Catalyseurs du ruthénium sélectifs pour la métathèse et la cycloisomérisation de diènes et d'énynes fonctionnalisés

Les complexes ruthénium-allénylidènes [RuCl(PCy3)(p-cymène)(=C=C=CPh2)]X sont de bons précurseurs pour la métathèse d'énynes fluorés. Le catalyseur de cycloisomérisation Cp*Ru(COD)Cl permet la transformation des mêmes énynes en aminoesters fluorés possédant deux doubles liaisons exocycliques. La nature de sel des complexes ruthénium-allénylidènes permet la transposition de la réaction de métathèse dans les solvants ioniques. Des études cinétiques nous ont permis de mieux comprendre la réaction de métathèse des diènes par les complexes ruthénium-allénylidènes. Des complexes de type (arène-carbène)ruthénium-allénylidènes et (carbène)-(arène)-ruthénium-allénylidènes conduisent sélectivement aux produits de métathèse ou de cycloisomérisation. L'utilisation d'un nouveau système catalytique généré in-situ permet la métathèse d'énynes possédant un groupement allylsiloxane. Ce même système catalytique généré in-situ transforme sélectivement les diènes-1,6 en produits de cycloisomérisation. L'emploi d'un acétylénique réoriente l'action du catalyseur et permet alors d'obtenir les produits de métathèse.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Calix[4]arènes fonctionnels pour la chimie verte

Le travail présenté dans cette thèse visait à étendre le champ d applications de ligands calix[4]arèniques.La première partie de ce travail est consacrée à l utilisation en milieu aqueux ou sans solvant de bis-phosphitecalix[4]arènes hémisphériques. La transposition de réactions catalytiques à ces milieux non usuels permet d accroître l activité du catalyseur par rapport à une utilisation en milieu organique classique. Utilisés en hydroformylation d'oléfines, ces ligands conduisent sélectivement à l'aldéhyde linéaire, la régiosélectivité du système étant principalement contrôlée par les propriétés intrinsèques du ligand. De même, la réaction d hydroaminovinylation des a-oléfines catalysée par du rhodium conduit, en milieu totalement dépourvu de solvant, à des rapports produit linéaire/produit branché très élevés d énamines/amines (à partir d amines secondaires) et d imines (à partir d amines primaires). Dans les chapitres suivants, des calix[4]arènes portant un groupement PPh2 ou N=PPh2 comme seul groupe fonctionnel ont été testés en couplage croisé catalysé par du palladium et du nickel. Avec les bromures d aryle, des activités remarquablement élevées ont été obtenues. La capacité de ces ligands à catalyser efficacement les réactions de formation de liaison C-C est liée d une part à l encombrement stérique de l'entité calixarényle, mais aussi à l aptitude de ce fragment à piéger de manière supramoléculaire des entités métal-(p-arène). Ces deux propriétés sont de nature à favoriser la formation d une espèce mono-ligand M(0)L(ArX) (M = Pd, Ni), l étape d addition oxydante devenant alors plus facile à partir d une telle espèce qu à partir d une espèce M(0)L2.The aim of this work was to extend the scope of catalytic applications of ligands based on a calix[4]arene skeleton.The first part of this work focusses on new applications of hemispherical bis-phosphites calix[4]arenes in the rhodium catalysed hydroformylation of a-olefins, either in aqueous medium or under solvent-free conditions. These particular conditions resulted in enhanced activities compared to tests carried out in toluene. The ligands turned out to efficiently drive reactions towards the formation of linear products. The selectivity of the system is mainly controlled by the intrinsic properties of the ligand, which is able to tightly envelope the catalytic centre. In keeping with these observations, the application of solvent-free conditions to the rhodium-catalysed hydroaminovinylation of a-olefins resulted in high linear/branched ratios of enamines/amines (starting from secondary amines) or imines (starting from primary amines). In the following chapters, calix[4]arenes bearing a PPh2 or a N=PPh2 group as the sole functional group anchored at their upper rim were assessed in palladium or nickel-catalysed cross-coupling reactions. With arylbromides, these monodentate ligands led to remarkably high activities. The high performances probably arise from a combination of the bulkiness of the calixarenyl fragment as well as its ability to temporarely entrap metal-( 6-arene) moieties in a supramolecular fashion. Both properties favour the formation of mono-ligand intermediates M(0)L(ArX) (M = Pd, Ni), from which the following oxidative addition step is facilitated with respect to a step involving M(0)L2 species.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Tetra-hydroxy-calix[4]arene derivatives with two P(III) or P(V) units attached at the upper rim.

International audience5,17-Bis(diphenylphosphino)-25,26,27,28-tetra-hydroxy-calix[4]arene (2) and the corresponding bis- (phosphine oxide) (3) and bis-(phosphine sulfide) (4) have been synthesized. A single crystal X-ray diffraction study was carried out for bis(phosphine oxide) 3, which revealed a pinched cone conformation for the calixarene core. In the solid state, each calixarene is linked to two other calixarenes via hydrogen bonds involving the phosphoryl groups as well as two of the four hydroxyl groups, thereby generating a supramolecular polymeric structure. Selective formation of chelate complexes from diphosphine 2 failed, probably because of rapid trans annular rotation of the phenoxyl groups that prevents appropriate ligand preorganisation. Upon reaction with appropriate Ru-, Rh-, and Ir-complexes, ligand 2 readily formed dinuclear complexes. One of them, namely the complex [2 {RhCl(1,5-cyclooctadiene)}2] was assessed in the catalytic hydrogenation of linear and cyclic olefins

Pseudo-capsular behaviour of two trans-coordinated calixarenyl phosphines

International audienceThe square-planar complex trans-[PtCl2L2] (L = 5-diphenylphosphinyl-25,26,27,28-tetrabenzyloxy-calix[4]arene) was prepared in two steps from [PtCl2(cod)] (cod = 1,5-cyclooctadiene) and the corresponding phosphine. In the solid state, the calixarene moieties adopt a typical pinched cone conformation; they are both turned towards the Cl-Pt-Cl rod, thereby forming a capsule that hosts the platinum centre

Crystal structure of trichlorooxo-17-bis[(diphenylphosphoryl)methyl]-4(24),6(10),12(16),18( 22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]areneuranium(V ) - dichlorodioxo-17-bis[(diphenylphosphoryl)methyl]-4(24),6(10),12(16),18 (22)- tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]areneuranium(VI) - hexane (1:3:3), UCl3O(C78H86O10P2)center dot 3UCl(2)O(2)(C78H86O10P2)center dot 3C(6)H(14)

International audienceCi(65)H(193)CL(4.36)O(23.64)P(4)U(2), triclinic, P (1) over bar (no. 2), a = 15.495(1) angstrom, b = 18.855(2) angstrom, c =30.532(3) angstrom, alpha = 90.717(9)degrees, beta = 101.253(7)degrees, gamma = 109.575(9)degrees, V = 8213.9 angstrom(3), Z = 2, R-gt(F)= 0.055, wR(ref)(F-2)= 0.152, T= 110 K

Resorcinarenyl-Phosphines in Suzuki-Miyaura CrossCoupling Reactions of Aryl Chlorides

International audienceTwo phosphines built on a bowl-shaped resorcin[4]arene skeleton, namely 5-diphenylphosphanyl- and 5-diisopropylphosphanyl-4(24),6(10),12(16),18(22)-tetramethylenedioxy-2, 8,14,20-tetrapentylresorcin[4]arene, have been synthesised and tested in the Suzuki-Miyaura cross-coupling reaction of aryl halides. Combining these ligands with [Pd(OAc)(2)] resulted in highly active catalysts that allowed the formation of o,o-biphenyls starting from aryl chlorides. The remarkable activities observed possibly arise from 1) the capacity of the phosphines to operate transiently as P,O chelators, thereby increasing the electron density of the metal, and 2) the ability of the ligands to embed metal-organic units, which, when occurring, makes the ligand considerably bulkier so as to disfavour the coordination of a second phosphine. Both features are known to facilitate the oxidative addition step

Cavitand Scission by Transition-Metal Centres – Cleaved Cavitand Chirality and Its Consequences

International audienceTwo molecules of the phosphine cavitand 5-diphenylphosphanyl-4(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene (1) each underwent cleavage of an O–CH2O bond when treated with 1 equiv. of [Ni(η5-C5H5)(1,5-cyclooctadiene)]BF4 to form a bis(phosphino–phenolato) complex (2) without a cyclopentadienyl ligand. The partially cleaved (P,O) ligands in 2 are chiral, and a single-crystal X-ray structure determination of 2 has shown that the complex molecule has close to twofold rotational symmetry with both ligand units in the same absolute configuration. As expected, the primary coordination sphere has a cis-NiO2P2 geometry. In contrast, C–O bond breaking occurred only once per metal centre when 1 was treated with [RuBr2(p-cymene)]2. This led to a crystallographically characterised complex [RuBr(P,O)(p-cymene)] (4) along with a minor amount of a species (5) that is assumed to be a stereoisomer. Upon crystallisation of 4, two distinct types of crystals were isolated from the same solution; some of these were the racemic compound, while the others were the racemic conglomerat

Resorcin[4]arene-derived mono-, bis- and tetra-imidazolium salts as ligand precursors for Suzuki-Miyaura cross-coupling.

International audienceEleven resorcinarene cavitands bearing either one, two or four (3-R-1-imidazolylium)-methyl substituents (R = (n)Bu, Ph, Mes, (i)Pr(2)C(6)H(3)) anchored at resorcinolic "ortho" positions have been synthesised from the appropriate bromomethylated precursor. Combining the imidazolium salts with palladium acetate and Cs(2)CO(3) gave active Suzuki-Miyaura cross coupling catalysts. The highest activities were observed with the doubly functionalised cavitands, which all have the imidazolylium groups attached to proximal resorcinol units

The Influence of Imidazolylidene Ligands with Bulky Resorcinarenyl Substituents on Catalysts for ­Suzuki–Miyaura Coupling

International audiencePEPPSI-type imidazolylidene palladium complexes having their carbenic ring N-substituted with an aryl ring and a cavity-shaped unit [25,26,27,28-tetrapropyloxycalix[4]aren-5-yl or 6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]aren-5-yl (TPR)] have been prepared and assessed in Suzuki–Miyaura cross-couplings. Remarkable efficiency in the coupling of aryl chlorides with sterically hindered arylboronic acids was observed for the carbene ligand having its N atoms (N1, N2) substituted by a mesityl and a TPR group, respectively. This good performance possibly arises from strong steric interactions between the pentyl-substituted cavitand unit and the catalytic centre, which favours reductive elimination. Two of the imidazolium salts used for complex synthesis were characterised by X-ray diffraction analysi

Palladium-catalysed Suzuki―Miyaura cross-coupling with imidazolylidene ligands substituted by crowded resorcinarenyl and calixarenyl units

International audienceTwo N -heterocyclic carbene (NHC) palladium complexes of formula [PdBr2 (NHC)(pyridine)] in which the carbenic ring is anked by sterically crowded cavitand substituents were prepared from appropriate imidazolium salts bearing either two resorcinarene or a combination of resorcinarene and calixarene fragments. Both complexes displayed high stability and good activities in the cross-coupling of aryl bromides with phenyl boronic acid. One of the imidazolium salts was characterised by an X-ray diffraction study