Isolation of a pentadentate ligand and stepwise synthesis, structures, and magnetic properties of a new family of homo- and heterotrinuclear complexes

A neutral pentadentate ligand, di(pyrazolecarbimido)amine (Hdcadpz), and its adduct with HClO4,[H(2)dcadPZ](+)[ClO4](-), were for the first time isolated from our previously reported [Cu-3(dcadpz)(2)(Hpz)(2)(ClO4)(2)](ClO4)(2)center dot H2O by the use of (NH4)(2)S to remove the Cu-II ions and characterized by IR, EA, UV, NMR, MS, and X-ray crystallography. Reactions of copper(II) or nickel(II) nitrate with Hdcadpz in a 1:2 molar ratio generated two mononuclear precursors of [Cu(dcadpz)(2)] (1) and [Ni(dcadpz)(2)]center dot 2/3DMF (2). Furthermore, three new linear homo- and heterotrinuclear complexes of the same motif [M{M '(dcadpz)(2)}M] (M = Co-II, Ni-II, M ' = Cu-II, Ni-II), [{Co(pdm)}(2){Cu(dcadpz)(2)}](NO3)(4) (3), [{Ni(pdm)}(2){Cu(dcadpz)(2)}](NO3)(4) (4), and [{Ni(MeOH)(H2O)(2)}(2){Ni(dcadpz)(2)}](NO3)(4) (5), were synthesized from these two precursors (pdm = 2,6-pyridinedimethanol) and characterized by X-ray crystallography. Magnetic studies show that the central Cu(dcadpz)(2) motif is antiferromagnetically coupled with both the terminal Co(II) atoms via the dcadpz(-) ligand in 3 with a J value of -5.27 cm(-1) and ferromagnetically coupled with both the terminal Ni(II) atoms in 4 with a J value of 2.50 cm(-1), while 5 behaves only as a Curie paramagnet between 2 and 300 K due to the diamagnetic character of the central square-planar Ni(II) atom.