Komplexe eines vierzehngliedrigen Tetraazadibenzo-Makrocyclus. Strukturen des freien und zweifach protonierten Liganden und seiner Nickel(II)-, Kupfer(II)-, Zink(II)- und Palladium(II)-Komplexe / Complexes of a 14-Membered N4 Dibenzo Macrocycle. Crystal Structures of the Free and Diprotonated Ligand and of its Nickel(II), Copper(II), Zink(II) and Palladium (II) Complexes
Abstract The synthesis and structural characterisation of complexes of the 14-membered macrocyclic trans-N4 dibenzo ligand 5,6,7,8,9,14.15,16,17,18-decahydrodibenzo[e,l][1,4, 8,11]-tetraazacyclotetradecine (L2) is described. The crystal structures of six compounds were determined by single crystal X-ray diffraction. The free ligand L2 has a saddle-shaped structure with short intramolecular hydrogen bonds. The N-N distances are 289 pm. The diprotonated species [H2L2]2+ has a different conformation due to intra- and intermolecular hydrogen bonds. The ligand is folded along an N-N axis in c/s-[Ni(L2)(H2O)2]2+, but displays a saddleshaped structure in the Cu(II), Zn(II) and Pd(II) complexes with a more or less planar arrangement of the four N donor atoms. The metal atoms are incorporated within the macrocyclic cavity in [Cu(L2)(CF3SO3)]+ and [Pd(L2)]2+. The metal-to-nitrogen bond lengths herein are rather small. Zn(II) is five-coordinate in [Zn(L2)(Cl)]+. The coordination polyhedron is intermediate between a trigonal bipyramid and a square pyramid. In all complexes the metalto- ligand distances originating at the nitrogen atoms in β-position (with respect to the aromatic ring) are significantly shorter then the donor bonds of the ‘anilinic’ N atoms