Effects of Ligands on the Cerium-Catalysed Ligand-to-Metal Charge Transfer

Benzoate anions coordinate to cerium ions. Excitation of such complexes by light leads to homolytic oxygen-cerium bond cleavage through ligand-to-metal charge transfer (LMCT). This process results in the reduction of the metal ion and the oxidation of the ligand via a single-electron transfer event. The resulting benzoic acid radical can serve as a potent hydro-gen atom abstractor, facilitating the activation of carbon atoms via C-H activation. This study investigated the scope of other oxo-anions and other ligands on cerium(IV) ions that undergo synthetically useful LMCT processes. As a model reaction, the nucleophilic carbon-centred radical from C-H abstraction in alkyl esters was reacted with phthalimide derivatives.