Nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II) complexes of tris(2-aminoethyl)phosphine oxide

New coordination compounds Ni(TEAPO)X-2. nH(2)O, Cu(TAEPO)(NO3)(2). 4H(2)O, Zn(TEAPO)(NO3)(2) . 2H(2)O, Cd(TEAPO)(NO3)(2). 2H(2)O, Hg(TEAPO)Br-2. 2H(2)O (TAEPO = tris(2-aminoethyl)phosphine oxide, X=Cl or ClO4, n = 4 or 2) have been synthesized and characterized. As revealed by a single-crystal X-ray analysis of Cu(TAEPO)(NO3)(2). 4H(2)O, the Cu(II) ion has a distorted octahedral arrangement of donor atoms with a CuN3O3 chromophore. Tris(2-aminoethyl)phosphine oxide acts as a tetradentate donor forming a bridge among three adjacent copper(II) atoms in the cyclic-chain, polymeric structure. Each central atom is coordinated by three nitrogens and one oxygen from three TAEPO ligands in a square-planar geometry. The coordination geometry of Cu(II) is completed by weaker interactions with two water molecules [Cu-O = 2.461(5), 2.601(5) Angstrom]. The remaining water molecules and nitrate anions are not coordinated.