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

The objective is to identify the count of paramagnetic complexes exhibiting an identical number of unpaired electrons. An examination of each species is as follows:

• $[Co(NH_3)_6]^{3+}$: Co³⁺, a low-spin d⁶ configuration, possesses 0 unpaired electrons.
• $[Co(C_2O_4)_3]^{3-}$: Co³⁺, also a low-spin d⁶, has 0 unpaired electrons due to the strong field of oxalate.
• $[MnCl_6]^{3-}$: Mn³⁺, a high-spin d⁴ configuration, has 4 unpaired electrons.
• $[Mn(CN)_6]^{3-}$: Mn³⁺, a low-spin d⁴ configuration, has 2 unpaired electrons owing to the strong field of cyanide.
• $[CoF_6]^{3-}$: Co³⁺, a high-spin d⁶ configuration, possesses 4 unpaired electrons.
• $[Fe(CN)_6]^{3-}$: Fe³⁺, a low-spin d⁵ configuration, has 1 unpaired electron.
• $[FeF_6]^{3-}$: Fe³⁺, a high-spin d⁵ configuration, possesses 5 unpaired electrons.

The analysis reveals that $[MnCl_6]^{3-}$ and $[CoF_6]^{3-}$ each have 4 unpaired electrons. Additionally, two complexes share 2 unpaired electrons. This suggests a count of 2 species with identical unpaired electrons. However, recalibrating based on field strength and hybridization factors, and a meticulous review of pairs, indicates a precise realization of 1 coherent count. The final count is 2.