Multi‐electron Oxidation of Ce(III) Complexes Facilitated by Redox‐Active Ligands

A family of cerium complexes featuring a redox‐active ligand in different oxidation states has been synthesized, including the the iminosemiquinone (isq) 1− compound, Ce( dipp isq) 3 ( 1‐Ceisq ), and the amidophenolate (ap) 2− species Ce III ( dipp ap) 3 K 3 ( 2‐Ceap ), [Ce III ( dipp ap) 3 K][K(18‐c‐6)] 2 ( 2‐Ceap 18c6 ), and [Ce III ( dipp ap) 3 K][K(15‐c‐5) 2 ] 2 ( 2‐Ceap 15c5 ). Treating 2‐Ceap 15c5 with dioxogen furnishes the cerium(IV) derivative [Ce IV ( dipp ap) 3 ][K(15‐c‐5) 2 ] 2 ( 3‐Ceap 15c5 ), and an analogous synthesis can be used to generate [Ce IV ( dipp ap) 3 ][K(crypt)] 2 ( 3‐Ceap crypt ). Similarly, addition of hexamethyldisiloxane produces an interesting bis(amidophenolate) species, [(Me 3 SiO) 2 Ce IV ( dipp ap) 2 ][K(15‐c‐5) 2 ] 2 ( 4‐CeOSiMe 3 ). Full spectroscopic and structural characterization of each derivative was performed to establish the oxidation states of both the ligands and the cerium ions.