Bis{(E)-2-eth-oxy-6-[2-(ethyl-ammonio)ethyl-iminometh-yl]phenolato}nickel(II) bis(perchlorate).

In the title centrosymmetric mononuclear nickel(II) complex, [Ni(C(13)H(20)N(2)O(2))(2)](ClO(4))(2), the Ni(II) atom is four-coordinated by the imine N and phenolate O atoms of the zwitterionic forms of two Schiff base ligands in a square-planar coordination geometry. In the crystal structure, mol-ecules are linked through inter-molecular N-H⋯O hydrogen bonds, forming chains running along the a axis.

In the title centrosymmetric mononuclear nickel(II) complex, [Ni(C 13 H 20 N 2 O 2 ) 2 ](ClO 4 ) 2 , the Ni II atom is four-coordinated by the imine N and phenolate O atoms of the zwitterionic forms of two Schiff base ligands in a square-planar coordination geometry. In the crystal structure, molecules are linked through intermolecular N-HÁ Á ÁO hydrogen bonds, forming chains running along the a axis.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SJ2526).
Complex (I) consists of a centrosymmetric mononuclear nickel(II) complex cation and two perchlorate anions. The Ni II atom in the cation, lies on an inversion centre, with the asymmetric unit made up from one half of the Ni(II) complex and one perchlorate anion. The Ni(II) atom is four-coordinated by two imine N and two phenolate O atoms from two zwitterionic Schiff base ligands in a square-planar coordination geometry. The coordinate bond lengths (Table 1) are typical and comparable to the corresponding values observed in similar nickel(II) Schiff base complexes (Zhao, 2007;Skovsgaard et al., 2005;Ma et al., 2008).
In the crystal structure, molecules are linked through intermolecular N-H···O hydrogen bonds (Table 2), forming chains running along the a axis (Fig. 2).

Experimental
The Schiff base compound was prepared by the condensation of equimolar amounts of 3-ethoxysalicylaldehyde with Nethylethane-1,2-diamine in a methanol solution. The complex was prepared by the following method. To a methanol solution (5 ml) of Ni(ClO 4 ) 2 .6H 2 O (36.6 mg, 0.1 mmol) was added a methanol solution (10 ml) of the Schiff base compound (23.6 mg, 0.1 mmol) with stirring. The mixture was stirred for 30 min at room temperature and filtered. Upon keeping the filtrate in air for a few days, red block-shaped crystals formed at the bottom of the vessel on slow evaporation of the solvent.

Refinement
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H distances in the range 0.93-0.97 Å, N-H distances of 0.90 Å, and with U iso (H) = 1.2U eq (C,N) and 1.5U eq (methyl C).
supplementary materials sup-2 Figures Fig. 1. The molecular structure of (I) with ellipsoids drawn at the 30% probability level. Unlabelled atoms are at the symmetry positions 2 -x, 1 -y, -z.