Relevant bibliographies by topics / NHC ligands

Academic literature on the topic 'NHC ligands'

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Published: 4 June 2021
Last updated: 11 February 2022

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Journal articles on the topic "NHC ligands"

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Rais, Eduard, Ulrich Flörke, and René Wilhelm. "Crystal structures of diiodidobis[(1S,5S)-4-mesityl-1,2,8,8-tetramethyl-2,4-diazabicyclo[3.2.1]octan-3-ylidene-κC3]palladium(IV) and dichlorido[(1S,5S)-4-mesityl-1,2,8,8-tetramethyl-2,4-diazabicyclo[3.2.1]octan-3-ylidene-κC3](triphenylphosphane-κP)palladium(IV)." Acta Crystallographica Section E Crystallographic Communications 71, no. 8 (July 11, 2015): 919–22. http://dx.doi.org/10.1107/s2056989015013055.

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The molecular structures of the chiral title compounds, [Pd(C19H28N2)2I2], (I), and [Pd(C19H28N2)Cl2(C18H15P)], (II), show a distorted square-planar coordination around the PdIIatoms with two halogenide (Hal) ligands each and two N-heterocyclic carbene (NHC) ligands in (I) or one NHC and one triphenylphosphane ligand in (II). The deviations of the PdIIatoms from theL2Hal2best plane (L= NHC or triphenylphosphane ligand) are 0.206 (1) Å for (I) and 0.052 (1) Å for (II). The crystal packings exhibit intermolecular C—H...Hal hydrogen bonds.
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Suresh, Lakshmi, Ralte Lalrempuia, Jonas B. Ekeli, Francis Gillis-D’Hamers, Karl W. Törnroos, Vidar R. Jensen, and Erwan Le Roux. "Unsaturated and Benzannulated N-Heterocyclic Carbene Complexes of Titanium and Hafnium: Impact on Catalysts Structure and Performance in Copolymerization of Cyclohexene Oxide with CO2." Molecules 25, no. 19 (September 23, 2020): 4364. http://dx.doi.org/10.3390/molecules25194364.

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Tridentate, bis-phenolate N-heterocyclic carbenes (NHCs) are among the ligands giving the most selective and active group 4-based catalysts for the copolymerization of cyclohexene oxide (CHO) with CO2. In particular, ligands based on imidazolidin-2-ylidene (saturated NHC) moieties have given catalysts which exclusively form polycarbonate in moderate-to-high yields even under low CO2 pressure and at low copolymerization temperatures. Here, to evaluate the influence of the NHC moiety on the molecular structure of the catalyst and its performance in copolymerization, we extend this chemistry by synthesizing and characterizing titanium complexes bearing tridentate bis-phenolate imidazol-2-ylidene (unsaturated NHC) and benzimidazol-2-ylidene (benzannulated NHC) ligands. The electronic properties of the ligands and the nature of their bonds to titanium are studied using density functional theory (DFT) and natural bond orbital (NBO) analysis. The metal–NHC bond distances and bond strengths are governed by ligand-to-metal σ- and π-donation, whereas back-donation directly from the metal to the NHC ligand seems to be less important. The NHC π-acceptor orbitals are still involved in bonding, as they interact with THF and isopropoxide oxygen lone-pair donor orbitals. The new complexes are, when combined with [PPN]Cl co-catalyst, selective in polycarbonate formation. The highest activity, albeit lower than that of the previously reported Ti catalysts based on saturated NHC, was obtained with the benzannulated NHC-Ti catalyst. Attempts to synthesize unsaturated and benzannulated NHC analogues based on Hf invariably led, as in earlier work with Zr, to a mixture of products that include zwitterionic and homoleptic complexes. However, the benzannulated NHC-Hf complexes were obtained as the major products, allowing for isolation. Although these complexes selectively form polycarbonate, their catalytic performance is inferior to that of analogues based on saturated NHC.
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Chan, Chung Ying, and Peter J. Barnard. "Rhenium complexes of bidentate, bis-bidentate and tridentate N-heterocyclic carbene ligands." Dalton Transactions 44, no. 44 (2015): 19126–40. http://dx.doi.org/10.1039/c5dt03295d.

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Rhenium(i) tricarbonyl complexes of a range of bidentate, bis-bidentate and tridentate NHC ligands have been prepared. These NHC ligands are of interest for possible applications in the development of Tc-99m or Re-186/188 radiopharmaceuticals and the stability of two complexes were evaluated in ligand challenge experiments using the metal binding amino acids l-histidine or l-cysteine.
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Iannuzzi, Theresa E., Yafei Gao, Tessa M. Baker, Liang Deng, and Michael L. Neidig. "Magnetic circular dichroism and density functional theory studies of electronic structure and bonding in cobalt(ii)–N-heterocyclic carbene complexes." Dalton Transactions 46, no. 39 (2017): 13290–99. http://dx.doi.org/10.1039/c7dt01748k.

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The combination of simple cobalt salts and N-heterocyclic carbene (NHC) ligands has been highly effective in C–H functionalization, hydroarylation and cross-coupling catalysis, though displaying a strong dependence on the identity of the NHC ligand.
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Diesel, Johannes, and Nicolai Cramer. "Modular Chiral N-Heterocyclic Carbene Ligands for the Nickel-Catalyzed Enantioselective C–H Functionalization of Heterocycles." CHIMIA International Journal for Chemistry 74, no. 4 (April 29, 2020): 278–84. http://dx.doi.org/10.2533/chimia.2020.278.

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N-Heterocyclic carbenes (NHCs) are the ligands of choice in a large variety of transformations entailing different transition metals. However, the number and variety of chiral NHCs suitable as stereo-controlling ligands in asymmetric catalysis remains limited. Herein we highlight the introduction of a modular NHC ligand family, consisting of a chiral version of the widely used IPr ligand. These chiral NHC ligands were applied in the nickel-catalyzed enantioselective C–H functionalization of N-heterocycles. Nickel-NHC catalysis unlocked the stereoselective C–H annulation of 2- and 4-pyridones, delivering fused bicyclic compounds found in many biologically active compounds. Applying a bulky, yet flexible ligand scaffold enabled the highly enantioselective C–H functionalization of pyridones under mild conditions. The introduction of a bulky chiral SIPr analogue enabled the nickel-catalyzed enantioselective C–H functionalization of indoles, yielding valuable tetrahydropyridoindoles. Additionally, pyrrolopyridines, pyrrolopyrimidines and pyrroles were efficiently functionalized, delivering chiral annulated azoles.
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Diaz-Rodriguez, Roberto M., Katherine N. Robertson, and Alison Thompson. "Classifying donor strengths of dipyrrinato/aza-dipyrrinato ligands." Dalton Transactions 48, no. 22 (2019): 7546–50. http://dx.doi.org/10.1039/c9dt01148j.

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Bouché, Mathilde, Bruno Vincent, Thierry Achard, and Stéphane Bellemin-Laponnaz. "N-Heterocyclic Carbene Platinum(IV) as Metallodrug Candidates: Synthesis and 195Pt NMR Chemical Shift Trend." Molecules 25, no. 14 (July 9, 2020): 3148. http://dx.doi.org/10.3390/molecules25143148.

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A series of octahedral platinum(IV) complexes functionalized with both N-heterocyclic carbene (NHC) ligands were synthesized according to a straightforward procedure and characterized. The coordination sphere around the metal was varied, investigating the influence of the substituted NHC and the amine ligand in trans position to the NHC. The influence of those structural variations on the chemical shift of the platinum center were evaluated by 195Pt NMR. This spectroscopy provided more insights on the impact of the structural changes on the electronic density at the platinum center. Investigation of the in vitro cytotoxicities of representative complexes were carried on three cancer cell lines and showed IC50 values down to the low micromolar range that compare favorably with the benchmark cisplatin or their platinum(II) counterparts bearing NHC ligands.
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Bertini, Simone, and Martin Albrecht. "O-Functionalised NHC Ligands for Efficient Nickel-catalysed C–O Hydrosilylation." CHIMIA International Journal for Chemistry 74, no. 6 (June 24, 2020): 483–88. http://dx.doi.org/10.2533/chimia.2020.483.

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A series of C,O-bidentate chelating mesoionic carbene nickel(ii) complexes [Ni(NHC^PhO)2] (NHC = imidazolylidene or triazolylidene) were applied for hydrosilylation of carbonyl groups. The catalytic system is selective towards aldehyde reduction and tolerant to electron-donating and -withdrawing group substituents. Stoichiometric experiments in the presence of different silanes lends support to a metal–ligand cooperative activation of the Si–H bond. Catalytic performance of the nickel complexes is dependent on the triazolylidene substituents. Butyl-substituted triazolylidene ligands impart turnover numbers up to 7,400 and turnover frequencies of almost 30,000 h-1, identifying this complex as one of the best-performing nickel catalysts for hydrosilylation and demonstrating the outstanding potential of O-functionalised NHC ligands in combination with first-row transition metals.
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Collado, Alba, Scott R. Patrick, Danila Gasperini, Sebastien Meiries, and Steven P. Nolan. "Influence of bulky yet flexible N-heterocyclic carbene ligands in gold catalysis." Beilstein Journal of Organic Chemistry 11 (October 2, 2015): 1809–14. http://dx.doi.org/10.3762/bjoc.11.196.

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Three new Au(I) complexes of the formula [Au(NHC)(NTf2)] (NHC = N-heterocyclic carbene) bearing bulky and flexible ligands have been synthesised. The ligands studied are IPent, IHept and INon which belong to the ‘ITent’ (‘Tent’ for ‘tentacular’) family of NHC derivatives. The effect of these ligands in gold-promoted transformations has been investigated.
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Yabune, Natsuki, Hiroshi Nakajima, and Takanori Nishioka. "Electronic and steric impact of bis-NHC ligands on reactions of Pt3S2 cores in trinuclear complexes bearing bis-NHC ligands with various lengths of alkylene bridges." Dalton Transactions 50, no. 35 (2021): 12079–82. http://dx.doi.org/10.1039/d1dt02747f.

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A silver(i) ion attacks the sulfide ligand of a triplatinum complex bearing ethylene-bridged bis-NHC ligands to afford a heptanuclear complex with two Ag–S bonds due to the steric hindrance of the ligands covering the Pt–Pt bonds.
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Dissertations / Theses on the topic "NHC ligands"

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Saker, Oliver John. "Mono- and tri-nuclear ruthenium complexes incorporating N-heterocyclic carbene ligands." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512305.

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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.

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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.
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Chemistry
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Doctor of Philosophy
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Thongpaen, Jompol. "Ligands NHCs bifonctionnels en fonctionnalisation C-H métallo-catalysée." Thesis, Rennes, Ecole nationale supérieure de chimie, 2019. https://www.ensc-rennes.fr/formations/doctorats.

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La fonctionnalisation directe des liaisons Carbone-hydrogène (C-H) a pris, au cours des deux dernières décennies, une place de plus en plus importante en synthèse organique. En particulier, la fonctionnalisation CH catalysée par un métal de transition (TM) a connu une amélioration croissante de ses performances, permettant ainsi d'élargir la palette d'outils disponibles pour la synthèse de matériaux organiques, de produits naturels et de principes actifs. Néanmoins, le développement de nouvelles transformations de liaisons C-H fonctionnant efficacement en conditions douces avec une large tolérance aux groupements fonctionnels et une sélectivité élevée reste un enjeu majeur. Parallèlement, les carbènes N-hétérocycliques (NHCs) sont devenus des ligands de choix en chimie de coordination et en catalyse. Leurs propriétés uniques sont a l’origine de catalyseurs robustes de métaux de transition permettant des stratégies de synthèse plus efficaces. Cependant, l'utilisation des ligands NHCs dans des procédés métallo-catalysés de fonctionnalisation C-H reste a ce jour limitée. Par ailleurs, les composes organoborés sont des intermédiaires polyvalents en chimie de synthèse. Les stratégies mettant en jeu la fonctionnalisation C-H représentent sans nul doute l’approche la plus simple pour accéder a ces blocs de synthèse. Cette Thèse décrit une stratégie efficace et simple pour la préparation de complexes de métaux de transition portant des ligands chélates de type NHC-carboxylate sans précédent dans la littérature. Ces complexes, présentent une efficacité et une sélectivité élevée en tant que catalyseurs dans des réactions de borylation regiosélective de liaisons C-H dites ≪ inertes ≫ en conditions douces, et notamment photochimiques
The direct functionalization of inert CH bonds has emerged over the past two decades as an increasingly important synthetic tool. In particular, transition metal (TM)-catalyzed C-H functionalization has witnessed continuing improvements in performance, allowing expansion of the toolbox available for organic material synthesis, natural products synthesis, and drug-discovery programs. In spite of this success, there is still a need for the development of methodologies to efficiently enable C-H bond transformation under mild conditions. During the past two decades, N-heterocyclic carbenes (NHCs) have become ubiquitous ligands in coordination chemistry and catalysis. Their unique properties, including strong σ- donation, are responsible for forming robust TM catalysts that allow for the development of more efficient synthetic procedures. Nevertheless, the use of NHC ligands in transition metal-catalyzed C-H functionalization has remained limited. Because organoboron compounds are versatile intermediates in synthetic chemistry, the development of new catalytic systems for selective borylation of unactivated C-H bonds would afford new perspectives in organometallic and catalysis. Herein, this Thesis discloses an efficient and straightforward strategy to access various types of transition metal complexes bearing bidentate NHC-carboxylate ligands which were fully characterized including solid-state structures. These unprecedented complexes possessing chelating-NHC ligands exhibited high efficiency and selectivity in site selective borylation of inert C-H bonds under mild conditions including a photosensitizer-free photocatalytic conditions
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Kong, Lingyu. "De ligands NHCs prochiraux à des complexes métal-NHC énantiopurs : nouvelles perspectives pour la catalyse asymétrique." Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0502.

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Les carbènes N-hétérocycliques (NHC) sont connus pour être de bons ligands des métaux de transition (TM). Dans ce manuscrit, le premier chapitre est consacré une présentation non exhaustive des différentes approches qui ont été utilisées dans la littérature pour le design de NHCs chiraux efficaces en catalyse enantiosélective. Au début du deuxième chapitre, le nouveau concept est présenté. Celui-ci repose sur la formation d’un axe de chiralité qui est créé lors de la coordination du ligand NHC à un métal de transition. Ce chapitre est consacré à la synthèse de complexes possédant une symétrie C1. Différents sels d’imidazolium, précurseurs des NHCs, ont été synthétisés et utilisé pour former des complexes palladium. Ils ont été sous forme énantiopure par HPLC chirale à l’échelle préparative. Ces complexes ont fait l’objet d’études concernant leurs propriétés chiroptiques et leurs barrières de rotation avant d’être testé en catalyse. Le concept a été ensuite étendu pour la synthèse de complexes d’or et de cuivre. Ces derniers se sont avérés être intéressants car non seulement ils ont permis d’obtenir de bons excès énantiomériques en catalyse mais leurs utilisations comme agent de transfert de ligands NHC a permis de proposer un mécanisme pour le procédé de transmétallation. Le troisième chapitre fait état des travaux qui ont été réalisés sur la préparation de complexes chiraux NHC-TM possédant une symétrie C2. Différents sels d’imidazolium symétriques ont été synthétisés et utilisés pour former des complexes de palladium. Les versions homochirales de ces complexes se sont avérées être d’excellents catalyseurs chiraux pour la réaction l’α-arylation d’amides (jusqu’à 98% ee)
N-heterocyclic carbenes (NHC) are recognized to be excellent ligands towards transition metals ™. In this manuscript, the first chapter is dedicated to a non-exhaustive presentation of the various approaches of the literature which have been used to design chiral NHCs efficient in enantioselective catalysis. As a prelude of the second chapter, the new concept lies on the formation of an axis of chirality during the coordination between the NHC ligand and the transition metal. This chapter is dedicated to the synthesis of complexes with a C1 symmetry. Various imidazolium salts, have been synthesized and then used to generate palladium complexes. These complexes have been obtained in a enantiopurically form thanks to a chiral HLPC resolution at a preparative scale. These homochiral complexes were firstly subjected to studies aiming the investigation of their chiroptic properties and the determination of their rotation barriers values. The concept was then successfully extended to the synthesis of gold- and copper-based complexes. Homochiral copper-NHC complexes were found of particular importance since their applications in catalysis allowed to reach good enantioinductions and as NHC transfer reagents brought some experimental proofs on the transmetalation process. The third chapter disclosed the works that have been done on the preparation of heterochiral NHC-TM complexes possessing a C2 symmetry. Various symmetric imidazolium salts have been synthesized and then used to form the corresponding palladium-based complexes. Homochiral complexes were found displaying good activities for α-arylation of amides and excellent enantioselectivities (up to 98% ee)
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Masoud, Salekh. "New olefin metathesis catalysts with fluorinated NHC ligands : synthesis and catalytic activity." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S136/document.

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La préparation efficace d’une nouvelle famille de sels de 1,3-bis(aryl)-4,5-dihydroimidazolium non symétriques comprenant un groupement encombrant hexafluoroisopropylmethoxy en position para- ou ortho- sur l’un des substituants N-aryle a été développée. De nouveaux sels d’imidazolium contenant un substituant fluoroalkyle en position ortho d’un des substituant aryle ont aussi été synthétisés. Ces sels sont d’excellents précurseurs de carbènes N-hétérocycliques qui ont permis l’accès efficace à une série de nouveaux complexes carbéniques du ruthénium à ligands NHC non symétriques. La méthode repose sur la génération in situ du carbène par traitement des sels d’imidazolium avec le potassium hexamethyldisilazide suivie d’un échange du ligand tricyclohexylphosphine à partir des complexes de Grubbs et Hoveyda de première génération. L’activité de ces nouveaux complexes a été étudiée sur des réactions modèles intra- et intermoléculaires de métathèse des oléfines. Il a été montré que la plupart des complexes synthétisés ont de bonnes activités catalytiques en fermeture de cycle à partir du diallylmalonate d’éthyle et en métathèse croisée de l’allylbenzène avec le 1,3-diacetoxybut-2-ene. Leurs performances sont comparables à celles des catalyseurs de Grubbs et Hoveyda de seconde génération, avec toutefois quelques différences dans les étapes d’initiation. Les effets structuraux et électroniques des ligands NHC non symétriques sur la réactivité des nouveaux complexes du ruthénium ont été étudiés. En particulier, il a été montré que les catalyseurs de type Hoveyda porteurs de ligands monosubstitués par un groupement fluoroalkyle en position ortho d’un des substituant N-aryle présentent une initiation très rapide dans les réactions de métathèse croisée. Au contraire, les complexes porteurs d’un groupement donneur alkyle ont montré une activité catalytique très faible, comme par exemple le complexe porteur d’un ligand (tert-butyl)NHC qui s’est révélé inerte à la fois en fermeture de cycle et métathèse croisée. Les complexes porteurs d’un ligand NHC symétrique avec deux groupes hexafluoroisopropylmethoxy ont des activités catalytiques nettement inférieures à leurs homologues non symétriques, révélant ainsi la forte influence de l’absence de symétrie du ligand carbène NHC dans l’activité catalytique des complexes
An efficient approach to a new family of unsymmetrical 1,3-bis(aryl)-4,5-dihydroimidazolium salts comprising bulky hexafluoroisopropylmethoxy group in para- or ortho-position in one of the N-aryl substituents has been developed. New imidazolinium salts with fluoroalkyl-containing mono-ortho-aryl substituent at one of the nitrogen atom have also been synthesized. It was found that these imidazolinium salts are effective NHC precursors and provided an efficient access to a series of new ruthenium carbene complexes with unsymmetrical fluorinated NHC ligands. The method involves in situ generation of the carbene via treatment of the starting salts with potassium hexamethyldisilazide and subsequent ligand exchange reaction with PCy3-containing first generation Grubbs and Hoveyda complexes. The catalytic activity of the new complexes has been investigated on model reactions of intra- and intermolecular olefin metathesis. It was found that most of the synthesized complexes exhibited high activity in cyclization of diethyl diallylmalonate and in cross metathesis of allyl benzene with 1,3-diacetoxybut-2-ene. Their performance has proved to be comparable with commonly used second generation Grubbs and Hoveyda catalysts, with sometimes some differences in the initiation step. Structural and electronic impact of fluorinated unsymmetrical NHC on reactivity of new ruthenium complexes has been studied. In particular, it was revealed that Hoveyda type catalysts with mono-ortho-aryl substituted NHC ligands have demonstrated very high initiation rate in CM reactions. On the contrary, catalysts with more donating N-alkyl NHCs have displayed low activity; for instance, the N-tert-butyl substituted complex has proved to be absolutely inert both in RCM and CM reactions. Symmetrical ruthenium carbene complexes bearing NHC ligands with two hexafluoroisopropylmethoxy group in para-positions of N-aryl moieties are significantly inferior in reactivity with respect to their asymmetric counterparts showing the strong influence of the desymmetrization factor on catalytic activity
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Baffert, Mathieu. "Synthesis of ruthenium complexes having one or more N-heterocyclic carbene ligands supported on hybrid mesostructured silicas and their use in the hydrogenation of carbon dioxide." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00838661.

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The goal of this PhD was to elaborate supported Ru-NHC catalytic materials based on hybrid organic-inorganic materials having imidazolium units perfectly distributed within a silica matrix. Passivation of these imidazolium materials followed by formation of NHC-carbene and reaction with [RuCl2(p-cymene)]2 provided these well-defined surface sites of general structures RuCl2(NHC)(L), where L was para-cymene (p-cymene) or THF depending on the reaction conditions, which could be further replaced by PMe3. These systems were then tested in the hydrogenation of CO2 in presence of amine to give formamides. The mono-NHC systems were highly active only in the presence of PMe3 ligands, but suffered from Ru leaching, evidencing the low stability of the NHC-Ru bond under the reaction conditions. On the other hand, dinuclear bis-NHC Ru systems were also developed, and they displayed much improved activity and stability in the hydrogenation of CO2 in the presence of PMe3 compared to the mono-NHC systems. This allowed the use of much higher reaction temperatures (200 °C) and provided heterogeneous catalysts with performances close to those obtained with the best homogeneous catalysts, Cl2Ru(dppe)2.
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Liu, Hai-Jie. "Mononuclear ruthenium complexes bearing N-Donor and NHC ligands: structure and oxidative catalysts." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/285382.

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En els últims anys, tant les metodologies de preparació de lligands de tipus carbè N-heterocíclic (NHCs) com l’aplicació d’aquests compostos en sistemes catalítics de diversa índole han crescut i millorat enormement. Més concretament, el desenvolupament de lligands d’aquesta família i la seva aplicació en reaccions d’ oxidació catalitzades per Ru és un dels camp d’alta efervescència amb resultats prometedors. Així doncs, un dels objectius d’aquesta Tesi Doctoral ha estat la síntesi i caracterització d’un nou conjunt de lligands híbrids N/C-donadors i l’avaluació del seu efecte en les propietats redox i en l’activitat catalítica en epoxidació d’olefines i oxidació d’aigua a oxigen molecular dels seus corresponents complexos de Ru. A més a més, i tenint en compte el baix nombre de complexos quirals de Ru formats per lligands de tipus NHC utilitzats en reaccions d’epoxidació asimètrica d’olefines, el segon objectius d’aquest Tesi Doctoral ha estat la introducció de quiralitat als complexos de Ru ja preparats durant la primera meitat de la tesi i l’avaluació de la capacitat dels complexos formats per a enantiodiferenciar substrats proquirals en reaccions d’epoxidació. Així doncs, al Capítol III d’aquesta tesi es descriu la síntesi i caracterització en solució (mitjançant RMN 1D i 2D) i en estat sòlid (difracció de Rajos-X) d’un nou lligand tetradentat dinucleant de tipus CNNC. Utilitzant aquets lligand, quatre nous complexos mononuclears de Ru amb fórmula: cis-[Ru(PhthaPz-R)(trpy)X]n+ (X = Cl, n = 1, X = H2O, n = 2; R = Metil, Isopropil; PhthaPz = 1-(1-methylimidazole)phthalene), [Ru(PhthaPz-R)(tpm)X]n+, (R = Methyl, tpm = Tris(pyrazol-1-yl)methane) and trans,fac-[Ru(PhthaP-R)(bpea)X]n+ (R = Metil, bpea = N,N-bis(pyridin-2-ylmethyl)ethanamine) anomenats respectivament C1-Cl/OH2, C2-Cl/OH2, C3-Cl/OH2 i C4-Cl/OH2 han estat preparats i caracteritzats mitjançant tècniques espectroscòpiques, electroquímiques i de difracció de Rajos-X (en el cas de C4-Cl). Seguidament, s’ha avaluat la capacitat catalítica dels quatre aqua-complexos d’oxidar químicament aigua a oxigen molecular i d’oxidar (química i electroquímicament) olefines a epòxids. El conjunt de complexos presenta una baixa estabilitat en actuar com a catalitzadors d’oxidació d’aigua, descomponent ràpidament a causa de l’oxidació dels lligands en el medi de reacció. Pel que fa a l’epoxidació d’olefines, es demostra amb claredat la superioritat en eficiència i selectivitat dels complexos que afavoreixen processos redox bielectrònics o “quasi”-bielectrònics (C1-OH2, C2-OH2 i C3-OH2) respecte als que els afavoreixen mono-electrònics (C4-OH2). La capacitat catalítica marcadament inferior de C3-OH2 s’atribueix a la potencial descomposició del lligand tpm en les condicions de reacció i/o al seu caràcter voluminós. Al capítol IV es prepara el lligand quiral [4,5]pinè-trpy (L2) per tal de reemplaçar el lligand trpy als complexos C1-OH2 i C2-OH2, generant-se i caracteritzant-se exhaustivament una nova família de complexos mononuclears de amb fórmula general: [RuII(PhthaPz-Ome)(L2)X]n+ (L2 correspon al lligand [4,5]pinè-trpy; X=Cl, n=1; X=OH2, n=2), C5-Cl/OH2. El complex C5-OH2 s’empra després de forma preliminar com a catalitzador d’epoxidació asimètrica d’estirè i cis-b-metilestirè en diclormetà, assolint-se valors vaixos d’enantioselectivitat (ee = 20%). Aquest resultat posa de manifest la capacitat de la combinació de lligands per a enantiodiferenciar substrats proquirals. Tot i això, la posició remota dels grups quirals de tipus pinè respecte al centre actiu de tipus Ru-O comporta l’obtenció de baixos valors d’excés enantiomèric.
The feasible preparation of N-heterocyclic carbenes (NHCs) together with the interesting properties of this compounds in very diverse catalytic systems has extraordinarily grown up during the last years. The development of ligands of this kind to be applied in Ru catalyzed oxidation reactions is one of the most encouraging research topics. Therefore, one of our aims in this Thesis has been the synthesis and characterization of a new set of hybrid N/C-donor ligands and the evaluation of their effect on the electrochemical properties and catalytic activity towards water oxidation and epoxidation of alkenes of their corresponding Ru complexes. In addition, since few Ru chiral complexes containing NHC ligands have been reported in the area of asymmetric alkene epoxidation catalyzed by organometallic compounds the second goal of this project has been the introduction of chirality to the Ru carbene complexes prepared in the first part of the Thesis and the study of the capacity of the obtained complexes in the enantioselective epoxidation of alkenes. In summary, In Chapter III a new dinucleating CNNC tetradentate ligand has been synthesized and thoroughly characterized in solution (1D and 2D NMR) and in the solid state (X-ray diffraction analysis). Four new Ru mononuclear complexes with general formula: cis-[Ru(PhthaPz-R)(trpy)X]n+ (X = Cl, n = 1, X = H2O, n = 2; R = Methyl, Isopropyl; PhthaPz = 1-(1-methylimidazole)phthalene), [Ru(PhthaPz-R)(tpm)X]n+, (R = Methyl, tpm = Tris(pyrazol-1-yl)methane) and trans,fac-[Ru(PhthaP-R)(bpea)X]n+ (R = Methyl, bpea = N,N-bis(pyridin-2-ylmethyl)ethanamine), respectively termed C1-Cl/OH2, C2-Cl/OH2, C3-Cl/OH2 and C4-Cl/OH2 have been thoroughly characterized in solution by means of spectroscopic (1D and 2D NMR and UV-vis) and electrochemical techniques (CV and DPV) and in the solid state (X-ray diffraction analysis) for the C4-Cl case. The catalytic performance of the four Ru-OH2 complexes has been analyzed with regards to the chemically driven water oxidation reaction and the chemically and electrochemically triggered epoxidation of alkenes. With regards to water oxidation, the four aqua complexes show poor stability due to ligand oxidation under the harsh reaction conditions. With regards to the epoxidation of alkenes, complexes favoring two-electronic processes (C1-OH2, C2-OH2 and C3-OH2) showed better performance and selectivity compared with those favoring mono-electronic processes (C4-OH2). The comparatively lower oxidation capacity of complex C3-OH2 potentially origins from the oxidative degradation of the tpm ligand under the conditions used or/and due to the high steric bulkiness of this facial ligand. In Chapter IV, the [4,5]pinene-trpy ligand (L2) has been prepared to replace trpy in complexes C1-OH2 and C2-OH2 and a new family of nononuclear complexes with general formula [RuII(PhthaPz-Ome)(L2)X]n+ (L2 is [4,5]pinene-trpy ligand; X=Cl, n=1; X=OH2, n=2), C5-Cl/OH2 have been prepared and fully characterized. C5-OH2 has been preliminary tested as a catalyst for the enantioselective epoxidation of styrene and cis-β-methylstyrene in dichloroethane giving low ee values of about 20%. This result demonstrates the capacity of the ligand combination to enantiodifferentiate prochiral substrates. However, the remote position of the chiral pinene moieties with regard to the Ru-O active site is probably responsible for the low ee values observed
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Marques, Carolina Silva. "Synthesis and evaluation of chiral phosphine and NHC-Ligands or heterogeneous asymmetric catalysis." Doctoral thesis, Universidade de Évora, 2013. http://hdl.handle.net/10174/15896.

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No âmbito deste trabalho, foram estudadas as reacções de arilação catalítica assimétrica em vários substratos, utilizando novos e já conhecidos catalisadores quirais, possuindo metais de transição. Esta metodologia levou à formação de novas ligações C-C, fornecendo uma panóplia de interessantes compostos, podendo-se revelar intermediários extremamente úteis na síntese de compostos biologicamente activos. Deve-se salientar a síntese de aminas quirais, α-hidroxiésteres, α-amino-ácidos e α-aminoésteres e também bi-arildiarilaminas, utilizando catalisadores de metais de transição, baseados em Pd, Rh e Ru. Reagentes organoboronados foram aplicados com sucesso neste estudo. Uma nova família de carbenos N-heterocíclicos (NHCs) foi obtida com bons rendimentos e aplicada, com sucesso, nas reacções catalíticas acima referidas. Um novo método de catálise homogénea sequencial (arilação/Suzuki-Miyaura) foi desenvolvido na síntese de bi-arilarilmetilaminas. Este método foi transformado eficientemente numa versão heterogénea utilizando Catálise com uma Fase líquida Iónica Suportada (SILPC), aplicado pela primeira vez neste tipo de catálise sequencial; ABSTRACT: The study of catalytic asymmetric arylations of appropriate substrates, using both known and novel chiral transition metal based catalysts was the focus of this thesis. This methodology leads to formation of C-C bonds, leading to the synthesis of interesting biologically active compounds. Chiral amines, α-hydroxyesters, α-amino esters and acids, and biaryldiarylamines were synthesized using a variety of different substrates and transition metal catalysts, based on Pd, Rh and Ru. Organoboron reagents were used successfully in all of these studies. A novel family of N-heterocyclic carbene (NHC) ligand precursors were synthesized in good yields, and applied successfully in these catalytic reactions. A novel homogeneous one-pot catalytic arylation/Suzuki-Miyaura sequence was developed to access bi-arylarylmethylamines. This was later transformed into an efficient heterogeneous variant, based on the Supported Ionic Liquid Phase Catalysis (SILPC) approach, which to date has never been used in such one pot procedures.
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Hameury, Sophie. "Oxygen-functionalized NHC ligands and their nickel(II), silver(I) and palladium(II) complexes." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF010.

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L’objectif de cette thèse portait sur la synthèse de complexes portant un ligand NHC associé à une fonction oxygénée et à leur application en catalyse d’oligomérisation de l’éthylène. Dans le but de synthétiser des complexes avec des ligands NHCalcool, les complexes d’argent correspondants ont été synthétisés et utilisés en transmétallation. Aucun résultat concluant n’a pu être obtenu avec le nickel à cause de l’acidité du proton alcoolique. Mais un ligand NHC-alcoolate a pu être obtenu par déprotonation directe du pro-ligand avec une base forte. Il fut alors possible d’accéder à des complexes de nickel polynucléaires, certains incorporant dans leur structure des cations lithium provenant de la base utilisée. Par comparaison, des complexes de palladium ont été synthétisés avec des NHCs-alcool ou -alcoolate par réaction des pro-ligands avec Pd(acac)2 suivie de réactions acido-basiques. Etant donné la difficulté d’obtention des complexes de nickel avec des ligands NHC-alcool, la fonction éther a été étudiée. Les complexes résultants ont été testés en oligomérisation de l’éthylène
The purpose of this work was the synthesis of complexes bearing O-functionalized NHC ligands in order to test their catalytic properties in ethylene oligomerization. In order to have access to alcohol-functionalized complexes, the corresponding silver complexes were synthesized for transmetallation purpose. Whereas no concluding results were obtained with the alcohol function in association with nickel, it was possible to access an alcoholate-functionalized NHC ligand by deprotonation of the corresponding pro-ligand. Thus, polynuclear nickel complexes were prepared, some of them included in their structure a lithium cation originating from the base. For comparison, alcohol- and alcoholate-functionalized NHC palladium complexes were synthesized by direct reaction of the pro-ligand with Pd(acac)2 followed by acidobasic reactions. Because of the complexity of the chemistry of NHC-alcohol ligands associated with nickel, the ether functionality was explored. A library of nickel complexes was synthesized and tested in the catalytic ethylene oligomerization
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Resch, Stefan Günter. "Dinuclear Copper and Nickel Complexes of New Multidentate N-heterocyclic Carbene Ligands: Structures, Dynamics and Reactivity." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/21.11130/00-1735-0000-0005-12D5-6.

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Book chapters on the topic "NHC ligands"

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Díez-González, Silvia, and Steven P. Nolan. "Palladium-catalyzed Reactions Using NHC Ligands." In N-Heterocyclic Carbenes in Transition Metal Catalysis, 47–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/978-3-540-36930-1_3.

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Ghana, Priyabrata. "Access to the First NHC-Stabilized Disilavinylidene." In Synthesis, Characterization and Reactivity of Ylidyne and μ-Ylido Complexes Supported by Scorpionato Ligands, 179–91. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-02625-7_10.

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Hahn, F. Ekkehardt. "Complexes with Protic N-Heterocyclic Carbene (NR,NH-NHC) Ligands." In Advances in Organometallic Chemistry and Catalysis, 111–32. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118742952.ch9.

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Hofmann, Peter, and Marcel Brill. "NHCP Ligands for Catalysis." In Molecular Catalysts, 207–34. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527673278.ch10.

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Kato, Tsuyoshi, Eddy Maerten, and Antoine Baceiredo. "Non-NHCs Stable Singlet Carbene Ligands." In Topics in Organometallic Chemistry, 131–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-04722-0_5.

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Stradiotto, Mark, and Rylan J. Lundgren. "Application of Sterically Demanding Phosphine Ligands in Palladium-Catalyzed Cross-Coupling leading to C(sp2)─E Bond Formation (E = NH2, OH, and F)." In Ligand Design in Metal Chemistry, 104–33. Chichester, UK: John Wiley & Sons, Ltd, 2016. http://dx.doi.org/10.1002/9781118839621.ch5.

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Frenking, G., S. Dapprich, T. Meisterknecht, and J. Uddin. "Structure and Bonding of M(CO)3(H2O), M(CO)5(NH3), and M(CO)5(PH3) (M = Cr, Mo, W)1." In Metal-Ligand Interactions in Chemistry, Physics and Biology, 73–89. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4245-8_4.

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Slaughter, LeGrande M. "Catalysis with Acyclic Aminocarbene Ligands: Alternatives to NHCs with Distinct Steric and Electronic Properties." In N-Heterocyclic Carbenes, 499–524. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527671229.ch16.

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Manning, M., A. S. Kolodziejczyk, A. M. Kolodziejczyk, S. Stoev, W. A. Klis, N. C. Wo, and W. H. Sawyer. "Highly potent and selective Tyr-NH2 9-containing linear V1 antagonists and D-Tyr2-containing linear V2 agonists: Potential radioiodinated ligands for vasopressin receptors." In Peptides 1990, 665–67. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3034-9_276.

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Storey, Caroline M., Hans P. Cook, and Adrian B. Chaplin. "Complexes of NHC-Based CEC Pincer Ligands." In Pincer Compounds, 173–89. Elsevier, 2018. http://dx.doi.org/10.1016/b978-0-12-812931-9.00008-6.

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Conference papers on the topic "NHC ligands"

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Huang, Tur-Fu, H. Lukasiewicz, C. J. Holt, and S. Niewiarowski. "CHARACTERIZATION OF FIBRINOGEN RECEPTORS ASSOCIATED WITH GLTCCPROIEIN IIb/IIIa (GPIIb/GPIIIa) COMPLEX BY TRIGRAMIN, A UNIQUE LOW MOLECULAR WEIGHT PEPTIDE PROBE." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643523.

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Trigramin (Mr weight 10 kDa), an acidic, cysteine rich peptide purified into homogeneity from Trimeresurus gramineus snake venom contained a single protein chain with EAGE at the NH2 terminal end. It inhibited platelet aggregation induced by various agents without affecting release reaction. It blocked competitively the binding of 125I-fibrincgen to AEP stimulated and chymotrypsin treated platelets (Ki= 2 × 10−8). 125-I trigramin bound to intact and to AEP stimulated platelets in a saturable manner (approx. 16,000 sites per platelet). However, AEP increased 5 fold, the binding affinity of trigramin to platelets (to Kd = 4 × 10−8M) suggesting that AEP is changing the conformation of receptors associated with GPIIb/GPIIIa complex. The binding of trigramin to thran-basthenic platelets was markedly reduced. The binding to normal platelets was significantly inhibited by EDTA and by monoclonal antibodies directed against GPIIb/GPIIIa complex but not by the antibodies directed against GPIIb or GPIIIa molecules. The binding of 125I-trigramin to AEP-stimulated platelets was inhibited by RGES (IC50 = 125 μM) and by YHHLGGAKOAGDV (C-terminal fragment of fibrinogen gamma chain, IC50 = 250 μM) suggesting that these or similar peptide sequences are required for interactions of various ligands with GPIIb/GPIIIa complex
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Balhorn, Monique Cosman, and Rod Balhorn. "Abstract 1171: Therapeutic applications of the selective high affinity ligand SH7139 may extend beyond NHL to many other types of solid tumors." In Proceedings: AACR Annual Meeting 2017; April 1-5, 2017; Washington, DC. American Association for Cancer Research, 2017. http://dx.doi.org/10.1158/1538-7445.am2017-1171.

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