Multistep synthesis and X-ray structures of carboxyl-terminated hybrid iron(II) phthalocyaninatoclathrochelates and their postsynthetic transformation into polytopic carboranyl-containing derivatives

A multistep general synthetic strategy towards polytopic carboranyl-containing (semi)clathrochelate metal complexes, based on the template synthesis, transmetallation, amide condensation and 1,3-dipolar cycloaddition reactions, is developed. Their mono(semi)clathrochelate precursors with a single reactive group were obtained using a transmetallation of the triethylantimony-capped macrobicyclic precursor. The thus obtained carboxyl-terminated iron(II) semiclathrochelate underwent a macrobicyclization with zirconium(IV) phthalocyaninate to form the corresponding phthalocyaninatoclathrochelate. The direct one-pot template condensation of the suitable chelating and cross-linking ligand synthons on the Fe2+ ion as a matrix was also used for its preparation. Further amide condensation of the aforementioned semi-clathrochelate and hybrid complexes with propargylamine in the presence of carbonyldiimidazole gave the (pseudo)cage derivatives with a terminal C equivalent to C bond. Their click reaction with an appropriate carbor-anylmethyl azide afforded the ditopic carboranosemiclathrochelates and the tritopic carboranyl-containing phthalocyaninatoclathrochelates with a flexible spacer fragment between their polyhedral entities. The obtained new complexes were characterized using elemental analysis, MALDI-TOF mass spectrometry, multinuclear NMR, and UV-vis spectroscopy, and by single crystal X-ray diffraction experiments. Their FeN6-coordination polyhedra show a truncated trigonal-pyramidal geometry, while the cross-linking hep-tacoordinate Zr4+ or Hf4+ cations in the hybrid compounds form the (MN4O3)-N-IV-coordination polyhedra with the geometry of a capped trigonal prism.

Automated summary

A multistep synthetic strategy for polytopic carboranyl-containing (semi)clathrochelate metal complexes involving template synthesis, transmetallation, amide condensation, and 1,3-dipolar cycloaddition reactions is developed. Various precursors were obtained through transmetallation and macrobicyclization, and further condensation reactions led to the formation of carboranosemiclathrochelates and phthalocyaninatoclathrochelates. The resulting complexes were characterized by various techniques and exhibited interesting coordination geometries.