Which of the following complexes is an inner orbtial complex ?

Options

A. `[FeF_6]^(3-)`
B. `[NiCl_4]^(2-)`
C. `[Ni(H_2O)_6]^(2+)`
D. `[Mn(CN)_6]^(3-)`

Answer

To determine which of the given complexes is an inner orbital complex, we need to analyze each complex based on its oxidation state, electronic configuration, and the nature of the ligands involved.

### Step-by-Step Solution:

1. **Identify the Complexes:**
We have four complexes to analyze:
- A) FeF6^3-
- B) NiCl4^2-
- C) Ni(H2O)4^2-
- D) Mn(CN)6^3-

2. **Determine the Oxidation State and Electronic Configuration:**
- **For A) FeF6^3-:**
- Oxidation state of Fe = +3
- Electronic configuration of Fe^3+ = [Ar] 3d^5 4s^0
- **For B) NiCl4^2-:**
- Oxidation state of Ni = +2
- Electronic configuration of Ni^2+ = [Ar] 3d^8 4s^0
- **For C) Ni(H2O)4^2-:**
- Oxidation state of Ni = +2
- Electronic configuration of Ni^2+ = [Ar] 3d^8 4s^0
- **For D) Mn(CN)6^3-:**
- Oxidation state of Mn = +3
- Electronic configuration of Mn^3+ = [Ar] 3d^4 4s^0

3. **Analyze the Ligands:**
- **A) FeF6^3-:** Fluoride (F-) is a weak field ligand, leading to an outer orbital complex.
- **B) NiCl4^2-:** Chloride (Cl-) is also a weak field ligand, resulting in an outer orbital complex.
- **C) Ni(H2O)4^2-:** Water (H2O) is a weak field ligand, thus forming an outer orbital complex.
- **D) Mn(CN)6^3-:** Cyanide (CN-) is a strong field ligand, which causes electron pairing in the d-orbitals, leading to an inner orbital complex.

4. **Determine the Hybridization:**
- **For A, B, C:** The hybridization is typically sp^3 or dsp^2, indicating outer orbital complexes.
- **For D:** The hybridization is d^2sp^3, indicating an inner orbital complex due to the strong field ligand pairing the electrons.

5. **Conclusion:**
The complex that qualifies as an inner orbital complex is **D) Mn(CN)6^3-**.

### Final Answer:
**D) Mn(CN)6^3-** is the inner orbital complex.