Coordination Chemistry PYQ: Unpaired Electrons in Fe–Co–Mn Complexes! ⚗️
❓ Question The number of unpaired electrons responsible for the paramagnetic nature of the following complex ions are, respectively: [ Fe(CN) 6 ] 3 − [ FeF 6 ] 3 − [ \text{FeF}_6 ]^{3-} [ CoF 6 ] 3 − [ \text{CoF}_6 ]^{3-} [ Mn(CN) 6 ] 3 − [ \text{Mn(CN)}_6 ]^{3-} 🖼️ Question Image ✍️ Short Solution We analyze each complex using: Oxidation state Electronic configuration Nature of ligand (strong field or weak field) High-spin vs low-spin Count unpaired electrons ✅ (1) [ Fe(CN) 6 ] 3 − [ \text{Fe(CN)}_6 ]^{3-} Step-1: CN⁻ is a strong-field ligand → large Δ₀ → low-spin . Oxidation state: Fe + 6 ( − 1 ) = − 3 ⇒ Fe 3 + \text{Fe} + 6(-1) = -3 \Rightarrow \text{Fe}^{3+} Fe 3 + : 3 d 5 \text{Fe}^{3+} : 3d^5 In low-spin d⁵ , electrons pair as much as possible: Configuration: t 2 g 5 e g 0 t_{2g}^5 e_g^0 Unpaired electrons = 1 ✅ (2) [ FeF 6 ] 3 − [ \text{FeF}_6 ]^{3-} F⁻ is a weak-field ligand → small Δ₀ → high-spin . Oxidation state o...