Light-, Middle- and Heavy-Lanthanide Ate-Complexes Bearing Ln(III)-Si bonds: Structural, Spectroscopic, and Bonding Analysis

Recent decades have witnessed a rapid development of the lanthanide silicon chemistry. In this research, by reacting [(THF)(3)LiSiPh3] with Cp(3)Ln(III)(THF) (Ln(III) = Sm(III), Tb(III), Dy(III), Yb(III)) or Cp2Lu(III)Cl(THF), a series of middle- and heavy-lanthanocene monosilyl/disilyl ate-complexes ([(DME)(3)Li][Cp(3)Ln(III)SiPh3] and [(DME)(3)Li][Cp2Lu(III)(SiPh3)(2)]) were synthesized. The structures of the obtained lanthanocene monosilyl/disilyl ate-complexes were determined by single crystal X-ray diffraction. Together with the previously reported [(DME)(3)Li][Cp3La(III)SiPh3] and [(DME)(3)Li][Cp3Ce(III)SiPh3], a complex group comprising silyl light-, middle- and heavy-lanthanocene with identical core coordination pattern are presented. The structure analysis of this group of complexes showed that their key geometric parameters, including the Ln(III)-Si bond lengths and Ln(III)-Si-C-ph/C-ph-Si-C-ph angles, were linearly correlated with the ionic radii of Ln(III) centers. Computational studies based on density functional theory calculations suggested the strongly polarized nature of the Ln(III)-Si bonds in these ate-complexes. The UV-Vis spectroscopy measurements of this group of ate-complexes showed that the characteristic absorptions were hypsochromically shifted for complexes with heavier Ln(III) centers. In addition, as revealed by the time-dependent density functional theory analysis, the HOMOs, in which the Ln(III)-Si s-bonding orbitals were the dominant components, of these complexes acted as main donor orbitals in the major electron transitions.