Question

Identify the homoleptic complex from the following.

• A. $[\text{Co}(\text{NH}_3)_6]^{3+}$
• B. $[\text{Co}(\text{NH}_3)_5\text{Cl}]\text{SO}_4$
• C. $[\text{Co}(\text{NH}_3)_4\text{Cl}_2]^+$
• D. $[\text{Co}(\text{H}_2\text{O})(\text{NH}_3)_5]\text{I}_3$

Hint:

Use the Greek prefixes to remember this definition: "Homo" means same and "Hetero" means different. Look only inside the square brackets; ignore any counter-ions written on the outside (like $\text{SO}_4$ or $\text{I}_3$) as they are not active ligands.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks to identify a homoleptic coordination complex from the provided options based on the types of ligands attached to the central metal atom.

Step 2: Key Formula or Approach:
Coordination complexes are classified into two structural groups depending on ligand diversity:

Homoleptic complexes: The central metal atom or ion is bound to exactly

one single type of donor ligand group.

Heteroleptic complexes: The central metal atom or ion is bound to

more than one type of donor ligand group.

Step 3: Detailed Explanation:
Let's look at the composition of the inner coordination sphere (inside the square brackets) for each option: In option (B), $[\text{Co}(\text{NH}_3)_5\text{Cl}]\text{SO}_4$, the Cobalt ion is bound to two different types of ligands: 5 ammine ($\text{NH}_3$) groups and 1 chloride ($\text{Cl}^-$) ion. (Heteroleptic) In option (C), $[\text{Co}(\text{NH}_3)_4\text{Cl}_2]^+$, the Cobalt ion is bound to 4 ammine groups and 2 chloride ions. (Heteroleptic) In option (D), $[\text{Co}(\text{H}_2\text{O})(\text{NH}_3)_5]\text{I}_3$, the Cobalt ion is bound to 1 aqua ($\text{H}_2\text{O}$) ligand and 5 ammine groups. (Heteroleptic) In option (A), $[\text{Co}(\text{NH}_3)_6]^{3+}$, the central Cobalt ion is coordinated exclusively to six identical ammine ($\text{NH}_3$) molecules. Since there is only a single variety of ligand within the coordination sphere, it matches the definition of a homoleptic complex.

Step 4: Final Answer:
The homoleptic complex is $[\text{Co}(\text{NH}_3)_6]^{3+}$, corresponding to option (A).