This thesis presents advancements in the chemistry of selenium-bearing pincer ligands with respect to their synthesis, metal association and reactivity in addition to the overall nature of selenium as a donor atom. The synthesis of a new disilylamido ligand HN(SiMe2CH2SePh)2 2.1 and its potassium salt 2.2 is reported. The attempted metal association of these species was unsuccessful with various transition metals. Multinuclear NMR data suggests coordination to silver(I), 2.3 and copper(I), 2.4 with dπ-dπ back donation from the metal to the selenium donors. It is suggested from this data that –SePh can potentially act as a π-acceptor ligand as well as a σ- donor with heavy d metals. Another explanation for the observed shielding is conformational restrictions introduced by chelation. The preparation of new selenium-bearing diarylamine compounds RN(C7H6SeMe)2 (R=H: 3.1; R= Me: 3.10; R= Boc 3.11) via aryllithium chemistry is reported. Unsuccessful attempts to synthesize the –SePh and –SetBu derivatives are described using: aryllithium chemistry, Buchwald-Hartwig Amination cross coupling and Pd-catalyzed C-Se cross coupling. When reacted with MCl2(COD) (M= Pd, Pt), compound 3.10 coordinates with PdII forming a bidentate complex 3.12, while 3.1 forms tridentate complexes with PdII and PtII. NMR spectroscopy suggests the formation of a silver(I) complex 3.1-Ag from 3.1 and AgOTf, but X-ray diffraction data is required to determine its coordination motif. The new ligands and complexes have been fully characterized by (1H, 13C, 77Se) NMR spectroscopy and X-ray crystal structures are reported for 3.10, 3.12, 3.3 and 3.4. The NMR spectrum of 3.1-Ag exhibits a similar effect as the complexes of disilylamido ligands with suggested potential dπ-dπ back donation from the metal to the selenium donors. The catalytic ability of the new complex 3.3 has been tested in the Suzuki-Miyaura cross coupling reaction without notable improvements to existing catalysts. The instability of reactive intermediates may contribute to the low conversions or the size of the methyl group may decrease nanoparticle formation, a suggested active species. / October 2016

A series of computational studies were carried out on Group 14 (C, Si and Ge) elements in organometallic and biological compounds. Theoretical studies on classical and H-bridged A3H3+ (A=C, Si and Ge) as p ligands with different organometallic fragments at B3LYP and B3P86 level reveal a reverse charge transfer from ligand to metal in Si and Ge complexes whereas in C complexes there is a small charge transfer from metal to ligand. The H-bridged complexes are more stable than the complexes based on Si3H3+ and Ge3H3+ ligands with terminal hydrogens. The stability of the bridged systems increases from Si to Ge. Corrective scale factors for computed harmonic CºO vibrational frequencies for 31 organometallic complexes have been determined at the HF and B3LYP levels. The scaled B3LYP frequencies exhibit a greater reliability than do HF frequencies. Experimental data have shown that Si/Ge-substituted decapeptides are advantageous over their C analog in vitro and in vivo studies in modern hormone therapy. A computational investigation was carried out on the synthesized decapeptides focusing on position 5 containing Si and Ge. The results have shown that there are some differences in C, Si and Ge-containing analogs. However, further investigations are needed to elucidate the observed advantages of Si/Ge over C analogs.

Thesis advisor: James P. Morken / Sesquiterpene quinones are a prolific class of marine natural products that are particularly interesting due to their antibacterial, antiviral, and anti-inhibitory properties. Hundreds of these biologically active molecules are based on decalin frameworks, both cis- as well as trans-fused, however, significantly less synthetic work has focused on targeting the cis-fused series of compounds. In this chapter, progress towards an asymmetric, general route to various sesquiterpene quinones in the cleordane family of natural products will be described. The key steps of the synthesis include a highly convergent and diastereoselective reductive alkylation to forge both the requisite cis-ring fusion well as the all carbon quaternary center, as well as a scandium-catalyzed ring expansion of a 6,5-ring system to deliver the decalin core of the molecule. Additionally, the chapter includes the development and substrate scope of both methodologies utilized in the key complexity building reactions. Iron complexes ligated by bis(imino)pyridine ligands are remarkably active catalysts for a vast range of organic transformations including polymerization, hydrogenation, hydrosilylation, and hydroboration. Whereas much work has been done to probe the importance of the imine-substituents on catalysis, significantly less information is known about the nature of the central pyridine donor. To study the effects of a more donating ligand in which the pyridine is replaced with an N-heterocyclic carbene, a series of novel ligands and their corresponding iron complexes were synthesized and characterized. Whereas imidazole-derived complexes exhibited exclusively bidentate binding modes, 4,5,6-trihydropyrimidylidene-based ligands adopted a tridentate pincer conformation analogous to complexes of bis(imino)pyridines. Bonding in the five-coordinate bis(imino)-N-heterocyclic carbene complex displayed considerably contracted iron-ligand bond distances compared to the analogous bis(imino)pyridine iron complex. The study of physical and electronic structure and bonding in organometallic compounds is a critical for understanding and predicting complex behavior and reactivity. Having synthesized a completely new type of N-heterocyclic carbene (NHC) ligand and the corresponding iron complex, a rigorous study of metal-NHC bonding, magnetism, and redox activity in bis(imino)-NHC (or carbenodiimine, CDI) complexes of iron was carried out. A series of oxidation and reduction reactions on CDI complexes of iron were performed, enabling access to complexes spanning from formally iron(0) to iron (III) oxidation states. A battery of spectroscopic and computational methods, including X-ray crystallography, Mössbauer spectroscopy, SQUID magnetometry, and EPR spectroscopy established the CDI ligand as a redox active chelator. Additionally, a unique iron-carbene interaction was discovered, in which the metal center antiferromagnetically couples with the carbon of the NHC. Intent on developing CDI complexes of iron into practical catalysts for both synthetic organic transformations and polymerization, a series of stoichiometric as well as catalytic reactions were carried out to evaluate the reactivity profile of the novel complexes. Halide atom abstraction generated a new cationic species, which demonstrated different coordination chemistry compared to the bis(imino)pyridine analogue. Furthermore, the addition of a hydride or alkyl lithium reagent to the parent (CDI)FeCl2 species resulted in interesting and unexpected reactivity involving the carbene ligand. Preliminary catalytic hydrogenation experiments established (CDI)FeCl2 as a competent catalyst for the reduction of simple alkenes in the presence of Na(Hg) as a reductant under 80 psi of hydrogen. Additionally, the dichloride species could be readily converted into bis(aryloxide) complexes that were active for the polymerization of lactide to produce poly(lactic acid). The polymerization is very controlled (PDI values are <1.3), and polymers with molecular weights of around 35 kDa can be obtained after 3 hours at room temperature. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Lawrence T. Scott / Thesis advisor: James P. Morken / Expeditious establishment of molecular complexity in a stereoselective manner is a prominent goal in organic synthesis. In this regard, multicomponent coupling reactions have received substantial attention due to their ability to access complex molecules from simple starting materials in a single step. Chapter 1 is a comprehensive review on catalytic bismetallative multicomponent reactions. The scope of this process in terms of both bismetallic reagents and the pi components are broad enough to be generally applied to more elaborate synthetic sequences. Particularly, contemporary applications of the bismetallative multicomponent coupling reactions, in which high enantio- and/or diastereoselectivities are displayed, have enabled the study of this area to make a significant step forward. Chapter 2 presents nickel-catalyzed coupling reactions of aldehyde, diene, and a diboron reagent in the presence of a trialkyl phosphine ligand. Compared to borylation reactions with one pi-component, these borylative multicomponent reactions (involving two pi components) lead to formation of a new C-C bond between the pi components as well as generation of highly functionalized, stereodefined products. Chapter 3 describes a remarkable turnover in regioselectivity of the borylative multicomponent coupling when PCy3 is replaced with P(SiMe3)3. In particular, the products from the reactions with P(SiMe3)3 feature three contiguous stereocenters and an alpha-chiral allylboronate. The effect of P(SiMe3)3 ligand on the product selectivity is intriguing. According to the experimental and computational results, it has an ability to act as an electron acceptor, which will facilitate reductive elimination from the intermediate nickel complex during the course of the reaction. In Chapter 4, we show that borylative ketone-diene coupling reactions can be accomplished in high yields and with excellent levels of diastereocontrol. This reaction occurs in a predictable fashion, yet with regioselection that is distinct from related aldehyde-diene coupling reactions. The reaction products from these coupling processes, which possess tertiary alcohol functionality and an allylic alcohol moiety, are particularly well suited for the preparation of polyketide natural products. Chapter 5 presents investigations on bowl-shaped geodesic polyarenes, which are the missing links between the "classic" planar polycyclic aromatic hydrocarbons (PAHs) and the spheroidal fullerenes. The present study has shown that open geodesic polyarenes can feature chemistry inherent to both classes of aromatics. The curved pi system induces unequal environments on the two faces of circumtrindene, significant strain energy to the molecule, and non-identical bond lengths. Along with the electronic effects, the stereoelectronic effect enabled the site-selective functionalization with fullerene-type chemistry. On the other hand, the edge carbons, which are not present in fullerenes, still possess reactivity of common planar PAHs. Chapter 6 describes the intermolecular oxidative cyclotrimerization reactions of alkenes and aromatic compounds with DDQ and trifluoromethanesulfonic acid. The Scholl-type oxidation reactions involving alkenes have never been demonstrated. Moreover, the DDQ/acid system has never been used for the intermolecular oxidative cyclization reactions. This convenient non-metallic reagent system (DDQ/TfOH) is advantageous over the metal-based Scholl-type oxidants because it eliminates the possibility of halogenation of aromatic compounds and the reduced oxidant can be reoxidized. In Chapter 7, the regioselective formation of cyclic trimers from substituted benzenes and heteroaromatic compounds is demonstrated. This DDQ/TfOH method provides a simple and convenient synthetic route toward star-shaped oligomers containing triphenylene or isotruxene cores. Furthermore, the experimental outcome suggests that this oxidative process proceeds by an electron transfer mechanism. This is the first experimental evidence for mechanistic details on the Scholl-type oxidation. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Palladium is one of the most common and versatile transition metals used in modern organometallic chemistry. The chemistry of palladium in its 0, +II, and +IV oxidation states is well-known; by comparison, the chemistry of palladium in its +III oxidation state is in its infancy. The work in this thesis involves the study of previously unknown Pd(III) complexes, including applications in materials chemistry and catalysis. / Chemistry and Chemical Biology

The chemistry and physical properties of actinide complexes has become increasingly significant and relevant since the dawn of the nuclear age. In addition to increasing the potency of nuclear power and the safety and disposal of its subsequent waste products, exploration of the chemistry of actinide complexes provides a fascinating insight into the increased complexity and divergence of reactivity of these complexes when compared to transition metal complexes. Chapter One provides a brief introduction to the chemistry of actinides and in particular, the major focus of this work, of thorium. This is followed by a survey of examples of rare examples of thorium complexes with a formal oxidation state other than Th (IV). Following this is a review of selected examples of thorium (IV) complexes exhibiting unusual reactivity surveying thorium hydride and alkyl complexes initially. This progresses into reviewing the chemistry of thorium complexes containing multiple bonds to non-metal atoms, beginning with carbon atoms and then progressing to atoms in the chalcogen and pnictogen groups. The introduction finishes with an investigation into the properties of the terphenolate ligands used in this study, including examples of unusual complexes that they have been shown to stabilise. In Chapter Two, an exploration into the catalytic activity of fairly simple actinide amide catalysts, N”2Th (IV) {k2-N(SiMe3)SiMe2CH2, N”2U (IV) {k2-N(SiMe3)SiMe2CH2} and UN”3, upon terminal acetylenes is presented. The chapter begins with a brief introduction summarising the previous reactivity observed in the catalysis of terminal acetylenes, with particular focus on actinide-based catalyst mediated reactions. The catalytic results on a variety of terminal acetylenes with different steric and electronic properties is then reported upon. It is found that high conversions and selectivities can be achieved upon optimisation of the catalytic process. It was also found that the different catalysts and substrates favoured different products, with selective oligomerisation and cyclotrimerisation reactions observed. The differing reactivities lend support to the role of f-electrons upon the catalytic route of the reaction. Conclusions are discussed at the end of the chapter. In Chapter Three, the synthesis and characterisation of heteroleptic terphenolate thorium chloride complexes and their subsequent reactivity was investigated. The synthesis and characterisation of ThCl2(OTerMes)2DME and ThCl2(OTerMes)2(H2O)3 are initially described. The reactivity of these complexes favoured transmetallation of the terphenolate ligands, with the complexes; [Li(OTerMes)THF]2, [Li(OTerMes)]2THF, μ3- (TerMesO)μ3-(CH2SiMe3)3Li4, LiAlH2(OTerMes)2, [(THF)K(OTerMes)]2, MgCl(OTerMes)(THF)2, MgBr(OTerMes)(THF)2 and Fe(OTerMes)2(py)2 synthesised and characterised from reactions attempting to transform the ancillary chlorido-ligands. The reactivity of ThCl2(OTerMes)2DME was found to not be solely transmetallation of the terphenolate ligands as elucidated by the synthesis and characterisation of [Th(OTerMes)2(Cl)2(4,4’- bipyridyl)1.5]∞ and [MgTh2μ2-Cl2μ3-Cl(OTerMes)2(C4H7)2μ-η3:η3(C4H7)H]. The synthesis of [MgTh2μ2-Cl2μ3-Cl(OTerMes)2(C4H7)2μ-η3:η3(C4H7)H] was found to proceed via a reductive elimination route with concomitant formation of a terphenolate transmetallation product Mg(OTerMes)2(THF)2. The formation of[Th(OTerMes)2(Cl)2(4,4’- bipyridyl)1.5]∞ was achieved via reaction with the Lewis base 4-4’ bipyridine. Reactions attempting to form heteroleptic uranium terphenolate complexes were also detailed. Conclusions are discussed at the end of the chapter. In Chapter Four, the synthesis and characterisation of heteroleptic terphenolate thorium borohydride complexes and their subsequent reactivity was investigated. It was found that the conversion of ThCl2(OTerMes)2DME to Th(BH4)2(OTerMes)2DME proceeded smoothly using a precedented reaction route. In contrast to ThCl2(OTerMes)2DME, reaction with a Lewis acid was found to result in abstraction of the solvating DME molecule, resulting in the synthesis and characterisation of Th(BH4)2(OTerMes)2. In similarity to ThCl2(OTerMes)2DME, Th(BH4)2(OTerMes)2DME was found to react with a Lewis base (4-4’ bipyridine) to form Th(BH4)2(OTerMes)2(4,4’ bipyridine)∞. However, despite the increased robustness and versatility of the borohydride complexes, transmetallation of the terphenolate complexes remained an issue as shown by the synthesis and characterisation of Mg(OTerMes)((μ-H)3BH)THF)2. Th(BH4)2(OTerMes)2 was found to be able to facilitate small molecule activation in a variety of substrates, encompassing CO, CO2 and CS2 amongst others. In most cases this small molecule activation favoured the formation of BMe3, with the concomitant formation of HB(OTerMes)2 in the case of CO2 and CS2. Attempts at catalysis of isonitriles and terminal acetylenes by Th(BH4)2(OTerMes)2 are presented with mixed results. Conclusions are discussed at the end of the chapter. In Chapter Five, investigations into the effects of changing the donor atom of the terphenyl moiety were probed. The chapter began by examining the differing properties of a phosphorous atom acting as a ligating atom, as opposed to the oxygen atom seen in Chapters Three and Four. The chapter continued by detailing the result of reactions attempting to synthesise and characterise terphenyl phosphino-actinide complexes. It was found that in the case of actinides with easily accessible lower oxidation states, i.e. U (IV), that reductive elimination was favoured, culminating in the isolation of (TerMesPH)2. Following this result attempts were made to modify the ligand system in an attempt to divert the reaction away from this product, in the hope of isolating a phosphino-actinide complex. Reactions attempting to ligate the terphenyl moiety via the aryl α-carbon to thorium were also detailed, resulting in radicular degeneration and the isolation of nBuTerTrip and ClTerTrip. Conclusions are discussed at the end of the chapter. Experimental and characterising data are provided in Chapter Six.

No description available.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24438号 / 理博第4937号 / 新制||理||1705(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 依光 英樹, 教授 若宮 淳志, 教授 畠山 琢次 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Light hydrocarbons activations, functionalization, and reactions have been a subjects of catalysis research for decades but dominated by the rarer and more expensive noble metals. Switching over to using the more earth abundant third row transition metals could be more economical and less toxic but come with their own challenges. Their use as catalysts with light hydrocarbons could be employed better utilize and more efficiently use our hydrocarbon resources that the world still depends on.

No description available.