Question

Which from following complexes is an example of \(\text{MA}_2\text{BC}\) type of distereoisomers?

• A. \([\text{Co(en)}_2\text{Cl}_2]^+\)
• B. \([\text{Pt(NH}_3\text{)(H}_2\text{O)Cl}_2]\)
• C. \(\text{Pt(NH}_3\text{)}_2\text{Cl}_2\)
• D. \([\text{Co(NH}_3\text{)}_4\text{Cl}_2]^+\)

Hint:

MA\(_2\)BC → two identical + two different ligands.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Stereoisomers that are not mirror images of each other are called diastereoisomers. In square planar coordination complexes (typically Pt(II)), the type \(\text{MA}_2\text{BC}\) can exhibit cis and trans isomers.
Step 2: Key Formula or Approach:
Match the general formula \(\text{MA}_2\text{BC}\) to the provided complex structures. Here, M is the metal, and A, B, C are monodentate ligands. 'A' is present twice.
Step 3: Detailed Explanation:
- (A) \([\text{Co(en)}_2\text{Cl}_2]^+\): This is an octahedral complex with bidentate ligands, formula \(\text{M(AA)}_2\text{X}_2\).
- (B) \([\text{Pt(NH}_3\text{)(H}_2\text{O)Cl}_2]\): This is a square planar complex of Pt(II). Here, metal M = Pt, ligands are: two \(\text{Cl}^-\) (A), one \(\text{NH}_3\) (B), and one \(\text{H}_2\text{O}\) (C). It matches the \(\text{MA}_2\text{BC}\) type. It shows cis and trans diastereoisomers.
- (C) \(\text{Pt(NH}_3\text{)}_2\text{Cl}_2\): This is of type \(\text{MA}_2\text{B}_2\).
- (D) \([\text{Co(NH}_3\text{)}_4\text{Cl}_2]^+\): This is of type \(\text{MA}_4\text{B}_2\).
Step 4: Final Answer:
The complex \([\text{Pt(NH}_3\text{)(H}_2\text{O)Cl}_2]\) fits the description.