Skip to main content
eScholarship
Open Access Publications from the University of California

UC Irvine

UC Irvine Electronic Theses and Dissertations bannerUC Irvine

Synthesis and Reductive Chemistry of Bimetallic Complexes of the Rare-Earth Metals

  • Author(s): Dumas, Megan T
  • Advisor(s): Evans, William J.
  • et al.
Abstract

This dissertation describes an expansion of reductive rare-earth metal chemistry focused on the synthesis and reduction of bimetallic complexes with the goal of examining metal-metal bond formation between two rare-earth ions. While rare-earth species with definitively identifiable metal-metal bonds were not obtained, this thesis analyzes the properties and reductive chemistry of a variety of bimetallic complexes of the rare-earth metals. Chapter 1 describes the synthesis of the bimetallic bridged-hydride precursors, [Cp′2Ln(μ–H)(THF)]2. (Ln = Y, Tb, Dy; Cp′ = C5H4SiMe3). Chapter 2 describes their reduction with potassium graphite to form dark-colored products characteristic of Ln(II) ions. The room temperature EPR spectrum of the yttrium product contains a broad signal at g = 1.983. Chapter 3 describes the synthesis and reduction of the methyl analogs of the hydrides, [Cp′2Ln(μ–CH3)]2 (Ln = Y, Tb, Dy). Reduction of these complexes generates dark-colored solutions and the yttrium complex has an axial EPR spectrum at 77 K consistent with an Y(II) ion. In Chapter 4, reduction with KC8 of the ansa-metallocene hydride, [CpAnY(μ–H)(THF)]2, [CpAn = Me2Si(C5H3SiMe3)2], is described. This generates [K(crypt)][CpAnY(μ–H)]2, the first structurally characterizable reduced bimetallic yttrium metallocene. This dark red-brown complex has a two-line EPR spectrum at room temperature characteristic of an Y(II) ion. The structural and spectroscopic characterization of the analogous reduced bimetallic dysprosium complex, [K(18-crown-6)(THF)2][CpAnDy(μ–H)]2, is presented in Chapter 5. Chapter 6 describes a new class of bimetallic complexes, {(C5Me5)2Ln[μ–O(C6H4)μ–NC]}2 (Ln = Y, Tb, Dy), discovered through the ring opening of benzoxazole to form a rare example of a bridging 2-isocyanophenolate ligand. Reduction of {(C5Me5)2Y[μ–O(C6H4)μ–NC]}2 forms a red-purple solution with an EPR spectrum consistent with reduction of the bridging ligand. Chapter 7 describes the spectroscopic characterization of the reduction of three additional classes of yttrium metallocene hydrides, (C5Me5)2Y(μ–H)(μ–η1:η5–CH2C5Me4)Y(C5Me5), [(C5Me4H)2Y(μ–H)]2, and {[SiMe2(C5Me4)2]Y(μ–H)}2. The reduction of [(C5Me4H)2Y(μ–H)]2, and the tuckover complex (C5Me5)2Y(μ–H)(μ–η1:η5–CH2C5Me4)Y(C5Me5) with KC8 provided EPR spectra at 77 K consistent with reduction. The attempted reduction of {[SiMe2(C5Me4)2]Y(μ–H)}2 with KC8 in toluene was not successful. Chapter 8 describes the synthesis of complexes with an unusual triphenylboranecarbonitrile ligand, (NCBPh3)1−, LnCl2(THF)4(NCBPh3) (Ln = Y, Dy). Exploration of this reaction led to the crystallization of LnCl2(THF)5[BPh4], [Ln(H2O)6Cl2]Cl (Ln = Y, Dy), [NEt4][PhBOBPhOBPh2], [K(crypt)]2[PhBOBPhOBPh2][BPh2(Me)(CN)], and [NEt4][Ph2BOBPh2CN].

Main Content
Current View