Imidazolin‐2‐iminato Cerium(IV) Chlorides: Synthesis, Structure and Electrochemical Properties

Cerium(IV) chlorides supported by imidazolin-2-iminato ligands were readily synthesized in good yields, the number of imidazolin-2-iminato ligands coordinated to the cerium center is associated with the steric hindrance of imidazolin-2-iminato ligands. Electrochemical studies revealed that the Ce(III/IV) couples for the imidazolin-2-iminato cerium complexes are more negative than those of the corresponding silylamido cerium complexes.

Abstract

The ligand field greatly affects the redox properties of cerium. Herein, cerium(III) and cerium(IV) complexes supported by imidazolin-2-iminato ligands were synthesized and structurally characterized, and their electrochemical properties were investigated. Silylamine elimination of cerium(III) amide Ce{N(SiMe₃)₂}₃ with imidazolin-2-imine Im^RNH (R=Mes, tBu, iPr) provided imidazolin-2-iminato cerium(III) complexes, [(Im^MesN)(Im^MesNH)Ce{N(SiMe₃)₂}₂] (1), [(Im ^tBuN)₂(Im ^tBuNH)Ce{N(SiMe₃)₂}] (2) and [(Im ^iPrN)₂(Im ^iPrNH)Ce(μ-Im ^iPrN)]₂ (4) in 71–85% yields. These cerium(III) complexes were successfully oxidized by Ph₃CCl or C₂Cl₆ to afford imidazolin-2-iminato cerium(IV) chlorides, [(Im^MesN)₂Ce{N(SiMe₃)₂}Cl] (5), [(Im ^tBuN)₃CeCl] (6) and [(Im ^iPrN)₂Ce(μ-Im ^iPrN)Cl]₂ (7) in 70%–76% yields. All complexes were characterized by the single-crystal X-ray diffraction, which showed that 1, 2, 5 and 6 are monomers while 4 and 7 are dimers. The electrochemical studies indicated that the Ce(III/IV) couples for 5 and 6 are more negative than those of silylamido cerium(IV) complexes, and the Ce(III/IV) couples for 1 and 2 have a similar trend.

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