Question

The correct statement(s) about the complexes I (K3[CoF₆]) and II (K₃[RhF₆]) is/are

• A. Both complexes are high spin.
• B. Complex I is paramagnetic
• C. Complex II is diamagnetic.
• D. The crystal field stabilization energy of complex II is more than that of complex I.

Answer 1

The Correct Option is B, C, D

To determine the correct statements about the complexes I (K₃[CoF₆]) and II (K₃[RhF₆]), we will analyze their electronic configurations and magnetic properties.

1. Electronic Configuration and Magnetic Properties:
   • Complex I: K₃[CoF₆]:
     • Here, cobalt is in the +3 oxidation state, so its electronic configuration is 3d⁶.
     • Fluoride (F^-) is a weak field ligand, leading to high spin configuration due to a small crystal field splitting energy (Δ).
     • For a high-spin d⁶ configuration, the electron arrangement is t_2g⁴e_g², resulting in unpaired electrons.
     • Thus, Complex I is paramagnetic.
   • Complex II: K₃[RhF₆]:
     • Here, rhodium is in the +3 oxidation state, so its electronic configuration is also 4d⁶.
     • Even though Fluoride is a weak field ligand, in the case of Rh³⁺, the pairing energy is lower for 4d elements.
     • This can lead to low-spin complexes with no unpaired electrons.
     • As a result, Complex II is diamagnetic.
2. Crystal Field Stabilization Energy (CFSE):
   • For both Co³⁺ and Rh³⁺, with F^- as the ligand, the CFSE depends on the crystal field splitting (Δ).
   • 4d elements, such as Rh, typically have greater Δ compared to 3d elements like Co. Therefore, the CFSE of complex II will be more than that of complex I.

Based on the above analysis, the correct statements are:

• Complex I is paramagnetic.
• Complex II is diamagnetic.
• The crystal field stabilization energy of complex II is more than that of complex I.