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Stoeckli-Evans, Helen
Nom
Stoeckli-Evans, Helen
Affiliation principale
Email
helen.stoeckli-evans@unine.ch
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Résultat de la recherche
Voici les éléments 1 - 10 sur 22
- 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)
; - 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)
; - 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. - PublicationAccès libreThe mixed-metal carbonyl cluster anion [Ru3Ir(CO)13]– : synthesis, molecular structure, fluxionality, reactivity(1997)
; - PublicationAccès libreWater-Soluble Arene Ruthenium Complexes Containing a trans-1,2-Diaminocyclohexane Ligand as Enantioselective Transfer Hydrogenation Catalysts in Aqueous Solution(2005)
; The cationic chloro complexes [(arene)Ru(H2N∩NH2)Cl]+ (1: arene = C6H6; 2: arene = p-MeC6H4iPr; 3: arene = C6Me6) have been synthesised from the corresponding arene ruthenium dichloride dimers and enantiopure (R,R or S,S) trans-1,2-diaminocyclohexane (H2N∩NH2) and isolated as the chloride salts. The compounds are all water-soluble and, in the case of the hexamethylbenzene derivative 3, the aqua complex formed upon hydrolysis [(C6Me6)Ru(H2N∩NH2)OH2]2+ (4) could be isolated as the tetrafluoroborate salt. The molecular structures of 3 and 4 have been determined by single-crystal X-ray diffraction analyses of [(C6Me6)Ru(H2N∩NH2)Cl]Cl and [(C6Me6)Ru(H2N∩NH2)OH2][BF4]2. Treatment of [Ru2 (arene) 2Cl4] with the monotosylated trans-1,2-diaminocyclohexane derivative (TsHN∩NH2) does not yield the expected cationic complexes, analogous to 1-3 but the neutral deprotonated complexes [(arene)Ru(TsN∩NH2)Cl] (5: arene = C6H6; 6: arene = p-MeC6H4iPr; 7: arene = C6Me6; 8: arene = C6H5COOMe). Hydrolysis of the chloro complex 7 in aqueous solution gave, upon precipitation of silver chloride, the corresponding monocationic aqua complex [(C6Me6)Ru(TsHN∩NH2)(OH2)]+ (9) which was isolated and characterised as its tetrafluoroborate salt. The enantiopure complexes 1-9 have been employed as catalysts for the transfer hydrogenation of acetophenone in aqueous solution using sodium formate and water as a hydrogen source. The best results were obtained (60 °C) with 7, giving a catalytic turnover frequency of 43 h-1 and an enantiomeric excess of 93 %. - PublicationAccès libre
- PublicationAccès libreNucleophilic addition reactions on the electron-deficient cluster dication [H4Ru4(C6H6)4]2+ : synthesis and structural characterisation of the water-soluble cluster cations [H3Ru4(C6H6)4 (CO)]+ and [H3Ru4(C6H6)4 (OH)]2(2001)
; The electron-deficient (58e) cluster cation [H4Ru4(C6H6)4]2+1 was found to react in aqueous solution with simple nucleophiles to give electron-precise (60e) clusters. With carbon monoxide, the cluster cation [H3Ru4(C6H6)4(CO)]+3 is formed. The reaction with water needs NaN3 as catalyst and yields the cluster dication [H3Ru4(C6H6)4 (OH)]2+4a; the reaction with alcohols leads to the analogous clusters [H3Ru4(C6H6)4 (OR)]2+ (R = Me: 4b, R = Et: 4c, R = PhCH2: 4d, R = Ph: 4e, R = 4-EtC6H4: 4f). The single-crystal X-ray structure analyses of the chloride salts of 3 and 4a reveal a tetrahedral Ru4 metal core. Each ruthenium atom is coordinated by a η6-benzene ligand, while the carbonyl or hydroxo ligands are found as µ3 capping ligands over a triangular face of the Ru4 tetrahedron. - PublicationAccès libreDinuclear manganese complexes containing 1,4-dimethyl-1,4,7-triazacyclononane ligands as well as carboxylato and oxo bridges(2006)
; ; - PublicationAccès libreCarbonate binding to copper(II) in solution: mixed-ligand complex formation and its application to the isolation and separation of the three isomers of [Cu(bpp)(H2O)][ClO4]2 [bpp = 2,6-bis(pyrrolidin-2-yl)pyridine](2002)
; ; The binding of the carbonate anion to [Cu(meso-bpp)(H2O)]2+ and rac-[Cu(bpp)(H2O)]2+ [bpp = 2,6-bis(pyrrolidin-2-yl)pyridine] in aqueous solution has been investigated. Formation constants of the carbonato complexes [Cu(meso-bpp)(CO3)] and rac-[Cu(bpp)(CO3)] (1.02 × 103 M–1 and 1.77 × 103 M–1, respectively, µ= 0.70 M) have been calculated from spectrophotometric measurements. The formation of these Cu2+ complexes can also be used for an improved synthesis and an easy isolation of the three diastereoisomers of bpp. The mixture of [Cu(meso-bpp)(H2O)]2+ and rac-[Cu(bpp)(H2O)]2+ is separated by elution from SP Sephadex C-25, either as hydroxo or carbonato derivatives. rac-[Cu(bpp)(H2O)]2+ is then resolved into the enantiomers [Cu(S,S-bpp)(H2O)]2+ and [Cu(R,R-bpp)(H2O)]2+, again on SP Sephadex C-25, by means of L-(+)-tartrate as chiral eluent. The three stereoisomers, meso-bpp, (S,S)-bpp and (R,R)-bpp are liberated from the corresponding copper(II) complexes by ligand displacement using trans-1,2-diaminocyclohexane-N,N,N’,N’-tetraacetic acid (H4cdta). The structure of the meso isomer was solved by a single crystal X-ray analysis using the perchlorate salt [meso-bppH2][ClO4]2•2H2O. - PublicationAccès libreMono-, di- and tetra-nuclear p-cymeneruthenium complexes containing oxalato ligands(1997)
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