligands
C.Two trans monodentate ligands
D.All the three bidentate ligands

Answer 1

Isomers are compounds with the same molecular formula but different chemical structure. This property of compounds exhibiting isomers is called isomerism. To show optical isomerism, the metal centre must be chiral.

Complete answer:
For the isomers, it is not necessary that they will share the same physical properties or chemical properties. There are two main types of isomers which are structural isomers and stereoisomers. The structural isomers are also known as constitutional isomers whereas the stereoisomers are also known as spatial isomers.
Stereoisomers are the isomers with the same molecular formula and bonds but differ in their three-dimensional arrangement.
Enantiomers: They are two stereoisomers that are non-superimposable mirror images of each other. They are also known as optical isomers. They can rotate the plane of polarized light. They have the same physical properties except for the direction in which they rotate the polarised light.
The coordination compounds which contain optical isomers can be considered as optically active. The coordination compounds which do not contain optical isomers can be considered as optically inactive. Optically active compounds will not show the plane of symmetry whereas optically inactive compounds will show the plane of symmetry.
Trans isomers of octahedral complexes will not reflect optical isomerism as they possess the plane of symmetry.
Octahedral complexes with six as their coordination number and three bidentate ligands will show optical isomerism because they do not show any kind of symmetry and they are non-superimposable mirror images of each other.

Therefore, the correct answer is option D, that is, all the three bidentate ligands.
Note:
Denticity can be defined as the number of donor atoms of a ligand which has the ability to attach to the central atom in a coordination complex. Ligands with one donor atom that has the ability to attach to the central atom are known as monodentate ligands whereas ligands with two donor atoms that have the ability to attach to the central atom are known as bidentate ligands.