Neutral “Cp-Free” Silyl-Lanthanide(II) Complexes: Synthesis, Structure, and Bonding Analysis

Complexes featuring lanthanide silicon bonds represent a research area still in its infancy. Herein, we report a series of Cp-free lanthanide (+II) complexes bearing σ-bonded silyl ligands. By reactions of LnI₂ (Ln = Yb, Eu, Sm) either with a 1,4-oligosilanyl dianion [K-Si­(SiMe₃)₂SiMe₂­SiMe₂Si­(SiMe₃)₂-K)] (<b>1</b>) or with <b>2</b> (Me₃Si)₃SiK (<b>3</b>) the corresponding neutral metallacyclopentasilanes ({Me₂Si­(Me₃Si)₂Si}₂)­Ln·(THF)₄ (Ln = Yb (<b>2a</b>), Eu (<b>2b</b>), Sm (<b>2c</b>)), or the disilylated complexes ({Me₃Si}₃Si)₂Ln·(THF)₃ (Ln = Yb (<b>4a</b>), Eu (<b>4b</b>), Sm (<b>4c</b>)), were selectively obtained. Complexes <b>2b</b>, <b>2c</b>, <b>4b</b>, and <b>4c</b> represent the first examples of structurally characterized Cp-free Eu and Sm complexes with silyl ligands. In both series, a linear correlation was observed between the Ln–Si bond lengths and the covalent radii of the corresponding lanthanide metals. Density functional theory calculations were also carried out for complexes <b>2a</b>–<b>c</b> and <b>4a</b>–<b>c</b> to elucidate the bonding situation between the Ln­(+II) centers and Si

Oligosilanylated Antimony Compounds

By reactions of magnesium oligosilanides with SbCl₃, a number of oligosilanylated antimony compounds were obtained. When oligosilanyl dianions were used, either the expected cyclic disilylated halostibine was obtained or alternatively the formation of a distibine was observed. Deliberate formation of the distibine from the disilylated halostibine was achieved by reductive coupling with C₈K. Computational studies of Sb–Sb bond energies, barriers of pyramidal inversion at Sb, and the conformational behavior of distibines provided insight for the understanding of the spectroscopic properties