Synthesis, Electrochemistry, and Reactivity of Cerium(III/IV) Methylene-Bis-Phenolate Complexes

A series of cerium complexes containing a 2,2'-methylenebis(6-tert-butyl-4-methylphenolate) (MBP2-) ligand framework is described. Electrochemical studies of the compound [Li(THF)(2)Ce(MBP)(2)(THF)(2)) (1) reveal that the metal based oxidation wave occurs at -0.93 V vs Fc/Fc(+). This potential demonstrates significant stabilization of the cerium(IV) ion in the MBP2- framework with a shift of similar to 2.25 V from the typically reported value for the cerium(III/IV) couple of E-o' = +1.30 V vs Fc/Fc(+) for Ce(ClO4)(3) in HClO4 solutions. Compound 1 undergoes oxidation to form stable cerium(IV) species in the presence of a variety of common oxidants. The coordination of the redox-active ligands 2,2'-bipyridine and benzophenone to 1 result in complexes in which no apparent metal-to-ligand charge transfer occurs and the cerium ion remains in the +3 oxidation state.