Ion-pair-mediated asymmetric synthesis of a configurationally stable mononuclear tris(diimine)-iron(II) complex.

Département de Chimie Organique Université de Genève quai Ernest Ansermet 30, 1211 Genève 4, Switzerland.
Angewandte Chemie International Edition (Impact Factor: 11.34). 08/2002; 41(13):2317-9. DOI: 10.1002/1521-3773(20020703)41:13<2317::AID-ANIE2317>3.0.CO;2-W
Source: PubMed
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    ABSTRACT: Three tricyclic diquats with an eight-membered ring were prepared and shown to be the first configurationally stable derivatives of their kind. Resolution was achieved by using chiral hexacoordinated phosphorus BINPHAT and TRISPHAT anions. The diquat cations were obtained in high diastereo- and enantiomeric purity (ee>96% in most cases). X-ray diffraction analysis coupled with circular dichroism (CD) measurements allowed a precise determination of the relative and absolute configuration of the salts. The barriers to racemization of these compounds were calculated by using CD time-course measurements at different temperatures, affording DeltaG(++) values above 25 kcal mol(-1). Derivatives 4a, 4b, and 4c are the first eight-membered-ring derivatives with only three ring constraints to be resolved. This manuscript also reports the first procedure to remove TRISPHAT anions after diastereomeric separation.
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    ABSTRACT: A series of ditopic ligands incorporating two 2,2′:6′,2″-terpyridine (tpy) metal-binding domains linked to a central naphthalenediyl core by ethyleneoxy chains of various lengths have been prepared and their iron(II) complexes prepared. The major thermodynamic products of complexation are ferracycles of [1 + 1], [2 + 2] or [3 + 3] stoichiometry. In the case of the [1 + 1] complexes, the linker between the two tpy domains is spatially restricted and the cations exhibit chirality associated with the conformation about the central N–Fe–N bonds. The dynamic processes by which the enantiomeric forms interconvert are investigated in the presence of chiral anions by NMR and circular dichroism spectroscopy making use of the Pfeiffer effect. We have shown that ditopic bis(2,2′:6′,2″-terpyridine) ligands give rise to conformationally restricted complexes with iron(II) centres. The absolute configuration of the cations in the diastereomeric ion pairs obtained through the Pfeiffer effect has been calculated using TDDFT methods.
    New Journal of Chemistry 01/2009; 33(2). · 2.97 Impact Factor
  • Angewandte Chemie International Edition 02/2009; 48(33):6073-7. · 11.34 Impact Factor


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May 27, 2014