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Stoeckli-Evans, Helen
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Stoeckli-Evans, Helen
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helen.stoeckli-evans@unine.ch
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Voici les éléments 1 - 10 sur 188
- PublicationMétadonnées seulement
- PublicationMétadonnées seulementConversion of ethylene into ethylidyne on a mixed-metal cluster: synthesis and structure of IrRu4(CO)(15)(mu(4)-CH3)(1999)
; The thermal reaction of the tetranuclear cluster HIrRu3(CO)(13) with ethylene in hexane (90 degrees C, 2 bar) affords, in addition to H3IrRu3(CO)(12), the pentanuclear cluster HIrRu4(CO)(15)(mu(4)-C-CH3) (1) in which the ethylidyne ligand is coordinated through a carbon atom to the four ruthenium atoms in the IrRu4 core. In this reaction, the CH2=CH2 molecule has been transformed into a C-CH3 moiety coordinated as a mu(4)-ligand to the cluster. (C) 1999 Elsevier Science S.A. All rights reserved. - PublicationMétadonnées seulementApplication of the novel tandem process Diels-Alder reaction/Ireland-Claisen rearrangement to the synthesis of rac-juvabione and rac-epijuvabione(2000-1-12)
; The novel tandem process Diels-Alder reaction/Ireland-Claisen rearrangement shows a high diastereoselectivity for the Ireland-Claisen rearrangement starting from the endo-product of the Diels-Alder reaction. Based on this mechanistic knowledge, the novel tandem process could be applied to the synthesis of rac-juvabione. - PublicationMétadonnées seulementMetal-framework degradation reactions of the mixed-metal cluster anions [M3Ir(CO)(13)](-) (M=Ru, Os) with bis(diphenylphosphino)methane and with tricyclohexylphosphine: synthesis and structure of HRu2Ir(CO)(5)(dppm)(3), HRu2Ir(CO)(6)(PCy3)(3), H2Os2Ir2(CO)(10)(PCy3)(2) and H3Os3Ir(CO)(8)(PCy3)(3)(1999)
; - PublicationMétadonnées seulementCatalytic Epoxidation of Alkenes by the Manganese Complex of a Reduced Porphyrinogen Macrocycle(2012)
; ; The present paper details the first application of a fully reduced meso-octamethylporphyrinogen macrocycle as an effective ligand for simple operative manganese-catalyzed alkene epoxidn. The efficiency of the novel catalyst was detd. in the presence of various oxidants, apical ligands and acidic/basic additives. Higher reactivity was found in favor of electron-rich alkenes, whereas an electron-deficient conjugated alkene appeared to be a poor substrate in the screening. Sulfur additives were active as apical ligands, whereas nitrogen-contg. additives influenced the reactivity only moderately. Cis-Stilbene and 3?-acetoxy-5-cholestene were epoxidized in a stereoselective manner. The x-ray structures of the new manganese complexes were detd. and showed a rigid planar coordination geometry of the satd. macrocyclic ligand to the metal center. [on SciFinder(R)] - PublicationMétadonnées seulement[(p-C6H4iPrMe)4Ru4Mo4O16]: An Amphiphilic Organoruthenium Oxomolyb-denum Cluster Presenting a Unique Framework Geometry(1997)
; - PublicationMétadonnées seulementThe anion [(As5Mo4O20)-Mo-III-O-VI(OCH3)](2-): a new heteropolyoxometalate containing an unusual As5O4 chain(2002)
; The heteropolyoxometalate [(HAsAsMoMo8O34)-As-III-Mo-V-Mo-V-O-VI](6-) reacts in aqueous solution with an excess of sodium metaarsenite to give a new arsenomolybdate [(As5Mo4O20)-Mo-III-O-VI(OCH3)](2-) which crystallize as the tetrabutylammonium salt. The single-crystal X-ray structure analysis reveals a heteropolyoxometalate anion containing an unusual chain of five arsenic atoms linked to each other by bridging oxygen atoms. (C) 2002 Elsevier Science B.V. All rights reserved. - PublicationMétadonnées seulementNew Ru-3(CO)(12) derivatives with bulky diphosphine ligands: synthesis, structure and catalytic potential for olefin hydroformylation(2001)
; The diphosphine clusters Ru-3(CO)(10)(dcpm) (1) and Ru-3(CO)(10)(F-dppe) (2) as well as the bis(diphosphine) clusters Ru-3(CO)(8)(dcpm)(2) (3) and Ru-3(CO)(8)(F-dppe)(2) (4) have been synthesised from Ru-3(CO)(12) and the bulky diphosphines 1,2-bis[bis(pentafluorophenyl)phosphino]ethane (F-dppe) and bis(dicyclohexylphosphino)methane (dcpm). While the single-crystal X-ray structure analyses of 1, 2 and 3 show the expected mu (2)-eta (2) coordination of the diphosphine ligands, that of 4 reveals an unusual structure with one mu (2)-eta (2)-diphosphine and one mu (1)-eta (2)-diphosphine ligand. The clusters 1-4 catalyse the hydroformylation of ethylene and propylene to give the corresponding aldehydes, 2 showing higher activities than those observed for Ru-3(CO)(12) and Ru-3(CO)(10)(dppc). (C) 2001 Elsevier Science Ltd. All rights reserved. - PublicationMétadonnées seulementNew diphosphine ligands containing ethylene glycol and amino alcohol spacers for the rhodium-catalyzed carbonylation of methanol(2002)
; ; The new diphosphine ligands Ph2PC6H4C(O)X(CH2)2OC(O)C6H4PPh2 (X = NH; X = NPh; X = O) and Ph2PC6H4C(O)O(CH2)2O(CH2)2OC (O)C6H4PPh2 (I) as well as the monophosphine ligand Ph2PC6H4C(O)X(CH2)2OH (II) have been prepd. from 2-diphenylphosphinobenzoic acid and the corresponding amino alcs. or diols. Coordination of the diphosphine ligands to rhodium, iridium, and platinum resulted in the formation of the square-planar complexes. In all complexes, the diphosphine ligands are trans coordinated to the metal center, thanks to the large spacer groups, which allow the two phosphorus atoms to occupy opposite positions in the square-planar coordination geometry. The trans coordination is demonstrated unambiguously by the single-crystal X-ray structure anal. of on of these complexes. In the case of the diphosphine ligand I, the spacer group is so large that dinuclear complexes with ligand I in bridging positions are formed, maintaining the trans coordination of the P atoms on each metal center, as shown by the crystal structure anal. of another complex. The monophosphine ligand II reacts with [{Ir(cod)Cl}2] (III) (cod = cyclooctadiene) to give the simple deriv. [Ir(cod)Cl] which is converted into the carbonyl complex [Ir(CO)2Cl] with carbon monoxide. The crystal structure anal. of III also reveals a square-planar coordination geometry in which the phosphine ligand occupies a position cis with respect to the chloro ligand. Some of these diphosphine ligands have been tested as cocatalysts in combination with the catalyst precursors [{Rh(CO)2Cl}2] and [{Ir(cod)Cl}2] or [H2IrCl6] for the carbonylation of methanol at 170°C and 22 bar CO. The best results (TON 800 after 15 min) are obtained for the combination X = NPh/[{Rh(CO)2Cl}2]. After the catalytic reaction, one complex is identified in the reaction mixt. and can be isolated; it is active for further runs without loss of catalytic activity. [on SciFinder(R)] - PublicationMétadonnées seulementDiastereoselective synthesis of (1S,2S,3R,6S) 3-chloro-3-methyl-6-isopropenyl-1,2-cyclohexanediol via Prins reaction induced by zinc and trimethylsilyl chloride(1996)
; While attempting to synthesize a potential inhibitor of the biosynthetic step of formation of PEG, a novel catalytic system inducing the Prins reaction was discovered. Treatment of epoxy geranial with Zn and trimethylsilyl chloride gave (1S,2S,3R,6S) 3-Chloro-3-methyl-6-isopropenyl-1,2-cyclohexanediol in high diastereoselcctivity.