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

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 (Cp3Ce)-Ce-Me(thf) and Cp'Ce-3(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 (Cp3Ce)-Ce-Me(OC6H4O) CeCp3Me and Cp'Ce-3(OC6H4O)CeCp'(3), or the chloride complexes (Cp3CeCl)-Ce-Me and Cp'3CeCl, respectively; the iodide complex Cp'3CeI was obtained from the reaction of Cp'Ce-3(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'Ce-3(OtBu). Trivalent [Cp'2CeCl](2) was synthesized by AlMe4 -> Cl exchange utilizing Cp'Ce-2(AlMe4) and AlMe2Cl. The reactivity of [Cp'2CeCl](2) towards the oxidants Ph3CCl, C2Cl6, 1,4-benzoquinone, and I-2 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.