Extension of an Encapsulating Macrobicyclic Ligand Using the Palladium-Catalyzed Suzuki-Miyaura Reaction of a Diiodoclathrochelate Iron(II) Tris-Glyoximate with Reactive Halogen Atoms in Its Apical Substituents

The ability to extend the apical substituents at a macrobicyclic tris-glyoximate framework using a palladium-catalyzed Suzuki-Miyaura C-C-cross-coupling was tested. The reaction of an iron(II) diiodoclathrochelate with phenylboronic acid was successfully performed in toluene using the catalytic system Pd(CH3COO)(2)/SPhos and CsF as inorganic base. The reflux at 110 degrees C gave a macrobicyclic iron(II) complex with two apical biphenyl substituents, characterized using the spectral methods and by the single crystal X-ray diffraction. Asymmetric unit of its crystal consists of two symmetrically independent clathrochelate molecules. Their FeN6-coordination polyhedra with heights h of 2.37 angstrom, Fe-N distances of 1.903(3)-1.916(2) angstrom, and the bite (chelate) angles alpha of 78.4 degrees-78.6 degrees possess a distorted trigonal prismatic-trigonal-antiprismatic geometry with the distortion angles phi of 18.5 degrees and 18.0 degrees, respectively; the encapsulated iron(II) ion is situated almost in their centers. The crystal packing is mainly governed by the intermolecular hydrophobic H center dot center dot center dot H, H center dot center dot center dot C, and C center dot center dot center dot C interactions and by the H center dot center dot center dot O, and H center dot center dot center dot N hydrogen bonds as well.