Synthesis and Characterization of Solvated and Base-Free Cerium(III) Mixed-Sandwich Complexes

Area of Science:

• Organometallic Chemistry
• Lanthanide Chemistry
• Coordination Chemistry

Background:

• Lanthanide complexes with cyclopentadienide (Cp) and cyclooctatetraenide (COT) ligands are crucial in catalysis and materials science.
• Understanding ligand effects on these early lanthanide metal complexes is vital for designing new functional materials.
• Previous studies have focused on solvated complexes, with limited exploration of base-free systems.

Purpose of the Study:

• To synthesize and characterize a series of solvated and base-free mixed-sandwich complexes of cerium and lanthanum.
• To investigate the impact of varying Cp and COT ligands on the structural, electrochemical, and photophysical properties of these complexes.
• To explore the influence of ligand choice on the topology and reducing capabilities of the metal complexes.

Main Methods:

• Synthesis of solvated complexes: [(C8H8)Ln(C5Me4R)(DME)] and [(dbCOT)Ln(C5Me5)(DME)] (Ln = Ce, La; R = -Me, -SiMe3, -H).
• Synthesis of base-free complexes: [(C8H8)Ce(C5Me5)], [(C8H8)Ce(C5Me4H)], and [(hdcCOT)Ce(C5Me5)].
• Characterization using solid-state structural analysis, electrochemical measurements, photophysical studies, and theoretical calculations.

Main Results:

• Successful synthesis of diverse solvated and base-free cerium and lanthanum mixed-sandwich complexes with variable Cp and COT ligands.
• Demonstrated influence of Cp and COT ligands on the solid-state structure, electrochemical potentials, and photophysical behavior of the complexes.
• Isolation of novel base-free monomeric and polymeric Ce(III) mixed-sandwich compounds, providing insights into ligand effects on complex topology and redox properties.

Conclusions:

• Ligand choice significantly modulates the structural, electronic, and photophysical characteristics of early lanthanide mixed-sandwich complexes.
• The study provides the first examples of base-free monomeric and polymeric Ce(III) mixed-sandwich compounds.
• These findings offer a foundation for the rational design of tailored lanthanide-based materials with specific functionalities.