Question

Determine the number of unpaired electrons expected for [Fe(NO2)₆]³⁻ and for [FeF₆]³⁻ in terms of crystal field theory.

a. 0 for [Fe(NO₂)₆]³⁻ and 3 for [FeF₆]³⁻
b. 1 for [Fe(NO₂)₆]³⁻ and 2 for [FeF₆]³⁻
c. 3 for [Fe(NO₂)₆]³⁻ and 0 for [FeF₆]³⁻
d. 2 for [Fe(NO₂)₆]³⁻ and 1 for [FeF₆]³⁻

Answer 1

In [Fe(NO2)6]³⁻, all six d-electrons will be paired while in [FeF6]³⁻ four of the six d-electrons will remain unpaired.

Step-by-step explanation:

In terms of crystal field theory, the number of unpaired electrons in a coordination compound can be determined based on the ligand's strength in splitting the d-orbitals of the central metal ion. In the case of [Fe(NO2)6]³⁻, nitrite is a strong-field ligand, resulting in a low spin complex.

Therefore, all six d-electrons will be paired, leading to 0 unpaired electrons. On the other hand, [FeF6]³⁻ involves weak-field ligand fluoride, leading to a high spin complex. In this case, four of the six d-electrons will remain unpaired, resulting in 4 unpaired electrons.