Give evidence that [Co(NH3)5Cl]SO4 and [Co(NH3)5(SO4)]Cl are ionisation isomers.
Ionisation isomers dissolve in water to yield different ions and thus react differently to various reagents. This provides evidence that [Co(NH₃)₅Cl]SO₄ and [Co(NH₃)₅(SO₄)]Cl are ionisation isomers.
When treated with Ba²⁺ ions, [Co(NH₃)₅Cl]SO₄ gives a white precipitate of BaSO₄ because SO₄²⁻ is present as a counter ion outside the coordination sphere. However, [Co(NH₃)₅(SO₄)]Cl shows no reaction with Ba²⁺ because SO₄²⁻ is inside the coordination sphere as a ligand.
Similarly, with Ag⁺ ions, [Co(NH₃)₅(SO₄)]Cl gives a precipitate of AgCl because Cl⁻ is present as a counter ion, while [Co(NH₃)₅Cl]SO₄ shows no reaction as Cl⁻ is bonded inside the coordination sphere.
Explanation
The textbook explicitly states in Section 5.4 that ionisation isomers dissolve in water to yield different ions and thus react differently to various reagents. The context provides the example reactions showing that the position of the ligand (inside or outside the coordination sphere) determines which ions are free to react. When SO₄²⁻ is outside, it reacts with Ba²⁺; when Cl⁻ is outside, it reacts with Ag⁺. This differential reactivity is the key evidence for ionisation isomerism.
Solution Steps
Step 1: Identify that ionisation isomers produce different ions in solution
Step 2: Test with Ba²⁺ ions - only the compound with SO₄²⁻ as counter ion gives BaSO₄ precipitate
Step 3: Test with Ag⁺ ions - only the compound with Cl⁻ as counter ion gives AgCl precipitate
Step 4: Conclude that different reactions with same reagents prove they are ionisation isomers