Synthesis and Applications of Organobismuth(III) Complexes: Novel Materials and Catalysts
Synthesis and Applications of Organobismuth(III) Complexes: Novel Materials and Catalysts
| dc.contributor.advisor | Hyvl, Jakub | |
| dc.contributor.author | Louis-Goff, Thomas Aiwei Finfgeld | |
| dc.contributor.department | Chemistry | |
| dc.date.accessioned | 2024-07-02T23:41:11Z | |
| dc.date.issued | 2024 | |
| dc.description.degree | Ph.D. | |
| dc.embargo.liftdate | 2026-06-24 | |
| dc.identifier.uri | https://hdl.handle.net/10125/108316 | |
| dc.subject | Organic chemistry | |
| dc.subject | Chemistry | |
| dc.subject | Bismuth | |
| dc.subject | catalysis | |
| dc.subject | difluorocyclopropanation | |
| dc.subject | Metallopolymer | |
| dc.subject | Organobismuth | |
| dc.title | Synthesis and Applications of Organobismuth(III) Complexes: Novel Materials and Catalysts | |
| dc.type | Thesis | |
| dcterms.abstract | PART IOrganobismuthanes have tremendous potential for utility ranging from optical and semiconductor materials to metallodrugs and catalysts in organic synthesis. Their potential stems from the unique properties of the bismuth atom: its large atomic size imparts high polarizability, available coordination sites from Bi-X bonds (Lewis acidity), and relativistic effects such as spin-orbit coupling. Importantly, bismuth is non-toxic and benign to the environment. As such, bismuth chemistry has experienced increased interest over the past decade. However, some classes of organobismuthanes are still elusive, due to relatively weak Bi-C bonds responsible for dismutation, a substituent scrambling process. In the first chapter, bismuth the element is introduced. Next, bismuth complexes and their applications are briefly reviewed. Then, the issue of their synthesis, specifically dismutation, is addressed, and a detailed study of dismutation modes on the synthesis of heteroleptic triarylbismuthanes is conducted. Although the dismutation is a mechanistically diverse phenomenon, at ambient or lower temperatures, dismutation is triggered mainly by an electrophilic bismuth source. Therefore, the selection of the electrophile, Ar12BiX (X = tosylate or iodide if Ar1 = mesityl) or Ar1BiX2 (X = tosylate), and its use in low concentration during the reaction is key to suppressing the dismutation, leading to new, streamlined protocols utilizing direct arylations of Ar12BiX (X = OTs or I) or Ar1Bi(OTs)2 with organozincs affording heteroleptic triarylbismuthanes Ar12Ar2Bi. In the second chapter, the syntheses of bismuth-bearing monomers based on the diaryl bismuth styrene are described. These new procedures utilize our newly developed method that avoids dismutation. The use of protecting groups on the styryl fragment improves purification of the monomers. Radically induced co-polymerization of the bismuth monomers with p-methyl and p-bromostyrene produce soluble polymers with high refractive indices, low glass transition temperatures, and high temperature degradation properties. Moreover, by varying the ratio of bismuth monomer and organic monomer, these properties can be tailored in a consistent and controlled manner. PART IIThe introduction of C-F bonds into organic molecules imparts favorable properties due to the strength of the C-F bond, including increased chemical and thermal stability, increased hydrophobicity and lipophilicity, and low friction coefficients. Because of this, fluorinated compounds are highly represented in lubricants, refrigerants, and pharmaceuticals, and new methods to install C-F bonds is an active field of synthetic chemistry. 1,1-Difluorocyclopropanes are a specific class of fluorinated compounds that have added utility due to the cyclopropane geometry and reactivity related to the release of ring-strain. However, current methods are either inefficient, or rely on toxic or expensive stoichiometric reagents. In the first chapter, a brief discussion of carbenes and their reactivity is presented, followed by strategies for stabilizing reactive intermediates. The importance of asymmetric catalysis is also highlighted, specifically in carbene and difluorocarbene transformations. Then, the development of an efficient, catalytic olefin difluorocarbenation affording 1,1-difluorocyclopropanes is presented. The catalyst, a hypervalent organobismuth complex bearing a tert-butyl (tBu) amine 5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocine scaffold, uses the inexpensive trifluoromethyltrimethylsilane (TMS-CF3) as a stoichiometric difluorocarbene source. A wide range of alkenes, including electron-deficient alkenes, and alkynes are viable substrates, demonstrating the generality of this new system. Ease of catalyst recovery from the reaction mixture and catalyst recyclability are other attractive features of this method. In-depth experimental and theoretical studies show that the key difluorocarbene generating step proceeds through a non-redox concerted mechanism generating highly reactive free CF2 in an endergonic pre-equilibrium with the bismuth complex. The reversible difluorocarbene generation and resulting low concentration leads to a high reagent efficiency while minimizing CF2-recombination side reactions. Then, two chiral hypervalent trifluoromethyl organobismuth complexes based on the 5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocine catalyst scaffold were prepared from commercially available chiral amines, (R)-1-cyclohexylethylamine and (1R, 2R, 3R, 5S)-(–)-isopinocampheylamine; however, only the complex from the latter amine was prepared as a single stereoisomer. The complexes were catalytically active in olefin difluorocarbenation with (TMSCF3), which was used as a terminal source of CF2. The enantiopure catalyst derived from isopinocampheylamine was screened with three prochiral olefins of various reactivity in DCM and toluene. All reactions afforded the 1,1-difluorocyclopropanes in good yields, but no enantiomeric excess was observed. In the second chapter, three new hypervalent trifluoromethyl organobismuth complexes were prepared from previously reported ligand scaffolds: azabismocine, thiabismocine and sulfoximine-bismocine. All three organobismuth complexes were fully characterized by NMR spectroscopy and single-crystal X-ray crystallography, revealing that the structures were similar to their previously reported parent complexes with a hypervalent Bi–N, Bi–O, and Bi–S bonds. The three new complexes were less reactive than the original tBu amine complex from our original study. We probed the catalytic cycle’s two steps to identify that the new complexes are significantly slower in the transmetallation step. | |
| dcterms.extent | 364 pages | |
| dcterms.language | en | |
| dcterms.publisher | University of Hawai'i at Manoa | |
| dcterms.rights | All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner. | |
| dcterms.type | Text | |
| local.identifier.alturi | http://dissertations.umi.com/hawii:12038 |
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