AIIMS 2019 Chemistry Crystal Field Theory MCQ Question

K₃[Fe(CN)₆] has the maximum crystal field stabilization energy (CFSE) because it features the strong field ligand CN⁻, which causes significant splitting of the d-orbitals in the octahedral complex, leading to a low-spin configuration and a higher CFSE value. In contrast, K₃[Co(Ox)₃] and K₃[CoF₆] contain weaker field ligands (Ox²⁻ and F⁻, respectively), resulting in lower CFSE due to less orbital splitting and potentially high-spin configurations. K₃[Co(CN)₆] also has CN⁻ as a strong field ligand, but the oxidation state of Co in this complex is +3, which can lead to a lower CFSE compared to the +2 oxidation state in K₃[Fe(CN)₆].