Versatile coordination mode of dicyanamide in nickel(II) complexes containing polyamines as blocking ligands

Triethylenetetramine (L-4) and dipropylenetriamine (L-3) were used as blocking ligands (tetradentate and tridentate, respectively) that, after complexation with Ni(II), leave two or three sites ready for ligation with N(CN)(2)(-) (dicyanamide, abbr. dca). The formed complexes are mononuclear, binuclear or polymeric. This was proven by the X-ray structure analysis for [NiL4(dca)(2)] (mononuclear, 1), [(dca)(LNi)-Ni-3(dca)(2)NiL3(dca)] (binuclear, 2) and [NiL4(dca)](ClO4) (polymeric, 3). The magnetic susceptibility measurements for 1 confirm that the Curie law is obeyed at higher temperatures whereas the zero-field splitting is effective below 10 K (D/hc = -4 cm(-1)); 2 shows a weak anti ferromagnetic coupling (J/hc = -0.6 cm(-1)); 3 exhibits a negligible exchange coupling (J/hc approximate to 0). (C) 2004 Elsevier Ltd. All rights reserved.