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

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Materials Science

Background:

• Lanthanide silicon bonds are an emerging area of research.
• Cyclopentadienyl (Cp) ligands are common in lanthanide chemistry, but Cp-free systems offer unique properties.

Purpose of the Study:

• To synthesize and characterize novel lanthanide (+II) complexes featuring direct lanthanide-silicon bonds.
• To explore the synthesis of Cp-free lanthanide silyl complexes.
• To investigate the structural and electronic properties of these new compounds.

Main Methods:

• Reaction of lanthanide diiodides (LnI2) with specific oligosilanyl dianions or silyl potassium reagents.
• Isolation and characterization of neutral metallacyclopentasilanes and disilylated complexes.
• X-ray crystallography for structural determination.
• Density functional theory (DFT) calculations to analyze bonding.

Main Results:

• Successfully synthesized two series of Cp-free lanthanide (+II) complexes with σ-bonded silyl ligands.
• Obtained neutral metallacyclopentasilanes ({Me2Si(Me3Si)2Si}2)Ln·(THF)4 and disilylated complexes ({Me3Si}3Si)2Ln·(THF)3.
• Complexes 2b, 2c, 4b, and 4c are the first structurally characterized Cp-free europium (Eu) and samarium (Sm) complexes with silyl ligands.
• A linear correlation was found between lanthanide-silicon bond lengths and lanthanide covalent radii.
• DFT calculations elucidated the bonding interactions between Ln(+II) and silicon.

Conclusions:

• This work significantly advances the field of lanthanide silicon chemistry by introducing new synthetic routes and characterized compounds.
• The findings provide fundamental insights into the nature of lanthanide-silicon bonds in Cp-free systems.
• The observed structure-property relationships and computational analysis pave the way for designing future lanthanide-based materials.