SYNTHESIS AND CHARACTERIZATION OF COPPER, NICKEL AND COBALT COMPLEXES OF N,N'-DIMETHYL-2,11-DIAZA[3,3](2,6)PYRIDINOPHANE

The properties of the tetraazamacrocyclic compound N,N'-dimethyl-2,11-diaza[3,3](2,6)pyridinophane (L-N(4)Me(2)) as a ligand for some selected metal chlorides have been examined. The crystal structure of the uncoordinated ligand reveals a syn chair-chair conformation. In solution, the ligand displays fluctional behavior. Reaction of L-N(4)Me(2) with the chlorides of copper(II), nickel(II), and cobalt(II) affords the complexes [Cu(L-N(4)Me(2))Cl-2] . H2O (3), [Ni(L-N(4)Me(2)) (H2O)Cl]Cl . H2O (4), and [Co(L-N(4)Me(2))Cl-2] . 2 H2O (5) in which the ligand adopts a syn boat-boat conformation. The crystal structures of 4 and 5 are presented. Due to the small cavity of the 12-membered ring of the ligand, exclusively distorted cis-octahedral coordination geometries are found at the metal sites. A comparison of structural data of several complexes with this ligand shows that the extent of the distortions from ideal octahedral geometry is mainly determined by the M-N-py bond strength. The electronic as well as the solution properties of the described complexes have been investigated by electronic absorption spectroscopy, ESR spectroscopy, and electrochemical methods.