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Synthesis and Characterization of Radical-Bridged, Asymmetric, and Ammonia-Containing Rare-Earth Metal Complexes

  • Author(s): Boshart, Monica
  • Advisor(s): Evans, William J
  • et al.

Rare-earth metal complexes are of interest in the use of new technologies such as single-molecule magnets (SMMs). New SMMs containing rare-earth metals can expand the limits of modern technology, but must first be made and studied before implementation. The synthesis of the new complexes (C5Me5)2Ln(μ-S)2M(μ-S)2Ln(C5Me5)2 (Ln = Y, Gd, Tb, Dy; M = Mo, W), Ln2M, and the subsequent reduction of the molybdenum compounds with Co(C5Me5)2 to form radical-bridged species [(C5Me5)2Ln(μ-S)2Mo(μ-S)2Ln(C5Me5)2][Co(C5Me5)2], (Ln2Mo)1− is described. An undetected ammonia impurity in the starting material led to the synthesis of asymmetric complexes [(C5Me5)2Ln(NH3)](μ-S)2M(μ-S)2Ln(C5Me5)2, Ln2MNH3, and the reduction of these complexes with KC8 in the presence of 18-crown-6 yielded [K(18-crown-6)](μ-S)2M(μ-S)2Ln(C5Me5)2, KMLn. Further exploration of the ammonia impurity led to the synthesis of the new yttrium metallocenes, (C5Me5)2Y(NH2)(THF), YNH2, and [(C5Me5)2Y(NH3)(THF)][BPh4], YNH3. Ammonia reactions with other lanthanide metallocenes (C5Me5)2Ln(THF)x (Ln = Sm, Yb; x = 0–2) and Cp′′3Ce (Cp′′ = C5H3(SiMe3)2) were pursued to create ammonia-containing complexes which could not be definitively characterized due to instability. In situ addition of the 2,4,6,-tri-tBu-phenoxyl radical yielded evidence for oxidation and hydrogen abstraction, but the complexes have not yet been crystallographically characterized. Finally, 89Y NMR spectroscopy was employed to obtain another method of characterization for yttrium compounds and the advantages of 1H89Y HMBC experiments over traditional 89Y NMR experiments are highlighted.

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