Which of the following statements are incorrect ?
(1) `Co^(+3)` with strong field ligand forms high magnetic moment complex.
(2) For `Co^(+3)` if pairing `"energy"(P) gt Delta_o` then the complex formed will have `(t_(2g)^(4),(e_g)^2)` configuration.
(3) For `[Co(en)^3]^( 3+) lambda_("absorbed")` is less than `lambda_("absorbed")` for `[CoF_6]^( 3–)`
(4) If `Delta_o = 18000 cm^(–1)` for `Co^(+3)` then with same ligands for it `Delta_t = 16000 cm^(–1)`

Options

A. 1,4
B. 2,3
C. 1,2
D. 1,2,3,4

Answer

To solve the question about the incorrect statements regarding cobalt (Co) complexes, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement 1**: `Co^(+3)` with strong field ligand forms high magnetic moment complex.
- **Analysis**: Cobalt in the +3 oxidation state has the electronic configuration of [Ar] 3d^6. When a strong field ligand is present, it causes pairing of electrons in the lower energy d-orbitals (t2g). Therefore, the expected configuration would be t2g^6 and eg^0, resulting in no unpaired electrons. Thus, the magnetic moment would be zero.
- **Conclusion**: This statement is **incorrect**.

2. **Statement 2**: For `Co^(+3)` if pairing energy (P) > Δo, then the complex formed will have (t2g^4, eg^2) configuration.
- **Analysis**: If the pairing energy is greater than the splitting energy (Δo), electrons will fill the orbitals singly before pairing occurs. Therefore, the configuration would indeed be t2g^4 and eg^2, with four electrons in the t2g orbitals and two in the eg orbitals.
- **Conclusion**: This statement is **correct**.

3. **Statement 3**: For `[Co(en)3]^(3+)`, λ_absorbed is less than λ_absorbed for `[CoF6]^(3–)`.
- **Analysis**: Ethylenediamine (en) is a strong field ligand, while fluoride (F) is a weak field ligand. Strong field ligands cause greater splitting (Δo) and thus absorb light at shorter wavelengths (higher energy). Therefore, the wavelength absorbed for [Co(en)3]^(3+) would indeed be less than that for [CoF6]^(3–).
- **Conclusion**: This statement is **correct**.

4. **Statement 4**: If Δo = 18000 cm^(-1) for `Co^(+3)`, then with the same ligands, Δt = 16000 cm^(-1).
- **Analysis**: The relationship between Δo and Δt for octahedral and tetrahedral complexes is given by Δt = (4/9)Δo. If Δo = 18000 cm^(-1), then Δt = (4/9) * 18000 = 8000 cm^(-1), not 16000 cm^(-1).
- **Conclusion**: This statement is **incorrect**.

### Final Conclusion:
The incorrect statements are **1 and 4**.

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