one undergoes a slight π anti-bonding interaction with the C α p z orbitals and the other one is non-bonding. The final two orbitals characterize a σ bonding interaction with the C α sp 2 hybrid orbitals. The seven 4f orbitals are very little admixed with the ligand orbitals, yet the ligand field splitting at the orbital level, or at the many-electron level, is relatively large compared to the case of O and N donor ligands (usually 200-300 cm -1 ). This is similar to the case of YbCp 3 , which has also been shown to exhibit a large ligand field splitting. The active 4f orbitals are mostly perturbed by electrostatic interactions, while the Yb valence 6s, 6p and 5d orbitals mostly participate in the bonding interactions with the C α sp 2 hybrid orbitals. As a result, population analysis of the ground spin-free CASSCF state (see Table ) leads to significant electron occupations in the Yb(III) atomic valence and Rydberg orbitals. and), are nicely reproduced within the DFT-optimized structure (Fig. ).