A major driving force for development of new catalyst systems is the need for more efficient synthesis of chemical compounds essential to modern life. Catalysts having superior performance offer significant environmental and economic advantages, but their discovery is not trivial. Well-defined, homogeneous catalysts can offer unparalleled understanding of ligand effects, which proves invaluable in directing redesign strategies. This thesis work focuses on the design of ruthenium complexes for applications in dinitrogen activation and olefin metathesis. The complexes developed create new directions in small-molecule activation and asymmetric catalysis by late-metal complexes. Also examined are the dual challenges, ubiquitous in catalysis, of adequate interrogation of catalyst structure and performance. Insight into both is essential to enable correlation of ligand properties with catalyst activity and/or selectivity. Improved methods for accelerated assessment of catalyst performance are described, which expand high-throughput catalyst screening to encompass parallel acquisition of kinetic data. A final aspect focuses on direct examination of metal complexes, both as isolated species, and under catalytic conditions. Applications of charge-transfer MALDI mass spectrometry to structural elucidation in organometallic chemistry is described, and the technique is employed to gain insight into catalyst decomposition pathways under operating conditions.

Optimized methods for the regioselective and stereospecific synthesis of both trisubstituted and tetrasubstituted olefins as single isomers from E-β-chloro-α-iodo-α,β-unsaturated esters have been developed from previous work done in the Ogilvie lab. These optimized methods have led to the synthesis of trans isomeric enediynes that can be photoisomerized to their respective cis isomers and subsequently undergo microwave-assisted Bergman cycloaromatizations. Furthermore, both cis and trans isomeric enediynes that have propargyl ether substituents have been found to be able to undergo photoactivated Bergman cyclizations without the need for an intermolecular hydrogen donor. A mechanism study has confirmed that the Bergman cyclization products that form without the presence of an intermolecular hydrogen donor undergo a series of 1,5-hydrogen shifts as intermediates. A series of optimizations to these reactions were carried out, in part by utilizing electron-donating or electron-withdrawing functional groups to help stabilize the resulting radicals that form on the intermediates, and thus increase the yield of the associated Bergman cyclization products.

Compounds containing multiple metal-carbon bonds are now widely used as catalysts for organic and materials synthesis. Among such transformations, olefin metathesis (OM) occupies a position of pre-eminent significance. Alkyne metathesis holds great promise, but remains in a much lower state of development. The OM-directed work in this thesis sought to advance the state of the art in living, Ru-catalyzed ringopening metathesis polymerizations (ROMP). Currently, the first- and third-generation Grubbs initiators, which exhibit the ease of handling characteristic of the late metal ruthenium, dominate ROMP applications. These initiators are characterized by extremes of reactivity, however. We describe the first ruthenium initiator capable of living ROMP at RT, irrespective of monomer bulk. Polydispersity indices as low as 1.03 are routinely attainable, and excellent control is maintained in synthesis of diblock copolymers from sterically demanding and sterically unencumbered monomers. Work on alkyne metathesis sought to expand existing understanding of the features that influence stability and reactivity in ruthenium carbynes. A classification system was developed in which Class A carbynes were defined as those that readily undergo conversion into an M=C entity (e.g. vinylidene, allenylidene, or alkylidene); Class B carbynes those that have a stable carbyne functionality. Four Ru carbyne complexes, all initially regarded as prospective Class B carbynes, were selected for study. Investigation of their reactivity resulted in categorization of several as Class A species, and development of design criteria that may open the door to assembly of stable, well-defined carbyne complexes of ruthenium.

La conversion du méthanol par les zéolithes est l'une des applications les plus prometteuses pour l'obtention d'hydrocarbures (oléfines, essences, gasoils) à partir de sources alternatives au pétrole (gaz naturel, charbon, biomasse). Dans cette thèse, un procédé catalytique multi-étapes permettant la conversion du méthanol en hydrocarbures à longue chaîne a été imaginé.Le méthanol est converti en oléfines légères par différents catalyseurs zéolithiques dans un réacteur à lit fixe sous flux continu et en phase gazeuse. L'utilisation de la ferrierite dessilicatée, de la chabazite désaluminée, de la MCM-22 et de la MCM-36 est détaillée. Les oléfines inférieures sont ensuite oligomérisées. L'oligomérisation de l'éthylène catalysée par des solides mésoporeux de type MCM-41 échangés au nickel et la co-oligomérisation des oléfines inférieures par catalyse acide sur H-MCM-41 ont été étudiées. Ces réactions ont été mises en oeuvre dans un autoclave semi-continu de type slurry. / Methanol conversion into hydrocarbons (olefins, gasoline and diesel fuel) over zeolites is one of the most promising applications involving non-oil based sources (natural gas, coal, and biomass). In this thesis, a multi-step catalytic process for converting methanol into long-chain hydrocarbons has been designed.Methanol was converted into light olefins by different zeolitic catalysts in a fixed bed reactor under continuous flow in gas phase. The use of dessilicated ferrierite, dealuminated chabazite, MCM-22 and MCM-36 has been investigated. Then, the lower olefins were oligomerized. The oligomerization of ethylene catalyzed by nickel exchanged mesoporous MCM-41 and co-oligomerization of lower olefins by H-MCM-41 acid catalyst were studied. These reactions were performed in a gas-slurry reactor operating in semi-batch mode.

In this thesis, the reactivity and synthesis of methylalumoxane (MAO) via electrospray ionization mass spectrometry (ESI-MS) was investigated. The olefin polymerization catalyst [Cp2Zr(μ-Me)2AlMe2]+ [B(C6F5)4]− was also used to evaluate the efficacy of a nitrogen generator as a source for desolvation gas for ESI-MS analysis. The same catalyst was then used to study catalyst deactivation after 1-hexene addition. MAO ionizes very selectively in the presence of octamethyltrisiloxane (OMTS) to generate [Me2Al·OMTS]+ [(MeAlO)16(Me3Al)6Me]−. The advantage of this transformation was used to examine the reactivity and synthesis of MAO. The reactivity of this ion pair with other trialkyl aluminum (R3Al) components was studied both offline and in real-time. The exchanges are fast and reversible, and the methyl groups on the cation are also observed to exchange with the added R3Al species. MAO is also famously intractable to structural elucidation, consisting as it does of a complex mixture of oligomers generated from hydrolysis of pyrophoric trimethylaluminum (TMA). Synthesis of MAO was probed in real-time by ESI-MS, and the principal activated product of the benchtop synthesis was found to be the same as that observed in industrial samples, namely [(MeAlO)16(Me3Al)6Me]–. Computationally, a new sheet structure for this ion was proposed. The increasing competitiveness of nitrogen generators, which provide gas purity levels that vary inversely with flow rate, prompted an investigation of the effect of gas-phase oxygen on the speciation of ions by ESI-MS. The most reactive species studied, the reduced titanium complex [Cp2Ti(NCMe)2]+[ZnCl3]− and the olefin polymerization pre-catalyst [Cp2Zr(μ-Me)2AlMe2]+[B(C6F5)4]−, only exhibited detectable oxidation when they were rendered coordinatively unsaturated through in-source fragmentation. The catalyst [Cp2Zr(μ-Me)2AlMe2]+[B(C6F5)4]− was further studied by ESI-MS to understand better the complexities of catalyst deactivation in the polymerization of 1-hexene. I also contributed to other projects, namely the interaction of neutral donors with MAO, saturation problems in ESI-MS, and ligand substitution reaction in ruthenium complexes, and my work on all these projects are summarized in this thesis. / Graduate

Les polyuréthanes (PUs) sont utilisés comme adhésifs depuis des décennies, mais l’utilisation d’isocyanates durant leur synthèse les place aujourd’hui dans la visée de nouvelles réglementations. Dans ces travaux, nous décrivons trois technologies alternatives potentielles aux Pus, basés sur la métathèse d’oléfines. La première technologie repose sur la synthèse de polyuréthanes sans isocyanates (NIPUs) à partir de motifs carbonate de vinylène (VC). Des polyoléfines VC2-téléchéliques ont été synthétisées par polymérisation par ouverture de cycle par métathèse / métathèse croisée (ROMP/CM) de cyclooléfines en présence d’un agent de transfert (CTA) de type VC. Cependant, la polyaddition avec une diamine a mis en évidence des reactions secondaires empêchant d’obtenir le matériaux désiré. La seconde technologie considérée est la synthèse de polyamides (PA). Des polyoléfines diazlactone (AZL)2-téléchéliques ont été synthétisées par ROMP/CM en presence d’un CTA de type AZL, puis ouvertes par une diamine. Des PAs ont ainsi été obtenus avec succès, mais en faibles quantités, ne permettant pas d’étudier leurs propriétés mécaniques ou adhésives. La dernière approche utilise les polymères silylés (SMPs). Trois types de SMPs ont été synthétisés par diverses stratégies de métathèse : des polypropylèneglycols (PPGs), des copolymères polycyclooctène (PCOE)/PPG et des copolymères polybutadiène (PBD)/PPG. La polycondensation de ces SMPs par différents systèmes catalytiques a été étudiée, ainsi que les propriétés mécaniques et adhésives des matériaux résultants. Parmi ceux-ci, les copolymères PCOE/PPG SMPs ont démontré de remarquables propriétés mécaniques et adhésives, meilleures que la plupart des SMPs commerciaux d’aujourd’hui. / Polyurethanes (PUs) have been used as adhesives for decades, but the toxic isocyanates needed for their synthesis is now on the scope of regulations. In this work, we describe three potential alternative technologies to classic PUs, based on a powerful polymerization tool: olefin metathesis. The first technology relies on the synthesis of nonisocyanate polyurethanes from vinylene carbonate (VC) functionalities. Telechelic VC polyolefins were synthesized by ring-opening metathesis polymerization/cross-metathesis (ROMP/CM) of cycloolefins with a VC chain-transfer agent (CTA). However, polyaddition attempts with a diamine evidenced side-reactions, preventing the isolation of the expected material The second technology considered is the synthesis of polyamide (PA). Following a similar strategy, telechelic azlactone (AZL) polyolefins were synthesized by ROMP/CM of cycloolefins with an AZL CTA, then, were subsequently opened by a diamine. PA were successfully obtained through this strategy, however in small quantities, thus, no mechanical nor adhesive tests were carried out. The last technology uses silyl modified polymers (SMPs). Three type of SMPs were synthesized, using diverse olefin metathesis strategies : polypropylene (PPG), polycylooctene (PCOE)/PPG copolymers and polybutadiene (PBD)/PPG copolymers. Curing of the trimethoxysilyl or triethoxysilyl groups inside these SMPs was studied using different catalytic systems, as well as the mechanical and adhesive properties of the materials obtained. Among them, PCOE/PPG copolymers displayed remarkable good mechanical and adhesive properties, better than the majority of commercial SMPs available today.

Thesis advisor: Amir H. Hoveyda / Chapter 1. In Situ Methylene Capping: A Key Strategy in Catalytic Stereoretentive Olefin MetathesisA general approach for in situ methylene capping that significantly expands the scope of catalyst-controlled stereoselective olefin metathesis is presented. By incorporation of stereodefined 2-butene as the capping reagent, the catechothiolate Ru complex is enabled to catalyze olefin metathesis reactions of terminal alkenes. Substrates bearing a carboxylic acid, an aldehyde, an aryl substituent, an α substituent were thus converted to the desired products in 47–88% yield and 90:10–98:2 Z:E selectivity. The capping strategy was also applied in ring-closing metathesis reactions leading to 14- to 21-membered macrocyclic alkenes (96:4–98:2 Z:E). The utility of this method was highlighted through synthesis of a platelet aggregate inhibitor and two members of the prostaglandin family compounds by cross-metathesis reaction, as well as a strained 14-membered ring stapled peptide by macrocyclic ring-closing metathesis. Examples of the corresponding E-selective cross-processes are provided as well. Chapter 2. Synthesis of Z- or E-Trisubstituted Allylic Alcohols and Ethers by Kinetically Controlled Catalytic Cross-MetathesisKinetically controlled Ru-catalyzed cross-metathesis reactions that generate Z- or E-trisubstituted alkenes are discussed. Reactions were catalyzed by catechothiolate Ru complex to generate trisubstituted allylic alcohols and ethers in up to 81% yield and >98% stereoisomeric purity. The approach is applicable to synthesis of products containing an alcohol, an aldehyde, a carboxylic acid or an alkenyl substituent. Mechanistic models that account for the observed trends in efficiency and stereoselectivity will be provided. Chapter 3. A New Ru-Based Catechothiolate Complex Bearing an Unsaturated NHC Ligand for Synthesis of Z-α,β-Unsaturated Carbonyl Compounds by Cross Metathesis Design and development of a new Ru catechothiolate complex that may be used to promote Z-selective cross-metathesis transformations that afford Z-α,β-unsaturated esters, acids, and amides (including Weinweb amides) are discussed. Comparison between Ru catechothiolate complexes with an unsaturated NHC and a saturated NHC ligand will be provided. Utility of the approach is demonstrated by an eight-step synthesis (15% overall yield) of an intermediate for synthesis of stagonolide E, and a five-step synthesis of a precursor to dihydrocompactin / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

To date there exists a great deal of energetic and economic inefficiency in the separation of olefins from paraffins because the principal means of achieving industrial purity requirements is accomplished with very energy intensive cryogenic distillation. Mitigation of the severe energy intensity of the propylene/propane separation has been identified as one of seven chemical separations which can change the landscape of global energy use, and membranes have been targeted as an emerging technology because they offer scalability and lower capital and operating costs. The focus of this work was to evaluate a new direction of material development for the very industrially relevant propylene/propane separation using membranes. The objective was to develop a rational design approach for generating highly selective membranes using a relatively new platform of materials known as polyimides of intrinsic microporosity (PIM-PIs), the prospects of which have never been examined for the propylene/propane separation. Structurally, PIMs comprise relatively inflexible macromolecular architectures integrating contortion sites that help disrupt packing and trap microporous free volume elements (< 20 Å). To date most of the work reported in the literature on this separation is based on conventional low free volume 6FDA-based polyimides which in the best case show moderate C3H6/C3H8 selectivities (<20) with C3H6 permeabilities too low to garner industrial interest. Due to propylene and propane’s relatively large molecular size, we hypothesized that the use of more open structures can provide greater accessibility to the pores necessary to enhance membrane sieving and flux. It has been shown for numerous key gas separations that introduction of microporosity into a polymer structure can defy the notorious permeability/selectivity tradeoff curve and induce simultaneous boosts in both permeability and selectivity. The cornerstone approach to designing state of the art high performance PIM-PI membranes for the light gas separations involving maximizing the intra-segmental rigidity of the polymer chain was applied to the C3H6/C3H8 separation. A study regarding a stepwise maximization of intra-molecular rigidity and its effects on C3H6/C3H8 permeation was evaluated by conducting systematic structural modifications to high performance PIM-PIs. State of the art increases in performance were observed in pure-gas measurements as there were significant increases in C3H6/C3H8 selectivity and C3H6 permeability upon doing so. However, mixed-gas measurements showed that there were 65% losses in selectivity due to competitive sorption and mainly plasticization. Based on the conclusions drawn, a fundamental departure from conventional PIM design principles was used, instead emphasizing enhancing inter-chain interactions by introduction of a flexible diamine and functionalization with hydroxyl groups to attempt to immobilize the polymer chains. In doing so, the polymer chains may be able to pack more efficiently and upon sub-Tg annealing cause a microstructural reorganization to form a coplanarized configuration due to the combination of inter-chain charge transfer complexes (CTC) and hydrogen bonding networks. This approach successfully mitigated plasticization, but more importantly resulted in a tightening of the microstructure, especially in the ultra-microporous range (<7 Å) thereby yielding significant boosts in C3H6/C3H8 selectivity. Based on the PIM platform and novel polymer design approach thereof, the C3H6/C3H8 upper bound was thrust to new limits and led to the generation of the most selective solution processable polymers reported for the C3H6/C3H8 separation. Although the PIM platform has redefined the polymer upper bound, the permeability/selectivity tradeoff still endures, as the C3H6 permeabilities were on the order of 1 to 3.5 Barrer for the most selective polymers. To bridge that gap in permeability, several different approaches were taken. For the first time attempted for C3H6/C3H8 separation, high temperature heating of a PIM-PI to form thermally-rearranged and carbon molecular sieve membranes was employed. The TR membrane showed increased C3H6 permeability and about 50% losses in C3H6/C3H8 selectivity, while the CMS membrane formed at 600 oC showed modest gains in C3H6/C3H8 selectivity with significant improvements in C3H6 permeability. Finally, hybrid nanocomposite membranes incorporating a metal-organic framework structure into a PIM-PI matrix was used. ZIF-8, which has demonstrated high diffusive selectivities for C3H6/C3H8, was dispersed within the polymer, since previous work by the Koros group indicated that its incorporation into polyimide matrices can facilitate major improvements in both C3H6/C3H8 selectivity and C3H6 permeability compared to the respective neat polymer. Focus was directed towards attempting to improve polymer/nanoparticle adhesion by enhancing the interactions between the polymer and filler particles to mitigate the interfacial defects notorious in mixed-matrix membranes (MMM). To do so, ZIF-8 was dispersed into one of the best performing hydroxyl functionalized PIM-PI for the C3H6/C3H8 separation. The highest loaded mixed-matrix membrane in a glassy polymer to date of 65% (w/w) was achieved. The membranes showed pure-gas selectivities ranging from 34 with 10 Barrer at 30% loading to 43 with 38 Barrer at 65% loading. Strong performance and plasticization resistance were sustained in mixed-gas experiments even to feed pressures approaching the vapor pressure of the C3H6/C3H8 mixture, as selectivities well over 20 were achieved with high permeabilities, thereby demonstrating the potential commercial viability. Based on the work reported in this dissertation, we hope to help lay a framework to be able to tailor membrane performance and future membrane design to meet the demands of the different applications of the propylene/propane separation and hence show that there can be a marketplace for membranes in the separation. These include the debottlenecking of cryogenic distillation towers for production of polymer-grade propylene (99.5%) to reduce the associated extensive energy load, production of chemical-grade propylene (92-95% propylene), or for the recovery and recycling of olefins from reactor purges of petrochemical processes.

Thesis advisor: X. Peter Zhang / Among recent advances in devising different strategies for stereoselective homolytic reactions, metalloradical catalysis (MRC) has emerged as a conceptually new approach for controlling stereoselectivity of radical reactions. As stable metalloradicals, cobalt(II) complexes of D₂-symmetric chiral amidoporphyrins [Co(D₂-Por)] have proven to be effective catalysts for homolytically activating a series of diazo compounds to generate α-Co(III)-alkyl radicals for various C-centered radical transformations with well-confined reactivity and selectivity. Nevertheless, the applications of donor-, donor/donor- and alkyl diazo compounds have been largely underdeveloped. This dissertation mainly focuses on how the chemistry of these types of diazo compounds was initiated by using commonly available aldehyde-derived sulfonylhydrazones as diazo surrogates. In the context of Co(II)-MRC, in situ-generated diazo compounds can be effectively activated for various asymmetric radical transformations, including intermolecular radical cyclopropanation of alkenes and intramolecular radical alkylation of C–H bonds. First, as a proof of concept, we have demonstrated the feasibility of using aryl aldehyde-derived sulfonylhydrazones as new radical precursors for diastereo- and enantioselective radical cyclopropanation of alkenes, and proven that the diazo in situ-generation protocol is well compatible with the catalytic radical process. Second, we have expanded the application of Co(II)-based MRC to a new territory by employing aliphatic diazo compounds for asymmetric cyclopropanation. The system is highlighted by the excellent enantioselectivity together with remarkable cis-selectivity. Finally, with the utilization of linear aliphatic aldehyde sulfonylhydrazones as diazo precursors, we have presented a new radical cyclization mode, involving hydrogen atom abstraction and radical substitution, for enantioselective synthesis of common five-membered rings via radical C–H alkylation. The system would offer a new retrosynthetic paradigm for construction of ring structures, where C–C bond can be disconnected as common C=O and C–H units of linear aldehydes. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Abstract: Metal-Organic Frameworks (MOFs) are a class of highly porous, hybrid, functional and crystalline extended coordination compounds. Their exceptional properties renders them ideal for a wide range of applications including gas storage and catalysis. Especially for catalysis, MOFs are receiving attention as well-defined supports for organometallic heterogeneous catalysis with noticeably the post-synthetic grafting of transition metal complexes on secondary building units (SBU) containing hydroxides moieties. The objective of this dissertation is to explore the synthesis, reactivity and functionalization of MOFs with SBU containing hydroxides units by transition metal catalyst using the Surface Organometallic Chemistry (SOMC) approach. Chapter 1, gives an introduction to the field of MOF and their applications to catalysis through the functionalization of hydroxide containing SBUs. This chapter introduces also the SOMC strategy with an overview of its catalytic application for olefin metathesis and CO2 conversion. Chapter 2 and 3 give a detailed application of SOMC to MOFs with the selective grafting of the W(≡CtBu)(CH2tBu)3 complex on the highly crystalline and mesoporous Zr-NU-1000 MOF. The obtained single site material, Zr-Nu-1000-W, is fully characterized using state of the art experimental methods and all the steps leading to the final grafted moieties were identified by DFT. Zr-NU-1000-W is active for olefin metathesis and is further fine-tuned by activation with EtAlCl2 giving a more selective and stable catalyst. Moreover, the nature of the grafted species could be modulated by pre-activation of the initial W(≡CtBu)(CH2tBu)3 complex with dmpe giving W(≡CtBu)(=CHtBu)(CH2tBu)(dmpe) also grafted on Zr-NU-1000. Chapter 4 and 5, describe the deliberate design and bulk synthesis of a new zirconium MOF, Zr-she-MOF-2, and highlight the discovery of a new highly connected MOF, RE-urx-MOF-1, based on a careful combination of rare earth (RE) metals with heterobifunctional triangular tetrazolate-based ligand. Additionally, the replacement of the tetrazolate functionality by carboxylate, leads to the formation of a different MOF structure RE-gea-MOF-4 having the gea topology with the presence of 18-connected nonanuclear RE cluster. Both Zr-she-MOF-2 and RE-gea-MOF-4 are active for the coupling of epoxides with CO2 to form cyclic carbonate in the presence of Bu4NBr. Finally, Chapter 6 will discuss the conclusions and perspectives of this dissertation.