Our modelling shows that the constrained structural geometries imposed by sterically demanding ligands can have a significant effect on the energy of d-orbitals, even in the case of the AE metals for which there are negligible crystal field effects. Though NBO analysis reveals a predominant s-character for the LUMO and SOMO(α) in all precursors and reduced species respectively, the involvement of d-orbitals in frontier orbitals is significant. It is noteworthy that d-character in Sc 2+ , Y 2+ and La 2+ species (isoelectronic with Ca + , Sr + and Ba + respectively) has been evaluated via X-ray absorption methods, but, to the best of our knowledge, details of NBO or Mulliken analysis of frontier orbitals have not been reported. In the case of the Lu 2+ complex [K(crypt)][Lu(Cp′)3] ([Xe]5f 14 4d 1 ) Mulliken population showed 42% metal character and 48% d-character in the SOMO(α). In our studies, the NBO analysis of the SOMO(α) of invoked to describe deviation from linearity in the geometry of AE metallocenes and halides, but have not been taken into consideration as a potential characteristic of monovalent AE species.