Synthesis, structure and reactivity of iron(II) clathrochelates with terminal formyl (acetal) groups

• Published in: Inorganica Chimica Acta 2016-01, Vol.440, p.154-164
• Main Authors: Zelinskii, Genrikh E., Belov, Alexander S., Lebed, Ekaterina G., Vologzhanina, Anna V., Novikov, Valentin V., Voloshin, Yan Z.
• Format: Article
• Language: English
• Subjects: Clathrochelates; Ligand reactivity; Macrocyclic compounds; Vector groups
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2015.11.001

Direct template condensation on an iron(II) ion and nucleophilic substitution of the hexachloroclathrochelate precursor gave iron(II) macrobicycles with terminal reactivity formyl (acetal) groups. Those underwent further functionalization with biologically relevant isoniazid substituents thus giving hydrazonate cage complexes with vector groups. [Display omitted] •The first 3- and 4-formylphenylboron-capped iron(II) clathrochelates were synthesized.•The formyl cage complexes underwent H+-catalyzed condensation with isoniazid.•The formyl-terminated iron(II) hexachloroclathrochelate precursor was obtained.•Nucleophilic substitution afforded hexa-mercaptobenzoic sulfide iron cage complex. 3- and 4-Formylphenylboron-capped aliphatic iron(II) clathrochelates were obtained by direct template condensation of the corresponding α-dioxime with 3- and 4-formylphenylboronic acids on an iron(II) ion as a matrix under mild reaction conditions in methanol or acetonitrile media; with methanol as a solvent, such one-pot reactions gave also their acetals. The latters were converted to the formyl-terminated iron(II) clathrochelates by H+-catalyzed hydrolysis. The reactive formyl-terminated cage complexes obtained underwent their further H+-catalyzed condensation with isoniazid as a hydrazone component giving the hydrazonate cage complexes with vector apical substituents of this type. The formyl-terminated iron(II) hexachloroclathrochelate was synthesized by template reaction of dichloroglyoxime on an iron(II) ion with 3-formylphenylboronic acid. Nucleophilic substitution of its reactive chlorine atoms with thiolate ions generated in situ from para-mercaptobenzoic acid afforded hexasulfide iron(II) cage complex with six ribbed para-mercaptobenzoic substituents and formyl groups in its apical substituents. The iron(II) complexes synthesized were characterized using elemental analysis, MALDI–TOF mass spectrometry, IR, UV–Vis, 1H and 13C{1H} NMR spectroscopies and by X-ray crystallography (for three aliphatic macrobicyclic acetals).