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Stoeckli-Evans, Helen
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Stoeckli-Evans, Helen
Affiliation principale
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helen.stoeckli-evans@unine.ch
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Voici les éléments 1 - 10 sur 106
- PublicationAccès libreTri- and Tetranuclear Mixed-Metal Clusters Containing Alkyne Ligands : Synthesis and Structure of [Ru3Ir(CO)11(RCCR’)]-, [Ru2Ir(CO)9(RCCR’)]-, and [HRu2Ir(CO)9(RCCR’)](1999)
; - 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)] - PublicationAccès libreTriruthenium–iridium clusters containing alkyne ligands : synthesis, structure, and catalytic implications of [(µ-H)IrRu3(CO)11(µ3-η2-PhC≡CPh)] and [IrRu3(CO)10(µ4-η2-PhC≡CPh)(µ-η2-PhC=CHPh)](1998)
; - PublicationMétadonnées seulementTransfert réciproque d'oxygène et d'hydrogène entre deux ligands coordonnés à une ossature dinucléaire de ruthénium : synthèse et structure moléculaire de RU2 (CO) 6 (MU-PCY 2) MU P (O) CY 2(1993)
; ; Walther, Bernhard - PublicationMétadonnées seulementReactions of the cationic complex [(eta(6)-C6Me6)(2)Ru-2(mu(2)-H)(3)](+) with nitrogen-containing heterocycles in aqueous solution(1998)
; The dinuclear cation [(eta(6)-C6Me6)(2)Ru-2(mu(2)-H)(3)](+) (1) reacts in aqueous solution with pyrazole and 4-methylpyrazole to give the bispyrazolato complexes [(eta(6)-C6Me6)(2)Ru-2(mu(2)-H)(mu(2)-eta(1),eta(1)-N2C3H2R)(2)](+) (R = H: 2, R = Me: 3). The reaction with 1,2,4-triazole results in the formation of the bistriazolato complex [(eta(6)-C6Me6)(2)Ru-2(mu(2)-H)(mu(2)-eta(1),eta(1)-N3C2H2)(2)](+) (4) Successive protonation of the triazolato ligands in 4 leads to the complexes [(eta(6)-C6Me6)(2)Ru-2(mu(2)-H)(mu(2)-eta(1),-N3C2H2)(mu(2)-eta(1),eta(1 )-N3C2H3)](2+) (5) and [(eta(6)-C6Me6)(2)RU2(mu(2)-H)(mu(2)-eta(1),eta(1)-N3C2H2)(2)](3+) (6). The reaction of 1 with 1,2,3-triazole gives a 1:1 mixture of the bistriazolato complexes [(eta(6)-C6Me6)(2)Ru-2(mu(2)-H)(mu(2)-eta(1),eta(1)-N3C2H2)(2)](+) with parallel (7a) and anti-parallel (7b) coordination of the triazolato ligands. The single-crystal X-ray structure analyses of 2 (hexafluorophosphate salt) and 4 (tosylate salt) reveal for both complex types a ruthenium-ruthenium backbone being bridged by the two heterocyclic ligands with the N-N axis coordinated in a mu(2)-eta(1),eta(1)-fashion. A single-crystal X-ray structure analysis of title complex 1 (hexafluorophosphate salt) confirms the presence of three bridging hydride ligands with a Ru-Ru distance of only 2.47 Angstrom. (C) 1998 Elsevier Science S.A. All rights reserved. - PublicationMétadonnées seulement
- PublicationMétadonnées seulement[(eta(6)-p-Pr(i)C6H4Me)(2)Ru2Mo2O6(OMe)(4)]: a new tetranuclear mixed-metal oxo cluster presenting a cube-based chair structure(1999)
; The title complex was obtained by reaction of [(eta(6)-p-Pr'C6H4Me)(4)Ru4Mo4O16] with methanol in the presence of p-hydroquinone. It contains an Mo2Ru2O2(OMe)(4) core consisting of two Mo2RuO(OMe)(3) half-cubes fused together to form a choir-like structure. (C) 1999 Elsevier Science S.A. All rights reserved. - PublicationAccès libreMono and oligonuclear vanadium complexes as catalysts for alkane oxidation : synthesis, molecular structure, and catalytic potential(2004-01-30)
; ; ; Shul’pin, Georgiy B.A series of mono- and oligonuclear vanadium(V) and vanadium(IV) complexes containing various chelating N,O-, N3-, and O2-ligands have been prepared. The biphasic reaction of an aqueous solution of ammonium vanadate and a dichloromethane solution of hexamethylphosphoramide (hmpa) and pyrazine-2-carboxylic acid (pcaH) or pyrazine-2,5-dicarboxylic acid (pdcaH2) or pyridine-2,5-dicarboxylic acid (pycaH2) yields yellow crystals of [VO2 (pca)(hmpa)] (1), [(VO2)2(pdca)(hmpa)2] (2), and [VO2(pycaH)(hmpa)] (3), respectively. The single-crystal X-ray structure analyses reveal 1 and 3 to be mononuclear vanadium(V) complexes, in which a VO2 unit coordinates to one nitrogen and one oxygen atom of a pca or pycaH chelating ligand, and 2 to be a dinuclear vanadium(V) complex, in which two VO2 units are coordinated through one nitrogen and one oxygen atom of a pdca bridging ligand; in the three complexes the vanadium atoms also coordinate to the oxygen atom of a hmpa ligand. The reaction of N,N,N′,N′-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane (hptbH) and VOSO4 in methanol gives the cationic complex [(VO)4(hptb) 2(μ-O)]4+ (4), which can be crystallized as the perchlorate salt. In this tetranuclear complex, two dinuclear vanadium(IV) units are held together by a μ-oxo bridge. The known complex [VOCl2 (tmtacn)] (5) was synthesized from the reaction of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) and VCl3 in acetonitrile; the reaction of tetrabutylammonium vanadate with pyro-cathecol (catH2) in acetonitrile gives the known anionic complex [V(cat)3]− (6), in which the vanadium(V) center is bonded to three cat chelating ligands through the oxygen atoms, obtained as the tetrabutylammonium salt. All compounds synthesized are highly efficient oxidation catalysts for the reaction of cyclohexane with air and hydrogen peroxide in the presence of four equivalents of pcaH per vanadium, although the catalytic activity of the complexes containing bulky chelating ligands 4 and 5 is somewhat lower in the initial period of the reaction. During this period the active species are formed from the complexes and final turnover numbers are high. The catecholate ligands of complex 6 may reduce from V(V) to V(IV) in the beginning of the process, thus providing very high initial oxidation rates.