Question

Identify the solvate isomer pair from the following:

• A. \([\text{Co(NH}_{3})_{5}(\text{NO}_{2})]^{2\oplus }\) and \([\text{Co(NH}_{3})_{5}(\text{ONO})]^{2\oplus }\)
• B. \([\text{Co(NH}_{3})_{5}\text{SO}_{4}]\text{Br}\) and \([\text{Co(NH}_{3})_{5}\text{Br}]\text{SO}_{4}\)
• C. \([\text{Co(NH}_{3})_{6}][\text{Cr(CN)}_{6}]\) and \([\text{Cr(NH}_{3})_{6}][\text{Co(CN)}_{6}]\)
• D. \([\text{Cr(H}_{2}\text{O})_{6}]\text{Cl}_{3}\) and \([\text{Cr(H}_{2}\text{O})_{5}\text{Cl}]\text{Cl}_{2}\cdot \text{H}_{2}\text{O}\)

Hint:

Solvate isomers differ in how many solvent molecules are inside the coordination sphere and how many are outside it.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
Solvate (hydrate) isomers have the same formula but differ in the number of solvent (water) molecules directly attached to the metal.

Step 2: Study the Options
(A) \(\text{NO}_{2}\) and \(\text{ONO}\): linkage isomers.
(B) \(\text{SO}_{4}^{2-}\) and \(\text{Br}^{-}\) exchange: ionisation isomers.
(C) Metal exchange between cation and anion: coordination isomers.

Step 3: Study Option D
\([\text{Cr(H}_{2}\text{O})_{6}]\text{Cl}_{3}\) has six water ligands.
\([\text{Cr(H}_{2}\text{O})_{5}\text{Cl}]\text{Cl}_{2}\cdot\text{H}_{2}\text{O}\) has five water ligands and one water of crystallisation.
These are solvate isomers.

Final Answer:
The pair with water inside and outside the coordination sphere is option (D). \[ \boxed{\text{(D) }[\text{Cr(H}_{2}\text{O})_{6}]\text{Cl}_{3}\text{ and }[\text{Cr(H}_{2}\text{O})_{5}\text{Cl}]\text{Cl}_{2}\cdot\text{H}_{2}\text{O}} \]