Browsing by Subject "Bimetallic"

Now showing 1 - 4 of 4
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    Synthesis and Characterization of a Dicobalt Catalyst for the Silylation of Dinitrogen
    (2016-06) Siedschlag, Randall
    Several dicobalt compounds were synthesized and characterized. Through these studies, dinitrogen binding was found at to happen in three oxidation states of the dicobalt core. This finding lead to the exploration of dinitrogen fixation, specifically the reduction of dinitrogen to tris(trimethylsiyl)amine. The complex was found to generate a turnover number (TON) of 195 for the catalytic silylation of dinitrogen, putting as the top performing catalyst for this process. Mechanistic insight was gained through computational modeling. The modeling studies lead to a road map for the isolation of potential intermediates along the catalytic pathway. All of these studies will be discussed within.
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    Synthesis, Characterization, and Reactivity of Early-Late Multimetallic Complexes Supported by Phosphinopyrrolides
    (2018-07) Dunn, Peter
    Interest in metal-metal bonding in polymetallic complexes has undergone a recent resurgence due to potential application towards small molecule transformations with green energy implications. In particular, complexes containing both a late transition metal and early transition metal have been the focus of extensive study, under the presumption that pairing highly differentiated metal centers may significantly alter the fundamental chemistry of the resulting molecules. To further understand and develop multimetallic chemistry, new ligand scaffolds are necessary to support multiple metal sites. This research focuses on the use of a new 2-diphenylphosphinopyrrolide ligand to synthesize group 4, 5, and 6 based metalloligands. Successful treatment with a late transition metal results in both bi- and trimetallic complexes. The fundamental structure, bonding, and reactivity of these complexes will be discussed as well as potential strategies for the synthesis of other polymetallic complexes.
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    The Systematic Design of Nickel Complexes Toward Energy-Relevant Bond Activations
    (2022-07) Prat, Jacob
    The production of catalysts capable of the efficient and selective reactivity of CO2, H2, and CO toward useful products is required to lower global energy costs and allow for a sustainable carbon neutral future. To this end the design and synthesis of metal complexes capable of controlling the reactivity of these small molecules is highly desired. Bimetallic complexes allow for a greater chemical space allowing for high tailorability of metal catalyst properties presenting a new strategy for solving these issues. The tuning of a Z-type nickel-support bond toward small molecule reactivity unifies the chemistry described herein. In the introductory chapter the environmental and energy considerations motivating this work is made explicit. Inspired by enzymatic catalysis, a nickel-iron bimetallic complex for CO2 reduction to CO was studied in depth by NMR, Mössbauer, and electrochemical studies is detailed in Chapter 2. In Chapter 3 the role of a group 13 support on H2 binding and hydride transfer reactivity was investigated with the synthesis and characterization of a set of nickel-boron complexes. In Chapter 3 the combination of open ligand choice and metal support for the modulation of CO and CO2 binding was explored with iron and tin bimetallic nickel complexes.
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    Tuning Nickel Electronics and Hydrogenation Reactivity with Rare Earth Metalloligands
    (2020-08) Ramirez, Bianca
    Industrially, many chemical transformations require the use of expensive precious metal catalysts to proceed. A major chemical pursuit aims at replacing these expensive metals with inexpensive, Earth-abundant transition metals. Unfortunately, Earth-abundant transition metals are often poor catalysts for challenging multi-electron processes. One strategy to circumvent this problem makes use of σ-accepting (or Z-type) ligands to control the electronic characteristics and reactivity of a metal center. However, a heavy focus on main group metals within this field has yielded a lack of diversity in the metals employed as Z-type ligands. In this vein, this dissertation investigates the use of rare earth metals as Z-type ligands to promote homogenous transition metal catalysis. A series of nickel–rare earth (Sc, Y, lanthanides) heterobimetallic complexes were synthesized using new phosphinoamide ligands. The complexes were characterized using a suite of spectroscopic, electrochemical, and computational methods. The electronic effects of the rare earth supporting metals poised the Ni metal center for the hydrogenation of olefins to alkanes as well as alkynes to (E)-alkenes. Furthermore, it was found that altering the coordination sphere of the rare earth support significantly impacts the resulting properties and catalytic activity of the active Ni metal center. By quantitatively comparing structure, redox properties, and mechanistic intermediates, the effects of the supporting metal on the Ni electronics, catalytic activity, and kinetics of the Ni−M complexes were elucidated. Collectively, this work demonstrates that modulating a transition metal center via an appended rare earth support metal can favorably alter the properties of inexpensive metals, thus promoting a new reactivity paradigm in homogenous transition metal catalysis.