Match List-I with List-II.
| List-I (Type of isomerism) | List-II (Arises when) |
|---|---|
| (A) Linkage isomerism | (I) ligands are interchanged between the cationic and the anionic entities of different metal ions in a complex |
| (B) Coordination isomerism | (II) a solvent molecule is directly bonded to the metal ion in one isomer but is present as a free molecule in the crystal lattice in the other |
| (C) Ionisation isomerism | (III) the coordination compound contains an ambidentate ligand |
| (D) Solvate isomerism | (IV) the counter ion is itself a potential ligand and can displace a ligand, which then becomes the counter ion |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A-III, B-I, C-IV, D-II
All four are structural isomers: the isomers have different bonds. Each type is named after what changes from one isomer to the other.
(A) Linkage isomerism — This matches (III). An ambidentate ligand can bind through either of two donor atoms, e.g., NO2− through N (yellow form) or through O (red form) in [Co(NH3)5(NO2)]Cl2.
(B) Coordination isomerism — This matches (I). Ligands are interchanged between the cation and the anion, as in [Co(NH3)6][Cr(CN)6] and [Cr(NH3)6][Co(CN)6].
(C) Ionisation isomerism — This matches (IV). The counter ion and a ligand change places, as in [Co(NH3)5(SO4)]Br and [Co(NH3)5Br]SO4.
(D) Solvate isomerism — This matches (II). A solvent molecule is a ligand in one isomer and free in the lattice in the other, as in [Cr(H2O)6]Cl3 (violet) and [Cr(H2O)5Cl]Cl2.H2O (grey-green).
NCERT (2026-27 edition):
5.4.3 Linkage Isomerism – “Linkage isomerism arises in a coordination compound containing ambidentate ligand.”
5.4.4 Coordination Isomerism – “This type of isomerism arises from the interchange of ligands between cationic and anionic entities of different metal ions present in a complex.”
5.4.5 Ionisation Isomerism – “This form of isomerism arises when the counter ion in a complex salt is itself a potential ligand and can displace a ligand which can then become the counter ion.”
5.4.6 Solvate Isomerism – “Solvate isomers differ by whether or not a solvent molecule is directly bonded to the metal ion or merely present as free solvent molecules in the crystal lattice.”