key term - [Co(NH3)6]^{3+}

Definition

[Co(NH3)6]^{3+} is a coordination complex where cobalt (Co) is the central metal ion surrounded by six ammonia (NH3) ligands, resulting in a +3 charge. This term is significant in understanding the magnetic properties of coordination compounds, as the arrangement of ligands around the metal ion influences its electronic structure and magnetism.

5 Must Know Facts For Your Next Test

1. [Co(NH3)6]^{3+} has a coordination number of 6, meaning it forms an octahedral geometry with ammonia ligands arranged symmetrically around the cobalt ion.
2. Cobalt typically has a +2 oxidation state but can be oxidized to +3 in this complex, which influences its magnetic properties.
3. The presence of six NH3 ligands stabilizes the +3 oxidation state of cobalt due to their ability to donate electron pairs.
4. [Co(NH3)6]^{3+} is a low-spin complex because ammonia is a strong field ligand, leading to paired electrons in the lower energy d-orbitals.
5. This complex exhibits diamagnetism when all electrons are paired, as there are no unpaired electrons contributing to magnetism.

Review Questions

• How does the coordination number of [Co(NH3)6]^{3+} affect its geometric structure?
  • The coordination number of [Co(NH3)6]^{3+} is 6, which results in an octahedral geometry. In this arrangement, six ammonia ligands surround the cobalt ion symmetrically. This specific geometric structure allows for optimal overlap between the orbitals of the ligands and the d-orbitals of cobalt, which is crucial for understanding its magnetic properties.
• Discuss the role of ammonia as a ligand in determining the magnetic properties of [Co(NH3)6]^{3+}.
  • Ammonia acts as a strong field ligand in [Co(NH3)6]^{3+}, influencing its electronic structure significantly. Because it induces pairing of electrons in lower energy d-orbitals, this results in a low-spin configuration. Consequently, since all d-electrons are paired, [Co(NH3)6]^{3+} exhibits diamagnetism, contrasting with high-spin complexes that contain unpaired electrons.
• Evaluate how changes in oxidation state and ligand field strength might alter the magnetic behavior of [Co(NH3)6]^{3+} if another ligand replaced NH3.
  • If another ligand that is weaker than ammonia replaced NH3 in [Co(NH3)6]^{3+}, it could change both the oxidation state and ligand field strength of cobalt. A weaker field ligand might lead to a high-spin configuration, allowing unpaired electrons in higher energy d-orbitals. This would shift [Co(NH3)6]^{3+} from being diamagnetic to potentially paramagnetic, depending on whether enough unpaired electrons are present. Such changes highlight the delicate balance between oxidation state, ligand type, and resulting magnetic properties.

Related terms

Coordination Number: The number of ligand donor atoms that are bonded to the central metal atom in a coordination complex.

Ligand Field Theory: A theory that describes how the arrangement of ligands around a central metal ion affects its electronic energy levels and magnetic properties.

High Spin vs Low Spin: Refers to the arrangement of electrons in d-orbitals under the influence of ligand fields, where high spin indicates more unpaired electrons and low spin indicates fewer unpaired electrons.