Which of the following isomerism is not possible for complexes having molecular formulae?
(I) `Pt(SCN)_(2)*3PE t_(3)`,
(II) `CoBr*SO_(4)*5NH_(3)`
(III) `FeCl_(2)*6H_(2)O`

Options

A. Optical
B. Linkage
C. Ionisation
D. Hydrate

Explanation

To determine which type of isomerism is not possible for the given coordination complexes, we will analyze each complex one by one.

### Step 1: Analyze the first complex `Pt(SCN)₂·3PET₃`
- The complex contains thiocyanate (SCN) ligands, which are ambidentate ligands. This means that SCN can coordinate through either the sulfur (S) or the nitrogen (N) atom.
- Because of this ambidentate nature, this complex can exhibit **linkage isomerism**.
- Therefore, this complex can show linkage isomerism.

### Step 2: Analyze the second complex `CoBr·SO₄·5NH₃`
- This complex contains bromide (Br) and sulfate (SO₄) ligands.
- The isomerism possible here is **ionization isomerism**, where the bromide ion can be inside the coordination sphere while the sulfate ion is outside, and vice versa.
- Thus, this complex can show ionization isomerism.

### Step 3: Analyze the third complex `FeCl₂·6H₂O`
- This complex contains chloride (Cl) and water (H₂O) ligands.
- It can exhibit **hydrate isomerism** because the number of water molecules can vary inside and outside the coordination sphere.
- Therefore, this complex can show hydrate isomerism.

### Step 4: Determine which isomerism is not possible
- From the analysis:
- The first complex can show linkage isomerism.
- The second complex can show ionization isomerism.
- The third complex can show hydrate isomerism.
- However, none of these complexes can show **optical isomerism**. Optical isomerism requires the presence of a chiral center, which is not present in any of these complexes.

### Conclusion
The type of isomerism that is **not possible** for the given complexes is **optical isomerism**.

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