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)2Ce­(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 ∼2.25 V from the typically reported value for the cerium­(III/IV) couple of E°′ = +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.