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Small Molecule Activation and Coordination Chemistry of Bismuth, f-Element, and Alkaline Earth Complexes

  • Author(s): Kindra, Douglas
  • Advisor(s): Evans, William J
  • et al.
Abstract

This dissertation describes the synthesis, characterization, and reactivity of unique organometallic compounds of bismuth, samarium, uranium, and barium metal in efforts to expand the fundamental knowledge of their coordination and redox chemistry, particularly with respect to small molecule activation. This dissertation research involves the investigation of the NCN pincer ligand supported bismuth complex, Ar′BiCl2, to form bismuth benzyl, aryloxide, and dianionic ligand complexes, as well as studies of the reduction chemistry of (C5Me5)2Sm(THF)x in support of density functional theory research, along with projects with uranium and barium metallocenes.

Chapter 1 describes the synthesis, characterization, and structure of the first two bismuth-benzyl compounds, namely Ar′Bi(η1-CH2Ph)2 and Bi(η1-CH2Ph)3, synthesized by reaction of the analogous chloride salts with the Grignard reagent MgCl(CH2Ph).

Chapter 2 describes the reactivity of the unique oxyaryl bismuth compound Ar′Bi(C6H2tBu2-3,5-O-4), containing the unusual dianionic oxyaryl ligand (C6H2tBu2-3,5-O-4)2−. The first examples of carbon dioxide and carbonyl sulfide insertions into a bismuth-carbon bond are reported along with formal 1,5-addition of R3SiX (R = Me, Ph; X = Cl, CN, N3) reagents tothis complex. Chapter 3 further expands this chemistry by coupling the facile carbon dioxide insertion with protonation or silylation to functionalize CO2 to generate 3,5-di-tert-butyl-4-hydroxybenzoic acid or 3,5-di-tert-butyl-4-(trimethylsilyloxy)benzoate, respectively, in a cyclic process. This is a rare example of bismuth small molecule functionalization.

Chapter 4 describes the reactivity of Ar′Bi(C6H2tBu2-3,5-O-4) with nitric oxide (NO) gas and the NO delivery reagent Ph3CSNO. The first examples of NO insertion into a bismuth-carbon bond are reported with three spectroscopically and crystallographically characterized complexes. In each case, the monoanionic oximate [ON=(C6H2tBu2O)]1− is generated by formal oxidation of the dianionic ligand and concomitant reduction of nitric oxide to (NO)1−.

Chapter 5 describes the reactivity of bismuth with the tripodal ligands N,N′,N′′-[2,2′,2′′-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido) ([MST]3−) along with the analogous tridentate bipodal ligand N,N'((methylazanediyl)bis(ethane-2,1-diyl))bis(4-methylbenzenesulfonamide) ([TSB]2−). Synthesis and crystallographic characterization of Bi[MST] and the polymetallic bismuth cluster, Bi5Na2O5[TSB]5, are reported.

Chapter 6 describes the ligand transfer chemistry of Ar′Bi[O2C(C6H2tBu2-3-5-O-4)-κ2O,O′], with the dianionic ligand [O2C(C6H2tBu2-3,5-O-4)]2−, with oxophilic metal compounds, namely (C5Me5)2UCl2, SmI2(THF)2, and (C5H5)2TiCl2. Successful ligand transfer was accomplished and the product, (C5Me5)2UCl[O2C(C6H2tBu2-3-5-OH-4)-κ2O,O′] was structurally and spectroscopically characterized. Chapter 7 explores the magnetic properties of uranium complexes in detail. Over 500 literature examples from the last 50 years are compiled and examined to find trends dependent on metal oxidation state and ligand identity.

Chapter 8 describes the reaction chemistry of the samarium oxide [(C5Me5)2Sm]2(μ-O) with CO2 to test DFT rationales for the formation of the oxalate [(C5Me5)2Sm]2(μ-η2:η2-O2CCO2)from (C5Me5)2Sm(THF)x with CO2. Analogously, the reaction of (C5Me5)2Sm(THF)x with pyridine and 1-hexyne in support of DFT work on the affects of ligand donation strength on Sm2+ reactivity and carbon-carbon coupling of alkynes is reported.

Appendix A describes the exploration of the reduction chemistry of the alkaline earth metallocenes Cp2M and [Cp3M][K(chelate)] (M = Ba, Ca; Cp = C5H4SiMe3, C5H3(SiMe3)2; chelate = 18-crown-6, 2.2.2.-cryptand) in efforts to isolate monovalent alkaline earth species. Spectroscopic analysis of the reduced barium species along with initial reactivity is reported.

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