Добірка наукової літератури з теми "Complexe de carbone(0)"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся зі списками актуальних статей, книг, дисертацій, тез та інших наукових джерел на тему "Complexe de carbone(0)".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Статті в журналах з теми "Complexe de carbone(0)":
1
Zhao, Lili, Chaoqun Chai, Wolfgang Petz, and Gernot Frenking. "Carbones and Carbon Atom as Ligands in Transition Metal Complexes." Molecules 25, no. 21 (October 26, 2020): 4943. http://dx.doi.org/10.3390/molecules25214943.
Анотація:
This review summarizes experimental and theoretical studies of transition metal complexes with two types of novel metal-carbon bonds. One type features complexes with carbones CL2 as ligands, where the carbon(0) atom has two electron lone pairs which engage in double (σ and π) donation to the metal atom [M]⇇CL2. The second part of this review reports complexes which have a neutral carbon atom C as ligand. Carbido complexes with naked carbon atoms may be considered as endpoint of the series [M]-CR3 → [M]-CR2 → [M]-CR → [M]-C. This review includes some work on uranium and cerium complexes, but it does not present a complete coverage of actinide and lanthanide complexes with carbone or carbide ligands.
2
Liénard, Amandine, and Gilles Colinet. "Transfert en cadmium et zinc vers l’orge de printemps en sols contaminés et non contaminés de Belgique : évaluation et prédiction." Cahiers Agricultures 27, no. 2 (February 28, 2018): 25002. http://dx.doi.org/10.1051/cagri/2018008.
Анотація:
En Région wallonne, des sols agricoles situés à proximité d’anciens sites de traitements de minerais ont été impactés par des retombées atmosphériques contaminées en cadmium (Cd), plomb (Pb) et zinc (Zn). Afin d’étudier l’impact de ces contaminations sur la qualité des productions agricoles, une étude du transfert en Cd et Zn du sol vers l’orge de printemps (Hordeum vulgare L.) a été réalisée sur une de ces zones contaminées. Dix-huit prélèvements d’orges ont été effectués en zone contaminée, 10 autres en zone témoin non contaminée et chacun d’eux a été subdivisé en trois sous-échantillons (tige, épi et grain). Un prélèvement a été réalisé dans l’horizon de surface du sol (de 0 à 20 cm) à l’emplacement de chaque prélèvement de plantes. Les concentrations disponibles et pseudo-totales en éléments traces et majeurs ainsi que pHeau, pHKCl, carbone organique total et azote total ont été mesurés sur les échantillons de sols. Les concentrations en Cd et Zn ont été dosées dans les grains, les épis et les tiges. Les concentrations en Cd et Zn mesurées dans les plantes récoltées sur la zone contaminée sont de 2 à 9 fois supérieures à celles mesurées dans les orges témoins. Il existe peu de relations entre la concentration en cadmium dans les grains (CdGrain), la concentration en zinc dans les grains (ZnGrain) et les propriétés des sols à l’exception des teneurs en Cd et Zn du sol. Une analyse Cate-Nelson a permis d’estimer CdGrain à 0,027 mg de Cd/kg matière sèche (MS) pour des teneurs pseudo-totales en Cd dans le sol allant de 0 à 1,23 mg/kg, et à 0,118 mg de Cd/kg de MS pour des teneurs pseudo-totales en Cd dans le sol allant de 1,24 à 6,87 mg/kg. ZnGrain est estimé à 19,2 mg/kg de MS pour des teneurs pseudo-totales de Zn dans le sol allant de 0 à 131 mg/kg, et à 40 mg/kg de MS pour des teneurs pseudo-totales de Zn dans le sol allant de 132 à 570 mg/kg. Une estimation du transfert en Cd et Zn reste toutefois complexe dans ces sols multicontaminés.
3
Chaton, Corinne, and Coline Metta-Versmessen. "Le contrat carbone pour différences, un outil adapté pour la décarbonation de l’hydrogène ?" Revue économique Vol. 74, no. 5 (January 4, 2024): 705–37. http://dx.doi.org/10.3917/reco.745.0705.
Анотація:
Le marché carbone EU-ETS n’est pas suffisant pour décarboner rapidement les secteurs où les technologies bas-carbone sont trop coûteuses par rapport aux technologies existantes. Pour y remédier, cette étude caractérise un « contrat carbone pour différences » (CCfD). Il s’agit d’un instrument qui garantit aux producteurs bas-carbone un prix carbone suffisant pour assurer la compétitivité de leur technologie par rapport à celles émettrices. Nous proposons une méthodologie pour concevoir les CCfD selon la région et le secteur d’application. Nous nous concentrons sur le développement de l’hydrogène par électrolyse comme alternative au vaporeformage du méthane. Du fait du double impact du prix carbone, nous soutenons que ce CCfD est un contrat complexe et qu’il devrait être défini pour des zones ayant un mix électrique homogène . Classification JEL : D47, H23, O38, Q48, Q52.
4
BIDDULPH, George Elliot, Yannick Enock BOCKO, Pierre BOLA, Bart CREZEE, Greta DARGIE, Ovide EMBA, Selena GEORGIOU, et al. "Connaissances actuelles et orientations futures des recherches sur le complexe de tourbières de la Cuvette centrale du Congo." BOIS & FORETS DES TROPIQUES 355 (March 1, 2023): 73–86. http://dx.doi.org/10.19182/bft2023.355.a37152.
Анотація:
La Cuvette centrale est le plus vaste complexe de tourbières tropicales au monde, qui s'étend sur environ 145 000 km2 en République du Congo et en République démocratique du Congo. Ce complexe stocke environ 30,6 Pg C, soit l'équivalent de trois années d'émissions mondiales de dioxyde de carbone, et représente désormais le premier site Ramsar transnational. Malgré sa taille et son importance mondiale en tant que puits de carbone, les aspects clés de son écologie et de son histoire, notamment sa formation, l'ampleur des flux de gaz à effet de serre, sa biodiversité et l'histoire de l'activité humaine, demeurent relativement peu connus. Nous synthétisons ici les connaissances disponibles sur la Cuvette centrale, en identifiant des domaines clés pour la poursuite des recherches. Enfin, nous examinons le potentiel des modèles mathématiques pour évaluer les trajectoires futures des tourbières en termes d’impacts prévisibles de l'exploitation de ressources et du changement climatique.
5
Frenking, Gernot, and Ralf Tonner. "Divalent carbon(0) compounds." Pure and Applied Chemistry 81, no. 4 (January 1, 2009): 597–614. http://dx.doi.org/10.1351/pac-con-08-11-03.
Анотація:
Quantum chemical studies show that there is a class of carbon compounds with the general formular CL2 where the carbon atom retains its four valence electrons as two lone pairs. The C-L bonds come from L → C donor-acceptor interactions where L is a strong σ-donor. Divalent C(0) compounds (carbones) are conceptually different from divalent C(II) compounds (carbenes) and tetravalent carbon compounds, but the bonding situation in a real molecule may be intermediate between the three archetypes. There are molecules like tetraaminoallenes which may be described in terms of two double bonds (R2N)2C=C=C(NR2)2 where the extraordinary donor strength of the dicoordinated carbon atom comes only to the fore through the interactions with protons and Lewis acids. They may be considered as "hidden divalent C(0) compounds". The donor strength of divalent C(0) molecules has been investigated by calculations of the binding energies with protons and with main-group Lewis acids and the bond dissociation energies (BDEs) of transition-metal complexes.
6
Frański, Rafał, Błażej Gierczyk, Grzegorz Schroeder, Stefan Pieper, Andreas Springer, and Michael Linscheid. "Electrospray ionization mass spectrometric study of mercury complexes of N-heterocyclic carbenes derived from 1,2,4-triazolium salt precursors." Open Chemistry 5, no. 1 (March 1, 2007): 316–29. http://dx.doi.org/10.2478/s11532-006-0050-0.
Анотація:
AbstractBy mixing 1,2,4-triazolium salts (precursors of N-heterocyclic carbenes 1–6) with mercury acetate, a number of complexes have been obtained under electrospray ionization condition. Carbenes 1 and 2 contain one carbene center; therefore, they are able to bond only one mercury cation. Carbenes 3–5 contain two carbene centers; therefore, they can bond two mercury cations. Mercury complexes of 1–5 always contain an acetate anion attached to a mercury cation. Carbene 6 also contains two carbene centers; however, its structure allows formation of a complex containing mercury bonded simultaneously to both centers, therefore, the complex that does not contain an acetate anion. The MS/MS spectra taken for complexes of carbenes 1–5 have shown formation of a cation corresponding to N1 substituent (adamantyl or benzyl), and those of complexes of carbenes 3–5 (doubly charged ions) have also shown the respective complementary partner ions. Mercury complex of 2 has yielded some other interesting fragmentation pathways, e.g. a loss of the HHgOOCCH3 molecule. The fragmentation pathway of the mercury complexes of 6 was found to be complicated.
7
Wernert, Carole. "Les héritages d’une trajectoire énergétique dans un ancien bassin houiller : le cas complexe d’une transition à Sarrebruck." Réactions d’épidémie, no. 2 (November 1, 2020): 127–47. http://dx.doi.org/10.57086/rrs.144.
Анотація:
Cet article vise à contribuer à la déconstruction de la vision monolithique du processus de transition énergétique bas carbone à travers la notion de trajectoire énergétique. L’objectif principal est d’identifier les différents marqueurs susceptibles d’enclencher ou de ralentir la transition bas carbone à travers une analyse historique, multiscalaire et politisée de la trajectoire énergétique de la ville allemande de Sarrebruck. Située au cœur du bassin houiller sarro-lorrain (concurrent de celui de la Ruhr), la ville a longtemps été dépendante d’un mix énergétique fondé sur le charbon local. Mais au tournant des années 1990, la ville et son entre- prise municipale de l’énergie (Stadtwerk) se sont positionnées en tant que pionnières dans l’élaboration de programmes d’énergies renouvelables et de sobriété énergétique. La trajectoire énergétique de la ville de Sarrebruck montre alors un processus de transition bas carbone non linéaire, à séquences alternées.
8
Ning, Yalan, Robert D. J. .Froese, Peter Margl, Edward L. Lee, SonBinh T. Nguyen, Thomas H. Peterson, Nicole Wagner, Charlotte L. Stern, and Amy A. Sarjeant. "Efficient Carbene and Carbyne Formation in Molybdenum(0) and Tungsten(0) Dinitrogen Complexes." Organometallics 33, no. 5 (February 21, 2014): 1120–25. http://dx.doi.org/10.1021/om4006214.
9
Gabor, Barbara, Carl Krüger, Bernd Marczinke, Richard Mynott, and Günther Wilke. "Nickel(0)-Carbene Complexes." Angewandte Chemie International Edition in English 30, no. 12 (December 1991): 1666–68. http://dx.doi.org/10.1002/anie.199116661.
10
Filippou, Alexander Constantin, and Walter Grünleitner. "Säure-induzierte CC-Kupplung von Isocyanid-Liganden in homoleptischen Alkylisocyanid-Komplexen von Mo(0) und W(0) / Acid-Induced CC-Coupling of Isocyanide Ligands in Homoleptic Alkylisocyanide Complexes of Mo(0) and W(0)." Zeitschrift für Naturforschung B 46, no. 2 (February 1, 1991): 216–30. http://dx.doi.org/10.1515/znb-1991-0216.
Анотація:
Reactions of the electron-rich, homoleptic alkylisocyanide complexes M(R N C)6 (1a-2b) (1: M = Mo, 2: M = W; a: R = Et, b: R = tBu) with electrophiles have been studied. A coupling of two isocyanide ligands to a complexed alkyne ligand is observed, when M(R N C)6 is treated with two equivalents of HX(X = Br, I) and leads to the bis(alkylamino)acetylene complexes [X (R N C )4M[η2-R(H)NC ≡ CN(H)R]]X (3a′-4b″) (3: M = Mo, 4: M = W). Treatment of W (EtNC)6 (2a) and W (tBuNC)6 (2b) with one equivalent of Me3SiOTf results in the quantitative formation of the aminocarbyne complexes [(EtNC)5W ≡ CN (SiMe3)Et]OTf (6c) and [(tBuNC)5W ≡ C N (SiMe3)tBu]OTf (6d), respectively. In comparison, an equilibrium between W(tBuNC)6 (2b) and the aminocarbyne complex [(tBuNC)5W ≡ C N (SiMe3)tBu]Cl (6e) is found, when 2b is treated with Me3SiCl. The compounds 6c and 6d are structurally related to the aminocarbyne complexes [(EtNC)5M ≡ C N E t2]BF4 (5a: M = Mo, 6a: M = W) and [(tBuNC)5W ≡ C N (Et)Bu]BF4 (6b), which are obtained from ethylation of M (EtNC)6 (1a, 2a) and W (tBuNC)6 (2b) with Et3OBF4. 5a and 6a undergo with HI a carbyne-isocyanide coupling reaction to give the alkyne complexes [I(EtNC)4Mo[η2-Et2NC≡CN(H)Et]]BF4 (7a) and [I(EtNC)4W[η2-Et2NC≡CN(H)Et]]BF4 (8a), respectively. Similar reactivity is exhibited by 6b, which yields with HI the alkyne complex [I(tBuNC)4W[η2-tBu(Et)N C ≡ C N (H)tBu]]BF4 (8b). The reported transformation of a complexed isocyanide to an aminocarbyne and the acid-induced aminocarbyne-isocyanide coupling reaction are experimentally verified to be important steps in the reductive coupling of isocyanide ligands in [M(RNC)6X]+-complexes yielding the bis(alkylamino)acetylene compounds [X(R N C)4M[η2-R (H )N C ≡ C N (H )R ]]+.
Дисертації з теми "Complexe de carbone(0)":
1
Gigou, Thomas. "Vers des complexes de carbone(0) à l'aide de la chimie de l'iode hypervalent : Nouveaux ylures d’iodonium nucléophiles stabilisés par une sulfone." Electronic Thesis or Diss., Bordeaux, 2023. http://www.theses.fr/2023BORD0501.
Анотація:
Les bis-ylures sont des espèces carbonées divalentes dans lesquelles un atome de carbone central porte deux charges négatives, chacune d’elles étant stabilisée par un hétéroatome chargé positivement en α du carbone. Transférer sélectivement l’atome de carbone central en se servant des deux fonctions ylures simultanément représente un grand intérêt pour les chimistes de synthèse. De telles sources atomiques de carbone restent toutefois rares, le carbone de la plupart des bis-ylures développés jusqu’à présent étant trop étroitement liées avec les deux ligands adjacent. Dans ce contexte, cette thèse se concentre sur le développement de bis-ylures et autres espèces réactives comprenant un ligand iodonium, fragment d’une extrême labilité qui permettrait une libération efficace du carbone central. Le premier chapitre est consacré à l’état de l’art des composés « carbone(0) » et à leur application en tant que source de carbone atomique, ainsi qu’à la structure et la réactivité de composés iodés hypervalents. Un second chapitre traite du relargage de bis-ylures après la rupture d’une liaison covalente, soit une liaison P–C d’ylures mixtes de phospho-iodonium stabilisés par une phosphine oxydée, soit une liaison Si–C d’ylures mixtes de phospho-iodonium stabilisés par un silane. Le troisième chapitre reporte nos tentatives d’obtenir des précurseurs de bis-ylures d’iodonium par iodation direct d’ylures de phosphonium ou de sulfoxonium nucléophiles. Le dernier chapitre concerne notre tentative de développer un yldiure d’iodonium, espèce pour laquelle seule une des deux charges négatives portées par le carbone est adjacente à un atome chargé positivement, l’autre n’étant stabilisé que par les effets inductifs et mésomères d’un groupement sulfonyle électroattracteur. Les résultats de ces tentatives nous ont permis d’identifier un nouvel ylure d’iodonium mono-stabilisé nucléophile, dont la réactivité avec des aldéhydes est décrite en fin de chapitreBis ylides are divalent carbonated s pecies on which a central carbon atom bears two negative charges, both stabilized by two α, positively charged heteroatoms. Selectively transferring the central carbon atom, using both ylides simultaneously is of great interest for synthetic chemists. Such atomic carbon sources are scarce, as most of the bis ylides developed until now were too tightly bind to his ligands. With this in mind, this thesis ambitions to develop bis ylides and other reactive species containing an iodonium ligand, an extremely labile fragment which could allowed an efficient liberation of the central carbon atom. The first chapter is dedicated to the state of the art of “carbon(0)” compounds and their application as atomic carbon sources, as well as the structure and reactivity of hypervalent iodine compounds. The second chapter is about releasing bis ylides by cleaving a covalent bond, either a P C bond from a phosphine oxide stabilized mixt phospho iodonium ylide, or a Si C bond from a silane stabilized mixt phospho iodonium ylide. A third chapter explains our attempts to obtain bis ylides precursor by direct iodination of nucleophilic phosphonium or sulfoxonium ylides. The last chapter is dedicated to our attempt to develop an iodonium yldiide, in which only one of the two negative charges borne by the central carbon is next to a positively charged heteroatom, the other being stabilized by a sulfonyl mesomeric and inductive effects. The results of those attempts allowed us to describe the reactivity of a new nucleophilic, mono stabilized iodonium ylide towards aldehydes
2
Boussouf, Karim. "Etude systématique des complexes Znq+Imn (où q = 0, 1, 2; n = 1 – 4)." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1094/document.
Анотація:
Le but de ce travail est d'examiner la capacité des fonctionnelles M05-2X, M05-2X+D3, PBE0, PBE0+D3, PBE, PBE+D3 et M11 avec ou sans inclusion de la correction de dispersion de Grimme (D3) pour la description précise et simultanée des complexes organométalliques de taille moyenne et leur utilisation dans l’étude de la structure d’équilibre, la stabilité, la spectroscopie et la liaison chimique (covalente, transfert de charge et Van der Waals (vdWs). Ceci a été fait par une comparaison directe des résultats obtenus par ces fonctionnelles avec ou sans inclusion de la correction de dispersion de Grimme (D3) et ceux issus des méthodes explicitement corrélées (R)CCSD(T)-F12 et (R)MP2-F12. Nous avons démontré que les fonctionnelles M05-2X+D3 et PBE0+D3 en connection avec la base 6-311++G(d,p) sont les fonctionnelles de choix. Ceci a été illustré à travers une étude systématique des complexes Zn+qIm (q=0, 1,2) qui jouent un rôle important en chimie, en biologie, en environnement et en industrie. Pour les complexes Zn+qIm (q=0, 1, 2), nous avons comparé les résultats obtenus aux niveaux M05-2X, M05-2X+D3, PBE0, PBE0+D3, PBE, PBE+D3, M11 et ceux issus des méthodes explicitement corrélées (R)CCSD(T)-F12 et (R)MP2-F12. A travers ces comparaisons, nous avons établi que la capacité et la fiabilité de la fonctionnelle M05-2X(+D3) pour la décrire précisément les interactions covalentes et non-covalentes entre Znq+ et Im car elle donne des résultats en excellent accord avec ceux issus des méthodes ab initio hautement corrélées. Les fonctionnelles PBE0 et M11 peuvent être aussi utilisées pour les applications.Par la suite, nous allons profiter de la haute performance des fonctionnelles M05-2X et PBE0 avec ou sans inclusion de la correction de dispersion de Grimme (D3) en connection avec la base 6-311++G(d,p) pour étudier la structure d’équilibre, la stabilité, la spectroscopie et la liaison chimique (covalente, transfert de charge et van der Waals (vdWs) des complexes Znq+Imn (q = 0, 1, 2 ; n = 1–4). Ce travail à l’échelle microscopique, est utile pour comprendre la structure et la liaison se produisant dans les sites actifs contenant du zinc dans des systèmes biologiques (e.g. protéines). De plus, nos résultats peuvent être utilisés pour la détermination des champs de force précis pour les métalloprotéines ou les ZIFs.Les structures de type zéolithe–imidazole (Zeolitic–Imidazolate Frameworks ou ZIFs) sont composées de molécules organiques (e.g. molécules imidazoles) liées entre elles par des ions métalliques bivalents M+2 (e.g. M2+ = Zn+2/Co+2). Ces composés présentent une structure topologique bien stabilisée avec une large diversité de structure. Ils présentent ainsi une forte porosité qui est potentiellement utilisé dans la capture et le stockage du CO2 et dans son piégeage sélectif.Ces quantités au niveau microscopique sont nécessaires pour déduire les propriétés macroscopiques et thermochimiques de ces composés avec une bonne précision après incorporation dans des simulations dynamiquesThe main goal of this work is to examine the capabilities of M05-2X, M05-2X+D3, PBE0, PBE0+D3, PBE, PBE+D3 and M11 functionals with and without inclusion of D3 dispersion correction for the accurate description of medium sized organometallic compounds and therefore their use for the determination of study of the equilibrium structure, the stability, the spectroscopy and the chemical bonding (covalent, charge transfer and van der Waals) of Znq+Im (q = 0,1,2) complexes. This is done through close comparisons of the results obtained by the M05-2X, M05-2X+D3, PBE0, PBE0+D3, PBE, PBE+D3, M11 functionals with and without inclusion of D3 dispersion correction and those from the standard ((R)MP2 and (R)CCSD(T)) and explicitly correlated ab initio methods (R)CCSD(T)-F12 and (R)MP2-F12. Therefore, we definitely establish that M05-2X+D3 and PBE0+D3 in connection with the 6-311++G(d,p) basis set are the methods of choice for the accurate description of medium sized organometallic compounds. This is illustrated through a systematic study of Zn+qIm of (q=0, 1, 2) complexes which play crucial roles in chemical, biological and industrial domains. Through these comparisons, we show that the results obtained at the M05-2X, M05-2X+D3, PBE0, PBE0+D3, PBE, PBE+D3, M11 levels are in good agreement with those explicitly correlated (R)MP2-F12 and (R)CCSD(T)-F12 methods. Through these comparisons, our study establishes the ability and reliability of M05-2X(+D3) functional for the accurate description of covalent and noncovalent interactions between Znq+ and Im since it leads to close agreement with the large ab initio techniques. PBE0 and M11 may be used also for that purposes. Then, we used high performance M05-2X and PBE0 functionals with and without inclusion of D3 dispersion correction in connection along with the 6-311++G(d,p) basis set to study the equilibrium structure, the stability, the spectroscopy and the chemical bonding (covalent, charge transfer and van der Waals) of Znq+Imn (q = 0, 1, 2, n = 1−4) complexes. This work, at the microscopic level, is useful for understanding the structural and bonding occurring in naturally zinc-binding sites and to figure out the behavior of much more complex biological systems. This should help for designing new zinc-binding proteins and more generally new metal sites in known proteins or ZIFs. The structural backbone of ZIFs is constructed from tetrahedral units formed by one bivalent metal ion (M2+ = Zn2+/Co2+) and four imidazolate anions. Such compounds present a well-established structural topology with a large structural diversity. They exhibit a high porosity which is potentially used for gas storage and separation techniques.Such quantities at the microscopic level are needed to deduce the macroscopic and thermochemical properties of these compounds with good accuracy after incorporation into dynamical simulations
3
Levell, Tamzyn J. "Substituted Fischer carbene complexes of molybdenum(0)." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/46250.
Анотація:
The synthesis and structure elucidation of fourteen novel Fischer ethoxy- and amino carbene
complexes of molybdenum and chromium metals of the type [(CO)3L2M=C(X)R] were performed.
Substitution of the parent pentacarbonyl complex [(CO)5M-C(OEt)(R)]; M = Mo, Cr; R = 2-thienyl,
2-furyl; with mono- and bidentate phosphine ligands yielded the corresponding tetracarbonyl
complexes [(CO)4(PR’3)M-C(OEt)R] with M = Mo, Cr, R = 2-thienyl, 2-furyl and R’ = Ph, Cy or
tricarbonyl complexes [(CO)3(DPPE)Mo-C(OEt)(2-furyl)], respectively. Aminolysis of these novel
complexes resulted in substitution of the ethoxy substituent with an amino group. Full
characterisation of these novel complexes included infrared spectroscopy, NMR (1H, 13C, 31P)
spectroscopy, x-ray crystallography and mass spectral analyses. From the characterisation data, it
was found that the cis isomer was dominant for the tetracarbonyl carbene complexes whereas the
mer isomer was favoured in most cases for the tricarbonyl carbene complexes.
Structural elucidation of nine of the novel complexes was confirmed with x-ray crystallography. The
amino carbene complexes showed preference for a syn conformation of the oxygen atom of the
furyl moiety and the nitrogen atom of the amino moiety in the crystal form. The ethoxy carbene
complexes showed a preference for the anti conformation in the crystal form. The NMR analysis
showed that resonance between the metal-carbene carbon-heteroatom stabilisation is more
prevalent in the case of the amino carbene complexes.
DFT calculations were performed for eleven of these complexes and their isomers. The infrared
stretching modes were calculated and compared to experimental data. The HOMO and LUMO
position and energy gaps were calculated. It was observed that the HOMO in all calculated
complexes lay on the metal centre, while the LUMO was centred on the carbene carbon. It was
found that the HOMO-LUMO gap was larger for the amino Fischer carbene complexes than for the
ethoxy Fischer carbene complexes. From frontier orbital considerations, it is concluded that ligand
substitution of carbonyls by phosphines as well as carbene substituent alterations does not seem to
improve the reactivity of the novel complexes of this study particularly for the potential application
as metathesis catalysts. The performed DFT calculations, in the future, can help determine which
type of catalytic reactions these fourteen complexes would be most effective for.Dissertation (MSc)--University of Pretoria, 2014.
tm2015
Chemistry
MSc
Unrestricted
4
Fraser, Roan. "Fischer and N-heterocyclic carbene complexes of chromium(0)." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/31504.
Анотація:
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
5
Pretorius, René. "Fischer and N-heterocyclic carbene complexes of tungsten(0)." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/31515.
Анотація:
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
6
Raude, Amandine. "Modélisation thermomécanique d'un composite carbone/carbone à texture complexe." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0260/document.
Анотація:
Les composites C/C sont utilisés dans les domaines du spatial et de l'aéronautique pour leurs excellentes propriétés thermomécaniques depuis la température ambiante jusqu'aux très hautes températures (> 3000°C). Ces matériaux ont une architecture complexe constituée de nappes de fibres stratifiées et aiguilletées. Leur utilisation en zones fortement sollicitées et à haute température nécessite une maîtrise des propriétés thermiques et mécaniques. Actuellement, la conception du matériau se fait de manière empirique et itérative. Pour l'accélérer, le développement d'un modèle numérique multi-échelle prédictif du comportement du composite C/C est proposé. Ce matériau a tout d'abord été caractérisé morphologiquement à ses différentes échelles caractéristiques, les propriétés thermomécaniques de ses constituants élémentaires ont également été identifiées. A l'échelle microscopique, les fils sont représentés de façon homogène et thermoélastique à partir des taux de constituants qui leurs sont associés. A l'échelle mésoscopique, deux aspects morphologiques semblent prédominants : son architecture ainsi que ses porosités et endommagements. Leur effet sur le comportement effectif du composite C/C est étudié dans le but d'évaluer leur influence relative et d'aboutir à une description suffisamment fine de leurs morphologies dans la modélisation effectuée. Un modèle de matériau idéalisé ainsi qu'un modèle basé images ont été développés. La simulation d'essais macroscopiques a révélé que ces deux aspects avaient un effet non-négligeable sur le comportement effectif du composite C/C et ont permis le développement et la validation d'un modèle prédictif multi-échelle de ce matériau, prenant en compte les caractéristiques précédentes, et permettant le lien entre l'échelle de ses constituants élémentaires et celle macroscopiqueC/C composites are used in space and aeronautics for their excellent thermomechanical properties from room temperature to very high temperatures (> 3000°C). These materials have a complex architecture consisting of layers of laminated and needled fibers. Its use in highly stressed areas and at high temperature requires control of thermal and mechanical properties. Currently, the design of the material is done empirically and iteratively. To accelerate it, the development of a multi-scale digital model of the C/C composite is proposed. This material was first morphologically characterized at its different characteristic scales, the thermomechanical properties of its elementary constituents were also identified. At the microscopic scale, the wires are represented homogeneously and thermoelastically from the constituent levels associated with them. At the mesoscopic scale, two morphological aspects seem to predominate: its architecture as well as its porosities and damages. Their effect on the effective behavior of the C/C composite is studied in order to evaluate their relative influence and to arrive at a sufficiently fine description of their morphologies in the modeling carried out. An idealized material model as well as an image based model have been developed. The simulation of macroscopic tests revealed that both aspects had a non-negligible effect on the effective behavior of the C/C composite and allowed the development and validation of a multi-scale predictive model of this material, taking into account the preceding characteristics, and allowing the link between the scale of its elementary constituents and the macroscopic one
7
Rochon, Alexandra. "Cycloaddition Reactions of Ni(0) Difluorocarbene Complexes: Investigating the Formation of Various Perfluorometallacycles." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39026.
Анотація:
Formation of carbon–fluorine and carbon–fluoroalkyl bonds via transition metal complexes represents an efficient synthetic route towards a wide array of valuable fluorinated organic compounds and fluorinated metallacycles offer a potentially green and atom economical pathway towards these functionalized fluorocarbons. This thesis is focused on cycloaddition reactions of Ni=CF2 complexes with fluoroalkenes (FAs) and acetylenes.
Cycloaddition reactions of the FAs vinylidene fluoride (CF2=CH2) and perfluoro(methyl vinyl ether) [CF2=CF(OCF3)] with the electron-rich Ni(0) fluorocarbene, Ni=CF2[P(OMe)3](dppe) affords stable metallacyclobutane complexes, likely through a 1,4-diradical mechanism previously investigated for analogous reactions using computational chemistry. With CF2=CHF (TrFE), however, the observed products are the C3 alkene E-CHF=CF(CF3) and the metallacyclopentane complex, Ni(C4H2F6)(dppe), derived from oxidative coupling of two additional equivalents of TrFE. It is proposed that the instability of the initially formed metallacyclobutane gives rise to a 2,1-F shift, yielding the C3 alkene complex. Reaction of the latter with excess TrFE then liberates the C3 alkene, forming the TrFE alkene complex followed by the observed metallacyclopentane product. In the reaction of 1a with chlorotrifluoroethylene (CF2=CFCl) a single regioisomer of the metallacyclobutane is observed, but reacts further in THF solvent via α-Cl migration to Ni, affording the tetrafluoroallyl complex, NiCl(CF2CF=CFH), in which one F has been replaced by a hydrogen. Finally, reaction of 1a with hexafluoropropene [CF2=CF(CF3), HFP] takes an unprecedented turn, affording the Ni trifluoromethyl perfluoroalkenyl complex from formal transfer of one F from HFP to the Ni=CF2 moiety.
The capability of 1a to perform cycloaddition with a broader substrate scope was investigating by reacting it with terminal aryl-acetylenes of varying electronic parameters. Reaction of 1a with 1.5 equivalents of 4-R-phenylacetylene afforded the expected difluorometallacyclobutenes (R = H, Cl, tBu). Further observation revealed a second acetylene insertion to yield a nickelacyclohexadiene in the first example of a 4- to 6-membered ring expansion of perfluorometallacycles. The six-membered metallacycle then undergoes reductive elimination to furnish a difluorocyclopentadiene. The electronic parameters of the aryl-acetylene substrate play a dramatic role in the selectivity of product formation. The more electron-donating substrates 4-tert-butylphenylacetylene and 1-hexyne stabilize the metallacyclobutene, while the electron-withdrawing 4-chlorophenylacetylene affords a more reactive metallacyclobutene making it more prone to the second acetylene insertion. Phenylacetylene represented a middle-ground between the two systems and proved effective for further characterization studies. The electronic effect of the surrounding ancillary ligand system was also studied by substituting dppe in 1a for P(OMe)3 and dipe to give analogous Ni(0) difluorocarbene complexes 1b and 1c (dipe = 1,2-bis(diisobutylphosphino)ethane). The -acidic phosphite ligands in 1b gave exclusively nickelacyclohexadiene and difluorinated cyclopentadiene due to a reactive metallacyclobutene, whereas the more electron rich 1c formed the metallacyclobutene product almost exclusively. The results presented here will allow for future investigations of fluorinated metallacycle reactivity, increasing our ability to prepare value-added fluorocarbon products for pharma, agrochemicals, and polymer applications.
8
Stortoni, Federica. "Clinique contemporaine des Français d’origine italienne : une posture complexe : "Je suis Français… mais mon père était italien…"." Paris 8, 2007. http://octaviana.fr/document/133380785#?c=0&m=0&s=0&cv=0.
Анотація:
A la suite d’un travail préliminaire d’une quarantaine d’entretiens de recherche avec des Italiens et leurs descendants à Paris, l’on a constaté, pour ce groupe spécifique, une posture complexe qui interroge, en psychologie, les théories identitaires, et qui peut se décrire comme une position d’invisibilité et de silence. En effet, les descendants des migrants italiens se décrivent à partir de leurs attachements français, tout en montrant à bas bruit leurs attachements italiens, qu’ils interrogent dans des moments de questionnement (naissance d’un enfant, mort d’un parent) et de difficultés dans la vie. Les diverses théories identitaires se sont néanmoins révélées insuffisantes pour interroger cette position singulière, parce que la notion d’attachements semble plus appropriée. L’auteur interroge alors leur histoire spécifique liée aux migrations pour comprendre comment ces générations ont été pensées par leurs parents, par la société et par les événements historiques. L’auteur fait alors deux hypothèses principales : Il existerait une stratégie de fabrication des Italiens qui resterait inachevée sur plusieurs générations. L’Italie appartenant à leurs questionnements pourrait constituer une source de dispositifs thérapeutiques, si l’on repère les éléments thérapeutiques actifs italiens et si on les met en œuvre dans un dispositif spécifique de clinique et recherche ethnopsychiatrique. Ces ressources fonctionneraient comme des leviers techniques de fabrication de devenirsAs a result of around forty research interviews with Italians and Italian descendants in Paris, the author has ascertained that this specific group demonstrates a complex position, which in psychology refers to identity theories and can be described as a position based on invisibility and silence. In fact, the descendants of Italian migrants describe themselves through their French “attachments” but simultaneously they discreetly demonstrate their Italian “attachments”, which return in moments of life transition (the birth of a child, the death of a parent) and in difficult life experiences. Various identity theories have proven to be insufficient for explaining this unique position, thus the notion of “attachments” seems more appropriate. The author investigates the particular history of this group, which is intimately connected to migration, in order to understand how these generations have been thought of by their parents, society and through various historical events. The author puts forth two main hypotheses: there is a construction strategy that remains incomplete over many generations. Italy, as part of the puzzle of this group, could be a source for therapeutic instruments and devices as long as the active therapeutic Italian elements are located and are applied in a specific system that is both clinical and dedicated to ethnopsychiatric study. These resources function as technical tools for constructing "becomings" (in the Deleuzian sense). "
9
Ansell, Melvyn B. "Novel (N-heterocyclic carbene)-palladium(0) complexes as catalysts in element-element bond additions to unsaturated moieties." Thesis, University of Sussex, 2017. http://sro.sussex.ac.uk/id/eprint/68072/.
Анотація:
The focus of this thesis is the synthesis of novel palladium(0) complexes bearing the ligand 1,3,4,5-tetramethylimidazol-2-ylidene (ITMe), a small percentage buried volume N-heterocyclic carbene. These complexes have been assessed as mediators for the 1,2-additions of hetero element-element bonds to unsaturated organic moieties. In particular, Si-Si, Si-B and B-B bond additions to alkynes and azobenzenes were chosen as reactions of interest due to their challenging nature. Chapter 1 introduces the concept of transition metal mediated element-element additions to alkynes and includes a thorough review on the current literature state. Chapter 2 describes the first solution based synthesis of [Pd(ITMe)2] and its in situ reactivity with Me3SiSiMe3 under mild conditions to form the novel complex cis-[Pd(ITMe)2(SiMe3)2], the first NHC-bearing complex resulting from the oxidative addition of hexamethyldisilane to a palladium centre. The use of this complex as a pre-catalyst for the bis(silyl)ation of electronically and sterically challenging internal acetylenes using non-activated disilanes is reported. A series of novel 1,2-disilylstilbenes were synthesized in high yield and with 100% Z-stereoselectivity. Chapter 3 details the use of [Pd(ITMe)2(PhC≡CPh)], the first bis(N-heterocyclic carbene)Pd(0)-alkyne complex, as a highly reactive pre-catalyst in the silaboration of terminal and internal alkynes to yield a number of known and novel 1-silyl-2-boryl alkenes. Unprecedented mild reaction temperatures for terminal alkynes, short reaction times and low catalytic loadings are reported. During mechanistic studies, cis-[Pd(ITMe)2(SiMe2Ph)(Bpin)] was directly synthesized by oxidative addition of PhMe2SiBpin to [Pd(ITMe)2(PhC≡CPh)]. This represents a very rare example of a (silyl)(boryl)palladium complex. A plausible catalyst decomposition route was also examined. In Chapter 4, [Pd(ITMe)2(PhC≡CPh)] acts as a highly reactive pre-catalyst in the unprecedented homogeneous catalyzed diboration of terminal and internal alkynes, yielding a number of novel and known syn-1,2-diborylalkenes in a 100% stereoselective manner. DFT calculations conducted by our collaborators suggest that a similar reaction pathway to that proposed for platinum phosphine analogues is followed, and that destabilization of key intermediates by ITMe is vital to the overall success for the palladium-catalyzed B-B addition to alkynes. Chapter 5 reports the use of [Pd(ITMe)2(PhC≡CPh)] as a highly active pre-catalyst in the diboration and silaboration of azobenzenes to synthesize a series of novel functionalized hydrazines. The reactions proceed using commercially available diboranes and silaboranes under mild reaction conditions. Preliminary investigations into further reactivity of [Pd(ITMe)2(PhC≡CPh)], [Pd(ITMe)2] and cis-[Pd(ITMe)2(SiR3)2] (SiR3 = SiMe2Ph or SiMe3) are reported in Chapter 6. This includes the oxidative cleavage of Me3GeGeMe3 by [Pd(ITMe)2(PhC≡CPh)] to form the novel cis-[Pd(ITMe)2(GeMe3)2] and an initial study into the catalytic alkyne digermylations. The hydrogenation of diphenylacetylene to form Z-stilbene using an amine-borane and catalytic quantities of [Pd(ITMe)2(PhC≡CPh)] was also investigated. Finally, the stoichiometric reactions of allyl bromides with cis-[Pd(ITMe)2(SiR3)2] to form the novel complexes trans-[Pd(ITMe)2(SiR3)(Br)] are detailed.
10
Autier, Antoine. "Charles Rist et la question de la dévaluation en France (1919-1937) : un "complexe monétaire" à l'épreuve des faits." Paris 8, 2012. http://octaviana.fr/document/177810785#?c=0&m=0&s=0&cv=0.
Анотація:
La thèse se propose d’expliquer les prises de position de l’économiste français Charles Rist alors qu’il est confronté, à deux moments distincts de la période 1919-1937, à une interrogation commune : faut-il ou non dévaluer le franc ? Cette thèse, où s’articulent Histoire de la pensée économique et Histoire des faits économiques, est structurée en trois parties. La première dresse un panorama de l’économie française sur l’ensemble de la période considérée. La deuxième met en évidence la façon dont Rist exprime ses idées sur la stabilisation monétaire dans les années 1920 et plus précisément la façon dont il participe à la stabilisation du franc. La troisième partie poursuit l’analyse des idées monétaires de Rist dans l’environnement des années 1930 où à la crise économique succède une crise monétaire donnant le branle à la dislocation de l’étalon-or, et précise l’évolution de sa position sur la dévaluation du franc. Dans la conclusion nous embrassons l’ensemble du parcours de Rist que nous éclairons à l’aide d’éléments analytiques tirés de ses travaux théoriques pour identifier l’existence d’un « complexe monétaire » chez lui, mais aussi pour déterminer dans quelle mesure il a pu ou non le dépasser dans des contextes historiques différentsThe thesis aims at explaining the positions taken by the French economist Charles Rist when, at two different moments in the period 1919-1937, he was confronted to the same question: whether or not devaluating the franc? This thesis, which mixes the History of economic thought and the History of economic facts, is structured in three parts. The first provides an overview of the French economy in the entire period. The second shows how Rist expressed his ideas on monetary stabilization in the 1920s, and more precisely the way he took part to the stabilization of the franc. The third goes on analyzing the monetary ideas of Rist in the environment of the 1930s when the economic crisis was followed by a currency crisis setting in motion the collapse of the gold standard, and specifies the evolution of his position on the devaluation of the franc. In the conclusion we embrace the whole course of Rist and we enlighten it with analytical elements derived from his theoretical work to identify the existence in him of a "monetary complex", but also to determine how much he could overcome it in different historical contexts
Книги з теми "Complexe de carbone(0)":
1
Hansen, Shaevitz Marjorie, ed. Le complexe de la superfemme. Montréal, Qué: Éditions Québec/Amérique, 1986.
2
Chauvin, Remi, and Yves Canac, eds. Transition Metal Complexes of Neutral eta1-Carbon Ligands. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-04722-0.
3
Fischer, H., ed. Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals. Part 1. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-48466-0.
Частини книг з теми "Complexe de carbone(0)":
1
Sakaki, Shigeyoshi, and Yasuo Musashi. "Hydrogenation of Carbon Dioxide." In Catalysis by Metal Complexes, 79–105. Boston, MA: Springer US, 2002. http://dx.doi.org/10.1007/0-306-47718-1_4.
2
Dierick, Steve, and István E. Markó. "NHC Platinum(0) Complexes: Unique Catalysts for the Hydrosilylation of Alkenes and Alkynes." In N-Heterocyclic Carbenes, 111–50. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2014. http://dx.doi.org/10.1002/9783527671229.ch05.
3
Solà, Miquel, Miquel Duran, and Maricel Torrent. "The Dötz Reaction: A Chromium Fischer Carbene-Mediated Benzannulation Reaction." In Catalysis by Metal Complexes, 269–87. Boston, MA: Springer US, 2002. http://dx.doi.org/10.1007/0-306-47718-1_11.
4
Cosin, S., Carolina A. Pinto, P. Souza Santos, and Francisco Rolando Valenzuela-Díaz. "Complex Carbon-Mineral Sorbents from Common Clay." In Advanced Powder Technology IV, 734–39. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-984-9.734.
5
Bockstedte, M., A. Gali, T. Umeda, N. T. Son, J. Isoya, and Erik Janzén. "Signature of the Negative Carbon Vacancy-Antisite Complex." In Silicon Carbide and Related Materials 2005, 539–42. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-425-1.539.
6
Gali, A., T. Hornos, Peter Deák, N. T. Son, Erik Janzén, and W. J. Choyke. "Theoretical Investigations of Complexes of p-Type Dopants and Carbon Interstitial in SiC: Bistable, Negative-U Defects." In Materials Science Forum, 519–22. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-963-6.519.
7
Yusop, Mohd Rafii, Yusuff Oladosu, Abdul Rahim Harun, Asfaliza Ramli, Ghazali Hussin, Mohd Razi Ismail, and Norhani Abdullah. "Application of mutation techniques and genotype × environment interaction for grain yield in ion beam induced mutant rice lines tested in multiple locations in Malaysia." In Mutation breeding, genetic diversity and crop adaptation to climate change, 226–34. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789249095.0023.
Анотація:
Abstract Genotype evaluation for stability and high yield in rice is an important factor for sustainable rice production and food security. These evaluations are essential, especially when the breeding objective is to release rice with high yields, adaptability and stability for commercial cultivation. To achieve this objective, this study was carried out to select high-yielding rice genotypes induced by ion beam irradiation. Seeds of the rice variety 'MR219' were subjected to different doses of 320 MeV carbon-ion beam irradiation to determine the optimum dose to produce high mutant frequency and spectrum. The optimum dose was 60 Gy. After several cycles of selection and fixation between 2009 and 2014 (M0-M6), six prospective lines with desirable characters were selected at the M6 generation. The selected mutant lines along with other mutant varieties were then tested at five locations in two planting seasons to select high-yielding and stable genotypes. The experiment was conducted in a randomized complete block design with three replications across the locations and seasons. The pooled analysis of variance revealed highly significant differences (p ≤ 0.01, 0.05) among genotypes, among locations and among genotypes by location by season (G×L×S interaction) for the yield traits except for seasons and genotype by season (G×S interaction). Based on univariate and multivariate stability parameters, rice genotypes were classified into three main categories. The first group comprised genotypes with high yield stability along with high yield per hectare. These genotypes include ML4 and ML6 and are widely adapted to diverse environmental conditions. One line exhibited high yield per hectare but low stability; this genotype (ML9) is suitable for specific environments. The last group had low yield per hectare and high stability and included 'MR220', 'Binadhan4' and 'Binadhan7'. This final group is more suitable for breeding specific traits or perhaps has yield component compensation. Hence, rice mutant lines ML4 and ML6 were recommended for commercial cultivation in Malaysia.
8
Chung Wai Mak, Thomas, Yu-San Cheung, Gong-Du Zhou, and Ying-Xia Wang. "Structural Chemistry of Group 14 Elements." In Structural Chemistry across the Periodic Table, 129–208. Oxford University PressOxford, 2023. http://dx.doi.org/10.1093/oso/9780198872955.003.0004.
Анотація:
Abstract This chapter covers the following topics: allotropic modifications of carbon; compounds of carbon, bonding in carbon compounds; gold and silver carbone complexes; phosphine-sulfoxide carbon(0) complexes; structural chemistry of silicon; structures of halides and oxides of heavier Group 14 elements; polyatomic anions of Ge, Sn, and Pb; organometallic compounds of heavier Group 14 elements; tetrel bonding interactions in tin and lead compounds; as well as tetrylones.
9
Ostrowska, Sylwia, and Steven P. Nolan. "Carbon-Carbon Bond Formation Via Metal Carbene Complexes." In Reference Module in Chemistry, Molecular Sciences and Chemical Engineering. Elsevier, 2022. http://dx.doi.org/10.1016/b978-0-32-390644-9.00091-3.
10
"Carbon-carbon bond formation." In Catalysis by Metal Complexes, 209–36. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/0-306-47510-3_6.
Тези доповідей конференцій з теми "Complexe de carbone(0)":
1
Kosmachevskaya, Olga Vladimirovna, Elvira Ilgizovna Nasybullina, Natalya Nikolaevna Novikova, Konstantin Borisovich Shumaev, and Alexey Fedorovich Topunov. "HEMOGLOBIN THIOLS: BIOLOGICAL SIGNIFICANCE AND REGULATION." In International conference New technologies in medicine, biology, pharmacology and ecology (NT +M&Ec ' 2020). Institute of information technology, 2020. http://dx.doi.org/10.47501/978-5-6044060-0-7.20.
Анотація:
Human hemoglobin has two reactive cysteines (Cys-93β) located on the surface of the molecule. Inclusion of
these thiols in the composition of dinitrosyl iron complexe is one way of regulating their reactivity. The thiols
bound into complexes exhibit enhanced reactivity with electrophiles and are protected from oxidation by
tert-butyl hydroperoxide.
2
Ghorbel, Elhem, and Mariem Limaiem. "Efficiency of Bio-Sourced Composites in Confining Recycled Aggregates Concrete." In 4th International Conference on Bio-Based Building Materials. Switzerland: Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/www.scientific.net/cta.1.505.
Анотація:
This research investigates the efficiency of using Flax Fibers reinforced bio-sourced polymer by comparison to traditional system based on Carbone Fiber Reinforced Epoxy Polymer in order to confine recycled aggregates concrete. Four concrete formulations have been formulated by incorporating recycled aggregates from demolition waste (0%, 30%, 50% and 100%). An air-entraining agent was added to the formulations to achieve the level of 4% occluded air. The main objective is to discuss and to evaluate the effectiveness of confining them using bio-sourced composite by comparison to traditional ones. To hit this target, the developed approaches are both experimental and analytical. The first part is experimental and aimed to characterize the mechanical behavior of the materials: the composites used in the confining process the unconfined concrete (effect of incorporating recycled aggregates on the overall mechanical characteristics). We establish that bio-sourced composites are efficient in strengthening recycled aggregates concrete especially if they are air-entrained. The second part of this work is dedicated to analytical modeling of mechanical behavior of confined concrete with composite under compression based on Mander’s model. The input parameters of the model were modified to consider the rate of recycled aggregates incorporation. Comparison between experimental results and the modified Mandel’s Model is satisfactory.
3
Liu, Zhenshun, and Hongdong Zhen. "Research on Simplified Method of Transients Combining and Loading in Fatigue Crack Growth Analysis of Carbon Steel Nuclear Piping." In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81640.
Анотація:
The fatigue crack growth analysis of nuclear piping is a nonlinear calculation process. The loading sequence and combination mode could affect the results. How to consider these effects is unclear. Fatigue crack growth analysis includes a large number of nonlinear iterative calculations, and the calculation speed is slow. This paper selects carbon steel nuclear piping as the research object. Based on the analysis process provided by ASME code XI volume, a simplified analysis method is explored by introducing the reference crack depth a’ and the envelope transient. The simplified analysis method is conservative because it has been proved that the crack growth rate is positively related to the crack size only if the maximum stress intensity factor is greater than 0 and the minimum stress intensity factor is less than 0. The simplified analysis method is proved to be able to significantly improve the calculation speed by comparing the number of iterative calculations in the simplified analysis method and in the conventional analysis method. The results indicate that the simplified analysis method could provide a conservative way of loading and combining the complex transients and could significantly reduce the number of nonlinear iterative calculations in the process of crack fatigue growth analysis for carbon steel nuclear piping when the maximum stress intensity factor greater than 0 and the minimum stress intensity factor is less than 0.
4
SYCHLA, JAKUB, and K. T. TAN. "INVESTIGATING EFFECTS OF FIBER LAYERS IN 3D PRINTED CARBON FIBER REINFORCED POLYMER COMPOSITES." In Proceedings for the American Society for Composites-Thirty Seventh Technical Conference. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/asc37/36490.
Анотація:
The prominence of carbon fiber reinforced polymers (CFRP) has made advancements in many industries including aerospace, automotive, and sporting goods. Using additive manufacturing to produce the CFRPs allows prototyping complex geometries while keeping the structure lightweight and producing a high strength material. This work studies the printing parameters and flexural strength of 3D printed onyx based CFRP samples, looking at the effect of variable parameters affecting the carbon fiber layers. A Markforged Mark 2 3D printer, which utilizes a dual head print head, is used to print nine different configurations of the CFRP composite. Each sample consists of 24 layers of material with an infill of 50%, two wall layers, as well as four roof and floor layers. The configurations examine the extreme of three parameters with reference to the carbon fiber, being the fiber angle, number of fiber layers, and the position of the fiber layers. The carbon fiber print angle is printed with layers at 0˚, 0˚/45˚, and 0˚/90˚ with the latter two switching between the respective angles for every layer of carbon fiber printed. The number of fiber layers are set to be either 4 or 16. The position of fiber layers includes all layers (excluding roof/floor); the two outer most layers (which are directly below/above the roof/floor layers); and the four middle layers of the sample. The 3D printed CFRP specimens are subjected to three-point bend test, and three samples are tested for each configuration. One sample is chosen from each configuration to undergo pre-test and post-test inspection using X-ray micro-computed tomography to examine any internal damages.
5
Kalia, Karun, and Amir Ameli. "Tensile Properties of 3D-Printed Polycarbonate/Carbon Nanotube Nanocomposites." In ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/smasis2018-8048.
Анотація:
Fused deposition modeling (FDM) is highly commercialized Rapid Prototyping (RP) technology for its ability to build complex parts with low cost in a short period of time. The process parameters in the FDM play a vital role in the mechanical properties of the polymeric parts. Most of the research studies show that the variable parameters such as orientation, layer thickness, raster angle, raster width, and air gap are some of the key parameters that affect the mechanical properties of FDM-processed polymeric parts. However, no reports have been made regarding the influence of nozzle diameter with raster width on the tensile properties of FDM fabricated polymeric parts. This work was devoted to achieving improved and isotropic mechanical properties in polycarbonate (PC) and PC/carbon nanotube (PC/CNT) nanocomposites by investigating the effect of printing parameters in FDM process. The nozzle diameter to raster width ratio, α was found to significantly affect the mechanical properties. The printing direction dependency in tensile properties were studied with the ratio α < 1 and α≥ 1 at three different raster angles of 0°, 45°/−45° and 90°. For α < 1, Ultimate tensile strength and modulus of elasticity were higher for 0°, compared to 45°/−45° and 90° raster angles. However, for α ≥ 1, the ultimate tensile strength and the modulus of elasticity showed little dependency to print direction. This certainly determines the decrease in anisotropy at higher values of α. Mesostructure characterization with microscopy and image analysis were used to further explain the printing behavior and the resultant properties of the printed samples.
6
Sheikh-Ahmad, Jamal, and Rahul Yadav. "Force Prediction in Milling of Carbon Fiber Reinforced Polymers." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81909.
Анотація:
Fiber reinforced polymers are widely used in the transportation, aerospace and chemical industries. In rare instances these materials are produced net-shape, and secondary processing such as machining and assembly may be required to produce a finished product. Because fiber reinforced polymers are heterogeneous materials, they do not machine in a similar way to metals. Thus, the theory of metal machining is not valid for the analysis of machining of fiber reinforced composites. Previous attempts in modeling this problem have adopted Merchant’s theory for metal cutting by assuming that chip formation takes place in a shear plane where the inclination angle is determined by the minimum energy principle. This class of models showed that model predictions are valid only for fiber orientations less than 60°. Furthermore, these models are incapable of predicting cutting forces for multidirectional laminates or complex tool geometry. The work presented here focuses on providing a predictive model for the cutting forces in milling both unidirectional and multidirectional laminates. The model is based on the specific cutting energy principle and accounts for a wide range of fiber orientations and chip thickness. Results from this model were found to be in good agreement with experimental results over the entire range of fiber orientations from 0 to 180°.
7
Xiao, Huining, Robert Pelton, and Archie Hamielec. "Novel Non-ionic Polymeric Flocculants for Mechanical Pulps: An Overview." In The Fundamentals of Papermaking Materials, edited by C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1997. http://dx.doi.org/10.15376/frc.1997.2.1121.
Анотація:
Novel comb copolymer with long polyacrylamide backbones bearing very short polyethylene glycol (PEG) pendant chains were prepared by the free-radical copolymerisation of acrylamide (AM) and PEG acrylate macromonomers. The copolymers are effective retention aids for mechanical pulps in retaining fines and precipitated calcium carbonate (PCC). The optimum copolymer stricture had a molecular weight greater than 3 million and contained 0.5 – 1 .0 % of PEG pendant chains with 9 to 23 polyether repeat units. The retention of fines induced by copolymer/phenolic resin (PFR) dual-polymer system follows the mechanism called “complex bridging flocculation” . According to this mechanism, the copolymer molecules aggregate in the presence of PFR to form a colloidal dispersed polymer complex which hetero-flocculates with fine particles. The interpolymer complex formation were experimentally observed through precipitate isotherms measurement, dynamic viscosity measurement and fluorescent microscopy.
8
MONDAL, ANIRBAN, KUNTAL MAITY, MRINAL C. SAHA, and YINGTAO LIU. "DIRECT-INK-WRITING (DIW) OF HIGHER WEIGHT CONCENTRATION OF MILLED CARBON FIBER (MCF) REINFORCED EPOXY COMPOSITE." In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35760.
Анотація:
Additive manufacturing or 3D printing of short carbon fiber composites is highly inclined toward thermoplastic material. Recently, there is some interest in developing 3D printing technology for thermosetting polymers and composites. Direct-ink-writing (DIW) of short fiber epoxy composites containing milled carbon fibers (MCF) exhibits the potential to replace the traditional composite material as it showcases the inherent capability of fabricating complex geometries, facile material processing, continuous printing capability coupled with low cost. Previous research in 3D printing of short carbon fiber epoxy composites suffered heavily from the limitation of printing low carbon fiber weight concentrations. This study developed a straightforward technique of designing the epoxy ink containing high weight concentration MCF (~40wt%) and a small concentration of thixotropic filler (3-wt%) for DIW using a pneumatic pressure-driven extruder having micron size tapered nozzle. This paper also intends to contribute to a better understanding of the effect of printing parameters on DIW. Furthermore, the printing parameters were optimized using non-dimensionalized constant C. Optimized printing condition was further used to print different geometry ranging from dog bone with 100% infill to 4-layer hollow circle and 3-layer hollow square with 0% infill. Lastly, ink exhibits the capability to self-support multi-layer geometrical structures during printing.
9
Atong, Duangduen, and Viboon Sricharoenchaikul. "Enhanced Gasification of Waste Glycerol Over Ni/SiC Catalyst for Fuel Gas Production." In ASME 2009 3rd International Conference on Energy Sustainability collocated with the Heat Transfer and InterPACK09 Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/es2009-90283.
Анотація:
The amount of waste glycerol from biodiesel production increases sharply due to greater use of this alternative fuel from high cost and adverse environmental effect of conventional fossil fuel. The crude glycerol can convert to fuel gas (mainly CO, H2, and CH4) through thermochemical conversion processes such as gasification and pyrolysis. In this study, pyrolysis and gasification of glycerol waste were studied in a laboratory scale quartz tube reactor using silicon carbide (SiC) as a bed medium. In order to improve the conversion efficiency while minimizing tar formation, nickel catalyst supported by SiC was synthesized using wet impregnation method and used in some trials. It was found during pyrolysis runs that carbon and hydrogen conversion of glycerol increased with temperature of 600–800°C in the range of 18.72–95.33% and 16.26–96.30%, respectively. When varying the air fuel ratio from 0–0.25 at 800°C, complete conversion of crude glycerol may be achieved both for pyrolysis and gasification conditions. This may be due to the dominant of steam gasification reactions from 13.56% moisture content in crude glycerol which controls the overall reactions at that high temperature. However at lower temperature of 600°C, carbon and hydrogen conversion of crude glycerol decreased to 18.72–42.23% and 16.26–35.27%, respectively. Increase in residence time from 1.3–4.0 second did not significantly affect the conversion efficiency for pyrolysis at 600°C which indicated that the kinetic of these decomposition reactions proceed at rapid rates even at the minimum hold time used in this work. Catalytic conversion of crude glycerol with 10% nickel on silicon carbide (Ni/SiC) was performed using pyrolysis condition at 600°C to obtain higher conversion efficiency. The results revealed that non-reduced and reduced catalyst, could increase the production of synthesis gas as much as 1.02 and 0.56 times when compared with non-catalytic process, respectively. It may be suggested from high energy content as well as product gas quality that using Ni/SiC catalyst is suitable for thermal conversion of waste glycerol to fuel gas that may be further utilized with minimum treatment. The obtained synthesis gas may be utilized for direct heat and power or further transformed to other alternatives fuels which help increase value and at the same time minimize the waste management requirement of this industrial waste.
10
Zhang, Feng, Hui Zhang, Fei Qiu, and Qian Chen. "A Quantitatively Determining Gas Saturation Method Using Pulsed-Neutron Element Logging in Tight Gas Reservoirs." In 2022 SPWLA 63rd Annual Symposium. Society of Petrophysicists and Well Log Analysts, 2022. http://dx.doi.org/10.30632/spwla-2022-0087.
Анотація:
Tight sandstone and carbonate gas reservoirs are important types of unconventional oil and gas, and their exploration and development are of great significance to increase production and economic development. It is difficult to accurately determine gas saturation for tight gas reservoirs due to their low porosity and permeability, which differs from conventional reservoirs. In the past few decades, pulsed neutron logging technology is one of the most important means to evaluate gas saturation, especially the ratio of gamma-ray counts from pulsed neutron logging tool with long spacing detector was generally used to improve detection sensitivity for quantitatively evaluating gas saturation. However, there are complex formation minerals and pore fluid composition in tight sandstone and carbonate reservoirs, and then it will obviously affect gas saturation evaluation. In the previous study, we introduced a three-detector pulsed neutron consisting of a DT pulsed neutron generator, two He-3 thermal neutron detectors, and a LaBr3 detector located between the two thermal neutron detectors. The logging tool performs elemental measurement. In addition, the formation porosity was calculated according to the information of gamma ray and thermal neutron detected by the three detectors in previous research. In this paper, the thermal-neutron ratio of near to extra-far detector and the lithology factors from elemental yields based on the measuring information from three detector are also used to determine gas saturation and eliminate the influence of lithology. The SuperMC software is employed to build three-dimension model with the pulsed neutron tool and formation which contains different minerals, gas saturation and salinity to obtain the responses of thermal neutron and gamma-ray under complex formation conditions. In addition, the spectrum of the inelastic gamma and capture gamma are used to acquire the yields of elements, such as iron, silicon, potassium, aluminum, magnesium, calcium and carbon. The regression coefficients of different elements are obtained from the relationship between the ratio of thermal neutron count ratio and the ratio of elemental yield of the formation, which is combined with the information of thermal neutron count ratio and elemental yield to build a new interpretation model for gas saturation. The new model eliminates the influence of lithology and improves the accuracy of gas saturation determination. A complex formation containing quartz, calcite, plagioclase, chlorite and pyrite with 12% porosity and 50% gas saturation is evaluated by the conventional interpretation model with 0% gas saturation, while the interpretation model proposed in this paper evaluates 48% gas saturation, and the relative error is reduced from 100% to 4%. Finally, a field example of a tight gas reservoir from Shanxi verifies the accuracy of the new model of gas saturation.
Звіти організацій з теми "Complexe de carbone(0)":
1
Chefetz, Benny, Baoshan Xing, Leor Eshed-Williams, Tamara Polubesova, and Jason Unrine. DOM affected behavior of manufactured nanoparticles in soil-plant system. United States Department of Agriculture, January 2016. http://dx.doi.org/10.32747/2016.7604286.bard.
Анотація:
The overall goal of this project was to elucidate the role of dissolved organic matter (DOM) in soil retention, bioavailability and plant uptake of silver and cerium oxide NPs. The environmental risks of manufactured nanoparticles (NPs) are attracting increasing attention from both industrial and scientific communities. These NPs have shown to be taken-up, translocated and bio- accumulated in plant edible parts. However, very little is known about the behavior of NPs in soil-plant system as affected by dissolved organic matter (DOM). Thus DOM effect on NPs behavior is critical to assessing the environmental fate and risks related to NP exposure. Carbon-based nanomaterials embedded with metal NPs demonstrate a great potential to serve as catalyst and disinfectors. Hence, synthesis of novel carbon-based nanocomposites and testing them in the environmentally relevant conditions (particularly in the DOM presence) is important for their implementation in water purification. Sorption of DOM on Ag-Ag₂S NPs, CeO₂ NPs and synthesized Ag-Fe₃O₄-carbon nanotubebifunctional composite has been studied. High DOM concentration (50mg/L) decreased the adsorptive and catalytic efficiencies of all synthesized NPs. Recyclable Ag-Fe₃O₄-carbon nanotube composite exhibited excellent catalytic and anti-bacterial action, providing complete reduction of common pollutants and inactivating gram-negative and gram-positive bacteria at environmentally relevant DOM concentrations (5-10 mg/L). Our composite material may be suitable for water purification ranging from natural to the industrial waste effluents. We also examined the role of maize (Zeamays L.)-derived root exudates (a form of DOM) and their components on the aggregation and dissolution of CuONPs in the rhizosphere. Root exudates (RE) significantly inhibited the aggregation of CuONPs regardless of ionic strength and electrolyte type. With RE, the critical coagulation concentration of CuONPs in NaCl shifted from 30 to 125 mM and the value in CaCl₂ shifted from 4 to 20 mM. This inhibition was correlated with molecular weight (MW) of RE fractions. Higher MW fraction (> 10 kDa) reduced the aggregation most. RE also significantly promoted the dissolution of CuONPs and lower MW fraction (< 3 kDa) RE mainly contributed to this process. Also, Cu accumulation in plant root tissues was significantly enhanced by RE. This study provides useful insights into the interactions between RE and CuONPs, which is of significance for the safe use of CuONPs-based antimicrobial products in agricultural production. Wheat root exudates (RE) had high reducing ability to convert Ag+ to nAg under light exposure. Photo-induced reduction of Ag+ to nAg in pristine RE was mainly attributed to the 0-3 kDa fraction. Quantification of the silver species change over time suggested that Cl⁻ played an important role in photoconversion of Ag+ to nAg through the formation and redox cycling of photoreactiveAgCl. Potential electron donors for the photoreduction of Ag+ were identified to be reducing sugars and organic acids of low MW. Meanwhile, the stabilization of the formed particles was controlled by both low (0-3 kDa) and high (>3 kDa) MW molecules. This work provides new information for the formation mechanism of metal nanoparticles mediated by RE, which may further our understanding of the biogeochemical cycling and toxicity of heavy metal ions in agricultural and environmental systems. Copper sulfide nanoparticles (CuSNPs) at 1:1 and 1:4 ratios of Cu and S were synthesized, and their respective antifungal efficacy was evaluated against the pathogenic activity of Gibberellafujikuroi(Bakanae disease) in rice (Oryza sativa). In a 2-d in vitro study, CuS decreased G. fujikuroiColony- Forming Units (CFU) compared to controls. In a greenhouse study, treating with CuSNPs at 50 mg/L at the seed stage significantly decreased disease incidence on rice while the commercial Cu-based pesticide Kocide 3000 had no impact on disease. Foliar-applied CuONPs and CuS (1:1) NPs decreased disease incidence by 30.0 and 32.5%, respectively, which outperformed CuS (1:4) NPs (15%) and Kocide 3000 (12.5%). CuS (1:4) NPs also modulated the shoot salicylic acid (SA) and Jasmonic acid (JA) production to enhance the plant defense mechanisms against G. fujikuroiinfection. These results are useful for improving the delivery efficiency of agrichemicals via nano-enabled strategies while minimizing their environmental impact, and advance our understanding of the defense mechanisms triggered by the NPs presence in plants.