Question

Why do tetrahedral complexes form only high spin complexe examples?

Answer 1

Let me start with what causes high spin. It occurs when Pairing energy i.e. the energy required to pair the electrons is larger than the orbital splitting energy. Therefore in such a case making a jump to the higher orbital is more feasible than pairing the electron.

Now in a tetrahedral complex, there is less number of ligands and the contribution to orbital splitting is very low, there causing a very low orbital splitting energy. In this case the orbital splitting energy is always lower than pairing energy, leading to high spin always.

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