Redox Active Hexanuclear Mixed Valence Dicationic Ce(III)/Ce(IV) Coordination Clusters

A series of mixed valence hexanuclear dicationic coordination clusters containing two µ 4 ‐O 2– bridges with general formula M 2+ (X – ) 2 [ M = Ce IV 2 Ce III 4 (µ 4 ‐O) 2 (L–R) 4 (val) 6 (H 2 O) 2 ; 1 2+ , 3 2+ : R = H, 2 2+ : Me; 1 2+ , 2 2+ : X = Ce III 2 (val) 3 (NO 3 ) 4 , 3 2+ : X = NO 3 ] were synthesized, isolated and characterized. The reaction of cerium(III)nitrate hexahydrate with Schiff base ligand (H 2 L–R) and o ‐vanillin (val‐H) under basic condition led to the formation of M 2+ (X – ) 2 and the reaction progress was monitored by mass spectrometric studies. The molecular structures of all complexes were unambiguously characterized by single‐crystal X‐ray diffraction. The magnetic susceptibility measurements of M 2+ (X – ) 2 showed that the Ce(III) ions are weakly antiferromagnetically coupled. Thermal stability and molar conductivity of M 2+ (X – ) 2 were also studied. Complex 3 2+ (X – ) 2 was further studied by X‐ray photoelectron spectroscopy to confirm the oxidation states of Ce(III/IV) ions. The M 2+ cation was shown to catalyze the TEMPO‐free oxidation of functionalized benzyl alcohols quantitatively to the corresponding benzaldehyde derivatives at 100 °C in presence of aerial O 2 using DMF as the solvent.