Among the following complexes, the total number of diamagnetic species is ______.
[Mn(NH3)6]3+, [MnCl6]3−, [FeF6]3−, [CoF6]3−, [Fe(NH3)6]3+, and [Co(en)3]3+
[Given, atomic number: Mn = 25, Fe = 26, Co = 27;
en = H2NCH2CH2NH2]
[Mn(NH3)6]3+, [MnCl6]3−, [FeF6]3−, [CoF6]3−, [Fe(NH3)6]3+, and [Co(en)3]3+
[Given, atomic number: Mn = 25, Fe = 26, Co = 27;
en = H2NCH2CH2NH2]
Correct Answer: 1
Approach Solution - 1
Step 1: Understanding Diamagnetism
- A species is diamagnetic if all its electrons are paired.
- Transition metal complexes can be classified based on their ligand field strength and electronic configuration.
Step 2: Electronic Configurations of the Metal Ions
- Mn3+: [Ar] 3d4
- Fe3+: [Ar] 3d5
- Co3+: [Ar] 3d6
Step 3: Determining the Magnetic Properties of Each Complex
- [Mn(NH3)6]3+ (NH3 is a weak field ligand, high-spin d4 configuration) → Paramagnetic
- [MnCl6]3− (Cl- is a weak field ligand, high-spin d4 configuration) → Paramagnetic
- [FeF6]3− (F- is a weak field ligand, high-spin d5 configuration) → Paramagnetic
- [CoF6]3− (F- is a weak field ligand, high-spin d6 configuration) → Paramagnetic
- [Fe(NH3)6]3+ (NH3 is a weak field ligand, high-spin d5 configuration) → Paramagnetic
- [Co(en)3]3+ (en is a strong field ligand, low-spin d6 configuration) → Diamagnetic
Step 4: Conclusion
- Only [Co(en)3]3+ is diamagnetic.
- Total number of diamagnetic species = 1.
Approach Solution -2
To solve the problem, determine the number of diamagnetic species among the given complexes by analyzing their oxidation states, d-electron counts, ligand field strengths, and spin states.
Given complexes:
1. \([Mn(NH_3)_6]^{3+}\)
2. \([MnCl_6]^{3-}\)
3. \([FeF_6]^{3-}\)
4. \([CoF_6]^{3-}\)
5. \([Fe(NH_3)_6]^{3+}\)
6. \([Co(en)_3]^{3+}\)
Step 1: Determine metal oxidation state and d-electron count
| Complex | Metal | Oxidation State | d-electrons (dn) | Ligand Field Strength |
|---|---|---|---|---|
| [Mn(NH3)6]3+ | Mn (25) | +3 | d4 | NH3 (strong field) |
| [MnCl6]3− | Mn | +3 | d4 | Cl− (weak field) |
| [FeF6]3− | Fe (26) | +3 | d5 | F− (weak field) |
| [CoF6]3− | Co (27) | +3 | d6 | F− (weak field) |
| [Fe(NH3)6]3+ | Fe | +3 | d5 | NH3 (strong field) |
| [Co(en)3]3+ | Co | +3 | d6 | en (strong field) |
Step 2: Determine spin states and diamagnetism
- Diamagnetic means all electrons paired.
- [Mn(NH3)6]3+: d4 strong field → likely low spin → 2 unpaired electrons → paramagnetic
- [MnCl6]3−: d4 weak field → high spin → 4 unpaired electrons → paramagnetic
- [FeF6]3−: d5 weak field → high spin → 5 unpaired electrons → paramagnetic
- [CoF6]3−: d6 weak field → high spin → 4 unpaired electrons → paramagnetic
- [Fe(NH3)6]3+: d5 strong field → low spin → 1 unpaired electron → paramagnetic
- [Co(en)3]3+: d6 strong field → low spin → all electrons paired → diamagnetic
Step 3: Count diamagnetic species
Only <\(Co(en)_3]^{3+}\) is diamagnetic.
Final Answer:
\[ \boxed{1} \]
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