Question:

Which of the following complex will show largest splitting of $d$-orbitals?

Updated On: Mar 21, 2025
  • $\left[ F _{ e }\left( C _2 O _4\right)_3\right]^{3-}$
  • $\left[ F _{ e }( CN )_6\right]^{3-}$
  • $\left[ F _{ e }\left( NH _3\right)_6\right]^{3+}$
  • $\left[ F _{ e } F _6\right]^{3-}$
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The Correct Option is B

Solution and Explanation

The splitting of d-orbitals in a complex depends on the strength of the ligand according to the spectrochemical series. Strong field ligands cause greater splitting, while weak field ligands result in smaller splitting. Among the given complexes:

  1. (1) \( [\text{Fe}(\text{C}_2\text{O}_4)_3]^{3-} \): Oxalate (\( \text{C}_2\text{O}_4^{2-} \)) is a moderately strong field ligand, causing moderate splitting.
  2. (2) \( [\text{FeF}_6]^{3-} \): Fluoride (\( \text{F}^- \)) is a weak field ligand, causing minimal splitting.
  3. (3) \( [\text{Fe(CN)}_6]^{3-} \): Cyanide (\( \text{CN}^- \)) is a very strong field ligand, causing the largest splitting of d-orbitals.
  4. (4) \( [\text{Fe(NH}_3)_6]^{3+} \): Ammonia (\( \text{NH}_3 \)) is a moderate field ligand, causing less splitting compared to cyanide.

Thus, the complex \( [\text{Fe(CN)}_6]^{3-} \) will show the largest splitting of d-orbitals due to the presence of cyanide ligands. 

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Concepts Used:

Coordination Compounds

A coordination compound holds a central metal atom or ion surrounded by various oppositely charged ions or neutral molecules. These molecules or ions are re-bonded to the metal atom or ion by a coordinate bond.

Coordination entity:

A coordination entity composes of a central metal atom or ion bonded to a fixed number of ions or molecules.

Ligands:

A molecule, ion, or group which is bonded to the metal atom or ion in a complex or coordination compound by a coordinate bond is commonly called a ligand. It may be either neutral, positively, or negatively charged.