The First Characterized Coordination Compounds of Macrocyclic Ligands Including Incorporated Tetrazole Rings

Abstract

The macrocyclic binuclear tetrazole, 2,2,5,5-tetramethyl-12-oxa-1,6,7,8,16,17,18,19-octaazatricyclo[13.2.1.16,9]nonadeca-7,9(19),15(18),16-tetraene (L), reacts with copper(II) chloride or copper(II) tetrafluoroborate hexahydrate to give complexes [Cu3Cl6L2] (1) or [CuL2(H2O)2](BF4)2(H2O) (2), respectively. According to single crystal X-ray analysis, both complexes were found to be coordination polymers. In the crystal structure of complex 1, there are neutral linear bibridged trinuclear units Cu3Cl6, in which the copper atoms are linked together by double chlorine bridges. Neighboring Cu3Cl6 units are bonded to each other by two bridging macrocyclic ligands L due to coordination bonds Cu–N between terminal copper atoms of Cu3Cl6 units and the tetrazole ring nitrogen atoms of ligands L to form polymeric chains. In complex 2, the copper atom is bonded to three ligands L via the tetrazole ring nitrogen atoms, and to two water molecules, with formation of a square-pyramidal coordination of the metal. In this complex, one of two independent ligands L shows monodentate coordination, whereas another ligand plays the role of a bridge between two neighboring copper atoms being responsible for formation of polymeric cationic chains [CuL2(H2O)2]n2n+. A complex system of hydrogen bonds connects the chains and the anions BF4– into a three-dimensional network. The temperature-dependent magnetic susceptibility measurements of complex 1 revealed that the copper(II) ions were ferromagnetically coupled showing a coupling constant J of 50 cm–1.