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Is Fe(CN)6 High Spin or Low Spin?

Published in Chemistry 1 min read

The complex ion Fe(CN)6 is low spin.

Here's why:

  • Strong Field Ligands: Cyanide (CN-) is a strong field ligand. Strong field ligands cause a large splitting of the d-orbitals in the metal ion. This large splitting results in pairing of electrons in the lower energy d-orbitals.
  • Electron Configuration: Iron (Fe) in its +2 oxidation state has 6 d-electrons. In a low spin complex, these electrons will pair up in the lower energy d-orbitals before occupying the higher energy ones. This results in a diamagnetic complex.
  • Diamagnetism: The low spin configuration of Fe(CN)6 makes it diamagnetic, meaning it is repelled by a magnetic field.

In contrast, high spin complexes:

  • Have weak field ligands, which cause a smaller splitting of the d-orbitals.
  • Have unpaired electrons in the higher energy d-orbitals, making them paramagnetic (attracted to a magnetic field).

Examples of high spin complexes:

  • [Fe(H2O)6]2+

Examples of low spin complexes:

  • [Fe(CN)6]4-

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