[2-Formyl-4-methyl-6-({2-[2-(4-nitrobenzylamino)ethylamino]ethylimino}methyl)phenolato]nickel(II) perchlorate

In the unsymmetrical title complex, [Ni(C20H23N4O4)]ClO4, the coordination geometry for the NiII atom can be described as square planar. The aromatic rings in the two ligands are almost vertical, with a dihedral angle of 85.3°. In the crystal, cations and anions are linked by weak C(N)—H⋯O hydrogen bonding.

In the unsymmetrical title complex, [Ni(C 20 H 23 N 4 O 4 )]ClO 4 , the coordination geometry for the Ni II atom can be described as square planar. The aromatic rings in the two ligands are almost vertical, with a dihedral angle of 85.3 . In the crystal, cations and anions are linked by weak C(N)-HÁ Á ÁO hydrogen bonding.
In the title complex, [NiC 20 H 23 N 4 O 4 ].ClO 4 , the Ni II atom is four-coordinated by three amino N atoms from the ligand L 2 and one O atom from the ligand L 1 , the basal bond distances around the Ni II atom are in the range of 1.829-1.936 Å ( Fig.   1, Table 1), and the Ni-O distance shorter than that of Ni-N. The four atoms are coplanar with mean plane deviation of 0.027 (4) Å.

Experimental
All the solvents and chemicals were of analytical grade and used without further purification. 2,6-Diformyl-4-methylphenol was prepared according to the literature method (Mandal et al. 1989;Long et al. 1983). N 1 -(2-aminoethyl)-N 2 -(4nitrobenzyl)ethane-1,2-diamine was prepared according to the literature method (Jian et al. 2004;Hu et al. 2011). L 2 (0.119 g, 0.5 mmol) dissolved in 10 mL water was added dropwise to a solution of L 1 (0.082 g, 0.5 mmol) and Ni(ClO 4 ) 2 .6H 2 O (0.183g, 0.5 mmol) in anhydrous ethanol (25 mL), the mixture was stirred at ambient temperature for 8 h and filtered. The orange block crystals suitable for the X-ray measurement were obtained by evaporation of the filtrate at room temperature for three weeks.

Refinement
All H atoms for C-H distances were placed in calculated positions and included in the refinement in the riding-model approximation, with U(H) set to -1.2Ueq of the parent atom.

Computing details
Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 (2) where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.49 e Å −3 Δρ min = −0.44 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.