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

Abstract

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).