Synthesis of dinuclear metal complexes of a macrocyclic ligand with multi-ligating pendant-arms. Crystal structures of its manganese(II) and cadmium(II) complexes

A series of dinuclear metal complexes, [M2L](ClO4)(2) (M = Mn2+, Ni2+, Zn2 and Cd2+), of a pendant-arm macrocyclic ligand (H2L) have been prepared vi a the cyclocondensation between sodium 2,6-diformyl-4-chlorophenolate and N -(2-methylenepyridinyl)tris(2-aminoethyl)ami and the subsequent transmetali ation with metal perchlorates, and characterized spectroscopically. Among t hese, the crystal and molecular structures of [Mn2L](ClO4)(2) and [Cd,L](Cl O4)(2) have been determined by X-ray diffraction. The structure of the mang anese complex indicates that each pendant-arm is bonded bidentately to the adjacent metal atom and both arms are on the same side of the resulting tet ra-imine macrocycle. The six-coordinated manganese ion has a distorted octa hedral configuration in which an uncommon eight-membered chelating ring has been formed due to the non-bonding tertiary nitrogen. In the structure of the cadmium complex, the pendent arm binds in the same manner to the metal as in the manganese complex. Each metal atom is coordinated by all the dono r atoms including the tertiary nitrogen atom in one chamber of the macrocyc le, and the cadmium ion is seven-coordinated with a geometry of a highly di storted pentagonal bipyramid. The manganese(II) ions in the macrocycle are both essential high spin, with only a very weak antiferromagnetic interacti on. The manganese compound showed only a moderate activity in the catalytic decomposition of hydrogen peroxide. (C) 2000 Elsevier Science S.A. All rig hts reserved.