Which of the following statement is true?

Options

A. In `[PtCl_(2)(NH_(3))_(2)]^(2+)` the cis form is optically inactive while trans form is optically active
B. In `[Fe(C_(2)O_(4))_(3)]^(3-)`, geometrical isomerism does not exist while optical isomerism exists
C. In Mabcd, square planar complexes show both optical as well as geometrical isomerism
D. In Mabcd tetrahedral compoex, optical isomerism cannot be observed

Explanation

To determine which of the statements is true, we will analyze each statement one by one, eliminating the false ones until we find the true statement.

### Step 1: Analyze the first statement
**Statement:** PTCl2(NH3)2 is optically inactive in the cis form while it is optically active in the trans form.

- **Analysis:**
- The complex PTCl2(NH3)2 can exist in both cis and trans forms.
- The cis form has two identical ligands (NH3) adjacent to each other, which can lead to a plane of symmetry, making it optically inactive.
- The trans form has the identical ligands opposite each other, which can lead to a lack of symmetry and thus can be optically active.

- **Conclusion:** This statement is **false**.

### Step 2: Analyze the second statement
**Statement:** Fe(C2O4)3 does not exhibit geometrical isomerism but does exhibit optical isomerism.

- **Analysis:**
- Fe(C2O4)3 is an octahedral complex.
- It can have different arrangements of oxalate ligands (C2O4) around the central iron atom.
- In this case, it can show geometrical isomerism (cis and trans forms) due to the arrangement of the ligands.
- However, it can also show optical isomerism because the mirror images of certain arrangements are non-superimposable.

- **Conclusion:** This statement is **false**.

### Step 3: Analyze the third statement
**Statement:** Square planar complexes of the type MABCD show both optical and geometrical isomerism.

- **Analysis:**
- Square planar complexes can exhibit geometrical isomerism due to the arrangement of ligands.
- However, for optical isomerism to occur, there must be a lack of symmetry (i.e., no plane of symmetry).
- In a square planar complex like MABCD, there is a possibility of having a plane of symmetry, which would make it optically inactive.

- **Conclusion:** This statement is **false**.

### Step 4: Analyze the fourth statement
**Statement:** Tetrahedral complexes of the type MABCD do not exhibit optical isomerism.

- **Analysis:**
- Tetrahedral complexes can exhibit optical isomerism because they can have non-superimposable mirror images.
- For example, if we have a tetrahedral arrangement of four different ligands, it can exist as two enantiomers (D and L forms).

- **Conclusion:** This statement is **false**.

### Final Conclusion
After analyzing all four statements, we find that all the statements provided are false. However, if we consider the correction mentioned in the video transcript regarding the first statement, we can conclude that the correct answer is:

**The true statement is:** "Fe(C2O4)3 does not exhibit geometrical isomerism but does exhibit optical isomerism." (with the understanding that geometrical isomerism can exist under certain conditions).