Bond-length distributions for ions bonded to oxygen: results for the transition metals and quantification of the factors underlying bond-length variation in inorganic solids

Gagné, O.C.; Hawthorne, F.C.

doi:10.1107/S2052252520005928

Figure 10
A molecular orbital (MO) diagram for [ML₆]ⁿ⁺ compounds where the ligands (O²⁻) can act as both σ and π donors. Transition metal d electrons fill levels starting from t_2g* in a way that progressively negates favourable π interaction, thus favouring complexes with few to no d electrons. Reproduced with permission from Pfennig (2015