Dicyanamido-metal(II) complexes. Part 4: Synthesis, structure and magnetic characterization of polynuclear Cu(II) and Ni(II) complexes bridged by mu-1,5-dicyanamide

摘要

The one pot aqueous reaction of M(ClO4)(2) (M = Cu2+ or Ni2+) with N-methylbis[2-(2-pyridylethyl)] amine (MeDEPA) and N,N'-dimethyl-N,N'-bis(2-pyridylmethyl) ethylenediamine (bpmen) and 1,4,7,10-tetraazacyclododecane (cyclen) in presence of sodium dicyanamide (Nadca) yielded dicyanamido-bridged polynuclear complex {[Cu(MeDEPA)(mu-1,5-dca)]ClO4}(n) (1), and two dinuclear complexes [Cu-2(bpmen) 2 (mu-1,5-dca)](2)(ClO4)(5)dca ( 2) and [Ni(cyclen)(mu-1,5-dca)](2)(ClO4)(2) ( 3). These complexes were characterized by IR and UV-Vis spectroscopy. Room temperature single-crystal X-ray studies have confirmed that the Cu(II) centers in 1 and 2 adopt geometries that are more close to trigonal bipyramidal (TBP) in 1 and close to square pyramidal (SP) in 2, whereas in 3, the Ni(II) centers are located in octahedral environment with doubly bridged mu-1,5-dca bonding mode. The intermolecular M center dot center dot center dot M distances in these complexes are in the range of 7.3-8.6 angstrom. Variable temperature magnetic susceptibility studies have confirmed that the dca-bridges mediate very weak antiferromagnetic interaction between the M( II) centers with J values of -0.35, -0.18 and -0.43 cm(-1) for 1, 2 and 3, respectively. The results are compared and discussed in the light of other related bridged mu-1,5-dca Cu(II) and Ni(II) complexes.