5 years ago

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

Ceric Cyclopentadienides Bearing Alkoxy, Aryloxy, Chlorido, or Iodido Co-Ligands
Reiner Anwander, Nicole Harmgarth, David Schneider, Frank T. Edelmann
A series of heteroleptic tris(cyclopentadienyl) CeIV complexes has been isolated and crystallographically characterized, revealing the broad accessibility of such organocerium(IV) compounds. The oxidation of complexes CpMe3Ce(thf) and Cp′3Ce(thf) (CpMe=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 CpMe3Ce(OC6H4O)CeCpMe3 and Cp′3Ce(OC6H4O)CeCp′3, or the chloride complexes CpMe3CeCl 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 AlMe4Cl 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 CeIII/CeIV 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. Organocerium complexes: Tris(cyclopentadienyl) scaffolds provide broad access to tetravalent organocerium complexes. The application of a diverse set of oxidants gives new insights into the oxidizability of homo- and heteroleptic cyclopentadienyl cerium(III) compounds (see scheme). All new compounds have been characterized by spectroscopy and X-ray diffraction.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201700743

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