Dissertations / Theses on the topic 'Heterocyclic Carbene'
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Ellul, Charles. "Trimetallic N-heterocyclic carbene complexes." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538279.
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Hippolyte, Laura. "New syntheses of N-heterocyclic carbene-stabilized gold nanoparticles." Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS148.pdf.
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Récemment, les carbènes N-hétérocycliques (NHC) ont suscité un intérêt important dans le domaine de la chimie des matériaux. En effet, cette nouvelle catégorie de ligands forme des liaisons très fortes avec une diversité de métaux et leur structure, ainsi que leurs propriétés électroniques, peuvent être adaptées par de la synthèse organique. Cette forte liaison est d’un intérêt particulier dans le domaine des nanoparticules d’or (NP) et des synthèses ont déjà été proposées. En effet, les NPs présentent de nombreuses applications potentielles, par exemple dans les capteurs, en catalyse ou médecine, mais ces applications sont parfois freinées par un manque de stabilité du ligand de surface. Ce travail de thèse s’est concentré sur le développement de nouvelles synthèses de nanoparticules d’or stabilisées par des NHC. D’abord, en revisitant une procédure existante à base de sels d’imidazoliums, ce qui a mené à une synthèse n’utilisant que les composés commerciaux : AuCl et NaBH4 et des halogénures d’imidazolium, facilement obtenus. Une synthèse totalement nouvelle a ensuite été développée en utilisant des NHC-boranes qui sont des adduits de Lewis stables. Nous avons montré pour la première fois que les NHC-boranes peuvent être utilisés comme réactifs "2-en-1" dans la synthèse de NP : comme réducteurs du précurseur d’or et comme source de NHC. Enfin, nous sommes les premiers à décrire la synthèse de NP stabilisées par des carbènes mésoioniques (MIC).Les MICs sont une sous-catégorie des NHCs qui sont préparés par « chimie click » et qui présentent des propriétés électroniques uniques. Un intérêt particulier a été porté à la caractérisation des nanoparticules, notamment par XPSOver the past decade, N-heterocyclic carbenes (NHC) have drawn considerable interest in the field of materials chemistry. Indeed, this relatively new class of ligands forms strong bonds with a wide range of metals and their structures and electronic properties can be tuned “at-will” through organic synthesis. This strong bond is of particular interest for gold nanoparticles. Indeed, gold nanoparticles have many potential applications, for example in sensors, catalysis or medicine, but those potential applications are sometimes hindered by a lack of stability of the surface ligand. A few syntheses of NHC-stabilized gold nanoparticles have already been described in the literature but each presents their own set of drawbacks. This thesis work has focused on the development of new syntheses of NHC-stabilized gold nanoparticles. First, by revisiting a literature procedure starting from imidazolium salts, we managed to develop a one-pot synthesis starting only from commercially available AuCl, NaBH4 and easily synthesized imidazolium salts. A totally new synthesis was developed using NHC-boranes, which are stable Lewis adducts. Here, we reported for the first time their use as a 2-in-1 reagent, able to reduce the metallic precursor and provide the nanoparticles stabilizing ligands. Finally, we are the first to report a synthesis of gold nanoparticles stabilized by mesoionic carbenes (MIC). MICs are a sub-class of NHCs synthesized by well-known “click-chemistry”, which present unique electronic properties. Throughout this work, special care was taken to characterize the nanoparticles, notably by XPS
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Casely, Ian J. "Electropositive metal N-heterocyclic carbene complexes." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3873.
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The first chapter is an introduction to the f-elements, with a focus on the synthesis and chemistry of tetravalent cerium complexes. The synthesis, characterisation and reactivity of carbenes, particularly N-heterocyclic carbenes (NHCs), and anionic-functionalised NHC ligands is discussed. The synthesis and reactivity of s-block, Group three and fblock NHC complexes is reviewed. The synthesis of the alcohol-functionalised unsaturated imidazolium proligand, [H2L]I [H2L = HOCMe2CH2(1-CH{NCHCHNiPr})], is extended to saturated imidazolinium analogues, [H2LR]X, [HOCMe2CH2(1-CH{NCH2CH2NR})]X (R = iPr, abbreviated to P; R = Mes, abbreviated to M; R = Dipp, abbreviated to D, X = Cl, I). Mono-deprotonation results in the isolation of bicyclic imidazolidines HLR, which can be ring-opened and silylated by treatment with Me3SiI, to afford [HLR, OSiMe3]I, R = iPr and Mes. Further deprotonation of HLR with MN"2 (M = Mg, Zn; N" = N(SiMe3)2) affords LRMN" (M = Mg and Zn) and ZnLR 2. These complexes proved active for the polymerisation of raclactide at room temperature without the need for an initiator. The third chapter focuses on cerium chemistry. Repetition of the literature synthesis of CeIV tert-butoxide compounds affords the unsolvated Ce(OtBu)4 and also the cluster Ce3(OtBu)11. Treatment of Ce(OtBu)4 with HL did not yield a CeIV-NHC complex, but one bearing a tethered imidazolium group, (OtBu)3Ce( -OtBu)2( -HL)Ce(OtBu)3. The synthesis of a CeIII-NHC complex, CeL3, and the oxidation of this forms an unprecedented CeIV-NHC complex, CeL4, via ligand redistribution; the complex contains two bidentate ligands and two alkoxide-tethered free NHC groups. Functionalisation of the free NHCs with boranes affords the adducts Ce(L)2(L-B)2, where B = BH3 or 9-BBN (9-Borabicyclo[3.3.1]nonane). A number of cerium complexes of the saturated-backbone NHC, LR, LRCeN"2 and LR 2CeN", have been synthesised and their oxidation chemistry and reactivity investigated. The final chapter contains an NMR study of the synthesis of a series of yttrium LR adducts, LP xYN"(3-x) (x = 1, 2 or 3), and of the synthesis of uranium complexes LRUN"2, R = Mes or Dipp, including a range of small molecule reaction chemistry. The uranyl NHC complexes, UO2LR 2, R = Mes or Dipp, have also been synthesised and characterised; these possess very high frequency carbene carbon chemical shifts.
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Rodden, Mark. "Alkoxide functionalised N-heterocyclic carbene complexes." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423306.
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Williamson, Craig. "Imidazolylidenes in N-heterocyclic carbene organo-catalysis." Thesis, University of Aberdeen, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440601.
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A library of chiral and achiral imidazolium salts was prepared, and evaluated as potential pre-catalysts of the benzoin condensation. It was found that although the carbenes derived from these compounds possess catalytic activity, this was not as pronounced as that observed for alternative heterocycle classes. Asymmetric induction, although observed from imidazolylidenes for the first time in this work, is not of an order that could be considered useful, as has been seen for other NHC catalysts. This is attributed to the use of harsh reaction conditions, required to promote catalytic activity in this system. Two modifications were thus made to the imidazolium salt pre-catalysts in an attempt to make the reaction conditions less extreme. Imidazolium carboxylates were found to be suitable pre-catalysts, thus allowing the reaction to be performed under neutral conditions. Purinium salts were also investigated, based on the theory that these more electron deficient fused heterocycles would allow access to carbenes under milder conditions. Although problems were encountered in the synthesis of these salts, one example was prepared, however the available data indicate this exists as the incorrect regioisomer. Two strategies for catalyst immobilisation have also been investigated. It was found that polymer supported imidazolylidenes are capable of catalysing the benzoin condensation of a range of aromatic aldehydes, under a range of conditions, and can undergo a limited number of recycles. Imidazolium salts supported on silica were found to be unsuitable for the catalysis of this reaction. This was blamed on incompatibility of the persistently acidic matrix with the basic conditions required by the carbene. Application of imidazolylidenes to the intra-molecular Stetter reaction was also attempted, however this revealed NHC have the ability to act catalytically as bases. Further investigation of this observation suggested the effect is limited to α,β-unsaturated carbonyl compounds.
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Tulloch, Arran Alexander Dickon. "Novel mixed donor N-Heterocyclic carbene complexes." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249941.
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Bemowski, Ross David. "Novel N-heterocyclic dicarbene ligands and molybdenum and dimolybdenum N-heterocyclic carbene complexes." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/1291.
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The syntheses of a new class of polycyclic TriAmino DiCarbenes (TADCs), based on 3,9-diazajulolidine, and their precursors and adducts are described.
Starting with 2,6-dimethyl-nitrobenzene, 2,6-bis ((alkylamino)methyl)anilines (alkyl = isopropyl, mesityl, and tert-butyl) were synthesized in 40% yield over five steps. These triamines were then di-cyclized stepwise to diformamidinium dications or formamidinium/2-methoxyformaminals using oxonium salts and trialkyl orthoformates. A diformamidinium dication was characterized by single-crystal X-ray diffractometry. Treatment with various bases, particularly lithium hexamethyldisilylazide, led to the novel TADCs and monocarbenes, two of which were isolated and characterized by 1H and 13C NMR spectroscopies. In both cases, treatment with elemental sulfur trapped the TADCs as dithiobiurets. No TADC-transition metal complexes were successfully isolated from reactions of the diformamidinium dications or LiHMDS TADC complex with a number of transition metal complexes.
With the exception of these two cases, all other TADCs were not isolated because they rapidly reacted to form dimers, trimers, and tetramers. One of these dimers was isolated and its structure determined using 1D and 2D NMR spectroscopies, along with high-resolution electrospray ionization mass spectrometry. This revealed that the TADC had dimerized to form an ene-triamine, likely via 1,3-shift of a benzylic proton.
Novel N-heterocyclic Carbene (NHC) complexes of molybdenum were also synthesized and characterized. Reaction of Cp2Mo2(CO)4 (Cp = C5H5) with dimesityl-imidazol-2-ylidenes (IMes) or dimesityl-imidazolidin-2-ylidenes (SIMes) yielded the molybdoradicals CpMo(CO)2(NHC) (NHC = IMes or SIMes). The carbonyl infrared stretching frequencies and the relative metal-to-NHC π-backbonding for IMes and SIMes complexes are compared. Reaction of the less bulky dimethyl-imidazol-2-ylidene (IMe) with Cp2Mo2(CO)4 yielded the Mo-Mo triple bond complex Cp2Mo2(CO)3(IMe) by CO substitution. This is the first example of an NHC-ligated metal-metal multiply bonded complex. Single crystal X-ray diffractometry of these new organomolybdenum and organodimolybdenum complexes is discussed.
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Zhang, Pinglu. "Cyclodextrin-(N-Heterocyclic Carbene)-Metal Complexes for Cavity-Dependent Catalysis." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066380/document.
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Des complexes de Cyclodextrine (CD)-NHC-Métaux (NHC= Carbènes N-Hétérocycliques), comprenant des métaux tel que AgI, CuI et AuI ont été synthétisés. Une étude structurale a mis en évidence la position intra-cavitaire du métal, induisant des interactions C-H…M, C-H…X et π…X. L’influence du type de cavité (α-, β-, γ-CD) et du type de dérivés NHC (Imidazole, benzimidazole, triazole) a été étudiée. Les interactions diminuent avec l’augmentation de la taille de la cavité et en parallèle, celles-ci ont été amplifiées avec des dérivés NHC possédant un effet donneur plus fort. Les complexes de cuivre correspondants montrent une bonne réactivité pour la réaction d’hydroboration des alcynes. Il a de plus été observé que la sélectivité est dépendante de la taille de la cavité. En effet, alors que le complexe α-CD-Cu donne le produit linéaire, le complexe β-CD-Cu oriente vers la formation de l’isomère branché. Les espèces CD-Cu potentiellement impliquées dans le cycle catalytique ont été étudiées. Deux mécanismes différents sont ainsi proposés. Dans la réaction catalysée par le complexe α-CD-Cu, le processus catalytique a lieu en dehors de la cavité; tandis que lorsque la cavité est plus grande (β-CD) la catalyse a lieu à l’intérieur de la celle-ci. Par ailleurs, les complexes ont également montré une différente énantiosélectivité et régiosélectivité dans une réaction de cycloisomerization catalysée par des comlexes dor, en fonction de la taille de la cavité de ces catalyseurs. Les résultats catalytiques ont prouvé que les complexes CD-NHC-Métaux fonctionnent comme des catalyseurs pour lesquels la taille de la cavité influe sur la séléctivitéCyclodextrin (CD)-NHC-Metal complexes (NHC=N-Heterocyclic Carbene), including the AgI, CuI and AuI complexes were synthesized. A structural study showed that the metal was inside the cavity, and induced by C-H…M, C-H…X and π…X interactions. Variations on α-, β-, γ-CD cavities and NHC derivatives (midazole, benzimidazole, triazole) were studied. When the size of the cavity increased, these interactions decreased. Furthermore, stronger σ-donating effects lead to stronger interactions. CD-Cu complexes showed good activity in catalytic hydroboration of alkynes. The selectivity is depending on the size of the cavity of the catalyst. α-CD copper complex gives linear hydroboration products, while β-CD copper complex yields the branched isomers. The CD-Cu species potentially involved in the catalytic cycle were studied, two different mechanisms were thus proposed. In the α-CD-Cu complex catalyzed reactions, the catalytic process takes place outside the cavity; while a bigger cavity β-CD permits the catalysis to take place inside the cavity. Furthermore, the gold complexes also show different enantioselectivity and regioselectivity in cycloisomerization using different cavity-based catalysts. Catalytic results evidenced the selectivity of a catalytic reaction is dependent on the cavity of the CD-NHC-metal complexes
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Maluenda, Borderas Irene. "(N-heterocyclic carbene) : metal catalysed carbon-carbon and carbon-heteroatom bond-forming reactions." Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/76274/.
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Sirokman, Gergely. "(N-heterocyclic-carbene)Copper(I)-catalyzed carbon-carbon bond formation using carbon dioxide." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39584.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.Vita.
Includes bibliographical references.
This thesis presents work towards the development of a new catalytic C-C bond forming reaction. Alkynes and olefins insert into [(IPr)CuH]2 (IPr = N,N-bis-(2,6-diisopropylphenyl)-1,3-imidazol-2-ylidene) to give copper vinyl and copper alkyl complexes. These copper complexes insert CO2 into the Cu-C bond to form copper acrylate and copper carboxylate complexes. Acrylic and carboxylic acids can be isolated by hydrolysis. A catalytic cycle based on (IPr)copper(I) was developed. Alkynes undergo reductive carboxylation to give acrylic acids in moderate yields. Unexpected interactions between several components of the catalytic system led to a number of side reaction, most importantly between [(IPr)CuH]2 and the product silyl acrylate. The use of silylcarbonate salts to desylilate the product enhanced yield. In addition, silylcarbonates can also serve as a source of CO2.
by Gergely Sirokman.
Ph.D.
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Ling, Xiang. "N-heterocyclic carbenes coated nanocrystals and supracrystals." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066334/document.
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Les nanomatériaux ont beaucoup captivé l'attention pour leur propriétés uniques, fortement associées à leurs dimensions nanoscopiques. En particulier, les nanoparticules (NP) à base de métaux nobles (Au, Ag) présentent des propriétés mécaniques, électroniques, optiques et magnétiques particulières intéressantes pour le développement d'applications dans de nombreux domaines à fort impact sociétal. En raison de leur stabilité élevée par rapport aux autres nano- particules métalliques, les nanoparticules d'or ont été abondamment explorées pour les nanotechnologies. Ces dernières décennies, les NHC ont émergé en tant que classe essentielle de ligands neutres en chimie organométallique. Les NHC sont caractérisés par leur flexibilité synthétique élevée, leur géométrie spécifique, et une liaison métal–Ccarbène très forte dans les complexes métalliques. Toutes ces propriétés ont été largement étudiées et exploitées pour les applications en catalyse homogène et pour le développement de complexes biologiquement actifs. Par comparaison, l'utilisation des NHC dans les matériaux reste largement peu explorée. Dans ce travail, le potentiel de ligands NHC dans le domaine des nanomatériaux, comme des agents de revêtement pour le produit nanocristaux de synthèse de l'or (et l'argent), la produit de stabilisation et de l'auto-assemblage dans supracrystals ont été explorés. Tout d'abord, des complexes d'argent et d'or-NHC qui sont bien définies avec différents ligands qui sont connus comme le NHC, sont étudiés pour leur pertinence afin de générer des astable nanocristaux (NCs) dans des conditions réductrices avec un bon contrôle de la taille des nanocristaux. Nous démontrons que le Au et le Ag NCs peuvent tous être formés par la réduction des complexes métal-NHC avec les amine-boranes. L'efficacité du procédé, la taille moyenne et la taille de la répartition des nanocristaux dépendent fortement de la structure du ligand NHC. Cependant, nous démontrons dans cette partie que les différentes voies sont impliqués à générer des nanocristaux par Au ou Ag précurseurs, comme une spécifique réaction observée entre Ag-NHC et thiols conduisant à la formation de thiolates argent alors que le Au-NHC correspondant reste inchangéNanomaterials have received extraordinary attention owing to their unique properties, strongly associated to their nanoscale dimensions. In particular, noble metal (Au, Ag) nanoparticles (NPs) exhibit particular mechanical, electronic, optical and magnetic properties and present a high potential for developing applications in many domains with important societal impacts. Due to their higher stability by comparison with other metal-based nanoparticles, Au NPs have been extensively investigated for research in nanotechnology. In the last decades, N-Heterocyclic carbenes (NHCs) have emerged as an essential class of neutral ligands in organometallic chemistry. NHCs are characterized by their high synthetic flexibility, their specific geometry, and a very strong metalCcarbene bond in metal complexes. All these properties have been widely studied and exploited for applications in homogeneous catalysis and for the development of biologically active complexes. By comparison, the use of NHCs in nanomaterials remains largely unexplored. In this work, the potential of NHC ligands in the field of nanomaterials, as coating agents for gold nanocrystals synthesis, stabilization and self-assembly into supracrystals has been explored. First, well-defined silver and gold–NHC complexes with different well-known NHC ligands are investigated for their relevance to generate stable nanocrystals (NCs) under reductive conditions with a good control of nanocrystals size. We demonstrate that both Au and Ag NCs can be formed by reduction of metal-NHC complexes with amine-boranes. The efficiency of the process and the average size and size distribution of the nanocrystals markedly depends on the structure of the NHC ligand. However, we demonstrate in this part that different pathways are involved to generate nanocrystals from Au or Ag precursors, as a specific reaction is observed between Ag-NHCs and thiols leading to the formation of silver thiolates whereas the corresponding Au-NHCs remain unchanged
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Reddy, Y. S. V. "Enantioselective construction of six - membered heterocycles and carbocycles using N - heterocyclic carbene (NHC) - organocatalysis." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2016. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2079.
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Collinson, John Michael. "Immobilised N-heterocyclic carbene metal complexes in catalysis." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/42227.
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Transition metal-based catalysts are one of the most powerful tools available to chemists and the development of ligand systems with which to modify their activity is a constant area of research. In the last twenty years N-Heterocyclic carbenes (NHCs) have established themselves at the forefront of organometallic chemistry. To increase the lifetime of the catalyst these ligands are increasingly being immobilised on supports as, this allows recovery and reuse while attempting to retain the activity. Cleaner, greener and safer processes are increasingly important and the recovery of the catalyst by simple separation also removes contamination and enables the possibility of re-use. This thesis describes the development of a new concept to immobilise transition metal complexes through an N-heterocyclic carbene ligand. The introductory Chapter provides an overview of transition metal catalysis, introducing the use of supported catalysis including the use of magnetic nanoparticles to aid the recovery of the catalyst systems. A discussion is included of N-heterocyclic carbene ligands, including their synthesis, activity in catalysis as ligands for metal complexes as well as attempts to support the systems and their use in various reactions. Chapter 2 provides an in-depth introduction to palladium catalysis, focusing on cross-coupling and dehalogenation reactions. The design of palladium catalysts, concentrating on palladium-NHC complexes and covers the use of supported catalysts. The synthesis and immobilisation of a novel palladium carbene complex is also described. The supported and unsupported complexes were screened in the Suzuki-Miyaura reaction and dehalogenation reaction. The activity and recycling properties of the supported catalyst system are discussed. The next Chapter outlines the use of copper-NHC complexes in the 1,3-dipolar cycloaddition reaction of azides and alkynes to form 1,2,3-triazoles. The preparation and characterisation of a novel N-heterocyclic carbene ligand is described, along with the construction of the supported copper systems. These catalysts were then investigated in the cycloaddition reaction and assessed for their activity and recovery. The scope of the reaction is also explored, investigating functional group tolerance. The final Chapter contains experimental procedures and characterisation data for all compounds synthesised during this project.
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Bourghida, Ahmed. "Heterocyclic ring synthesis using alkylidene carbene insertion reactions." Thesis, University of Warwick, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247946.
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Chardon, Edith. "N-Heterocyclic carbene complexes : toward innovative anticancer agents." Strasbourg, 2011. http://www.theses.fr/2011STRA6265.
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Parmi les agents thérapeutiques utilisés en chimiothérapie, la molécule la plus connue et utilisée dans le monde est le cisplatine ou cis-diamminedichloroplatinum(II) démontrant le potentiel des métaux en chimie médicinale. Malheureusement, le cisplatine engendre de nombreux effets secondaires importants et une résistance cellulaire. Dans la quête de nouveaux agents anticancéreux, les complexes de carbènes N-hétérocycliques (NHC) de métaux de transition constituent des candidats prometteurs. C’est dans ce contexte que s’est inscrit l’objet du projet de thèse qui a consisté en la synthèse et l’étude de nouveaux complexes NHC cytotoxiques de métaux de transition (notamment le platine). Deux nouvelles voies de synthèse simples, reproductibles et facilement modulables ont été développées permettant la fonctionnalisation post-complexation de composés NHC (a) par réaction de cycloaddition 1,3-dipolaire et (b) par substitution sélective de ligand. Ces stratégies de fonctionnalisation ont alors été étendues à l’accrochage des molécules hydrosolubles, d’agents permettant le ciblage sélectif des cellules tumorales par interaction avec des récepteurs spécifiques souvent surexprimés dans le cas des cellules tumorales ou encore d’agents fluorescents. Les activités cytotoxiques de ces nouveaux composés ont été mesurées in vitro sur une variété de lignées cellulaires cancéreuses. Pour la majorité de ces composés, les activités observées sont supérieures à celle du cisplatine et certains ont également démontré une sélectivité vis-à-vis des cellules tumorales. Ces premiers résultats encourageants ouvrent ainsi de nouvelles perspectives thérapeutiques en cancérologieAmong the existing anticancer agents, cisplatin or cis-diamminedichloroplatinum(II), represents the most known and commonly used chemotherapeutic drug worldwide highlighting the potential of metals in medicinal chemistry. However, its clinical effectiveness is also accompanied by severe side toxicities and cell-resistance mechanisms. These therapeutic limitations have encouraged the development of substitutes to cisplatin and have led to the discovery of N-heterocyclic carbene (NHC) complexes of several late transition metals as new anticancer agents with similar to higher in vitro activities than cisplatin. In this context, the present project dealt with the synthesis and the study of novel cytotoxic NHC complexes of some transition metals (mainly platinum). Two simple, reproducible and modular synthetic routes were developed for the easy functionalization post-complexation of NHC derivatives using (a) ruthenium-catalyzed alkyne-azide cycloaddition and (b) ligand substitution. In order to improve the efficacy and selectivity of the NHC complexes, we have extended these strategies of functionalization to the attachment of biologically interesting moieties such as targeting agents, hydrosoluble groups and fluorescent dyes. In vitro cytotoxic activities of these newly synthesized complexes were measured against a wide variety of cancerous cells. The majority of the compounds demonstrated higher activities than the benchmark cisplatin and some were selective toward tumoral cells. These promising early-stage results offer new perspectives in cancer therapy while giving alternatives to the biomedical limitations of cisplatin
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Robinson, William J. III. "Development of Tetrathiafulvalene Fused N-Heterocyclic Carbene Compounds." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1610382201476554.
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Serre, Veronique. "Synthesis of new N-heterocyclic carbene metal complexes." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/34833.
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This thesis describes the synthesis of new N-heterocyclic carbene complexes through the synthesis of 1,4-bis-substituted imidazolium salts or tricyclic saturated imidazolium salts. The introduction highlights some of the most successful methods for preparing N-heterocyclic carbenes and corresponding metal complexes. Examples of the use of these complexes in transition metal-catalysed processes are provided towards the end of this chapter. The second chapter is dedicated to our efforts to synthesize 1,4-bis-substituted imidazolium salts as precursors for the synthesis of N-heterocyclic carbene complexes. The first part of this chapter describes the synthesis of 1,4-bis-substituted imidazolium salts using 1,4-bis-substituted diazabutadienes. Following this, attempts to deprotonate imidazolium salts to afford the desired N-heterocyclic carbenes are discussed. On the basis of the results obtained for the synthesis of 1,4-bis-substituted imidazol-2-ylidenes, the synthesis of N-heterocyclic carbene complexes, where the carbene is generated in situ are explored at the end of this chapter. The synthesis of enantiomerically pure tricyclic saturated imidazolium salts via enantiomerically pure diamines is discussed in the third chapter. Firstly, different methods were tested for the preparation of diamines from 6,6'-dimethyl-2,2'-bipyridine, 2,2'-biquinoline and (S,S)-6,6-bis-(1-methoxy-2,2'-dimethylpropyl)-2,2'-bipyridine. Following this, is reported the synthesis of tricyclic saturated imidazolium salts. Suzuki cross coupling of 4-chlorotoluene with phenylboronic acid was investigated in the presence of different imidazolium salts. This chapter concludes with a few suggestions for the synthesis of enantiomerically pure 2,6-bipiperidines. The fourth chapter is the experimental section and is dedicated to the methods of synthesis and characterization of the compounds mentioned in the previous chapters. X-ray reports regarding the crystallographic representation of the structures presented in chapter two and three are provided in chapter five.
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Hodgson, Richard. "Novel chiral di-N-heterocyclic carbene and hybrid phosphine-N-heterocyclic carbene ligands and their application to transition metal mediated asymmetric catalysis." Thesis, University of York, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423839.
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Martínez, Lombardía Alberto. "Heterogenized n-heterocyclic carbene metal complexes for selective catalysis." Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/386577.
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La present tesi doctoral està adreçada al desenvolupament de catalitzadors que permetin dur a terme processos sintètics de manera més eficient i sostenible. Es presenten dues noves famílies de catalitzadors suportats, ambdues pertanyents al grup de complexos organometàl·lics moleculars immobilitzats sobre un suport sòlid. La primera família inclou complexos de Pd amb lligands carbè N-heterocíclic monodentats de gran impediment estèric, immobilitzats sobre òxids inorgànics, com ara sílicas, alúmina o òxid de titani. Aquesta família de catalitzadors es va aplicar en dos tipus de reaccions: i) reaccions d'acoblament C-C i ii) semireducción d'alquins. Entre les reaccions d'acoblament esmentades, els complexos de [Pd (NHC)] immobilitzats es van aplicar a les reaccions de Suzuki, Heck i Sonogashira, i es van avaluar en base a la seva activitat, selectivitat i reciclabilitat. A més, en el cas de les reaccions de Suzuki i Sonogashira, aquests catalitzadors també es van aplicar en condicions de flux continu. L'aplicació d'aquesta família de catalitzadors en la semireducció selectiva d'alquins es va dur a terme utilitzant dues metodologies diferents: utilitzant hidrogen molecular, o bé utilitzant el sistema trietilamina / àcid fòrmic com donador de H (condicions de transferència d'hidrogen).
La segona família de catalitzadors suportats contempla complexos de Rh (I) estabilitzats amb lligands bidentats de tipus carbé N-heterocíclic, amb quiralitat axial, i funcionalitzats amb un grup piré. La immobilització d'aquests complexos de Rh sobre la superfície de nanotubs de carboni "multi-walled" va tenir lloc mitjançant interaccions de tipus "pi-pi stacking" entre la superfície dels nanotubs i el grup piré present en el lligand. Finalment, es presenten els resultats obtinguts en l'aplicació d'aquests complexos de Rh en diversos processos catalítics.La presente tesis doctoral se centra en el desarrollo de catalizadores que permitan llevar a cabo procesos sintéticos de manera más eficiente y sostenible. Se presentan dos nuevas familias de catalizadores soportados, ambas pertenecientes al grupo de complejos organometálicos moleculares inmovilizados sobre un soporte sólido. La primera familia incluye complejos de Pd con ligandos carbeno N-heterocíclico monodentados de gran impedimento estérico, inmovilizados sobre óxidos inorgánicos, como sílicas, alúmina u òxido de titanio. Esta familia de catalizadores se aplicó en dos tipos de reacciones: i) reacciones de acoplamiento C-C y ii) semireducción de alquinos. Entre las reacciones de acoplamiento mencionadas, los complejos de [Pd(NHC)] inmovilizados se aplicaron en las reacciones de Suzuki, Heck y Sonogashira, y se evaluaron en base a su actividad, selectividad y reciclabilidad. Además, en el caso de las reacciones de Suzuki y Sonogashira, estos catalizadores también se aplicaron en condiciones de flujo continuo. La aplicación de esta familia de catalizadores en la semireducción selectiva de alquinos se llevó a cabo utilizando dos metodologías diferentes: utilizando hidrógeno molecular, o bien utilizando el sistema trietilamina/ácido fórmico como dador de H (condiciones de transferencia de hidrógeno). La segunda familia de catalizadores soportados contempla complejos de Rh(I) estabilizados con ligandos bidentados de tipo carbeno N-heterocíclico, con quiralidad axial, y funcionalizados con un grupo pireno. La inmovilización de estos complejos de Rh sobre la superficie de nanotubos de carbono "multi-walled" tuvo lugar mediante interacciones de tipo "pi-pi stacking" entre la superficie de los nanotubos y el grupo pireno presente en el ligando. Finalmente, se presentan los resultados obtenidos en la aplicación de estos complejos de Rh en varios procesos catalíticos.
The present PhD thesis aims at contributing to the development of more efficient and sustainable synthetic processes through catalysis. In this regard, two families of new solid-supported catalysts are presented. Both families belong to the group of molecularly defined organometallic complexes immobilized onto a solid support. The first family includes Pd complexes of sterically hindered monodentate N-Heterocylic Carbene ligands supported onto inorganic oxide materials, namely silicas, alumina and titania. This family of catalysts was applied in two types of reactions: i) C-C cross-couplings and ii) semireduction of alkynes. Among cross-coupling reactions, the supported [Pd(NHC)] complexes could be applied in Suzuki, Heck and Sonogashira couplings and their performance was assessed in terms of activity, selectivity and reusability. For the Suzuki and Sonogashira couplings, the catalysts were also appied under continuous flow conditions. The application of this family of catalysts in the selective reduction of alkynes was carried out following two different methodologies: using hydrogen gas, or using triethylamine/formic acid as the H-donor system (transfer hydrogenation conditions). The second family of solid-supported catalysts features Rh(I) complexes bearing axially chiral bidentate N-Heterocyclic carbene ligands functionalized with a pyrene moiety. Immobilization of these Rh complexes onto the surface of multi-walled carbon nanotubes was achieved by means of "pi-pi stacking interactions" between the surface of the nanotubes and the pyrene moiety present in the ligand. Results obtained from the application of these complexes as catalysts in various reactions are presented.
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Charra, Valentine. "Coordination of multidentate N-heterocyclic carbene ligands to nickel." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF019/document.
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Le sujet de cette thèse porte sur la synthèse de ligands de type bis-NHC (carbène N-Hétérocyclique) et leur réactivité vis-À-Vis des complexes d’argent(I), de cuivre(I) et de nickel(II).Après avoir exploré les différentes méthodologies de synthèse des complexes de nickel(II) bis-NHC, le but était de tester leurs activités en catalyse d’oligomérisation de l’éthylène. Une série de nouveaux complexes d’argent(I) et de cuivre(I) fut synthétisée. Cinq voies furent testées pour la formation de complexes de nickel. Les résultats les plus probants furent obtenus par transmétallation à partir des complexes d’iodure ou de bromure d’argent(I)The purpose of this work was the synthesis of bis-NHC (N-Heterocyclic carbene) ligands, theformation of the corresponding silver(I), copper(I) and nickel(II) complexes and the assessment ofthe catalytic activity of the bis-NHC nickel(II) complexes in ethylene oligomerization. A series of new bis-NHC silver(I) and copper(I) complexes was synthesized. Five different synthetic routes were tested for the formation of nickel(II) bis-NHC complexes. The most significant results were obtained by transmetalation from the silver(I) iodide or bromide complexes
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Arentsen, Katherine. "Application of palladium N-heterocyclic carbene complexes in catalysis." Thesis, University of Sussex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430951.
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Newman, Christopher P. "Phenylpyridine and N-heterocyclic carbene complexes of platinum (II)." Thesis, University of Warwick, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425555.
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Martin, Thomas Antony. "Unravelling the photochemistry of organometallic N-heterocyclic carbene complexes." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547630.
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This thesis describes the synthesis, characterisation and reactivity of new manganese and rhenium(I) NHC complexes, which have been investigated both thermally and photochemically and the results contrasted with existing phosphine analogues in the literature. Cp’Mn(CO)2(NHC) (NHC = IEt2Me2 1, IMes 2, IiPr2Me2 3 and IPr 4) were synthesised and investigated by TRIR spectroscopy. Loss of CO was observed after 355 nm irradiation to form agostically stabilised intermediates, which reformed the parent species by recombination with CO on the nanosecond timescale. Loss of NHC was not observed, in contrast to Cp’Mn(CO)2(PPh3) which lost both CO and PPh3 upon photolysis. [Re(NHC)(Bpy)(CO)3]BAr4F (NHC = IEt2Me2 5, IMes 6) were synthesised and investigated by TRIR spectroscopy and UV/Vis absorption and emission spectrometry. Inclusion of an NHC altered the excited state manifold of the complexes, favouring population of the 3MLCT over the 3IL excited state. The lowest energy excited state for both 5 and 6 proved to be a 3MLCT excited state at 298 and 77 K. In contrast, [Re(PPh3)(Bpy)(CO)3]BAr4F exhibited 3MLCT at 298 K, but 3IL at 77 K. A series of complexes, M(NHC)(CO)4X and M(NHC)2(CO)3X (M = Re, X = Cl; M = Mn, X = Br) formed upon reaction of the corresponding M(CO)5X species and free NHC. The substitution pattern was dictated by the steric bulk of the NHC. Generation of the corresponding cations by halide abstraction was investigated. M(NHC)2(CO)3X was found to form agostic stabilised species upon halide abstraction by NaBAr4F in CH2Cl2. Under the same conditions, Re(IPr)(CO)4Cl was found to form the dichloromethane complex, [Re(IPr)(CO)4(η1-CH2Cl2)]BAr4F. In C6H5F solution under an atmosphere of dihydrogen, the CH2Cl2 ligand could be displaced by H2 to form the dihydrogen species, [Re(IPr)(CO)4(H2)]BAr4F.
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Marr, Isobel Helen. "Synthesis and reactivity of scandium N-heterocyclic carbene complexes." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/17970.
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Chapter one introduces N-heterocyclic carbenes (NHCs) and discusses their use as ligands for rare earth metal complexes, with particular emphasis upon compounds synthesised from 2009 until the present day. Chapter two details the synthesis and characterisation of the homoleptic scandium-NHC complex [Sc(L)3] (L = [OCMe2CH2(1-C{NCHCHNiPr})]). Reactions of [Sc(L)3] with boranes, CO2 and CS2 are described which exploit the relative lability of the Sc–Ccarbene bond and allow formation of [Sc(L)2(OCMe2CH2(1-B'C{NCHCHNiPr}))] (B' = 9-BBN, BPh3, B(C6F5)3, BH3), [Sc(OCMe2CH2(1-O2CC{NCHCHNiPr})3]n, [Sc(L)2(OCMe2CH2 (1-S2CC{NCHCHNiPr})] and [Sc(L)(OCMe2CH2(1-S2CC{NCHCHNiPr})2]2. The chapter also discusses the reactivity of [Sc(L)3] towards substrates containing acidic C–H and N–H bonds and substrates containing polar E–X bonds (where E = C, Si, B, P and X = Cl, I). Chapter three describes the synthesis and characterisation of the NHC substituted scandium benzyl complexes [Sc(Bn)2(L)]2 and [Sc(Bn)(L)2], and the attempted synthesis of NHC substituted scandium aminobenzyl complexes. The reactivity of [Sc(Bn)2(L)]2 with RX substrates (R = alkyl) is discussed in detail; depending on the nature of the alkyl group, these reactions can allow formation of R–Bn , the result of carbon-carbon coupling. The complex [Sc(Bn)(L)Cl]2 has been isolated from these reactions and is structurally characterised. The reactivity of [Sc(Bn)2(L)]2 towards C–H bonds is explored and attempts to prepare NHC substituted scandium hydrides are described. Comparisons of the relative stability and reactivity of [Sc(Bn)2(L)]2 and [Sc(Bn)3(thf)3] are drawn. Chapter four documents the synthesis and characterisation of [Sc(Odtbp)2(L)] (Odtbp = 2,6-di-tert-butylphenoxide), [Sc(Odtbp)(L)2], and the samarium analogue [Sm(Odtbp)(L)2]. The reactivity of these complexes towards various small molecules is described. The chapter also details attempts to prepare the cationic scandium complexes [Sc(L)2][Bort] (Bort = bis[3,3',5,5'-tetra-(tert-butyl)-2,2-diphenolato]borate) and [Sc(L)2][B(Ph)4]. Chapter five provides overall conclusions to the work presented in this thesis. Chapter six contains all experimental and characterising data for the complexes and reactions detailed in this work.
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Durmus, Semih. "Silver(I) and Gold(I) N-Heterocyclic Carbene Complexes." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1165247084.
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Fraser, Roan. "Fischer and N-heterocyclic carbene complexes of chromium(0)." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/31504.
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The central focus of this study was the synthesis, structural investigation and characterisation of multiple chromium carbene complexes. Fifteen novel chromium(0) complexes were synthesised. The synthesis of the primary monocarbene starting material [Cr(CO)5{C(OEt)(heteroaryl)}], heteroaryl = thiophene, furan, 2,2’-bithiophene, was carried out utilising typical Fischer methodology. A wide variation of spacer ligands were reacted to obtain different carbene substituents. The ligand substitution reaction between carbonyl ligands and the bidentate ligands followed the techniques proposed in literature and produced distinctive chelated monocarbene complexes with the resulting structure mer- [Cr(CO)3(dppe){carbene)}]. An extensive collection of more sophisticated monocarbene complexes was synthesised via modification pathways (aminolysis). Conversion of original ethoxy-bearing monocarbenes through aminolysis provided the corresponding amine analogues, possessing both novel structure and unique chemical reactivity. The aminolysis reactions involved different sized amino reagents; both ammonia and cyclohexyl amine (bulky, cyclic chair amines) were employed to produce derivatives of the monocarbene starting complexes. Lastly, the synthesis of unique N-heterocyclic carbene (NHC) complexes was envisaged. Synthesis of both the pentacarbonyl-bearing and phosphine-bearing NHC complexes was attempted utilising an adapted version of a methodology proposed in literature. The synthesis of chelate NHC complexes, however, proved difficult and the resulting products were not obtained.
All Fischer and N-heterocyclic carbene complexes were characterised using infrared spectroscopy, nuclear magnetic resonance spectroscopy and mass spectrometry. In cases where single crystals were obtained, X-ray crystallography was used to confirm molecular structures. X-ray crystallographic studies indicated that carbonyl substitution reactions performed on monocarbene starting material, will favour the formation of the meridonial isomer in molecules where the carbene substituents are less bulky. Due to steric considerations, the substitution of labile carbonyl ligands in the trans position to the carbene moiety will be favoured. Density functional theory (DFT) calculations were performed on the complexes synthesised in this study. The results obtained indicated the favoured isomeric form to be facial in some cases whereas crystallographic data signified the meridonial isomer as the more stable product, irrespective of the bulkiness of the carbene substituents. Bond lengths, geometry and bond angles were all comparable to those of the single-crystal X-ray data. Single-point energy calculations show clearly that modelling methods provide good estimations of energetically favourable geometries, and accurate DFT calculations also predict the HOMO and LUMO orientations around the metal or ligand spheres. The majority of the structures provided by the computed model, illustrated that the 3d atomic orbitals of the metal contributed significantly to the HOMO, whereas the LUMO was mostly orientated around the carbene carbon atom. Metathesis and polymerisation catalytic reactions were attempted on [Cr(CO)3(dppe){C(OEt)(thiophene)}], 2, whereas only metathesis studies were employed for [Cr(CO)3(dppe){C(NHCy)(thiophene)}], 6. Both complexes presented as inert to either reaction and no catalytic capability was witnessed. Gas chromatography was used to indicate the level of progression of the reaction and the chromatogram verified that neither pre-catalyst found application in metathesis or, in the case of 2, in polymerisation.Dissertation (MSc)--University of Pretoria, 2012.
Chemistry
MSc
Unrestricted
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Pretorius, René. "Fischer and N-heterocyclic carbene complexes of tungsten(0)." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/31515.
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The synthesis of novel Fischer and N-heterocyclic tungsten(0) carbene complexes was endeavoured in this study and resulted in the synthesis, isolation and characterisation of eighteen new complexes.
Sixteen novel Fischer carbene complexes were synthesised. In these complexes, both carbene ligand substituents were varied. Ethoxy as well as amino heteroatom substituents were used. Heteroaryl compounds thiophene and furan were employed as the second substituents on the carbene ligand. Complexes with combinations of these different substituents were synthesised and investigated to assess the influence the various substituents of the carbene ligand may have on the carbene complex itself. In addition, the metal ligand sphere was altered by substitution of one or two carbonyl ligands for either an amine or a phosphine ligand/s. These substitutions resulted in the formation of metal pentacarbonyl, metal tetracarbonyl as well as metal tricarbonyl systems. The complexes were successfully characterised by means of NMR and IR spectroscopy, and in selected cases X-ray diffraction and mass spectrometry.
Synthesis of N-heterocyclic carbene complexes derived from isopropyl and mesityl imidazolium chlorides was attempted. The products were obtained in crude form, but could not be isolated due to decomposition during purification. Two novel decomposition products, which point towards a unique decomposition route, were isolated.
Theoretical models of both the novel Fischer carbene complexes and the N-heterocyclic carbene complexes were calculated. This allowed for identification of infrared modes observed in experimental data. Furthermore, the HOMO and LUMO distributions and the HOMO-LUMO energy gaps were calculated, along with electrostatic potential maps. In all the Fischer carbene complexes the HOMOs were located on the metal centre and the LUMOs on the carbene ligand. In contrast, the HOMO and the LUMO were both located on the metal centre for the N-heterocyclic carbenes. The HOMO-LUMO energy gap decreased as follows:
NHC complexes > Amino Fischer carbene complexes > Ethoxy Fischer carbene complexes
Lastly, in all the complexes studied, the electrostatic potential maps indicated that the highest amount of electron density was found on the carbonyl ligands of these complexes.
Both experimental and theoretical data indicated marked differences in the various classes of compounds, suggesting that these complexes would not only have different reactivities but also be suited to different applications. Experimental studies on reactivity and applications are thus future avenues of study which are made available from these results.Dissertation (MSc)--University of Pretoria, 2012.
Chemistry
MSc
Unrestricted
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Sprick, Reiner Sebastian. "Polytriarylamines containing fused ring and heterocyclic structures prepared using N-heterocyclic carbene complexes of palladium." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/polytriarylamines-containing-fused-ring-and-heterocyclic-structures-prepared-using-nheterocyclic-carbene-complexes-of-palladium(c09188eb-490b-452c-945a-22979f58c76d).html.
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For the preparation of semiconducting polymers often ‘standard’ catalytic systems are used without further optimisation. New ligands, such as N-heterocyclic carbenes have shown excellent activity in cross-coupling reactions (e.g. Suzuki-Miyaura reaction, or Hartwig-Buchwald amination). These systems show excellent conversions under mild conditions and even allow the use of aryl chlorides as reagents. Nevertheless, previously no system has been reported for the synthesis of conjugated polymers, e.g. the Suzuki polycondensation or Buchwald-Hartwig type polycondensation using these catalysts. A NHC-Pd based catalytic system was optimised for a polyamination reaction and the catalyst [(IPr)Pd(allyl)Cl] was found to be the most active. Polytriarylamines were synthesised using the optimised catalytic system and tested in organic field-effect transistors. Mobilities found were low which was found to be attributed to the presence of high molecular weight fractions. Molecular weights were controlled using an in situ end-capping approach and polymers tested in the semiconducting layer of OFETs gave similar mobilities tothose reported earlier. Several polytriarylamines, which have not been reported previously, were synthesised using NHC-chemistry and the in situ end-cappingapproach, as well as polytriarylamines that have been reported previously using Pd/phosphine catalysts. One library containing polymers based on biphenyles andbridged biphenyles and another library containing polymers with bridged oligoarenes were synthesised. Suzuki polycondensation was also studied besides the polyamination protocol and low catalyst loadings and reaction temperatures could be realised using a NHC-Pd catalyst. Sulfur containing monomers that could not be polymerised using the polyamination were polymerised successfully. All polymers were fully characterised and studied as the active layer in organic field-effect transistors. The highest mobilities determined for these polymers (~10-2 cm2/Vs) is close to the highest reported for this class of polymer reported to date.
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Wang, Yinli. "Development of A New Heterocycle Forming Reaction and Kinetic Resolution with N-Heterocyclic Carbenes." Kyoto University, 2018. http://hdl.handle.net/2433/232320.
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Panzner, Matthew John. "SILVER N-HETEROCYCLIC CARBENES AND SUBSTITUTED CYCLOTRIPHOSPHAZENES." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164744266.
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Germeroth, Anne Inger. "Reactivity of electropositive f-block metal N-heterocyclic carbene complexes." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/9519.
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The combination of Lewis acidic f-block metals and a labile nucleophilic carbene can be an excellent means to activate small molecules such as silanes, CO2 and other traditionally inert substrates. Furthermore, bidentate alkoxy-NHC ligands have shown promise in the support of unusual high oxidation state organometallic complexes, including examples of CeIV, PdIV and UVI. In this thesis the synthesis and reactivity of a series of f-block metal NHC complexes is described. Chapter One introduces N-heterocyclic carbenes and their f-block metal complexes, in particular of cerium, praseodymium and uranium. Furthermore, it will give an overview of small molecule activation by NHCs, lanthanides and specifically [Ce(LAr)N"], (L = OC(CH3)2CH2(CNCH2CH2NMes) the magnetic properties and use of lanthanides e.g. as single molecule magnets and oxo-functionalisation of the uranyl moiety. Chapter Two describes the addition-elimination reaction chemistry of CeIII and UIV NHC complexes in which polar reagents add in a heterocyclic fashion across the MNHC bond. It also describes the synthesis of the lithium salt of the alkoxycarbene proligand [LiLAr]4 and its reactivity towards f-element halide and aryloxide salts. A series of reactions to target the formation of metal-metal bonds is described. Chapter Three focuses on the synthesis of novel cerium and praseodymium complexes [Pr(LAr)N"2], [Pr(LAr)2N"], [Pr(OAr2,6-tBu)3] and [Ce(OAr2,6-tBu)3] and their reactivity towards oxidants. A series of alkoxide bridged lanthanide dimers [(Cl)Ce(μ- LAr)2Ce(Cl)2], [N"(LAr)Ce(μ-OAr2,6-tBu)OAr2,6- 2Ce(LAr)N"] and [N"(Cl)Pr(μ LAr)2Pr(Cl)N"] have been made and characterised including by SQUID variable temperature magnetometry. Chapter Four evaluates the synthesis and reactivity of uranyl complexes [UO2(LAr)2], [UO2N"2(py)2] and [UO2(OAr2,6-tBu)2(py)2], specifically their reactivity towards haloboranes in different solvents. Additionally, the oxo-functionalisation of uranyl compounds with haloboranes is discussed. Chapter Five draws conclusions and provides a summary of the work presented. Chapter Six comprises the experimental details and analytical data.
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Fyfe, Andrew Alston. "d- and f-metal alkoxy-tethered N-heterocyclic carbene complexes." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/15862.
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Chapter one is an introduction, outlining the structure and bonding of N-heterocyclic carbenes (NHCs). It then goes on to give examples of f -metal NHC complexes and describes any reactivity or catalytic activity. Chapter two describes the synthesis of the transition metal NHC complexes [Fe (LMes)2] 3 and [Co(LMes)2] 4 (LMes = OCMe2 CH2(1-C{NCH2CH2NMes})). The heterobimetallic complexes [(LMes)Fe(μ-LMes)U(μ-{N(SiMe3)Si(Me)2CH2})(N(Si Me3)2)2] 5 and [(LMes)Co(μ-LMes)U(μ-{N(SiMe3)Si(Me)2CH2})(N(SiMe3)2)2] 6 were prepared from the reaction between [({Me3Si}2N)2U(NSiMe3SiMe2CH2)] and 3 or 4, respectively. Complex 5 was also synthesised by the reaction between 3 and [U(N{SiMe3}2)2]. The diamagnetic analogue [(LMes)Zn(μ-LMes)Th(μ-{N(SiMe3)Si (Me)2CH2})(N(SiMe3)2)2] 9 was prepared from the reaction between [Zn(LMes)2] and [({SiMe3}2N)2Th(NSiMe3SiMe2CH2)]. The reactivity of 5 is discussed. When 5 was reacted with 2,6-dimethylphenyl isocyanide, [({SiMe3}2N)2U{N(SiMe3)Si(Me2)C(CH2)N(2,6−Me−C6H3)}] 8 was isolated. The reaction with CO resulted in the formation of [({Me3Si}2N)2U{N(SiMe3) Si(Me2)C(CH2)CO}]. 5 showed no reactivity with azides, boranes or m-chloroperbenzoic acid and decomposed when exposed to H2, CO2 or KC8. The reaction between 6 and 2,6-di-tert-butylphenol formed the previously reported monometallic complex [({SiMe3}2N)2U(OC6H3tBu2)]. The serendipitous synthesis of the iron ate complex [Na(Fe{LMes}2)2]+ [Fe(ArO)3]– 10 (Ar = 2,6-tBu-C6H3) is also described. Chapter three describes the synthesis of the aryloxide complexes [HC(3-tBu-5-Me- C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2O)Co(THF)]2 11 and [HC(3- tBu-5-Me-C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2O)Zn(THF)n] 13. Treatment of 11 with pyridine N-oxide resulted in the formation of the pyridine-Noxide adduct [HC(3-tBu-5-Me-C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2 O)Co(C5H5NO)]2 12. When 11 was treated with [({Me3Si}2N)2U(NSiMe3SiMe2C H2)], no reaction occured at room temperature but at 80◦C decomposition occured. When 11 was treated with [(NH4)2Ce(NO3)6] the protonated proligand HC(3-tBu- 5-Me-C6H2OH)3 reformed. The reactivity of 11 with [({Me3Si}2N)Ce(LiPr)2] is also discussed. Chapter three also discusses the preparation of the heterobimetallic complex [HC(3- tBu-5-Me-C6H2O)2-μ-(3-tBu-5-Me-C6H2O)KCo]2 14 and the salt-elimination chemistry of the complex. The preparation of [HC(3-tBu-5-Me-C6H2O)2-μ-(3-tBu-5- Me-C6H2O)KZn]2 15 is also outlined. Chapter four discusses the reactivity of [Ce(LiPr)3] (Li Pr =OCMe2CH2(1-C{NCHC HNiPr})) in C-H and N-H activation and as a catalyst for organic reactions. [Ce(LiPr)3] displayed no C-H activation chemistry with RC−−−CH (R = SiMe3, Ph, tBu), diphenyl acetone, indene or fluorene. [Ce(LiPr)3] also showed no N-H activation chemistry with pyrrole or indole, nor did it react with the lignin model compound PhOCH2Ph. When treated with an excess of benzyl chloride, [Ce(LiPr)3] underwent ligand decomposition to form the acylazolium chloride [(C6H5C(O))OCMe2CH2(1-C(C6H5C (O)){NCHCHNiPr})]Cl 18 and CeCl3. When [Ce(LiPr)3] was added to a mixture of benzaldehyde and benzyl chloride, as a coupling catalyst, the complex decomposed. [Ce(LiPr)4] was tested as a catalyst from the benzoin condensation and for the coupling of benzalehyde and benzyl chloride, however, it resulted in the decomposition of [Ce(LiPr)4]. Chapter four also outlines the catalytic activity of 3. The complex showed no reactivity as a hydrogenation catalyst towards alkenes, aldehydes or ketones but did display reactivity as a hydroboration catalyst for alkenes, aldehydes or ketones. Chapter five presents the conclusions for chapters two to four. The final chapter contains the experimental details from the previous chapters.
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Turner, Zoe Rose. "Small molecule activation using electropositive metal N-heterocyclic carbene complexes." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/8210.
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The versatility of N-heterocyclic carbenes (NHCs) is demonstrated by numerous practical applications in homogeneous transition metal catalysis, organocatalysis and materials science. There remains a paucity of electropositive metal NHC complexes and so this chemistry is poorly developed with respect to that of the late transition metal and main group elements. This thesis describes the synthesis of new alkoxy-tethered NHC proligands, their use in the synthesis of reactive metal amide and metal alkyl complexes, and finally small molecule activation using these complexes. Chapter One introduces NHCs and discusses their use as supporting ligands for early transition metal and f-block complexes. Small molecule activation using organometallic complexes is examined alongside the use of electropositive metal NHC complexes in catalysis. Chapter Two contains the synthesis and characterisation of new alkoxy-tethered NHC proligands and a variety of electropositive MII (M = Mg and Zn), MIII (M = Y, Sc, Ce and U) and MIV (M = Ce and U) amide complexes. X-ray diffraction studies and a DFT study are used to probe the extent of covalency in the bonding of the MIV complexes. Chapter Three investigates the reactivity of the amide complexes prepared in Chapter Two. The MII complexes are shown to be initiators for the polymerisation of raclactide into biodegradable polymers. The MIII complexes are used to demonstrate additionelimination reactivity of polar substrates across the M-Ccarbene bond which allows the formation of new N-E (E = Si, Sn, P or B) bonds. Treatment of the UIII silylamide complex U(N{SiMe3}2)3 with CO results in the reductive coupling and homologation of CO to form an ynediolate core -OC≡CO- and the first example of subsequent reactivity of the ynediolate group. The MIV complexes are used to examine the potential for forming MIV cationic species and alkyl complexes. Chapter Four examines the synthesis of MIII (M = Ce and Sc) aminobenzyl complexes and MIII (M = Y, Sc and U) neosilyl and neopentyl alkyl complexes. The addition-elimination reactivity discussed in Chapter Three is extended to include C-E bond formation (E = Si, Sn, P, B, I or C). Chapter Five provides overall conclusions to the work presented within this thesis. Chapter Six gives experimental and characterising data for all complexes and reactions in this work.
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Teasdale, Christopher William Thomas. "Novel N-heterocyclic carbene ligands for use in supported catalysis." Thesis, Durham University, 2005. http://etheses.dur.ac.uk/2953/.
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Ligands involving CNC structures have been of intense interest in research. With an aim to investigating this area, a modular synthesis was developed using condensation reactions between a base unit of 2,6-dichloroisonicotinic acid and N-alkyl imidazoles toprovide a range of 2,6-bis(imidazolium) salts. From this point several methods wereavailable to incorporate an active metal centre, however, state of the art microwaveaccelerated synthesis was found to be the most successful technique in forming the tridentate palladium complexes. Several strategies were investigated to attach these complexes to polymer resins, exploring a range of linking groups, coupling procedures and resins. The most effective strategy involved forming an acid functionalised palladium complex to allow loading onto an amino-functionalised resin. Although several reagents were investigated it was found that the commercially available reagent PyBop® was the most effective in forming the stable amide bond from the palladium complex to the polymer resin. By using an excess of coupling reagent and an excess of the acid functionalised palladium complex complete loading onto an amino functionalised resin could be achieved.The supported complexes were found to be highly stable catalysts in Heck, SuzukiMiyauraand Stille reactions, and capable of cross-coupling a range of aryl iodides in very high yields. The active catalysts showed very little leaching of palladium (ICPMS) and could be recycled up to fourteen times with no loss of activity. Long reaction times were overcome using tetra-n-butylammonium bromide as an additive or by using microwave irradiation. Following these catalytic studies and with an aim to using less active electrophiles, several strategies were investigated to develop enhanced activity catalysts. These strategies involved replacing one of the N-Heterocyclic carbene ligands with either an "inert" bulky group or with another alternative ligand. Full details of this research are presented in chapters 2 to 5.
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Li, Kai, and 李凯. "Photoluminescent organoplatinum (II) complexes containing N-heterocyclic carbene (NHC) ligands." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B50533915.
Full textAbstract:
The syntheses, structures, photophysical properties and applications of three types of photoluminescent organoplatinum(II) complexes containing N-heterocyclic carbene (NHC) ligands are described.
The tetradentate dianionic bis(phenolate-NHC) type ligands provide a superior scaffold for constructing thermally stable and efficient deep-blue phosphorescent Pt(II) complexes with λmax of ~440-460 nm and solid-state emission quantum yields of ~30%. Highly efficient blue OLEDs with CIEx, y of (0.19, 0.21) were fabricated based on these emitters with maximum brightness, peak current efficiency and power efficiency of ~9500 cd m^(-2), 24 cd A^(-1) and 17 lm W^(-1), respectively. Structural modification by extending the π-conjugation of the tetradentate bis(phenolate-NHC) ligand leads to strongly phosphorescent platinum(II) complexes with long-lived emissive electronic states that can be used as a luminescent sensor for oxygen. DFT/TDDFT calculations and time-resolved spectroscopic characterizations were performed to gain insight into the structure-photophysics correlation.
The N-heterocyclic carbene (NHC) ligand was incorporated into Pt(II) complexes containing tridentate deprotonated 1,3-bis(2-pyridyl)benzene (N^C^N) type ligand. In addition to the [(N^C^N)Pt(NHC)]PF6 type complexes with (N^C^N) in η3-tridentate coordination mode, Pt(II) complexes with η2-bidentate (N^CN) ligands, namely [(N^CN)Pt(NHC)2]PF6, have been isolated and structurally characterized. The highly phosphorescent [(N^C^N)Pt(NHC)]PF6 complexes were used for solution-processed green OLEDs fabrication. The peak current efficiency of 12.5 cd A^(-1) and maximum brightness higher than 2000 cd m^(-2) were achieved. The presence of the pendent pyridyl motif causes quenching of emission of the [(N^CN)Pt(NHC)2]PF6 complexes in solution at room temperature. Turning on solid-state emission of [(N^CN)Pt(nBu2Im)2]PF6 in the presence of an acidic vapor revealed its potential as a luminescent chemosensor.
A class of dicationic platinum(II) terpyridyl complexes containing NHC ligand, namely [Pt(tpy)(NHC)](PF6)2, has been synthesized and structurally characterized. Even in the presence of the strong σ-donating NHC ligand, these complexes are non- or weakly emissive in solution at room temperature. However, this class of complexes displays intense emissions in solid state (298 K and 77 K), in glassy solution (77 K butyronitrile) and in PMMA (2 wt.%, 298 K). The ligand (terpyridine) displacement reaction arising from CN attack onto the Pt(II) center has been observed for [Pt(tpy)(nBu2Im)](PF6)2 leading to its application as a chemodosimeter for selective cyanide sensing in aqueous solution.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
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Geraghty, Paul Bythell. "Studies towards the synthesis of fused N-Heterocyclic carbene precursors." Thesis, University of Canterbury. Chemistry, 2013. http://hdl.handle.net/10092/8197.
Full textAbstract:
This thesis describes the preparation of a various NHC ligands with five and six-membered rings, different fused aromatic cores and the subsequent synthetic development of their complexation of with Ag, Ru and Pd. The investigation and preparation of these compunds was with the intention of exploring their chemical and physical properties. The synthesis of the NHC ligands proved to be difficult, but analysis and characterisation of the side products from the reactions helped to establish successful synthetic methodologies. In both the five and six-membered research conducted a common attribute was established of a pyrid-2-yl substituent at the 1 position or both the 1 and 3 positions, thus providing new NHC ligands to investigate.
The organic syntheis of the research focused on two NHC ligand functionalites, five and six membered rings. The six memerbered rings focused on 1H-perimidine as the core unit and the design of both bidentate and tridentate NHC ligands to mimic the structural binding relationship of 2,2’- bipyridine (bpy) and 2,2’:6’2”-terpyridine (tpy) with various metal salts. The synthesis of the bpy analogues was achieved in good overall yields with minimal synthetic challenges. However, the tpy analogue was unable to be realised due to time constraints and problems associated with its synthesis. The five membered NHC ligands synthesised were to investigate the physical effects of systematically increasing the size of its aromatic core. The main focus of the research was on the phenanthrene imidazole NHC ligands. This was investigated due to the minimal research that has been conducted on this core unit and NHC-complexes. Synthesis of the two-bidentate NHC ligands with an imidazole head group and fused phenanthrene backbone were completed, but this was with a picolyl substituent at the 1 position rather than the pyrid-2-yl substituent. This failure to isolate this product was attributed to steric influences. Pyrene-fused-imidazole NHC ligands were also investigated and pyrene offers a NHC core that hasn’t been investigated previously. However, synthesis and isolation of the NHC ligands proved to be difficult and was associated with the poor solubility of the NHC ligands.
The organometallic NHC synthesis was studied extensively with the main focus on establishing appropriate conditions to give a NHC complex. The main metal investigated was ruthenium as subsequent NHC complexes were expected to have potentially interesting properties such as luminescence. The synthesis of a perimidine and phenanthrene NHC ruthenium complexes have not been isolated before, thus giving new NHC complexes. Many different synthetic routes were attempted to synthesise a perimidine NHC ruthenium complex. However, this proved difficult due to associated higher reactivity of the carbene carbon of perimidine with a new side product as a result of this research. The phenanthrene NHC complex synthesis suffered due to time constraints but potential methodology for their synthesis is stated.
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Rose, Marcus, Andreas Notzon, Maja Heitbaum, Georg Nickerl, Silvia Paasch, Eike Brunner, Frank Glorius, and Stefan Kaskel. "N-Heterocyclic carbene containing element organic frameworks as heterogeneous organocatalysts." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138636.
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A bifunctional imidazolium linker was used for the production of highly crosslinked element organic frameworks by Suzuki-coupling with tetrafunctional boronic acids. The resulting porous materials are good heterogeneous organocatalysts in the N-heterocyclic carbene-catalyzed conjugated umpolung of α,β-unsaturated cinnamaldehydeDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Marshall, Colin. "The synthesis of chiral C2-symmetric N-heterocyclic carbene complexes." Thesis, University of Aberdeen, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248633.
Full textAbstract:
The quaternisation of 1-substituted-azoles with a, w-dihaloalkanes furnished the diazolium salts. Conversion of the salts by deprotonation in the presence of sulphur generated the corresponding dithiones. A series of propylene diimidazolium salts and thiones gave an insight into the ease of handling, hygroscopic nature and yields associated with these compound. Propylene bridged diimidazol-2-ylidenes and ethylene bridged imidazolidin-2-ylidenes were never isolated from deprotonation of the salts or reductive desulphurisation of the thiones. In situ reactions with the salts and palladium acetate resulted in decomposition. The synthesis of both enantiomers of 4,5-bis(bromomethyl)-2,2-dimethyl-1,3-dioxolane from tartaric acid enabled the preparation of chiral bridged diazolium salts and thiones. Neither the diimidazol-2-ylidenes nor the dibenzimidazol-2-ylidenes were isolated due to electronically stabilised carbenes being incompatible with the bridge. The diimidazolidin-2-thiones gave the free dicarbene when the N-substituent was the 2,6-diisopropylphenyl group with the 2,4,6-trimethylphenyl derivative giving the dimer. Ligand exchange complexation with the diimidazolidin-2-ylidene and dimer failed to provide a means to ruthenium and palladium chiral chelating complexes due to steric congestion. In situ studies of the salts gave the nine membered cis 4,5-bis(1-cyclohexylbenzimidazol-2-ylidene-3-methyl)-2,2-dimethyl-1,3-dioxolane palladium dibromide. Utilising both enantiomers of 4,5-bis(bromoethyl)-2,2-dimethyl-1,3-dioxolane, that were prepared through asymmetric dihydroxylation, allowed the synthesis of eleven membered ruthenium benzylidene complexes from stable solutions of diimidazol-2-ylidenes. Square planar trans palladium dibromide complexes were prepared through in situ methods using the 1-cyclohexyl and 1-phenylbenzimidazolium salts.
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Davies, Caroline. "Trans-dihydride complexes of ruthenium bearing N-heterocyclic carbene ligands." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665402.
Full textAbstract:
Addition of 1,3,4,5 tetramethylimidazol 2 ylidene (IMe4) to Ru(PPh3)3HCl (in the presence of H2) or Ru(PPh3)4H2 gave the all trans isomer of Ru(IMe4)2(PPh3)2H2, whereas 1,3 diethyl 4,5 dimethylimidazol 2 ylidene (IEt2Me2) reacted with Ru(PPh3)4H2 to form cis, cis, trans Ru(IEt2Me2)2(PPh3)2H2. The previously reported trans dihydride complex, Ru(IMe4)4H2, was synthesized by a new method involving the reduction of Ru(IMe4)4Cl2 with KC8/H2. CO reacted with Ru(IMe4)2(PPh3)2H2 to give a mixture of Ru(IMe4)2(PPh3)(CO)H2, Ru(IMe4)(PPh3)2(CO)H2 and Ru(IMe4)2(CO)3; Ru(IEt2Me2)2(PPh3)2H2 reacted in a similar manner, although more slowly, allowing isolation of the monocarbonyl species Ru(IEt2Me2)2(PPh3)(CO)H2. Insertion of CO2 into one of the Ru H bonds of Ru(NHC)2(PPh3)H2 (NHC = IMe4, IEt2Me2) generated mixtures of major and minor isomers of the κ2 formate complexes Ru(IMe4)2(PPh3)(OCHO)H and Ru(IEt2Me2)2(PPh3)(OCHO)H. The hydridic nature of Ru(NHC)2(PPh3)2H2 (NHC = IMe4, IEt2Me2) was apparent by their reactivity toward MeI, which gave [Ru(IMe4)2(PPh3)2H]I, Ru(IEt2Me2)2(PPh3)HI, [Ru(IEt2Me2)2(PPh3)2H]I, and Ru(IEt2Me2)(PPh3)2HI. H/D exchange of Ru(IMe4)2(PPh3)2H2 with C6D6 (elevated temperature) or D2 (room temperature) gave Ru(IMe4)2(PPh3)2HD and Ru(IMe4)2(PPh3)2D2. Addition of P(C6D5)3 to a solution of the dihydride precursor resulted in the rapid substitution of the PPh3 ligands. Addition of D2 to Ru(IMe4)4H2 gave Ru(IMe4)4HD and Ru(IMe4)4D2. The dihydride complex activated benzene and toluene at room temperature and could catalyse H/D exchange between the two solvents. The catalytic activity of Ru(NHC)2(PPh3)2H2 (NHC = IMe4, IEt2Me2) for the reduction of CO2 by pinacolborane has been contrasted with that of the all NHC analogue Ru(IMe4)4H2. Despite the latter being substitutionally inert, it affords a far more active catalyst and yields a wider array of reduction products. These findings suggest that access to vacant coordination sites on the metal centre may not be a prerequisite for catalytic activity in the reduction of CO2 and that, in this case, the presence of a highly nucleophilic hydride ligand may be of greater relevance. The dihydridoborate hydride complexes Ru(IMe4)2(PPh3)(H2Bpin)H and Ru(IEt2Me2)2(PPh3)(H2Bpin)H were isolated by reaction of pinacolborane with Ru(NHC)2(PPh3)2H2 (NHC = IMe4, IEt2Me2) and were structurally characterized.
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Daly, Christopher Gary. "Applications of amido-N-heterocyclic carbene ligands in bifunctional catalysis." Thesis, University of Leicester, 2013. http://hdl.handle.net/2381/27800.
Full textAbstract:
This thesis describes the synthesis of amino/amido-N-heterocyclic carbene (NHC) complexes of late transition metals, in order to investigate bifunctional catalysis involving a metal-amido bond. Chapter one introduces bifunctional catalysis, with an emphasis on the mechanism of bifunctional bond-breaking during catalytic reactions. Mechanisms of C-H activation are described and the features of bifunctional C-H activation (AMLA) discussed. The ligand properties, and methods of synthesis, of NHC and amido ligands are described, and the choice of ligand to investigate bifunctional catalysis rationalised. Finally, the detailed aims and objectives of this research are stated. Chapter two gives an overview of the synthesis of N-donor functionalised imidazolium salts, as precursors to functionalised NHC ligands. The synthesis of imidazolium salts that are precursors to tridentate (CNC) amido-bisNHC pincer ligands and bidentate (C,NR) amino/amido-NHC ligands are described. Chapter three introduces the synthesis of pincer complexes containing NHC or amido donors. The syntheses of (CNC) amido-bisNHC complexes of palladium, platinum and nickel are described. Investigations into the stoichiometric bifunctional reactivity of a (CNC) Pd complex are also discussed. Chapter four describes the synthesis of complexes containing an amino/amido-NHC (C,NR) ligand of palladium, platinum, ruthenium, rhodium and iridium. The stoichiometric reactivity of an iridium amido complex towards electrophiles is reported. Chapter five reports the reactivity of amino/amido-NHC complexes in bifunctional catalysis. (C,NR) ruthenium, rhodium and iridium complexes are shown to be active precatalysts for the transfer hydrogenation (TH) of ketones. Evidence is presented that suggests that the metal-amido bond is participating in a bifunctional mechanism for TH. (C,NR) complexes of palladium are shown to be active precatalysts for the direct arylation (DA) of 2-n-butylfuran; however, DA of oxazole and thiazole proceeds only on addition of cocataytic pivalic acid. Evidence suggests that a metal-amido species is not involved in a bifunctional mechanism; a palladium-pivalate species is implicated in the C-H activation step of DA. Chapter six summarises the conclusions of the work reported in this thesis; potential future work is highlighted and discussed.
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Diebolt, Olivier. "N-heterocyclic carbene ligands in palladium and iridium organometallic chemistry." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/2126.
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The use of ligand in transition-metal catalysed reactions has had a considerable impact. The present manuscript aims at showing the influence of ligands in the palladium catalysed Suzuki-Miyaura cross-coupling reaction. In chapter one, the mechanism of this reaction will be described based on the numerous contribution published in the literature. It will be shown that the electronic and steric properties of the ligands have a huge repercussion on the catalytic activity of the metal. In the second chapter, the electronic and steric properties of the widely used Buchwald-phosphine ligand will be investigated. For this purpose, bis-carbonyl iridium(I) complexes were synthesized and their characterization allowed determining their TEP (Tolman electronic parameter) and their buried volume %V[subscript(bur)]. Then three next chapters of this thesis will focus on the syntheses and characterizations of new palladium complexes bearing N-heterocyclic carbenes (NHC). Their design was made in a view to obtain high activity in cross coupling reaction, particularly in the Suzuki-Miyaura cross coupling. Their activation under the catalytic conditions leads to the formation of palladium(0) species that can be mono- or bis-ligated. The influence of the ligand on the catalyst activity will be discussed. A palladium(II) precatalyst leading to mono-ligated active species will be described. Its activity in cross-coupling is very good, since activated and non-activated aryl chlorides could be coupled with aryl boronic acids at room temperature using low catalyst loadings. Unfortunately, the catalyst activity decreased with temperature. This result showed the fragility of the mono-ligated active species. In a view to obtain more robust catalysts that can perform high turnover numbers, new palladium(II) precatalysts bearing two ancillary ligands were developed. Mixed systems NHC- phosphites and NHC-phosphines are described. NHC-phosphites precatalysts displayed very good activity, but the phosphites are unfortunately sensitive to reaction conditions, limiting their role of active species shield. NHC-phosphine bearing complexes were highly active and could perform up to 10,000 turnovers with unactivated aryl chlorides. Very interestingly, these catalysts were also able to couple benzylchlorides and allyl chlorides with a wide range of boronic acids at very low catalyst loadings. These reactions had also the great advantage to proceed in aqueous solvents at very high substrate concentration. The activation mechanism of these complexes was investigated. Dichloropalladium(II) complexes were reduced under the catalytic conditions to lead palladium(0) species. Therein, it is shown that this reduction step was rate-determining in catalysis. Some palladium(0) intermediates xxiv were synthesized and showed good to excellent activities at low temperature under the exact same conditions. They displayed high reactivity towards oxygen and moisture and have to be handled under inert atmosphere. A particular complex had the ability to react with molecular dioxygen to form a stable peroxo-complex. Interestingly, this complex displayed excellent activity in water under aerobic conditions. This system was of great advantage since the reaction could be set up under air using cheap and user-friendly reagents displaying low toxicity. Moreover, the readily available distilled water used as solvent did not require prior degassing. Symmetrical and unsymmetrical bis-NHC palladium(0) complexes were successfully synthesized. They display excellent activity in the Suzuki-Miyaura cross coupling and turnover frequencies as high as 300 could be obtained at room temperature with unactivated arylchlorides and arylboronic acids. These complexes were also found excellent catalysts for the coupling of benzylchlorides with arylboronic acids. Mechanistic studies showed that no ligand dissociation occurred during the coupling suggesting as bis-ligated active species.
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Titcomb, Lisa Rae. "Novel palladium N-heterocyclic carbene complexes as catalysts for aminations." Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395012.
Full textAbstract:
The work described in this thesis is primarily focused on the synthesis and characterisation of two-coordinate zerovalent palladium complexes bearing an N-heterocyclic carbene ligand. These complexes have been assessed as pre-catalysts for coupling reactions in particular ami nation reactions involving the generation of a C-N bond. Chapter 1 presents the synthesis of complexes r, r bearing the ligand [CNCBu)(CH)2NCBu)]. An alternative synthesis for [Pd{CNCBu)(CH)2NCBu)h] 1 is reported involving reaction of [{Pd(T)3-C4H7)Clhl with sodium dimethyl malonate and carbene. Reaction of 1 with iodobenzene led to formation of a Pd(II) speCies, r , [Pd{CNCBu)(CHhNCBu)h(C6Hs)I] 2. An intermediate in the synthesis of 1, r [Pd(T)3-C4H7){CNCBu)(CHhNCBu)h(C6Hs)C] 3, has been isolated and fully characterised. Two r , mixed carbene phosphine complexes, [Pd{CNCBu)(CHhNCBu)}{P(o-tolylh}] 4 and r , [Pd{CNCBu)(CHhNCBu)} {PCY3} 1 S, have also been synthesised. Complexes 1,4 and S have been assessed as a pre-catalysts for ami nation couplings with limited success. Chapter 3 presents the r , synthesis of two complexes bearing the ligand [CN(Me)(CMe)2N(Me)]. Metal vapour synthesis was r , used to synthesise [Pd{CN(Me)(CMehN(Me)h] 6 and the diiodide complex r , [Pd{CN(Me)(CMehN(Me)hI2] 7 was also prepared. Complexes 6 and 7 were shown to have no activity as pre-catalysts in amination couplings. Chapter 4 presents the synthesis of complexes r· ~. bearing the ligand [CN(2,6-'Pr2-C6H3)(CH2hN(2,6-'PrrC6H3)]. The methodology used to synthesise r. ~. 1 was applied to the synthesis of [Pd{CN(2,6-'Pr2-C6H3)(CH2hN(2,6-'PrrC6H3)h] 8. Substitution of a phosphine ligand In [Pd {P(o-tolylh hl by carbene led to formation of r. ~. [Pd{CN(2,6-'PrrC6H3)(CH2hN(2,6-'PrrC6H3)}{P(o-tolyl)3}] 9. Complexes 8 and 9 were successfully employed as pre-catalysts for amination couplings. 4-Chlorotoluene was shown to couple to a variety of primary and secondary amines including cyclic, acyclic and aryl substituted as well as an imine. The same proceedure was also used to couple chloropyridines with morpho line Reactions were typically conducted with 2 mol% pre-catalyst and KOtBu base in dioxane at 100 °C and were found to be complete after 0.5-5 h. The isolated yields of product obtained were typically r· ~. above 95%. Reaction of 1 with [CN(2,6-'Pr2-C6H3)(CH2hN(2,6-'Pr2-C6H3)] led to formation of r \ r. ~. [Pd{CN(,Bu)(CH)2N(,Bu)} {CN(2,6-'Pr2-C6H3)(CH2hN(2,6-'Pr2-C6H3)}] 10. Complex 10 was found to be less active as a pre-catalyst for amination couplings than either 8 or 9. A copper carbene r. ~. complex [Cu {CN(2,6-'Pr2-C6H3)(CH2)2N(2,6-'Pr2-C6H3)} I] 11 was also synthesised and shown to facilitate the coupling of 4-iodotoluene with morpholine to give the coupled product in a 38% yield. Chapter 5 presents the results of some ligand substitution reactions. Complexes 1 and 8 were reacted with phosphines to give mixed carbene phosphine complexes 4, S and 9. The results obtained showed that phosphines can displace carbenes despite the strength of metal carbene bonds
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Dupuy, Stéphanie. "N-heterocyclic carbene gold hydroxide complexes as bond activation reagents." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6613.
Full textAbstract:
Although known since the 1930s, organogold chemistry has been dormant until recently, primarily due to preconceptions about the inertness of gold in transformations. However, this last decade has witnessed the emergence of a Golden Age with the development of a wealth of reports on gold in a plethora of reactions. In recent years, the drive for more atom- and step-economical and environmentally friendly reactions has become a field of intense research. In our on-going research on well-defined transition metal complexes bearing NHC ligands, our group recently discovered a new gold(I) hydroxide complex [Au(OH)(IPr)] (1a) that can be easily synthesised from the chloride precursor [AuCl(IPr)] (1b). A preliminary survey of the reactivity of this gold synthon has demonstrated interesting reactivity that holds great potential in bond activation reactions and the development of useful synthetic methods. Simplistically, this gold hydroxide complex can be seen as a strong Brønsted base. This thesis is dedicated to an in-depth examination of the reactivity of this complex in base-free bond activation reactions. Two themes predominate in the following chapters: the first part demonstrates the activity of gold(I) hydroxide as a bond activation agent to readily and efficiently access organogold complexes while the second part studies the reactivity of this compound in decarboxylation processes with carboxylic acids. Chapter 2 and 3 were dedicated to the development of new synthetic routes to access organogold complexes via base-free transmetalation reactions with organoborons and silanes using 1a. The combination of experimental and computational studies allowed identification and isolation of key intermediates in these reactions. Chapter 4 can be seen as a transition between the development of novel methodologies to synthesise aryl and heteroarylgold complexes and the first steps of gold hydroxide 1a as mediator in decarboxylation reaction. As a result, a novel mode of reactivity for gold was discovered and the synthetic route developed constitutes one of the greenest procedures to prepare organogold complexes with the generation of water and CO₂ as only side products. Chapter 5 and 6 venture further into the exploration of 1a in decarboxylation reactions and detail the development of a catalytic process for the protodecarboxylation reaction and subsequent mechanistic investigations of this reaction through stoichiometric experiments and kinetic and computational studies.
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Rose, Marcus, Andreas Notzon, Maja Heitbaum, Georg Nickerl, Silvia Paasch, Eike Brunner, Frank Glorius, and Stefan Kaskel. "N-Heterocyclic carbene containing element organic frameworks as heterogeneous organocatalysts." Royal Society of Chemistry, 2011. https://tud.qucosa.de/id/qucosa%3A27766.
Full textAbstract:
A bifunctional imidazolium linker was used for the production of highly crosslinked element organic frameworks by Suzuki-coupling with tetrafunctional boronic acids. The resulting porous materials are good heterogeneous organocatalysts in the N-heterocyclic carbene-catalyzed conjugated umpolung of α,β-unsaturated cinnamaldehyde.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Tomar, Pooja. "N-heterocyclic carbene derivatives for the activation of sulfur fluorides." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22932.
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Die metallfreie Aktivierung des Treibhasgases SF6 unter Verwendung von elektronenreichen N-heterocyclischen Carbenen (NHCs) resultierte in der Bildung des jeweiligen 2,2- Difluorimidazolins und Imidazolin-2-thions bzw. 2,2-Difluorimidazolidins und Imidazolidin-2-thions. Die Reduktion der NHCs mit SF4 liefert dieselben Produkte. Im Abbau von SF5CF3 mit NHCs werden ebenfalls die zuvor genannten Produkte erhalten, wobei zusätzlich das entsprechende 2-Fluor-2-trifluormethylderivat gebildet wird.
Exemplarisch wurde 1,3-Dimesityl-2,2-difluorimidazolidin [SIMes(F)2] als Fluorierungsreagenz von Aldehyden unter Bildung von Acylfluoriden sowie als Deoxyfluorierungsreagenz eingesetzt. In einem one-pot-Prozess kann zudem die Aktivierung von SF6 mit der Deoxyfluorierung von 1-Oktanol zu 1-Fluoroktan kombiniert werden. Des Weiteren konnte 1,3-Dimesityl-2-fluor-2-trifluormethylimidazolidin [SIMes(F)(CF3)] zur Trifluormethylierung von Me3SiCl und Arenen eingesetzt werden.
Der Einsatz von SIMes(F)2 ermöglicht die Darstellung von des NHC-stabilisierten Al(III)- Fluorids [(SIMes)Al(F)(Me)2] durch Monofluorierung von [(SIMes)AlMe3]. Durch Variation des Fluorierungsmittels (SF4, SF6, Me3SnF) kann ein höherer Fluorierungsgrad erreicht und [(SIMes)Al(F)3] synthetisiert werden. Dieser Al-Komplex konnte durch Halogenaustausch mit Me3SiCl in [(SIMes)Al(Cl)3] überführt werden.The metal-free activation of the greenhouse gas SF6 using electron-rich N-heterocyclic carbenes (NHCs) furnished 2,2-difluoroimidazolines or 2,2-difluoroimidazolidines and 2- thio derivatives of the NHC precursors. The NHCs can reduce SF4 as well to give same products. A complete degradation of an another greenhouse gas SF5CF3 also gave 2,2- difluoro- and 2-thio- derivatives along with the 2-fluoro-2-trifluoromethyl- derivative of the NHC precursors. The 1,3-dimesityl-2,2-difluoroimidazolidine [SIMes(F)2] was taken as an exemplary substrate to be applied in deoxyfluorination reactions and acyl fluorination of aldehydes via aldehydic C(sp2)–H bond activation. Additionally, the activation of SF6 and the fluorination of 1-octanol into 1-fluorooctane can be coupled in a one-pot process. Furthermore, trifluoromethylation of Me3SiCl and arenes was observed with the 1,3-dimesityl-2-fluoro-2- trifluoromethylimidazolidine [SIMes(F)(CF3)]. SIMes(F)2 was also used for the fluorination of complex [(SIMes)AlMe3] to synthesize the NHC stabilized Al(III) fluoride [(SIMes)Al(F)(Me)2]. Various alternative reaction routes have been developed to synthesize the NHC stabilized Al(III) fluorides [(SIMes)Al(F)(Me)2] and [(SIMes)Al(F)3] through the fluorination of [(SIMes)AlMe3] with SF4, SF6 and Me3SnF. The complex [(SIMes)Al(F)3] was successfully employed for a F/Cl exchange reaction by treating it with Me3SiCl to yield [(SIMes)Al(Cl)3] and Me3SiF.
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Truscott, Byron John. "N-heterocyclic carbene rhodium(I) and iridium(I) hydroxide complexes." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/7049.
Full textAbstract:
The unique reactivity that hard/soft-acid/base mismatched metal hydroxide complexes are capable of makes this elusive class of highly reactive organometallic complexes very interesting. The stabilisation of rhodium and iridium hydroxide bonds using electron rich N-heterocyclic carbene (NHC) ligands has enabled us to examine their rich chemistry and proved to be very rewarding. A general method was established for the preparation of a family of Rh(I)-NHC hydroxide complexes (four members), which proved to be highly active promoters of the conjugate addition of arylboronic acids to α,β-unsaturated ketones, achieving TONs and TOFs of 100,000 and 6,600 h⁻¹ respectively. In addition, we have studied the activity of Rh(I)-NHC hydroxides in catalysing the hydrosilylation and dehydrogenative silylation of terminal alkenes. The two competing reactions were studied under the same conditions and a scope for each transformation with good selectivity is presented. The scope of metal hydroxides was extended to include Ir(I)-NHC hydroxides (six members). Reactivity of this motif towards a wide range of organic substrates has been explored, undergoing reaction with arylboronic acids to form Ir(I)-aryl complexes and reacting with silanes to form Ir(I)-siloxides. The Ir(I)-hydroxide is able to deprotonate an array of O-H and N-H bonds to give new Ir(I)-alkoxides and Ir(I)-amides. In addition, C-H activation of a range of sp-, sp²- and sp³-hybridised carbon centres has been explored, delivering Ir(I)-alkyl complexes under very mild conditions, with the generation of H₂O as the sole by-product. Subsequently, we have examined the insertion of CO2 into a number of Ir(I)-O and Ir(I)-N bonds, leading to Ir(I)-carbonates and Ir(I)- carbamates, respectively. In the case of reaction between CO₂ and Ir(I)-hydroxide, a fascinating [{Ir(I)}₂-(µ-κ¹O:κ²O,O-CO₃)] complex was obtained under extremely mild conditions. This reaction has been studied in detail using kinetic and theoretical methods to calculate activation parameters and elucidate the insertion and concomitant dimerisation mechanism. In addition, we have utilised a series of methods for the preparation of a range of interesting fluorinated Rh(I)-NHC and Ir(I)-NHC complexes; bearing fluoride, bifluoride and trifluoromethyl groups. We disclose the first iridium bifluoride complexes and briefly discuss the relationship between these and the fluoride species in solution. We also report the first Ir(I)-NHC and Rh(I)-NHC trifluoromethyl complexes.
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Paine, Belinda Marie. "Ruthenium N-heterocyclic carbene complexes : C-H activation and catalysis." Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425799.
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Solinas, Gavino <1984>. "N-Heterocyclic carbene complexes of rhodium: structures, dynamics and catalysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5637/1/solinas_gavino_tesi.pdf.
Full textAbstract:
A series of imidazolium salts of the type [BocNHCH2CH2ImR]X (Boc = t-Bu carbamates; Im = imidazole) (R = Me, X = I, 1a; R = Bn, X = Br, 1b; R = Trityl, X = Cl, 1c) and [BnImR’]X (R’ = Me, X = Br, 1d; R’ = Bn, X = Br, 1e; R’ = Trityl, X = Cl, 1g; R’ = tBu, X = Br, 1h) bearing increasingly bulky substituents were synthetized and characterized. Subsequently, these precursors were employed in the synthesis of silver(I)-N-heterocyclic (NHC) complexes as transmetallating reagents for the preparation of rhodium(I) complexes [RhX(NBD)(NHC)] (NHC = 1-(2-NHBoc-ethyl)-3-R-imidazolin-2-ylidene; X = Cl; R = Me, 4a; R = Bn, 4b; R = Trityl, 4c; X = I, R = Me, 5a; NHC = 1-Bn-3-R’-imidazolin-2-ylidene; X = Cl; R’ = Me, 4d, R’ = Bn, 4e, R’ = Trityl, 4g; R’ = tBu, 4h).
VT NMR studies of these complexes revealed a restricted rotation barriers about the metal-carbene bond. While the rotation barriers calculated for the complexes in which R = Me, Bn (4a,b,d,e and 5a) matched the experimental values, this was not true for the complexes 4c,g, bearing a trityl group for which the values are much smaller than the calculated ones. Energy barriers for 4c,g, derived from a line shape simulation, showed a strong dependence on the temperature while for 4h the rotational energy barrier is stopped at room temperature.
The catalytic activity of the new rhodium compounds was investigated in the hydrosilylation of terminal alkynes and in the addition of phenylboronic acid to benzaldehyde.
The imidazolium salts 1d,e were also employed in the synthesis of new iron(II)-NHC complexes.
Finally, during a six-months stay at the University of York a new ligand derived from Norharman was prepared and employed in palladium-mediated cross-coupling.
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Solinas, Gavino <1984>. "N-Heterocyclic carbene complexes of rhodium: structures, dynamics and catalysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5637/.
Full textAbstract:
A series of imidazolium salts of the type [BocNHCH2CH2ImR]X (Boc = t-Bu carbamates; Im = imidazole) (R = Me, X = I, 1a; R = Bn, X = Br, 1b; R = Trityl, X = Cl, 1c) and [BnImR’]X (R’ = Me, X = Br, 1d; R’ = Bn, X = Br, 1e; R’ = Trityl, X = Cl, 1g; R’ = tBu, X = Br, 1h) bearing increasingly bulky substituents were synthetized and characterized. Subsequently, these precursors were employed in the synthesis of silver(I)-N-heterocyclic (NHC) complexes as transmetallating reagents for the preparation of rhodium(I) complexes [RhX(NBD)(NHC)] (NHC = 1-(2-NHBoc-ethyl)-3-R-imidazolin-2-ylidene; X = Cl; R = Me, 4a; R = Bn, 4b; R = Trityl, 4c; X = I, R = Me, 5a; NHC = 1-Bn-3-R’-imidazolin-2-ylidene; X = Cl; R’ = Me, 4d, R’ = Bn, 4e, R’ = Trityl, 4g; R’ = tBu, 4h).
VT NMR studies of these complexes revealed a restricted rotation barriers about the metal-carbene bond. While the rotation barriers calculated for the complexes in which R = Me, Bn (4a,b,d,e and 5a) matched the experimental values, this was not true for the complexes 4c,g, bearing a trityl group for which the values are much smaller than the calculated ones. Energy barriers for 4c,g, derived from a line shape simulation, showed a strong dependence on the temperature while for 4h the rotational energy barrier is stopped at room temperature.
The catalytic activity of the new rhodium compounds was investigated in the hydrosilylation of terminal alkynes and in the addition of phenylboronic acid to benzaldehyde.
The imidazolium salts 1d,e were also employed in the synthesis of new iron(II)-NHC complexes.
Finally, during a six-months stay at the University of York a new ligand derived from Norharman was prepared and employed in palladium-mediated cross-coupling.
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Patra, A. "N-heterocyclic carbene-organocatalyzed umpolung of aldehydes and imines for new synthetic transformations." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2017. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4272.
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