Homoleptic Trivalent Tris(alkyl) Rare Earth Compounds

Area of Science:

• Organometallic Chemistry
• Rare Earth Chemistry
• Inorganic Chemistry

Background:

• Lanthanoid organometallic compounds are of interest due to their unique electronic properties and potential catalytic applications.
• Development of stable, well-defined lanthanoid alkyl complexes is crucial for exploring their reactivity.
• Understanding the bonding and dynamic behavior in these complexes is key to their synthetic utility.

Purpose of the Study:

• To synthesize and characterize novel homoleptic tris(alkyl) rare earth complexes.
• To investigate the structural features, specifically the secondary Ln-Si interactions.
• To elucidate the dynamic exchange processes and isotopic effects in these complexes.

Main Methods:

• Synthesis of homoleptic tris(alkyl) rare earth complexes (Ln{C(SiHMe2)3}3) from lanthanoid triiodides and KC(SiHMe2)3.
• X-ray diffraction studies to determine the solid-state structures and pseudo-C3 symmetry.
• Variable-temperature Nuclear Magnetic Resonance (NMR) spectroscopy to study dynamic exchange processes and isotopic effects.
• Density Functional Theory (DFT) calculations to model intermediates and reaction pathways.

Main Results:

• Isostructural homoleptic tris(alkyl) rare earth complexes (Ln = La, Ce, Pr, Nd) were synthesized in high yield.
• X-ray diffraction revealed pseudo-C3-symmetric structures with significant secondary Ln-Si interactions.
• NMR studies demonstrated rapid exchange of Ln-Si and Si-H moieties at room temperature, with resolution at low temperatures.
• Variable-temperature NMR and DFT calculations provided insights into the exchange mechanism and revealed an inverse kinetic isotope effect.

Conclusions:

• The synthesized rare earth alkyl complexes are structurally robust and exhibit dynamic behavior in solution.
• The Ln-Si bonding and exchange mechanisms are well-characterized, providing fundamental insights.
• These stable complexes hold promise for diverse applications in synthetic organometallic chemistry, including the synthesis of new lanthanoid compounds.