Littérature scientifique sur le sujet « Diphosphines synthesis »

Gold Nanoclusters are of particular interest due to their many possible applications across a wide range of scientific fields. More specifically, nano-sized gold particles have potential to be used in drug delivery systems, cancer therapy and catalysis. This dissertation focuses on improving our understanding of ligated gold nanoclusters by examining the role of a variety of phosphine based ligands, novel methods to produce monodisperse solutions, and investigating the kinetics of water soluble ligated gold nanoclusters. The addition of ligands to solutions of Au have shown to produce small (< 20 Au atoms) clusters. All nanocluster solutions were prepared in a similar manner. Typically, a gold salt, either Chloro(triphenylphosphine) gold(I) (Au(PPh3)Cl), or Potassium gold (III) chloride (KAuCl4), were dissolved in various solvents. Next, an equal concentration of ligand was added to the solution and stirred until completely dissolved. Finally, all were reduced with 5X the concentration of borane-tert-butylamine (BTBC) after which were sonicated for ~20 minutes. The timing and method of adding the ligands and reducing agent varied depending on the solution and solubility of the ligands. Primarily we used Electrospray Ionization Mass Spectrometry (ESI-MS) and Ultraviolet – Visible Spectroscopy (UV-VIS) for the characterization of samples, however, occasionally Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and X-Ray Photoemission Spectroscopy (XPS) were used. The most recent research took advantage of the size selective nature of an alpha hemolysin (a-HL) nanopore to investigate the kinetics of thiol-ligated Au clusters ~2 nm in size. The relationship between ligand rigidity and solvent polarity and the size and dispersity of Au cluster suspensions was investigated. We observed the formation of stable monodisperse clusters with the shortest ligand, (L3), independent of solvent. With a longer flexible ligand, (L6), we observed primarily Au8-10 cores depending on the ratio of L6/PPh3. All other ligands yielded polydisperse distributions. These dispersions contained clusters with a nuclearity between 8 and 11, for example [Au10(PPh3)9]3+ in LBn and [Au8(PPh3)7]2+ in LBp, were observed in the initial stages, but they were not stable and precipitated out or plated the glass vial. We also observed that the polarity of the solvent did not play a significant role in the formation of MPC’s, however a correlation between the size of the solvent and MPC formation was observed. The growth and evolution of two unique gold structures was also observed via UV-Vis and ESI-MS. Solutions were prepared which contained Potassium gold (III) chloride and PPh2(CH2)3PPh2, i.e., 1,3-bis(diphenylphosphino)propane, denoted by L3, reduced with Borane tert-butylamine complex (BTBC) in a 1:1 diethyl ether:methanol mix, which yielded a stable [Au11(L3)5]+3. Starting with this known Au11 solution, the addition of Mn2+ has shown to lead to the formation of a stable diphosphine ligated Au8 and a new Au14 species. Additionally, we show that the co-reduction of NiCl2 and Au in the absence of the ligand (L3) does give us a simple method for the production of a monodisperse [Au9(PPh3)8]2+ cluster solution and via electroless deposition does give us a potential low temperature pathway to the formation of a AuNi nanoalloy particle.

Cette thèse examine les défis posés par l’accès incertain aux éléments chimiques, exacerbée par un paradigme économique linéaire de leur exploitation. L’étude se concentre sur le bore et le phosphore, dont l’utilisation et le recyclage restent sous-étudiés. Le bore, crucial dans diverses industries, nécessite des processus énergivores pour être transformé en hydroboranes actifs, utilisés en chimie fine. Deux voies existent pour leur synthèse : la méthode industrielle à partir de borate, et la réaction de BCl₃ avec un donneur d’hydrure. Utiliser H₂ comme agent réducteur pourrait améliorer ces processus. Cette recherche explore la synthèse d’hydroboranes [9-BBN]₂ et [Cy₂BH]₂ à partir de leurs dérivés halogénés et triflate, avec une base et H₂. Le criblage des bases a montré que les trialkylamines, surtout NEt₃, sont efficaces. La réaction repose sur un mécanisme type paire de Lewis frustrée pour activer le H₂. Il s’avère également que les dialkylboranes peuvent catalyser l’hydrogénolyse d’autres chloroboranes, en particulier de BCl₃, permettant d’obtenir HCl₂B·NEt₃ et H₂ClB · NEt₃. Enfin, cette stratégie a été étendue au phosphore, optimisant l’hydrogénolyse des chlorophosphines en diphosphines. La méthode, efficace pour divers substrats, procède en trois étapes : hydrogénolyse du catalyseur, transfert d’hydrure, et condensation en diphosphine, assistée par NEt₃. Ces transformations ont été modélisées chaque fois par théorie de la fonctionnelle de la densité (DFT) et présentent des temps de réactions souvent longs (jusqu’à plusieurs jours), mais avec en général de bons rendements (&gt; 70 %) en conditions douces de pression et température<br>This thesis examines the challenges posed by uncertain access to chemical elements, exacerbated by a linear economic paradigm of their exploitation. The study focuses on boron and phosphorus, whose usage and recycling remain understudied. Boron, crucial in various industries, requires energy-intensive processes to be converted into active hydroboranes, used in fine chemistry. Two methods exist for their synthesis: the industrial method from borate, and the reaction of BCl₃ with a hydride donor. Using H₂ as a reducing agent could improve these processes. This research explores the synthesis of hydroboranes [9-BBN]₂ and [Cy₂BH]₂ from their halogenated and triflate derivatives, with a base and H₂. Base screening showed that trialkylamines, particularly NEt₃, are effective. The reaction relies on a frustrated Lewis pair mechanism to activate H₂. It was also found that dialkylboranes can catalyze the hydrogenolysis of other chloroboranes, particularly BCl₃, yielding HCl₂B· NEt₃ and H₂ClB·NEt₃. Finally, this strategy was extended to phosphorus, optimizing the hydrogenolysis of chlorophosphines into diphosphines. The method, effective for various substrates, proceeds in three steps : catalyst hydrogenolysis, hydride transfer, and base-assisted condensation into diphosphine. These transformations were modeled each time using density functional theory (DFT) and often present long reaction times (up to several days), but usually with good yields (&gt; 70 %) under mild pressure and temperature conditions

Cyclodextrins (CDs) are cyclic oligosaccharides of various sizes containing several α-(1→4)-linked D-(+)- glucopyranose units. The commercially available ones comprise six, seven or eight glucose units, named respectively α-CD, β-CD and γ-CD. Their truncated cone-like and well-defined cavity are particularly attractive for the encapsulation of a variety of substrates. As such, they found numerous applications in many areas of chemistry. A recent development, from which the present work is inspired, consisted in covalently linking transition metals to CD cavities in order to perform and study catalytic reactions in a confined environment featuring steric repulsive or attractive noncovalent interactions with the substrate or/and the metal coordination sphere.The first part of this thesis focuses on reviewing transition metal-based cavitands, for which the first and second metal coordination spheres are controlled by their cavity-shaped ligand. The following chapters are concerned with the synthesis, coordination and catalytic properties of two new phosphane ligands built on a large β-CD scaffold. The first one, named WIDEPHOS, is a diphosphine having two phenylphosphinidene "PPh" units capping adjacent glucose units on a methylated β-CD. This ligand features two phosphorus lone pairs pointing to the cavity interior but not aligned. These geometrical features, combined with the large distance separating the two phosphorus atoms, promote the formation of "imperfect" trans-chelate complexes in which the metal centre swings about the ligand. This unprecedented molecular movement, christened "oschelation", allows each phosphorus atom to form an optimal bond in turn with the coordinated d8 and d10 transition metal ions. Further studies on WIDEPHOS proved that it is better suited for coordinating dinuclear fragments within the confinement of the large β-CD cavity. Severe steric constrains on the metal first sphere of coordination result in the formation of single μ-chlorido bridged dinuclear species. In this new type of square planar complexes, non-optimal orbital overlapping measured by the so-called tilt angle was also found to take place for one of the phosphorus atom together with an "oschelation" movement involving non identical donor atoms, namely a phosphorus and an oxygen atom. Static gold(I) dinuclear complexes displaying similar imperfect orbital overlapping for one of the phosphorus atom were also prepared.