Do f electrons play a role in the lanthanide-ligand bonds? A DFT study of Ln(NR2)(3); R = H, SiH3

The participation of 4f electrons in the bonding of the lanthanide complexe s Ln(NR2)(3); R = H, SiH3, has been investigated at the DFT level. Structur al parameters obtained with small core (f electrons in the valence) and lar ge core (f electrons in the core) effective core potentials (ECPs) suggest the nonparticipation of the f electrons to the Ln-N bonding. A methodologic al study has been carried out on the lanthanide contraction with various ab initio methods using large core ECPs. The calculated lanthanide contractio n (0.180 Angstrom) is in excellent agreement with the experimental value (0 .179 Angstrom). Comparison of calculated structural parameters with availab le X-ray data shows that calculations with large core ECPs and density func tional methods quantitatively reproduce the bonding at the lanthanide.