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

A series of solvated complexes: [(C₈H₈)Ln(C₅Me₄R)(DME)] Ln = La, R = −Me; (La-2) Ln = Ce, R = −Me, −SiMe₃, −H; (Ce-2, Ce-3, Ce-4), [(dbCOT)Ln(C₅Me₅)(DME)] (Ln-6), (dbCOT²⁻ = dibenzocyclooctadienide; Ln = Ce, La), [(dbCOT)Ce(C₅Me₄H)(DME)] (Ce-7) and [(hdcCOT)Ce(C₅Me₅)(DME)] (Ce-8) (hdcCOT²⁻ = hexahydrodicyclopentacyclooctatetraenide) and base-free mixed-sandwich complexes [(C₈H₈)Ce(C₅Me₅)] (Ce-9), [(C₈H₈)Ce(C₅Me₄H) (Ce-10) and [(hdcCOT)Ce(C₅Me₅)] (Ce-11) of the early lanthanide metals cerium and lanthanum comprising variable cyclopentadienide (Cp⁻) and cyclooctatetraenide (COT²⁻) ligands is described. To evaluate the effect of cyclopentadienide and cyclooctatetraenide ligands on the characteristics of these complexes, their solid-state structural, electrochemical, and photophysical properties were studied and accompanied by theoretical calculations. To further evaluate the effect of ligands on the topology of the complexes and the reducing properties of the complexes, syntheses of several base-free congeners were pursued, which led to isolation of the first base-free monomeric and polymeric Ce(III) mixed-sandwich compounds.