Ceric Cyclopentadienides Bearing Alkoxy, Aryloxy, Chlorido, or Iodido Co‐Ligands

Abstract

A series of heteroleptic tris(cyclopentadienyl) Ce^IV complexes has been isolated and crystallographically characterized, revealing the broad accessibility of such organocerium(IV) compounds. The oxidation of complexes Cp^Me₃Ce(thf) and Cp′₃Ce(thf) (Cp^Me=C₅H₄Me, Cp′=C₅H₄SiMe₃), bearing monosubstituted electron‐poor cyclopentadienyl ligands, with 0.5 equivalents of 1,4‐benzoquinone or C₂Cl₆ gave the cerium(IV) hydroquinolate complexes Cp^Me₃Ce(OC₆H₄O)CeCp^Me₃ and Cp′₃Ce(OC₆H₄O)CeCp′₃, or the chloride complexes Cp^Me₃CeCl and Cp′₃CeCl, respectively; the iodide complex Cp′₃CeI was obtained from the reaction of Cp′₃Ce(thf) with elemental iodine. The behavior of Cp′₃CeCl in salt metathesis protocols employing alkali metal amides or alkyl, alkoxide, and aryloxide reagents was investigated, which gave rise to the robust and isolable cerium(IV) alkoxide Cp′₃Ce(OtBu). Trivalent [Cp′₂CeCl]₂ was synthesized by AlMe₄→Cl exchange utilizing Cp′₂Ce(AlMe₄) and AlMe₂Cl. The reactivity of [Cp′₂CeCl]₂ towards the oxidants Ph₃CCl, C₂Cl₆, 1,4‐benzoquinone, and I₂ has been assessed, and has provided useful information on Ce^III/Ce^IV redox deactivation pathways. In addition to X‐ray structure analysis, all the complexes were characterized by NMR, DRIFT (diffuse reflectance IR Fourier transform), and UV/Vis spectroscopy as well as elemental analysis. The tetravalent compounds were further analyzed for their magnetic susceptibility by using Evans’ method.