Inorganic Chemistry, Vol.54, No.14, 7065-7072, 2015
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 sigma-bonded silyl ligands. By reactions of LnI(2) (Ln = Yb, Eu, Sm) either with a 1,4-oligosilanyl dianion [K-Si(SiMe3)(2)SiMe2SiMe2Si(SiMe3)(2)-K)] (1) or with 2 (Me3Si)(3)SiK (3) the corresponding neutral metallacyclopentasilanes ({Me2Si(Me3Si)(2)Si}(2))Ln center dot(THF)(4) (Ln = Yb (2a), Eu (2b), Sm (2c)), or the disilylated complexes ({Me3Si}(3)Si)(2)Ln center dot(THF)(3) (Ln = Yb (4a), Eu (4b), Sm (4c)), were selectively obtained. Complexes 2b, 2c, 4b, and 4c 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 2a-c and 4a-c to elucidate the bonding situation between the Ln(+II) centers and Si.