Octahedral splitting energy, Δo, is a measure of the difference in energy between the two sets of d orbitals in an octahedral field. The d orbitals in the lower set experience a greater attraction from the positively charged ligands than the d orbitals in the upper set. This results in an energy difference between the two sets of d orbitals, which is known as the octahedral splitting energy.
Factors Affecting Octahedral Splitting Energy
The octahedral splitting energy is affected by several factors, including:
- The nature of the metal ion
- The nature of the ligands
- The oxidation state of the metal ion
- The geometry of the complex
Each of these factors influences the amount of energy required to move an electron from one set of d orbitals to another.
Arranging Complexes in Order of Octahedral Splitting Energy
When arranging complexes in order of octahedral splitting energy, it is important to consider the factors that influence this energy. Based on these factors, the complexes can be arranged in the following order:
- High spin complexes with weak field ligands
- Low spin complexes with weak field ligands
- High spin complexes with strong field ligands
- Low spin complexes with strong field ligands
These complexes have a low octahedral splitting energy because the ligands do not strongly attract the metal ion. As a result, the electrons remain in the higher set of d orbitals, resulting in a high spin complex.
These complexes have a higher octahedral splitting energy than high spin complexes with weak field ligands because the electrons are partially attracted to the lower set of d orbitals. However, the energy required to move the electrons to the lower set is still relatively low, resulting in a low spin complex.
These complexes have a higher octahedral splitting energy than high spin complexes with weak field ligands because the ligands strongly attract the metal ion. However, the energy required to move the electrons to the lower set of d orbitals is still relatively low, resulting in a high spin complex.
These complexes have the highest octahedral splitting energy because the ligands strongly attract the metal ion and the energy required to move the electrons to the lower set of d orbitals is high. As a result, the electrons remain in the higher set of d orbitals, resulting in a low spin complex.
Examples of Complexes in Each Category
Some examples of complexes in each category are:
- High spin complexes with weak field ligands: [Fe(H2O)6]2+
- Low spin complexes with weak field ligands: [Fe(CN)6]4-
- High spin complexes with strong field ligands: [Co(NH3)6]3+
- Low spin complexes with strong field ligands: [Co(NH3)6]3+
These complexes illustrate the effect of the factors that influence octahedral splitting energy and how they can be used to arrange complexes in order of increasing energy.
Conclusion
Octahedral splitting energy is an important concept in coordination chemistry that describes the energy difference between the two sets of d orbitals in an octahedral field. The energy is affected by several factors, including the nature of the metal ion, the nature of the ligands, the oxidation state of the metal ion, and the geometry of the complex. By considering these factors, it is possible to arrange complexes in order of increasing octahedral splitting energy.
