Which of the following statement is not correct ?

Options

A. `[Ni(CN)_4]^(2-) and [Ni(CO)_4]` have the same magnetic moment
B. `[NiCl_4]^(2-) and [PtCl_4]^(2-)` have different shapes
C. Hybridisation states of Co in `[Co(OX)_3]^(3-)` is `sp^3 d^2`
D. In brown - ring complex `[Fe(H_2O)_5NO]SO_4` oxidation state of Fe is +1

Answer

To determine which of the following statements is not correct, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Analyze the Magnetic Moment of Ni(CN)4^2- and Ni(CO)4:**
- **Ni(CN)4^2-:**
- Nickel in this complex has an oxidation state of +2.
- The electron configuration of Ni in this state is [Ar] 4s^2 3d^8.
- CN^- is a strong field ligand, which means it causes pairing of electrons.
- Therefore, Ni(CN)4^2- has no unpaired electrons and a magnetic moment of 0.

- **Ni(CO)4:**
- Nickel in this complex is in the oxidation state of 0.
- The electron configuration is [Ar] 4s^2 3d^10.
- CO is also a strong field ligand, leading to pairing of electrons.
- Thus, Ni(CO)4 also has no unpaired electrons and a magnetic moment of 0.

- **Conclusion:** Both Ni(CN)4^2- and Ni(CO)4 have the same magnetic moment (0), making this statement correct.

2. **Analyze the Shapes of NiCl4^2- and PdCl4^2-:**
- **NiCl4^2-:**
- Nickel in this complex has an oxidation state of +2.
- The electron configuration is [Ar] 4s^2 3d^8.
- Cl^- is a weak field ligand, which does not cause pairing.
- The hybridization is sp^3, leading to a tetrahedral shape.

- **PdCl4^2-:**
- Palladium in this complex has an oxidation state of +2.
- The electron configuration is [Kr] 4d^8.
- Cl^- is a weak field ligand, and PdCl4^2- adopts a square planar geometry due to the dsp^2 hybridization.

- **Conclusion:** NiCl4^2- and PdCl4^2- have different shapes (tetrahedral vs. square planar), making this statement correct.

3. **Analyze the Hybridization of CO in [Co(NH3)6]3+:**
- **Cobalt in [Co(NH3)6]3+:**
- Cobalt in this complex has an oxidation state of +3.
- The electron configuration is [Ar] 3d^6.
- NH3 is a strong field ligand, which causes pairing of electrons.
- In an octahedral field, the 6 electrons will completely fill the t2g orbitals, leading to a hybridization of d^2sp^3.

- **Conclusion:** The hybridization of Co in [Co(NH3)6]3+ is d^2sp^3, not sp^3d^2. Therefore, this statement is incorrect.

4. **Analyze the Brown Ring Complex Fe(H2O)5(NO)SO4:**
- In this complex, iron is in the +1 oxidation state.
- The complex is known as the brown ring complex, which is correctly stated.

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

### Final Conclusion:
The statement that is not correct is the one regarding the hybridization of CO in [Co(NH3)6]3+, which is stated as sp^3d^2.