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Stoeckli-Evans, Helen

Nom
Stoeckli-Evans, Helen
Affiliation principale
Email
helen.stoeckli-evans@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/470

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  • Publication
    Accès libre
    Reactivity of mercury(II) halides with the unsymmetrical phosphorus ylide Ph2PCH2CH2PPh2=C(H)C(O)Ph: Crystal structure of {HgI2 [PPh2CH2CH2PPh2=C(H)C(O)Ph]}n
    (2007)
    Ebrahim, Mothi Mohamed
    ;
    Stoeckli-Evans, Helen 
    ;
    Panchanatheswaran, Krishnaswamy
    The unsymmetrical phosphorus ylide, Ph2PCH2CH2PPh2=C(H)C(O)Ph is shown to react with Hg(II) halides to form polymeric products with the composition {HgX2 [PPh2CH2CH2PPh2C(H)C(O)Ph]}n, where X = Cl (1), Br (2), I (3). The complexes have been characterized by elemental analysis, IR, 1H, 31P NMR spectra as well as by ESI mass spectra. In product 1 the ylide exhibits a P, C-bridging mode of coordination, while in 2 and 3 it shows a monodentate P-coordination with the dangling ylide. The structure of complex 3 has been characterized crystallographically. The monomeric –Hg–I–Hg– bridging in 3 leads to a zig-zag polymeric chain in which mercury assumes a distorted tetrahedral geometry.
  • Publication
    Accès libre
    Synthesis, crystal structures and spectra of Hg(II)-1,2-bis(diphenylphosphino)ethane monoxide complexes: Monomer and polymer formation
    (2007)
    Ebrahim, Mothi Mohamed
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    ;
    Panchanatheswaran, Krishnaswamy
    The reaction of mercury(II) halides with 1,2-bis(diphenylphosphino)ethane monoxide (dppeO) in 1:1 molar ratio yielded P,O-coordinated polymers having the empirical formula [HgX2 (dppeO)]n [X = Cl (1), Br (2), I (3)]. In contrast, the reaction between the same reactants in a 1:2 molar ratio yielded the P, P-coordinated monomeric complexes, HgX2 (dppeO)2[X = Cl (4), Br (5), I (6)]. The structures of 2, 3, 4 and 5 have been characterized crystallographically. The results indicate that the geometry around the mercury atom in each of these molecules is tetrahedral with considerable distortion. The 31P NMR spectra of the 1:1 complexes indicate the dissociation of the Hg–O bond in solution.
  • Publication
    Accès libre
    Synthesis, structure and magnetic properties of cobalt(II) and copper(II) coordination polymers assembled by phthalate and 4-methylimidazole
    (2004)
    Baca, Svetlana G.
    ;
    Malinovskii, Stanislav T.
    ;
    Franz, Patrick
    ;
    Ambrus, Christina
    ;
    Stoeckli-Evans, Helen 
    ;
    Gerbeleu, Nicolae
    ;
    Decurtins, Silvio
    New coordination polymers [M (Pht)(4-MeIm)2 (H2O)]n (M=Co (1), Cu (2); Pht2−=dianion of o-phthalic acid; 4-MeIm=4-methylimidazole) have been synthesized and characterized by IR spectroscopy, X-ray crystallography, thermogravimetric analysis and magnetic measurements. The crystal structures of 1 and 2 are isostructural and consist of [M (4-MeIm)2(H2O)] building units linked in infinite 1D helical chains by 1,6-bridging phthalate ions which also act as chelating ligands through two O atoms from one carboxylate group in the case of 1. In complex 1, each Co(II) atom adopts a distorted octahedral N2O4 geometry being coordinated by two N atoms from two 4-MeIm, three O atoms of two phthalate residues and one O atom of a water molecule, whereas the square-pyramidal N2O3 coordination of the Cu(II) atom in 2 includes two N atoms of N-containing ligands, two O atoms of two carboxylate groups from different Pht, and a water molecule. An additional strong O–HO hydrogen bond between a carboxylate group of the phthalate ligand and a coordinated water molecule join the 1D helical chains to form a 2D network in both compounds. The thermal dependences of the magnetic susceptibilities of the polymeric helical Co(II) chain compound 1 were simulated within the temperature range 20–300 K as a single ion case, whereas for the Cu(II) compound 2, the simulations between 25 and 300 K, were made for a linear chain using the Bonner–Fisher approximation. Modelling the experimental data of compound 1 with MAGPACK resulted in: g=2.6,