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Nickel Mediated Reactions in a High-speed Ball Mill

Haley, Rebecca
http://orcid.org/0000-0001-9013-3285
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535635347164016

Abstract Details

2018, PhD, University of Cincinnati, Arts and Sciences: Chemistry.
High-speed ball milling (HSBM), a type of mechanochemistry, has become a popular method for synthesis. This newfound interest in mechanochemistry is because, unlike traditional synthesis, solvent is not necessary to facilitate a chemical reaction. With solvents representing a large portion of the waste generated from a reaction step, HSBM can be viewed as an environmentally friendly solution to reducing solvent waste. This dissertation will delve more specifically into combining catalysis, another prominent technique in green chemistry, with HSBM. A nickel catalyzed [2 + 2 + 2 + 2] cycloaddition of terminal alkynes, sans ligand, was developed mechanochemically. Nickel pellets were found to be the most successful source of nickel to produce moderate to high yields of cyclooctatetraene derivatives. Addition of 1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene (SIMes) yielded primarily cyclotrimerization products. This finding suggests that the cycloaddition mechanism in HSBM is similar to the one proposed for the cycloaddition conducted in solution. Finally, heat was applied to the cyclotetramerization reaction. A higher temperature did not alter the selectivity for tetramers over trimers but did decrease the time required to give high conversions of the alkynes to the cyclooctatetraene products. To further explore how nickel can be used in a ball mill, reduction of various types of unsaturated bonds was investigated. Nickel nanoparticles have become popular catalysts to perform reactions of this type. High-speed ball mills have been previously used to synthesize nickel nanoparticles, so we hypothesized that nickel pellets could display similar reactivity. To create an even simpler and inexpensive method, water was used as a source of hydrogen. Without heat, the reduction of aldehydes with nickel and water did not result in adequate conversions to alcohol products. However, stainless steel and water produced moderate to high yields of alcohols. This result suggested that the reduction proceeded via a single electron transfer mechanism. To further investigate this phenomenon, the roles of iron, chromium, and nickel were studied individually. Iron was found to be the most effective electron donor, but the combination of nickel and iron in the stainless steel provided the most sustainable source of electrons. Mechanistic information was obtained to support a radical pathway. Finally, the substrate scope including various aldehydes, alkynes, and acetophenone was investigated. While using metals in their metallic form for catalysis is useful, there will still be situations where synthesizing a metal complex is more beneficial. Therefore, synthesis of these complexes from metallic starting material under HSBM conditions was explored. A nickel pincer complex was successfully synthesized from elemental nickel, suggesting that it is feasible to make organometallic complexes from such material. Additionally, HSBM has been advertised as a method greener than traditional methods, although it is has been rarely quantified and compared to other methods using green chemistry metrics. A dithiocarbamate ligand was synthesized under both HSBM and solvent conditions. The greenness of this synthesis was then quantified using atom economy, e-factor, and EcoScale. Comparing these metrics showed that for the synthesis of the dithiocarbamate ligand, it was greener to perform the reaction in solution.
Hairong Guan, Ph.D. (Committee Chair)
James Mack, Ph.D. (Committee Chair)
Michael Baldwin, Ph.D. (Committee Member)
David Smithrud, Ph.D. (Committee Member)
181 p.
Chemistry
Green Chemistry; Organic Chemistry; Nickel Catalysis; High Speed Ball Mill; Mechanochemistry

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Citations

  • Haley, R. (2018). Nickel Mediated Reactions in a High-speed Ball Mill [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535635347164016

    APA Style (7th edition)

  • Haley, Rebecca. Nickel Mediated Reactions in a High-speed Ball Mill. 2018. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535635347164016.

    MLA Style (8th edition)

  • Haley, Rebecca. "Nickel Mediated Reactions in a High-speed Ball Mill." Doctoral dissertation, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535635347164016

    Chicago Manual of Style (17th edition)

ucin1535635347164016
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This open access ETD is published by University of Cincinnati and OhioLINK.