Browsing by Subject "Copper(III)-hydroxide"

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    Copper-Sulfur, Copper-Oxygen, and Copper-Alkyl Complexes Relevant to Copper Protein Active Site Intermediates and Catalysis
    (2013-09) Tehranchi, Jacqui
    The report of the NNN-pincer ligands, N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide andN,N'-bis(2,6-dimethylphenyl)-2,6-pyridinedicarboxamide, are presented as supporting ligands for a variety of copper(II) and nickel(II) complexes. These dianionic ligands were used due to their ability to enforce a square planar geometry in order to stabilize both the metal(II) and metal(III) complexes. The stabilization of metal(II) and metal(III) oxidation states was proposed to be a key component for obtaining mechanistic details about the oxidation pathways of these molecules, which may provide insight into the mechanistic pathways of metallo-enzymes. Specifically, efforts were aimed at the creation of copper complexes capable of C-H bond activation. This work includes the synthesis of two novel moncopper(II)-sulfur complexes supported by the sterically hindered N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide ligand: [copper(II)-SH]1- and [copper(II)-SSiPh3]1-. These complexes have potential to act as building blocks for selectively building more complex copper-sulfur structures, such as those observed in the active sites of enzymes. Efforts to model copper proteins that active oxygen, led to an investigation of the effects of the substituent on the NNN-pincer ligand (isopropyl versus methyl substitution). The effect of steric protection on the stability and reactivity of copper(III)-OH complexes towards weak C-H bonds and their self-decay behavior is presented. In addition, this work reports the first [copper(II)-CH2CN]1- complex, which was obtained from the reaction of a [copper(II)-OH]1- complex with acetonitrile. The [copper(II)-CH2CN]1- complex can be oxidized to what is believed to be a copper(III)-CH2CN complex based on spectroscopic data and theoretical calculations. The analogous [nickel(II)-CH2CN]1- complex is also reported.
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    Properties and Hydrogen Atom Transfer Reactivity of Copper(III)-Hydroxide Complexes
    (2018-01) Dhar, Debanjan
    The conversion of C-H bonds in hydrocarbons to C-O bonds is one of the grand challenges in chemistry as it involves the energy demanding preliminary step of removing a hydrogen atom from the strong C-H bond via an initial hydrogen atom transfer step. A number of high-valent reactive transition metal-oxygen species are proposed to be the key intermediates that perform such hydrogen atom transfer reactions in biological and synthetic systems. The mononuclear copper(III)-hydroxide unit has been demonstrated to be a potent reactive species in this regard. The work in this thesis is focused on the chemistry of such synthetic mononuclear copper(III)-hydroxide cores generated using strongly electron donating pyridine di-carboxamido based ligand scaffolds. In particular the spectroscopic properties and hydrogen atom transfer reactivity of a series of such copper(III)-hydroxide complexes is explored in the light of the well established proton-coupled-electron transfer theory. The effects of ligand electronic perturbations on the properties and reactivity patterns of these compounds is explored through detailed spectroscopic and mechanistic invetsigations, with the ultimate aim of elucidating the intrinsic factors that contribute to the high efficiency of such species as hydrogen atom transfer reagents. A key conclusion from all of these studies is that the thermodynamic driving force plays a crucial role in determining the rates and mechanism of such hydrogen atom transfer reactions, and that a systematic tuning of the supporting ligand electronics modulates these intrinsic thermodynamic driving forces.