As the global population grows, so does the world's demand for energy. Consequently, there exists an increased interest in the development of fuel cells for power generation due to their low greenhouse gas emissions. For fuel cells to be a successful power source, a reliable hydrogen source is required. Ultimately, the goal is for hydrogen to be supplied from renewable energy technology however, this type of technology is currently not mature enough to meet the continuous demand of the world's energy systems. Producing hydrogen from fossil fuels can be seen as a temporary solution while further advances are made in developing renewable hydrogen infrastructure. A fuel processing train, therefore, remains an important alternative to producing hydrogen. A fuel processing train converts fossil fuels into hydrogen for use in fuel cells and eliminates the need for hydrogen storage as hydrogen is produced on demand. Currently, the water-gas shift (WGS) reactor is one of the largest components in a fuel processing train and thus opportunity exists to reduce the size of this reactor. To design future WGS catalysts and an optimised fuel processor, the reaction kinetics taking place must be understood and quantified. In this study, kinetic measurements were conducted at 2 bar(a) and across a temperature range of 270 - 300 °C using 16 parallel fixed bed reactors (high throughput experimentation) over a 0.5 wt% Pt/CeO₂ catalyst. The feed composition was varied over the ranges 2 - 12 mol% CO, 20 - 45 mol% H₂O, 4 - 15 mol% CO₂ and 25 - 55 mol% H₂. An online micro gas chromatograph (μGC) was used to analyse the dry gas composition. Fitting of experimental data to various kinetic models was accomplished with the gPROMS software package. An initial evaluation of several Langmuir-Hinshelwood (LH) type mechanisms to two data sets obtained from literature was undertaken to evaluate the strengths and weaknesses of different kinetic expressions. The results of the initial evaluation indicate that a dual-site mechanism with an intermediate species results in the best fit for reducible supports, while a single site mechanism offers a better fit for non-reducible supports. For both kinetic models, the formation of the intermediate species is most likely to be the rate determining step. A power-rate law empirical rate expression and a LH type rate expression were both found to predict the WGS outlet composition well within 10 % error at 2bar(a). The apparent activation energy of the reaction was determined to be 110 kJ/mol. This value was confirmed to be constant, throughout the range of conditions evaluated, by means of a classical Arrhenius analysis. Simulations of increasing total system pressure, using both the empirical and "best fitting" LH model, indicate a significant pressure effect for the LH type equation, whereas the power-rate law empirical equation predicts a small, negative effect on the reaction rate with increaseing pressure. Consequently, further experiments were conducted to determine the true effect of pressure. It was found that increasing system pressure increased the WGS reaction rate, which has also been reported by Twigg (1989:288). Only the LH type rate expression was able to predict this. It is therefore recommended that either the power-rate law empirical rate expression or the LH type rate expression be used to predict the WGS outlet composition when operating below 2 bar(a). Furthermore, when predicting reaction rates outside of the window in which the rate equations were derived, it is recommended that the LH model be used as it is expected to give a better prediction as it is based on fundamental steps.

Proton exchange membrane fuel cells (PEMFC) are identified as future energy conversion devices, for application in portable and transportation devices. The preferred catalyst for the PEMFC is a Pt-catalyst. However, due to the slow oxygen reduction reaction (ORR) kinetics, high Pt loadings have to be used. The high Pt loadings lead to high costs of the PEMFC. Pt-Co alloys have been identified as catalysts having higher ORR activity higher than of a Pt-catalyst. Therefore, in the present study, the Density Functional Theory (DFT) technique is used to gain fundamental insight into the ORR on the Pt₃Co(111) surface. The calculations have been performed using the plane wave based code, the Vienna ab-initio Simulation Package (VASP). DFT spin-polarized calculations, utilizing the GGA-PW91 functional, have been used to study the adsorption of the ORR intermediates, viz. O₂, O, OOH, OH, H₂O and HOOH on the Pt₃Co(111) surface. The results obtained on the Pt₃Co(111) surface are compared to the results obtained on the Pt(111) surface. The adsorption strength of the ORR intermediates has been shown to be affected by the presence of Co to varying extents on the Pt₃Co(111) surface relative to adsorption on the Pt(111) surface. The most strongly stabilised ORR intermediate on the Pt₃Co(111) surface relative to adsorption on the Pt(111) surface is O: on the Pt₃Co(111) surface O is 0.45 eV more strongly adsorbed than on the Pt(111) surface. The least affected ORR intermediate is H₂O: H₂O adsorption on the Pt₃Co(111) surface is 0.20 eV more stable than on the Pt(111) surface. The energetically favorable, i.e. most strongly bound adsorption configurations for all the ORR intermediates involves a configuration in which the ORR intermediate is bonded to a surface Co atom. Therefore, the surface Co atom stabilizes the adsorption of the ORR intermediates, relative to adsorption on the Pt(111) surface. Coadsorbed configurations have been used to study the formation and dissociation of the ORR intermediates. From the coadsorption studies, it is shown that there is an energy cost associated with moving the adsorbates from their lowest energy sites, while separately adsorbed, to the higher energy coadsorbed state, prior to reaction. Hence, adsorbate-adsorbate interactions are expected to destabilize the coadsorbed state at the coverages considered in the present study. The Climbing Image Nudged Elastic Band (CI-NEB) method has been used to locate the transition states and to calculate the activation energies of the different elementary reaction steps. The calculated dissociation reaction activation energies for the Pt₃Co(111) surface are found to be lower than the dissociation activation energies calculated on the Pt(111) surface. The most lowered dissociation activation energy is for the dissociation of O₂: on the Pt₃Co(111) surface the activation energy is 0.08 eV, whilst on the Pt(111) surface the activation energy is 0.59 eV. For the hydrogenation reaction steps, only the hydrogenation of O to form OH occurs with a lower activation energy of 0.86 eV on the Pt₃Co(111) surface, compared to 0.95 eV on the Pt(111) surface. For other hydrogenation reaction steps, the activation energies on the Pt₃Co(111) surface are higher than those on the Pt(111) surface. Based on the calculated activation energies of the elementary ORR reaction steps, the dissociative and the O-assisted H₂O dissociation mechanisms are identified as the mechanisms most likely to be dominant on the Pt₃Co(111) surface, due to having lower activation energies relative to the associative mechanisms. For both mechanisms, the reaction step with the highest activation energy is the step involving O, i.e. O hydrogenation to form OH for the dissociative mechanism, and the O* + H₂O* --> 2OH* reaction for the O-assisted H₂O dissociation mechanism. Thus, the reaction step involving the reaction of the strongly adsorbed O species, is identified as the potential rate limiting step of the ORR. Both the dissociative and the O-assisted H₂O dissociation mechanisms are expected to be in competition on the Pt₃Co(111) surface, since the potential rate limiting step for both mechanisms have similar activation energies. Hence, the preferred mechanism will depend on the relative abundances of the H species and H₂O on the Pt₃Co(111) surface. A microkinetic analysis would be need needed to fully account for concentration and entropic contributions to the rate of reaction for the different ORR elementary reaction steps.

Thesis advisor: X. Peter Zhang / Halogenated compounds are useful synthetic organic molecules. One valuable tool for synthesizing halogen containing molecules are atom transfer radical addition (ATRA) reactions which can difunctionalize olefins with a halogen moiety. Many transition complexes can catalyze these reactions but have drawbacks such as the need for harsh conditions and additives. Herein we describe the first ATRA reaction catalyzed by cobalt metalloradical catalysis (Co-MRC) which shows a broad substrate scope, moderate temperatures and uses no additives. This reaction showed excellent regioselectivity, when applicable, and low levels of enantioselectivity (up to 33% ee). / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Alkyl-arenes are important industry feedstock chemicals that are used as solvents, pharmaceutical precursors, and polymer monomer units. One alkyl-arene, ethylbenzene, is the main focus of this dissertation, and is produced in the million ton a year scale. As alkyl-arenes are important commodity chemicals, catalytic olefin hydroarylation is a lucrative alternative for their production rather than Friedel-Crafts alkylation or various coupling reactions that have lower atom economy, require strong acids, or are energetically demanding. Currently catalytic olefin hydroarylation still suffers from decomposition pathways of the active catalytic complexes, side reactions that lead to waste products, and unfavorable activation barriers, which represent high temperature and pressure. Modifications to the catalytically active system bipyridine platinum(II) (bpyPtII), through computational methods, are explored herein. The work presented here investigates catalytic olefin hydroarylation in order to mitigate the aforementioned difficulties. Included in this study are changes to the electronic profile of the supporting ligand, bpy, through the addition of electron withdrawing or electron donating R groups (methoxy, nitro), definite ligand replacements such as bpy to hydridotris(pyrazolyl)borate (Tp), changes in metal oxidation (II to IV), and replacing the metal center from Pt to Ni. Nickel was selected as a possible alternative to platinum as it is more Earth abundant reducing the monetary requirement for the catalyst. In addition to having a different catalytic energetic profile from platinum. Ni as expected could only facilitate single step hydrogen atom transfers due to its inability to access higher oxidations states.

Photoredox catalysis has revolutionized organic chemistry, and beyond, over the past 10 years. As a field, we’ve explored the scope of this methodology in synthesis, materials chemistry, and photoenzymatic catalysis. Even with these impressive advances in reactivity, photocatalysts carry flaws within their photophysics which remain largely unaddressed. We target specific photophysical processes to improve scalability, selectivity, and robustness in synthetic photoredox catalysis. Additionally, leveraging unique photophysical transitions uncovers hidden reactivity in organic synthesis. We begin by using photoredox catalyst as mild reductant of Co(II) for [2+2+2] cycloadditions to make benzenes and pyridines. Then, we apply this methodology to a temporally controlled polymerization. During these studies, we uncover ligand-to-metal charge transfer (LMCT) as a new mode of Co(II) activation. Later, we manipulate triplet fusion upconversion systems to address fundamental challenges in photoredox catalysis. Along that vein, we work towards using singlet fission to achieve multi-electron photoredox. Finally, we investigate the advantages of spin-forbidden excitations in scaling photoredox catalysis, achieving mole-scale photoredox.

The purpose of this work was to investigate the catalytic activity in both hydrogenation and hydroformylation reactions of rhenium preparations which have not been previously characterized. Rhenium pentacarbonyl was prepared in good yield from rhenium heptoxide and carbon monoxide. The optimum conditions for preparation were 25 hours per gram of dry rhenium heptoxide at 250° under 3000 psig. (initial) of carbon monoxide. Rhenium chloropentacarbonyl was prepared in 62% yield from potassium chlororhenite and carbon monoxide at high temperatures and pressures. The iodopentacarbonyl was prepared in 29% yield from potassium perrhenate, methyl iodide, and carbon monoxide. The preparation of rhenium hydrocarbonyl was attempted using sever approaches; however, no indication of the hydrocarbonyl was observed. Hydrogenative decomposition of rhenium pentacarbonyl in benzene solutions yielded an active catalyst which upon analysis proved to be metallic rhenium. Other solvents besides benzene were used but in each case the catalyst appeared as a rhenium mirror which was difficult to remove from the container. The use of rhenium pentacarbonyl as a homogeneous hydrogenation catalyst failed in attempts to reduce hexene-1 and cyclohexanone. The hydrogenation was accomplished only when temperatures were used which were high enough to decompose the carbonyl (200-250°). The metallic rhenium catalysts were characterized against a variety of substrates. With the exception of styrene, the substrates were all reduced in the temperature range 160-200°. Comparatively, the most successful reductions were those of benzene (179/3350 psig. for 22 hours) and acetic acid (2000/4190 psig. for 16 hours). Notably, nitrobenzene required 198° for complete reduction. When activated charcoal was added to the rhenium pentacarbonyl-benzene solution, a slightly more active catalyst was obtained. However, milder conditions of hydrogenative decomposition were not achieved. The addition of iron, zinc, or tin to acidified solutions of ammonium perrhenate resulted in the formation of a "rhenium black" which exhibited catalytic activity in hydrogenation reactions. This catalyst was obtained in a quantitative yield when an excess of reductant was present at all times. Analysis of this catalyst (both quantitatively and qualitatively) indicated that this catalyst was a hydrated rhenium oxide, probably ReO_2•3H_2O or ReO_2•2½H_2O. The activity of these hydrated rhenium oxide catalysts was greater than that of the metallic rhenium catalysts in all cases. Using the hydrated rhenium oxide catalyst, the carbon-carbon double bonds of hexene-1, cyclohexene, and styrene were reduced at 90-130°/3400-3900 psig. Interestingly, the presence of this catalyst did not effect the reduction of cycloheptanone until a temperature of 167° was reached. The reduction of 2-propyn-1-ol at 163° yielded both saturated and unsaturated alcohol. Adam's catalyst resulted in total decomposition of this substrate at 250° with no reduction occurring at lower temperatures. Benzene was also reduced at relatively mild conditions (177°/3935 psig. for 14 hours) using a hydrated rhenium oxide catalyst; pyridine was reduced at 230°/4520 psig. in 22 hours. Acetic acid was reduced at a mild 156° in the presence of a hydrated rhenium oxide catalyst. This is comparable with other rhenium catalysts and much better than Adam's catalyst which will not reduce acetic acid at 250° and better than any other reported catalyst except those of rhenium. The catalysts prepared using iron as a reductant were more active than those which were obtained using zinc; however, this difference was not great in the reduction of most substrates. The hydrated rhenium oxide catalysts were used in the reduction of a series of bifunctional substrates which contained the possible combinations of carbon-carbon double bond, carbonyl, carboxyl, and nitro groups. These reductions were compared with Adam's catalyst in many cases. The olefinic bonds in allylacetone and 2-allylcyclohexanone were preferentially reduced using both the hydrated rhenium oxide catalyst and Adam's catalyst. However, the rhenium catalyst reduced crotonaldehyde to n-butanol while Adam's catalyst yielded n-butyraldehyde. The olefinic bonds in vinyl-acetic, maleic, crotonic, and undecylenic acids were reduced in preference to the carboxyl group using the rhenium oxide catalyst. Under milder conditions, Adam's catalyst also reduced vinylacetic acid to n-butyric acid as expected. The carbonyl group was reduced completely in the presence of the carboxyl group in levulinic acid using the rhenium oxide catalyst. The nitro group was reduced (in the presence of the rhenium catalyst) in preference to the carbon- carbon double bond, carboxylic, or carbonyl groups in m-nitrostyrene, p-nitrophenyl-acetic acid, and m-nitroacetophenone, respectively. The same results were obtained using Adam's catalyst in the reduction of m-nitroacetophenone. The ease of reduction of different groups using the hydrated rhenium oxide catalyst was in the order: aromatic ring < carboxyl < carbonyl < carbon-carbon double bond < nitro. The order was the same using Adam's catalyst except that the carboxylic acid group and aromatic system were not reduced at all in the latter case under conditions of 250°/4500 psig. for 24 hours. However, the order of ease of reduction using the rhenium catalyst in the reduction of mono-functional substrates was aromatic ring < carboxyl < nitro < carbon-carbon double bond < carbonyl. Thus, the nitro group exhibited a poisoning effect when present in bifunctional substrates. Generally, the activity of the catalysts prepared in this study are comparable with previously characterized rhenium catalysts. This applies especially to the reduction of benzene and acetic acid. Rhenium pentacarbonyl, rhenium iodopentacarbonyl, and rhenium hepta-sulfide were used as catalysts in the attempted hydroformylation of cyclohexene and hexene-1 . However, in the temperature range 30-260° no hydroformylation was observed other than that which resulted from iron impurities. However, increased hydrogenation of substrate and products occurred when a rhenium compound was added as a catalyst. Dicobalt octacarbonyl was prepared and used in the hydroformylation reaction for comparison. As reported, the yields of hydroformylated products was excellent.

Following the first liquid phase hydrogenation in the early part of the twentieth century, it was quickly recognized that catalytic reductions were convenient research and industrial tools. Through catalytic hydrogenations unsaturated compounds can be saturated, aldehydes transformed into alcohols, nitro groups changed into amines in one step and usually with nearly quantitative yields to mention only a few possibilities. The improvement of existing catalysts and the search for new catalytic materials has been an important phase of catalytic hydrogenation research. A good hydrogenation catalyst should be active toward a variety of substrates at relatively low temperatures, be selective in its action toward different functional groups, and should be resistant to "poisoning." However, one of the greatest deterring factors facing the research chemist as well as the industrial chemist in hydrogenations of organic compounds is the ease wit h which the ordinary active catalysts are poisoned. This poisoning, by a rather large variety of compounds, decreases the efficiency of the catalyst, even to a point where it becomes entirely inoperative. One method, in common use, of circumventing this problem is by the use of catalysts which are not affected by the presence of foreign substances. Two such catalysts that are in common use are molybdenum trisulfide and cobalt polysulfide. This resistance to poisoning is achieved at the expense of a marked decrease in the catalytic activity of these sulfide catalysts as compared to the more active and more easily poisoned platinum (Adams catalyst) or nickel (Raney nickel). From its position in the periodic table and from its electronic configuration the element rhenium (element number 75) and possibly some of its compounds, might well be expected to exhibit catalytic activity. Previous investigations have found this to be the case. Among other compounds and preparations of rhenium, rhenium heptasulfide has been found to be resistant to poisoning yet much more active than either molybdenum trisulfide or cobalt polysulfide. The purpose of this investigation was to establish the catalytic activity of other rhenium compounds, and in particular to investigate the activity of a compound closely related to rhenium heptasulfide, viz., rhenium heptaselenide. This evaluation was done by preparing rhenium heptaselenide and establishing the fact that it has catalytic activity. Once this was done attention was directed toward determining the method of preparation that would yield the most active catalyst. The next step was the trial of the catalyst with a variety of substrates; comparing the ease of reducibility of different functional groups and structural features. Having once extablished the catalytic powers of rhenium heptaselenide, attention was then turned toward an investigation of the poison resistance of the new catalyst. When these things were known a comparison and critical evaluation of rhenium heptaselenide as compared to Raney nickel, Adams' Catalyst, rhenium heptasulfide, molybdenum trisulfide and cobalt polysulfide were made.

Rhenium is a comparatively newly discovered element and its catalytic properties have been poorly characterized. Therefore, this study was made to investigate more completely the catalytic properties of rhenium and its compounds. A complete review of the literature has been made on the reductions of carboxylic acids and the use of rhenium and its compounds as contact catalysts. The primary aspect of this investigation is the reduction of carboxylic acids with main interest in rhenium heptoxide in situ prepared catalysts. Reductions on various solvents with ex sity prepared catalysts also were studied. There have been about one hundred and fifty catalytic reductions on thirty-eight different substrates using rhenium prepared catalysts. The compounds to be reduced were either reagent grade or distilled to insure reasonable purity. The substrate along with rhenium heptoxide for the in situ reductions was placed in a rocking bomb using a glass liner and charged with hydrogen to 2000 psi. (occasionally 300 psi.). The usual procedure was to maintain low initial temperatures and if no appreciable reduction was observed, the pressure drop being the criterion, successively higher temperatures were used until reduction occurred, if at all. Thus minimal conditions were assured.

Thesis advisor: Masayuki Wasa / When a catalytic reaction is carried out between two reactants, usually only onereactant is activated by a single catalyst while the other component is pre-activated so that the sluggish reactivity was compensated. In order to broaden the substrate scope, the development of cooperative catalysts that can generate both electrophilic and nucleophilic species in situ represents a compelling research objective. This thesis is focused on the development of cooperative catalyst systems and their applications to α- and β-amino C−H bond functionalization. In the first chapter of this thesis, a brief summary of the present cooperative catalysts will be discussed. In the second chapter, the development of cooperative acid/acid catalysts for the α-alkynylation of N-alkylamines will be discussed. Typically, catalytic α-amino C−H alkynylation process is carried out under oxidative conditions, and enantioselective reactions are confined to tetrahydroisoquinoline derivatives. We disclose a strategy for the union of N-alkylamines and trimethylsilyl alkynes through cooperative actions of two Lewis acids, B(C 6 F 5 ) 3 and a Cu-based complex without the use of oxidants. We proposed that various propargylamines can be synthesized through the reaction between a L n Cu−alkynyl complex and an iminium ion that are generated in situ. Furthermore, the utility of this protocol was demonstrated by applications in late stage α-alkynylation of bioactive amines and stereoselective synthesis of propargylamines. In the third chapter of this thesis, catalytic and regioselective deuteration of β-amino C−H bonds in an array of N-alkylamine-based pharmaceutical compounds will be described. Isotopic labeling of β-amino C−H bond is promoted by the cooperative action of Lewis acidic B(C 6 F 5 ) 3 and Brønsted basic N-alkylamine, converting a bioactive amine first into an iminium ion and then the corresponding enamine. Meanwhile, the acid/base catalysts can also promote the dedeuteration of acetone-d 6 to afford a deuterated ammonium ion and a boron enolate. Ensuing deuteration of the enamine by deuterated ammonium ion followed by borohydride reduction leads to the formation of β-deuterated bioactive amines with up to 99% deuterium incorporation. / Thesis (MS) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

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