Template synthesis, structure and spectra of the semiclathrochelate and clathrochelate 1,4-pentadienylboron-capped iron(II) oximehydrazonates

The direct template condensation of diacetylmonooxime hydrazone with the 1,4-pentadienylboronates as Lewis acids on an iron(II) ion matrix led to the 1,4-pentadienylboron-capped semiclathrochelate iron(II) oximehydrazonates. The H⁺-ion-catalyzed macrocyclization of these precursors with an excess of triethyl orthoformate resulted in macrobicyclic complexes with a single apical 1,4-pentadienyl substituent. The complexes obtained were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV-Vis, ¹H, ¹¹B{¹H} and ¹³C{¹H} NMR, ⁵⁷Fe Mössbauer spectroscopies, and X-ray crystallography. The X-ray diffraction and NMR data for complexes obtained showed the syn,syn,syn-orientation of all ethoxy substituents in 1,3,5-triazacyclohexane capping fragment in relation to a clathrochelate framework.