POLYCHLORINATED BIARYL HETEROCYCLES AS POTENTIAL LIGANDS - REACTIONS BETWEEN OCTACHLORO-1,10-PHENANTHROLINE AND OCTACHLORO-2,2'-BIPYRIDINE WITH COPPER(I) AND OTHER METAL-IONS

Per-chlorinated derivatives of the common alpha-diimine chelate ligand s 2,2-'-bipyridine and 1,10-phenanthroline were synthesized and tested for their coordination behavior towards metal ions. Octachloro-1,10-p henanthroline (ocp) was obtained via chlorination with PCl5 under pres sure (300 degrees C, 18 h). It fails to form stable complexes with e.g . Fe2+, Mn2+, Ru2+, Ni2+, Zn or Cd2+, but yields complex cations [M(oc p)(2)](+) with M = Cu, AE. The crystal structure analysis of the red t etrafluoroborate of the copper(I) complex cation reveals a distorted t etrahedral coordination at the metal with a slight tendency towards th e trigonal-pyramidal arrangement; two essentially planar ligands with small bite angles intersect at almost right angle. Relative to convent ional bis(1,10-phenanthroline)copper(I) complexes with similar structu res, [Cu(ocp)(2)](+) has oxidation and reduction potentials shifted po sitively by about 1 V which leaves the energy of the main MLCT absorpt ion features little chan ed. Attempts to synthesize RuCl2(ocp)(2) in D MF produced as substituted product a symmetrical bis(dimethylamino)-he xachloro-1,10-phenanthroline which can be oxidized electrochemically i n two steps. In contrast to ocp, octachloro-2,2'-bipyridine (ocb) show ed no detectable complexation with Cu and a very negative reduction po tential, most probably due to its inability to exhibit a low-energy co planar conformation.