Synthesis and characterization of the inclusion compound of a methyltrioxorhenium(VII) adduct of 4-ferrocenylpyridine with β-cyclodextrin

An organometallic Lewis base adduct of methyltrioxorhenium(VII) (MTO), comprising the ligand 4-ferrocenylpyridine, has been isolated and characterized. The binuclear complex and also the precursor free ligand have been immobilized in β-cyclodextrin (CD) to give inclusion complexes with a one-to-one stoichiometry. Powder X-ray diffraction (XRD) indicates that the microcrystalline powders obtained are true homogeneous inclusion complexes. This is corroborated by thermogravimetric analysis (TGA), which indicates that the ferrocenylpyridine ligand gains an additional thermal stability upon encapsulation. FTIR and ¹³C-solid-state CP MAS NMR spectroscopy confirm that the Re-N ligation is intact for the included binuclear complex. The NMR results also support the conclusion that the monosubstituted ferrocene derivatives adhere to an inclusion model in which the ferrocene penetrates deeply into the CD cavity in axial mode while the substituent protrudes out.