), and determined their structures by single-crystal X-ray diffraction at 100 K along with their basic magnetic properties by variable-temperature measurements of their magnetic susceptibilities. We next investigate the full geometric and electronic structure of Yb[CH(SiMe 3 ) 2 ] 3 based on the most advanced EPR and solid-state NMR, supported by quantum chemical calculations. This approach enables a full characterization of the direct metal-carbon bonding as well as the nature of the secondary Yb• • • C γ interaction at low and room temperature. We discuss how this interaction influences the structure and ligand dynamics in solution and in the solid state, and how the CH(SiMe 3 ) 2 ligand leads to an unusual behavior in the crystal field interactions of the Yb(III) ion.