Cis-trans isomerism is found in square planar complexes of molecular formula: (a and b are monodentate ligands)

Options

A. `Ma_(4)`
B. `Ma_(3)b`
C. `Ma_(2)b_(2)`
D. `Mab_(3)`

Answer

To determine which of the given molecular formulas can exhibit cis-trans isomerism in square planar complexes, we will analyze each option step by step.

### Step 1: Understand Cis-Trans Isomerism
Cis-trans isomerism is a type of geometrical isomerism where the same molecular formula can have different spatial arrangements of atoms. In cis isomers, similar groups are adjacent (90 degrees apart), while in trans isomers, similar groups are opposite each other (180 degrees apart).

**Hint:** Remember that cis-trans isomerism requires at least two different types of ligands in the complex.

### Step 2: Analyze Each Option
1. **Option MA4**:
- This complex has four identical ligands (A).
- Since all ligands are the same, there is no possibility for cis or trans isomers.
- **Conclusion:** No cis-trans isomerism.

2. **Option MA3B**:
- This complex has three A ligands and one B ligand.
- The arrangement of A ligands does not allow for distinct cis or trans configurations because they are identical.
- **Conclusion:** No cis-trans isomerism.

3. **Option MA2B2**:
- This complex has two A ligands and two B ligands.
- The two A ligands can be arranged adjacent to each other (cis) or opposite each other (trans) with respect to the B ligands.
- **Conclusion:** This complex can exhibit cis-trans isomerism.

4. **Option MAB3**:
- This complex has one A ligand and three B ligands.
- The arrangement does not allow for distinct cis or trans configurations because there is only one A ligand.
- **Conclusion:** No cis-trans isomerism.

### Step 3: Final Conclusion
After analyzing all the options, the only molecular formula that can exhibit cis-trans isomerism in square planar complexes is **MA2B2**.

**Final Answer:** The correct option is **MA2B2**.