This work describes small molecule activation by copper and iron complexes with structurally and electronically modified bis(oxazoline) (BOX) ligand systems, focusing on dioxygen and nitric oxide as substrates. Dioxygen activation at low temperatures by copper(I) complexes with neutral BOX scaffolds generated the side on peroxo dicopper(II) systems that resemble the intermediates found in type III copper proteins, whereas those complexes with an anionic BOX-derived scaffold generated the bis(μ-oxido) dicopper(III) species. The bis(μ-oxido) system has recently been proposed as an active inte...

This thesis addresses the coordination chemistry and reactivity of copper and gold complexes with a focus on the elucidation of (i) the metal-mediated activation of σ-bonds and (ii) the migratory insertion reaction. Both processes are of considerable importance in organometallic chemistry, but remain elusive for Cu and Au complexes. In this work, the author contributes significant advances: The first σ-SiH complexes of copper are experimentally and computationally characterized, yielding valuable insights into σ-bond activation processes for copper. Evidence for a highly unusual migratory syn insertion of unsaturated organic molecules into the gold-silicon bond of silylgold (I) complexes is provided and the corresponding mechanism identified. The intermolecular oxidative addition of σ-SiSi, σ-CC and σ-CX (X=halogen) bonds with molecular gold (I) complexes is studied in detail, effectively demonstrating that this reaction, usually considered to be impossible for gold, is actually highly favored, provided an adequate ligand is employed. The use of small-bite angle bis (phosphine) gold (I) complexes allows for the first time the oxidative addition of σ-CC and σ-CX bonds for gold (I). These results shed light on an unexpected reactivity pattern of gold complexes and may point the way to 2-electron redox transformations mediated by this metal, opening up new perspectives in gold catalysis.

This thesis focuses on the activation of small molecules by dinuclear copper complexes. Initially, isolation of copper/oxygen intermediates on the basis of a non-symmetric pyrazolate/tacn scaffold was investigated. The employed ligand scaffold enforces a Cu-O-O-Cu torsion angle within the dinuclear peroxo complex close to 90°, making it a relevant model complex for the proposed intermediate along the trajectory of dioxygen binding at type III copper proteins. Further, interconversion of this non-symmetric peroxo complex to the hydroperoxo and superoxo intermediate was studied by UV/Vis spec...

Examples of late transition metal complexes with amido, alkoxo and sulfido ligands are relatively rare in part due to enhanced reactivity based on nucleophilicity and basicity of the heteroatomic ligand (X). The highly nucleophilic and basic character of formally anionic X ligands coordinated to metal centers with low oxidation states is attributable to the disruption of ligand-to-metal pi-bonding. Examples of common reactivity for these systems include nucleophilic addition reactions, insertions of unsaturated substrates, acid/base chemistry with acidic C-H bonds and C-H activation reactions with aromatic substrates. In addition to fundamental reactivity studies, these complexes also offer opportunities for incorporation into catalytic processes. Late transition metal complexes with non-dative X ligands have been implicated in several C-X bond forming reactions and have been demonstrated to activate non-polar substrates. Thus, in order to advance the understanding of these reactive systems and to exploit the prospects for synthetic applications toward small molecule transformations, further study is warranted. Presented herein is the study of (IPr)Cu(NR2), (IPr)Cu(OR) and (IPr)Cu(SR) {IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene} complexes in the catalytic hydroamination of electron-deficient olefins toward regioselective formation of C-N, C-O and C-S bonds. The substrate scope encompasses alkyl and aryl amines, including primary and secondary variants, as well as alcohols and thiols. Olefins with cyano, acyl, and ester functionalities and vinylarenes are reactive. In a demonstration of potential application, the hydroamination of p-nitrostyrene with N-methylbenzylamine by (IPr)Cu(NHPh) provides a straight-forward single-step route to an anti-arrhythmic agent. Mechanistic studies are consistent with a reaction pathway that involves intermolecular nucleophilic addition of the Cu-amido to free olefin. In an effort to obtain more active catalyst systems that.

Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO2, H2O, etc.) to useful liquid fuels. This project addresses these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers have targetted heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, with the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. In addition, metal-metal interactions have been shown to dramatically affect redox potentials and promote multielectron redox activity, suggesting that metal-metal interactions may provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project has provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, it is anticipated that the broad conclusions drawn from these investigations will be applicable to heterogeneous catalysis as well, particularly on heterogeneous processes that occur at interfaces in multicomponent systems.