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

Abstract

The one pot aqueous reaction of M(ClO 4) 2 (M = Cu 2+ or Ni 2+) 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)(μ-1,5-dca)]ClO 4} n ( 1), and two dinuclear complexes [Cu 2(bpmen) 2(μ-1,5-dca)] 2(ClO 4) 5dca ( 2) and [Ni(cyclen)(μ-1,5-dca)] 2(ClO 4) 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 μ-1,5-dca bonding mode. The intermolecular M···M distances in these complexes are in the range of 7.3–8.6 Å. 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 μ-1,5-dca Cu(II) and Ni(II) complexes.