SYNTHESIS AND STRUCTURES OF THE VANADYL, COBALT(III), NICKEL(II), COPPER(II), ZINC(II) AND PALLADIUM(II) COMPLEXES OF A 14-MEMBERED UNSATURATED TETRAAZADIBENZO MACROCYCLE

The synthesis and structural characterisation of complexes of the 14-m embered macrocyclic trans-N-4 dibenzo ligand 7,8,9,16,17,18-hexahydrod ibenzo[e,1][1,4, 8,11]-tetraazacyclotetradecine (L(1)) is described. T he crystal structures of six compounds were determined by single cryst al X-ray diffraction. In [CuL(1)](2+) the metal atom is tightly bound within the macrocyclic cavity. The Cu-N bonds [201.2(3) and 191.8(3)pm ] are rather short. Zn(II) is penta-coordinated in [Zn(L(1))Cl](+) wit h the metal center outside the cavity. L(1) is deprotonated at one or both secondary amine functions in the complexes [Ni(L(1)-H)](+), [Co(L (1)-2H)](+), [VO(L(1)-2H)] and [Pd(L(1)-2H)]. With the exception of [V O(L(1)-2H)] the metal ions assume nearly square planar N-4-coordinatio n, which is very rare for Co(lII). Salts of [Co(L(1)-2H)](+) display a temperature independent magnetic moment of 0,64 B. M. The nickel, cob alt and palladium complexes show remarkably short metal-nitrogen bond distances: Ni-N [183.8(8)1, Co-N [181.8(2)1 and Pd-N [194.5(6) pm], re spectively. The UV/Vis and EPR spectra, and the electrochemical behavi our of some of these complexes are also discussed.