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Synthesis of Reactive Metal Complexes Supported by 1,1’-disubstituted Ferrocene Ligands

  • Author(s): Brosmer, Jonathan Lee
  • Advisor(s): Diaconescu, Paula L
  • Zink, Jeffrey I
  • et al.
Abstract

Reliable transformation of low-cost rare-earth metal oxides to organometallic rare-earth metal complexes is a prerequisite for the advancement of non-aqueous rare-earth metal chemistry. We have recently developed an in situ method to prepare rare-earth alkyl and halide precursors supported by a diamidoferrocene NNfc, 1,1’-fc(NSiMe2Bu)2, as an ancillary ligand. We extended the scope of this method to other lanthanide ions including those that are redox active, such as cerium, praseodymium, samarium, terbium, thulium, and ytterbium. Specifically, samarium trisbenzyl could be generated in situ and then converted to the corresponding samarium benzyl or iodide complexes in good yield. However, it was found that ytterbium trisbenzyl could not be formed cleanly and the consequent conversion to ytterbium iodide complex was low yielding. By adapting an alternative route, the desired ytterbium chloride precursor could be obtained in good yield and purity.

The synthesis and characterization of two yttrium alkyl complexes supported by a bisphosphinimine ferrocene ligand, NPfc (1,1′-di(2,4-di-tert-butyl-6-diphenylphosphiniminophenoxy)ferrocene), were accomplished. Although (NPfc)Y(CH2Ph) and (NPfc)Y(CH2SiMe3) could be structurally characterized, these compounds are thermally sensitive and decompose at ambient temperature within hours. Their characterization was accomplished by NMR spectroscopy, electrochemical measurements, and elemental analysis. Reactivity studies were also carried out; however, the lack of prolonged thermal stability at ambient temperature of these molecules led to decomposition before a clean transformation to reaction products could be observed.

The synthesis and characterization of Ln-C4Ph4-K, [(NNTBS)Ln(η2-C4Ph4)][K(THF)x] (Ln = Sc, Y, Lu), rare-earth metal complexes supported by a ferrocene diamide ligand, NNTBS (NNTBS = fc(NSitBuMe2)2, fc = 1,1′-ferrocenediyl), were accomplished. The preparation of the half-sandwich compounds, Ln-naph-K, [(NNTBS)Ln(μ-C10H8)][K(THF)2] (Ln = Sc, Y, Lu, La), was necessary in order to obtain high yields of rare-earth metallacyclopentadienes. Unlike Y and Lu, La did not show the same reactivity toward PhCCPh. The characterization of the new metal complexes was accomplished by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction.

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