In Nature, the effective control of both the primary and secondary coordination spheres by metal-containing proteins has led to highly efficient and selective catalysts. Much effort has been put forth by the synthetic chemistry community to design complexes that explore the effects of modifying the primary coordination sphere. However, understanding the implications of both coordination spheres together is necessary to ultimately lead to the development of effective synthetic complexes for small molecule activation. For the research described herein, inspiration from biology has led to the design and preparation of ligands, paying special attention to both environments to meet the specific requirements of the small molecules targeted. Chapter 2 discusses the design and synthesis efforts of two new tripodal and tridentate ligands and complexes that feature both a redox-active primary coordination sphere and contain intramolecular H-bond donors in the secondary coordination sphere. This project was in collaboration with the laboratory of Alan Heyduk. Chapter 3 describes the synthesis and characterization of [Co II[superscript] H2bupa]− and [Ni II[superscript] H2bupa]− complexes. The reactivity of both of these complexes with dioxygen was explored in order to detect intermediates during activation yielding proposed Co III[superscript] -superoxo and Ni III[superscript] -hydroxo species. [Co II[superscript] H2bupa]− was also found to reduce dioxygen to water. Water measurements were carried out for [Co II[superscript] H2bupa]− and [Mn II[superscript] H2bupa]− in the presence of an internal standard. The turnover number for these complexes was determined and will also be discussed. Chapter 4 features the synthesis of a new tripodal ligand, H3btspa. It contains the carboxyamidopyridine group reminiscent of H5bupa, but contains two sufonamido groups capable of acting as H-bond acceptors. Upon deprotonation it ready forms complexes with Mn II[superscript], Fe II[superscript], Co II[superscript], and Zn II[superscript] salts. The stability of these complexes will also be described. Chapter 5 discusses nitrogen-containing complexes made from [Fe II[superscript] MST]-. Both the Fe II[superscript] and Fe III[superscript]-ammine complexes were synthesized along with the Fe II[superscript] -hydrazine complex. Attempts to deprotonate the Fe III[superscript]-ammine complex resulted in the reformation of the Fe II[superscript] ammine complex, leading to the proposal of a transient Fe III[superscript]-amido intermediate. Attempts to perform amination chemistry from the Fe II[superscript] and Fe III[superscript]-ammine complexes will also be highlighted.

The first to combine both the bioinorganic and the organometallic view, this handbook provides all the necessary knowledge in one convenient volume. Alongside a look at CO2 and N2 reduction, the authors discuss O2, NO and N2O binding and reduction, activation of H2 and the oxidation catalysis of O2. Edited by the highly renowned William Tolman, who has won several awards for his research in the field.

The ability of uranium to support multiple oxidation states, achieve various coordination numbers combined with the highly reducing nature of the U(III) ion makes this metal a great candidate for small molecule activation. The challenge lies in designing the appropriate ligand that can stabilize a highly reactive uranium center while simultaneously promoting activation and functionalization of small molecules in a controlled manner. Presented herein are the syntheses of two new ligand systems for uranium coordination chemistry. The effects of different ligand environments on the reactivity of trivalent uranium complexes toward small molecules are investigated. The U(III) complexes containing triazacylononane tris-aryloxide ligands [((R/ArO)3/tacn)U] (R = t-Bu, Ad) were found to stabilize charge-separated species with radical anionic ligands. Isolation of uranium ketyl radical complex, [((t-Bu/ArO3/tacn)UIV(OC*t-Bu/Ph2)], was achieved through a one-electron reduction of di-tert-butyl benzophenone with [((t-Bu/ArO3/tacn)U]. One-electron reduction of diphenyldiazomethane by [((Ad/ArO)3/tacn)U] generated a highly reactive charge-separated intermediate species [(([((Ad/ArO)3/tacn)U([Eta]2-NNCPh2)]+ that underwent C--H activation, N-insertion, and H2 elimination to yield the uranium indazole complex [((Ad/ArO)3/tacn)U([Eta]2-3-phen(Ind))]. A comparatively bulkier diamantyl functionalized ligand system was developed and the reactivity of the corresponding U(III) precursor complex was investigated. The molecular structures obtained for [((Dia/ArO3/tacn)U(Cl)] and [((Dia/ArO3/tacn)U(NTMS)] revealed a much deeper coordination cavity than in those of corresponding uranium complexes supported by the tert-butyl and adamantyl ligand systems. The deeper hydrophobic pocket is potentially advantageous for activation and functionalization of alkanes. A highly reactive trivalent uranium complex was also prepared supported by a more flexible single N-anchored ligand, [((Ad/ArO)3/N)U]. This U(III) complex is reactive towards a wide range of substrates. For instance, reductive cleavage of CO2 was observed to form bridging carbonate complex [{((Ad/ArO)3/N)U}2/[Mu]-[Eta]1:[Kappa]2/-CO3)]. A rare transformation involving reductive coupling of CS2 was achieved generating uranium thiooxalate complex [{((Ad/ArO)3/N)U}2/[Mu-[Kappa]2:[Kappa]2-C2S4)]. Activation of organic azides such as azidotrimethylsilane yielded [((Ad/ArO)3/N)U(N3)] and [((Ad/ArO)3/N)U(NTMS)]. Uranium mesitylimide complex [((Ad/ArO)3/N)U(NMes)] can also be synthesized from activation of mesityl azide. The trivalent uranium complex [((Ad/ArO)3/N)U] can also activate chalcogenides such as elemental sulfur and selenium to form bridging chalcogenide complexes of the type [{((Ad/ArO)3/N)U}2/[Mu]-E)], E = S, Se. In the presence of Na/Hg, [Na2][{((Ad/ArO)3/N)U}2/[Mu]-E)2]-type complexes, E = S, Se, Te were also obtained.

Pincer Compounds: Chemistry and Applications offers valuable state-of-the-art coverage highlighting highly active areas of research—from mechanistic work to synthesis and characterization. The book focuses on small molecule activation chemistry (particularly H2 and hydrogenation), earth abundant metals (such as Fe), actinides, carbene-pincers, chiral catalysis, and alternative solvent usage. The book covers the current state of the field, featuring chapters from renowned contributors, covering four continents and ranging from still-active pioneers to new names emerging as creative strong contributors to this fascinating and promising area. Over a decade since the publication of Morales-Morales and Jensen’s The Chemistry of Pincer Compounds (Elsevier 2007), research in this unique area has flourished, finding a plethora of applications in almost every single branch of chemistry—from their traditional application as very robust and active catalysts all the way to potential biological and pharmaceutical applications. Describes the chemistry and applications of this important class of organometallic and coordination compounds Includes contributions from global leaders in the field, featuring pioneers in the area as well as emerging experts conducting exciting research on pincer complexes Highlights areas of promising and active research, including small molecule activation, earth abundant metals, and actinide chemistry

Dinuclear complexes based on this two-in-one pincer ligand scaffold have exhibited fascinating magnetic properties and promise high reactivity in catalysis and small molecule activation. In this thesis, the main objective is to accomplish small molecule activation using dinuclear cobalt complexes as precursors and isolate important intermediate complexes for better understanding the possible mechanisms of small molecule activation. More specifically, this thesis work can be divided into five parts: N2 fixation and catalytic conversion of N2 (Chapters 2 and 3), the formation of diazene compl...

Modern energy and consumer demands have resulted in the anthropogenic rise in greenhouse gas emissions as well as an increase in environmental levels of chemical pollutants. With the continued threat of climate change and disruption of natural ecosystems, the recycling of environmentally detrimental small molecule pollutants is a critical, yet unresolved, challenge faced by the global community. Through synthetic chemistry methods, strategies for transformations converting these harmful compounds into value-added products provide opportunities for humans to find alternative pathways to restore balance to the disrupted natural carbon and nitrogen cycles. There are many approaches to the activation of small molecules, with the presented work spanning from the design of heterogeneous surface systems to synthetic organic- and organometallic-based strategies in solution. The first discussed is the development of new ligand frameworks for surface supported metal-organic coordination networks (MOCNs). A new aza-anthraquinone ligand was synthesized to self-assemble into uniform single-site surface species able to reduce added substrate. Solution-based studies of the ligand reveal favorable multi-electron redox chemistry coupled to coordination with low-valent transition metals but resulting surface studies give disordered structures. Factors contributing to the surface disorder as well as prospects for single sitecatalysts on a surface are further discussed. The next chapter takes an organic approach and explores the reactivity of simple pyrazine-based reductants. Their capabilities as stoichiometric reagents for the reduction of unsaturated organic compounds and the deoxygenation of high oxidation state main-group elements were evaluated and establish insights into the scope of reactivity and possible mechanistic details associated with silyl transfer. The final work presented focuses on the further development of deoxygenation strategies utilizing late transition metalsilylamides as an alternative vehicle for silyl transfer. Reactivity with CO2 demonstrates a capacity to deoxygenate and transfer a nitrogen atom to form cyanate, a useful building block for common polymer materials, in an overall redox-neutral transformation. Further insights into mechanistic details as well as alternate synthetic routes to organic compounds containing CO2-derived carbonare also discussed.