Question

The number of paramagnetic metal complex species among $ [Co(NH_3)_6]^{3+}, [Co(C_2O_4)_3]^{3-}, [MnCl_6]^{3-}, [Mn(CN)_6]^{3-}, [CoF_6]^{3-}, [Fe(CN)_6]^{3-} $ and $ [FeF_6]^{3-} $ with same number of unpaired electrons is _____.

Hint:

To determine the number of unpaired electrons in transition metal complexes, consider the oxidation state of the metal ion and the nature of the ligands (strong field or weak field), which affects the crystal field splitting and the filling of the d-orbitals. Paramagnetic species have one or more unpaired electrons.

Answer 1

Correct Answer: 3

Step 1: Determine the number of unpaired electrons for each complex using Crystal Field Theory.
\( [Co(NH_3)_6]^{3+} \) (\( d^6 \), strong field): 0 unpaired electrons (diamagnetic) \( [Co(C_2O_4)_3]^{3-} \) (\( d^6 \), weak field): 4 unpaired electrons (paramagnetic) \( [MnCl_6]^{3-} \) (\( d^4 \), weak field): 4 unpaired electrons (paramagnetic) \( [Mn(CN)_6]^{3-} \) (\( d^4 \), strong field): 2 unpaired electrons (paramagnetic) \( [CoF_6]^{3-} \) (\( d^6 \), weak field): 4 unpaired electrons (paramagnetic) \( [Fe(CN)_6]^{3-} \) (\( d^5 \), strong field): 1 unpaired electron (paramagnetic) \( [FeF_6]^{3-} \) (\( d^5 \), weak field): 5 unpaired electrons (paramagnetic)
Step 2: Identify the number of unpaired electrons for each paramagnetic species.
The paramagnetic species have 4, 4, 2, 4, 1, and 5 unpaired electrons respectively.
Step 3: Count the number of paramagnetic species that share the same number of unpaired electrons.
One unpaired electron: \( [Fe(CN)_6]^{3-} \) (1 species) Two unpaired electrons: \( [Mn(CN)_6]^{3-} \) (1 species) Four unpaired electrons: \( [Co(C_2O_4)_3]^{3-} \), \( [MnCl_6]^{3-} \), \( [CoF_6]^{3-} \) (3 species) Five unpaired electrons: \( [FeF_6]^{3-} \) (1 species)
The maximum number of paramagnetic species with the same number of unpaired electrons is 3 (all having 4 unpaired electrons).