Question

Which of the following ion/ions is/are diamagnetic?

• A. [CoF₆]³⁻
• B. [Co(NH₃)₆]³⁺
• C. [Fe(OH₂)₆]²⁺
• D. [Fe(CN)₆]⁴⁻

Hint:

Diamagnetic complexes have no unpaired electrons. Use crystal field theory to determine the spin state based on the ligand field strength.

Answer 1

The Correct Option is B, D

• [CoF₆]³⁻: Exhibits paramagnetism due to the presence of unpaired electrons in a high-spin arrangement.
• [Co(NH₃)₆]³⁺: Diamagnetic; the strong-field ligand NH₃ induces a low-spin configuration, resulting in no unpaired electrons.
• [Fe(OH₂)₆]²⁺: Shows paramagnetism because of unpaired electrons.
• [Fe(CN)₆]⁴⁻: Diamagnetic. The strong-field ligand CN⁻ forces a low-spin configuration with no unpaired electrons.