Question

Out of \([CoF_6]^{3-}\) and \([Co(C_2O_4)_3]^{3-}\), which complex is:} 
(i) More stable? 
(ii) The high-spin complex? 
 

Hint:

Chelating ligands like oxalate form more stable complexes due to their ability to bind to the metal at multiple points, resulting in greater stability.

Answer 1

Stability and Spin State of the Complexes

1. More Stable Complex:

The complex [Co(C₂O₄)₃]³⁻ is more stable than [CoF₆]³⁻ because oxalate (C₂O₄²⁻) is a chelating ligand, which provides additional stability through chelation.

2. High-spin Complex:

The complex [CoF₆]³⁻ is a high-spin complex because fluoride is a weak field ligand that does not cause significant pairing of electrons.

Explanation:

• Chelating ligands such as oxalate lead to greater stability due to their ability to form multiple bonds with the central metal.
• Weak field ligands, such as fluoride, lead to high-spin complexes where electrons occupy higher-energy orbitals to minimize electron-electron repulsion.