Crystal structure of a nickel compound comprising two nickel(II) complexes with different ligand environments: [Ni(tren)(H(2)O)(2)][Ni(H(2)O)(6)](SO(4))(2).

The title compound, di-aqua-[tris-(2-amino-eth-yl)amine]-nickel(II) hexa-aqua-nickel(II) bis-(sulfate), [Ni(C(6)H(18)N(4))(H(2)O)(2)][Ni(H(2)O)(6)](SO(4))(2) or [Ni(tren)(H(2)O)(2)][Ni(H(2)O)(6)](SO(4))(2), consists of two octa-hedral nickel complexes within the same unit cell. These metal complexes are formed from the reaction of [Ni(H(2)O)(6)](SO(4)) and the ligand tris-(2-amino-eth-yl)amine (tren). The crystals of the title compound are purple, different from those of the starting complex [Ni(H(2)O)(6)](SO(4)), which are turquoise. The reaction was performed both in a 1:1 and 1:2 metal-ligand molar ratio, always yielding the co-precipitation of the two types of crystals. The asymmetric unit of the title compound, which crystallizes in the space group Pnma, consists of two half Ni(II) complexes and a sulfate counter-anion. The mononuclear cationic complex [Ni(tren)(H(2)O)(2)](2+) comprises an Ni ion, the tren ligand and two water mol-ecules, while the mononuclear complex [Ni(H(2)O)(6)](2+) consists of another Ni ion surrounded by six coordinated water mol-ecules. The [Ni(tren)(H(2)O)(2)] and [Ni(H(2)O)(6)] subunits are connected to the SO(4) (2-) counter-anions through hydrogen bonding, thus consolidating the crystal structure.