Question

Low spin tetrahedral complexes are not known. 

Hint:

Low-spin complexes are more commonly seen in octahedral geometries where the ligand field splitting is stronger.

Answer 1

The absence of known low-spin tetrahedral complexes is attributable to their typically weaker ligand field splitting energy relative to octahedral complexes. Within a tetrahedral environment, the splitting energy (\(\Delta_T\)) is diminished, creating an insufficient energy differential between the d-orbitals to induce electron pairing. Consequently, electrons in tetrahedral complexes preferentially occupy all available orbitals individually (a high-spin state), rendering low-spin tetrahedral complexes unstable.