Cage iron(II) complexes with apical and ribbed adamantyl substituents: The creation of second (hydrophobic) shell of an encapsulated metal ion

The iron(II) clathrochelates with apical adamantyl substituents were synthesized by the direct template reaction on a metal ion matrix. The nucleophilic substitutions of reactive hexachloride precursors with adamantylthiolate anion afforded hexa- and octaadamantyl cage iron(II) complexes. Clathrochelates obtained have been characterized using elemental analysis, MALDI-TOF mass, IR, UV–Vis, 57Fe Mössbauer and 1H, 13C NMR spectroscopies, and X-ray crystallography. Configurations intermediate between trigonal prismatic and trigonal antiprismatic have been deduced for the low-spin iron(II) ion coordination polyhedra of all clathrochelates obtained using 57Fe Mössbauer parameters and confirmed by X-ray crystallography data. Two apical and up to six ribbed adamantyl substituents allow one to change the physical properties of clathrochelates synthesized in wide range. In particular, these substituents form second (hydrophobic) shell that opens up the possibility to membrane and cellular transport of the cage complexes.