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Stoeckli-Evans, Helen

Nom
Stoeckli-Evans, Helen
Affiliation principale
Fonction
Professeur.e émérite
Email
helen.stoeckli-evans@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/470
_
0000-0002-9960-3869

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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 of monoorganotin(IV) chloride complexes of cis-1,2-bis(diphenylphosphino)ethylene: Solution and solid state structures
    (2007)
    Ebrahim, Mothi Mohamed
    ;
    Stoeckli-Evans, Helen 
    ;
    Panchanatheswaran, Krishnaswamy
    Organotin(IV) complexes of the type [RSnCl3 (cis-Ph2PCH=CHPPh2)] [R = Me (1), nBu (2), Ph (3)] were prepared by the reaction of RSnCl3 with the rigid bisphosphine ligand, cis-1,2-bis(diphenylphosphino)ethylene in dichloromethane. The complexes have been characterized both in solution and the solid state. Low temperature 31P and 119Sn NMR studies indicate two different phosphorus environments. The crystal structures indicate a weak but chelating mode of coordination of the two phosphorus atoms to tin, leading to a distorted octahedral geometry. In solution the complexes 1–3 undergo a redistribution reaction to form [SnCl4 (cis-Ph2PCH=CHPPh2)] (4) as one of the products. In order to confirm the redistribution, complex 4 has been prepared separately and characterized both structurally and spectrally.