Which of the following are outer orbital complexes ?

Options

A. `[Co(NH_(3))_(6)]^(3+)`
B. `[Mn(CN)_(6)]^(3-)`
C. `[Ni(NH_(3))_(6)]^(2+)`
D. `[FeF_(6)]^(3-)`

Answer

To determine which of the given complexes are outer orbital complexes, we need to analyze the hybridization and the orbitals involved in each case. Here’s a step-by-step solution:

### Step 1: Understand the Concept of Outer Orbital Complexes
Outer orbital complexes are formed when the d-orbitals used in hybridization are from the outermost shell (n). This typically involves the use of the 4d or 5d orbitals, depending on the metal's position in the periodic table.

### Step 2: Analyze the Given Complexes
1. **[Co(NH3)6]³⁺**:
- Cobalt (Co) in +3 oxidation state has the electron configuration of [Ar] 3d⁶.
- NH3 is a strong field ligand, causing pairing of electrons.
- Hybridization: d²sp³ (uses inner d-orbitals).
- **Conclusion**: Inner orbital complex.

2. **[Co(CN)6]³⁻**:
- Cobalt (Co) in +3 oxidation state has the electron configuration of [Ar] 3d⁶.
- CN⁻ is a strong field ligand, also causing pairing.
- Hybridization: d²sp³ (uses inner d-orbitals).
- **Conclusion**: Inner orbital complex.

3. **[Co(NH3)6]²⁺**:
- Cobalt (Co) in +2 oxidation state has the electron configuration of [Ar] 3d⁷.
- NH3 is a strong field ligand.
- Hybridization: d²sp³ (uses inner d-orbitals).
- **Conclusion**: Inner orbital complex.

4. **[FeF6]³⁻**:
- Iron (Fe) in +3 oxidation state has the electron configuration of [Ar] 3d⁵.
- F⁻ is a weak field ligand, does not cause pairing.
- Hybridization: sp³d² (uses outer d-orbitals).
- **Conclusion**: Outer orbital complex.

### Step 3: Summary of Findings
- **Inner Orbital Complexes**: [Co(NH3)6]³⁺, [Co(CN)6]³⁻, [Co(NH3)6]²⁺
- **Outer Orbital Complexes**: [FeF6]³⁻

### Final Answer
The only outer orbital complex from the options provided is **[FeF6]³⁻**.

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