Synthesis and Reactivity of Copper Complexes Possessing Non-dative Ligands

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Title: Synthesis and Reactivity of Copper Complexes Possessing Non-dative Ligands
Author: Blue, Elizabeth Dodge
Advisors: T. Brent Gunnoe, Committee Chair
Abstract: C-N bonds are prevalent in many areas of chemistry including natural products, pharmaceuticals, conducting polymers, and materials for electronic applications. Late transition metals are often used to catalyze carbon-nitrogen bond-forming reactions with diverse substrates and under relatively mild conditions. Hydroamination and aryl amination catalysis may proceed via Cu(I) amido complexes, and Cu-catalyzed aziridination catalysis may proceed via Cu(III) nitrene intermediates. Detailed investigation of these potential intermediates and reaction mechanisms could further the development of these critical reactions. Besides potential catalytic application, many late transition-metal non-dative complexes possess significant basic and nucleophilic reactivity. Presented herein are the isolation and characterization of a number of new copper(I) halide complexes and the first two monomeric examples of copper(I) amido complexes, (dtbpe)Cu(NHPh) and (IPr)Cu(NHPh). These Cu(I) anilido complexes have been shown to be more nucleophilic than a related Ru(II) anilido complex in reactivity studies with bromoethane, and reveal increasing nucleophilicity in the order (SIPr)Cu(NHPh) < (IPr)Cu(NHPh) < (IMes)Cu(NHPh) < (dtbpe)Cu(NHPh). (IPr)Cu(NHPh) is thermodynamically favored over (IPr)Cu(Ph)⁄NH₂Ph or [(IPr)Cu(μ-H)]₂⁄NH₂Ph, respectively. Computational studies are consistent with the observed reactivity and indicate strong Cu-N bonds with nucleophilic amido nitrogen. (dtbpe)Cu(NHPh) and (IPr)Cu(NHPh) are active for hydroamination catalysis of electron-withdrawing olefins, and (IPr)Cu(NHPh) is observed to undergo stoichiometric and catalytic aryl amination with PhI and PhOTf. The mechanism and analysis of the scope of these reactions will continue to be investigated. Reactions towards synthesis of a Cu(III) nitrene complex with LCu(I) (L = dtbpe, NN, or IPr) complexes have largely resulted in decomposition to amine products and Cu(II) species. However, reactions with (NN)Cu(NCMe) complexes and phenyl azide did result in formation of a non-isolable transient species which may be either a Cu(III) nitrene or a Cu(II) species. Reaction of (IPr)Cu(OTf) with strong acid yields a protonated carbene ligand indicated by an downfield peak which binds η² through the imidazolium phenyl ring of the amido complex. The synthesis and reactivity studies described herein have provided a foundation for continued fundamental studies of copper(I) non-dative species and mechanistic and applied C-X (X = N, O, or S) bond-forming catalytic investigations.
Date: 2007-07-05
Degree: PhD
Discipline: Chemistry

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