Which of the following statement is/are correct?
I. The ligand thiosuphao, `S_(2)O_(3)^(2-)` can give rise to linkage isomers.
II. In metallic carbonyls the ligand CO molecule acts both as donor and acceptor.
III. The complex `[Pt(Py)(NH_(3))(NO_(2))ClBr]` exists in eight different geometrical isomeric forms
IV. The complex ferricyanide ion does not follows effective atomic numer (EAN) rule.

Options

A. I and II only
B. II and IV only
C. I, II and III
D. I, II and IV

Answer

To determine which statements are correct regarding the given complex and ligands, we will analyze each statement step by step.

### Step 1: Analyze Statement I
**Statement I:** The ligand thiosulfate, `S_(2)O_(3)^(2-)`, can give rise to linkage isomers.

- **Explanation:** Linkage isomers occur when a ligand can coordinate to a metal center through different atoms. In the case of thiosulfate, it can coordinate through sulfur or oxygen. Therefore, it can indeed form linkage isomers.
- **Conclusion:** This statement is **correct**.

### Step 2: Analyze Statement II
**Statement II:** In metallic carbonyls, the ligand CO molecule acts both as donor and acceptor.

- **Explanation:** Carbon monoxide (CO) can act as a Lewis base (donor) by donating a pair of electrons from the carbon atom to the metal. It can also act as a Lewis acid (acceptor) by accepting electrons into its empty π* orbital. Hence, CO can function as both a donor and an acceptor.
- **Conclusion:** This statement is **correct**.

### Step 3: Analyze Statement III
**Statement III:** The complex `[Pt(Py)(NH_(3))(NO_(2))ClBr]` exists in eight different geometrical isomeric forms.

- **Explanation:** The complex is square planar with four different ligands. For square planar complexes with four different ligands, the maximum number of geometrical isomers is 2 (cis and trans). Therefore, it cannot have eight different geometrical isomers.
- **Conclusion:** This statement is **incorrect**.

### Step 4: Analyze Statement IV
**Statement IV:** The complex ferricyanide ion does not follow the effective atomic number (EAN) rule.

- **Explanation:** The EAN rule states that the total number of valence electrons around the metal should be 18. For the ferricyanide ion, Fe is in the +3 oxidation state, contributing 23 electrons (26 - 3). Each cyanide ion (CN⁻) contributes 2 electrons, and with 6 cyanide ions, the total contribution is 12 electrons. Thus, the total is 23 + 12 = 35, which does not equal 18 or 36. Therefore, it does not follow the EAN rule.
- **Conclusion:** This statement is **correct**.

### Final Conclusion
The correct statements are I, II, and IV. Therefore, the answer is that statements I, II, and IV are correct.

### Summary of Correct Statements:
- **Correct Statements:** I, II, IV
- **Incorrect Statement:** III