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 a iron(II) ion matrix afforded 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 the macrobicyclic complexes with a single apical 1,4-pentadienyl substituent.