Crystal structure of [2-({2-[(2-azanidylbenzylidene)amino]benzylidene}amino)-4-chlorophenolato]nickel(II)

The metal atom of the title compound is four coordinated. The asymmetrically appended Cl atom and a widely spread π-conjugated system of the complex molecule construct the supramolecular structures of a hydrogen-bonded chain and a π–π interacted column.

The title complex, [Ni(C 20 H 14 ClN 3 O)], with an asymmetrically chlorideappended Schiff base ligand has been synthesized and structurally characterized at 100 K. In the compound, the central nickel(II) ion has a square-planar coordination geometry with N 3 O donors of the -conjugated tetradentate Schiff base ligand. In the crystal, the complexes are connected into an inversion dimer via an NiÁ Á ÁNi interaction [3.1753 (5) Å ] and a pair ofinteractions [centroid-centroid distance = 3.8416 (16) Å ]. The dimers are linked via a C-HÁ Á ÁCl hydrogen bond, forming a chain along the c-axis direction. The dimer chains interact with each other throughinteractions [centroid-centroid distance = 3.8736 (16) Å ], forming a layer expanding parallel to the ac plane.

Chemical context
Metal complexes with a tetradentate Schiff base ligand as represented by H 2 (salen) [N,N 0 -ethylenebis(salicylideneimine)] and its derivatives have played extremely important roles in the field of coordination chemistry. Up to now, a large number of salen derivatives have been prepared and used for complexation in the expectation of a wide range of features such as catalytic ability, magnetic, dielectric and luminescence properties and so on (Bermejo et al., 1996). In these cases, symmetric tetradentate ligands mainly produce N 2 O 2 or N 4 type coordination environments. In this research, we have designed asymmetric structures, both in the coordination environment and in the molecular configuration, for the construction of the supramolecular structure through intermolecular hydrogen bonds, and synthesized the title nickel(II) complex using an asymmetrically chloride-appended tetradentate Schiff base ligand.
The structure of the title compound, which features a widely spread -conjugated ring system, is also useful for supramolecular assemblies throughinteractions. The mononuclear copper(II) complex with a similar N 3 O type asymmetrical ligand was reported by Ghorai & Mukherjee (2014).

Supramolecular features
In the crystal, pairs of complex molecules related by an inversion centre are dimerized by an NiÁ Á ÁNi interaction [3.1753 (5) Å ] and a pair ofinteractions between the C1-C6 and C15-C20 benzene rings [centroid-centroid distance = 3.8415 (16) Å ]. Such dimerization caused by an NiÁ Á ÁNi interaction has also been observed in symmetric Ni(salen) compounds (Aulló n et al., 1996;Siegler & Lutz, 2009). The dimeric molecules of the title compound are linked by C-HÁ Á ÁCl hydrogen bonds (Table 1), producing a chain of dimers along the c axis (Fig. 2). The dimers further interact with each other throughinteractions between the C1-C6 and C8-C13 benzene rings [centroid-centroid distance = 3.8738 (17) Å ], forming a column along the a axis (Fig. 3). Together, these C-HÁ Á ÁCl andinteractions result in a layer parallel to the ac plane. The layers are further linked by a short C-HÁ Á ÁC contact (Table 1), giving a three-dimensional network (Fig. 4). The molecular structure of the title compound, showing displacement ellipsoids at the 50% probability level.

Figure 2
Packing diagrams of the title compound, showing (a) a chain structure running along the c axis formed by C-HÁ Á ÁCl hydrogen bonds (red dashed lines) and (b) the chains viewed along the a axis.
1.0 mmol) in methanol (50 ml) under stirring for 1 h. The resulting solution including the ligand was used for complexation with the Ni II ion. A methanol solution (50 ml) of Ni(CH 3 COO) 2 Á4H 2 O (0.249 g, 1.0 mmol) was added to the solution and stirred for 1 h. The resulting solution was allowed to stand for a few days, during which time dark-purple blockshaped crystals precipitated. They were collected by suction filtration and dried in air to give single crystals of the title compound suitable for X-ray diffraction.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The position of the N-bound H atom was refined with N-H = 0.86 (1) Å and U iso (H) = 1.5U eq (N). Other H atoms were treated as riding with C-H = 0.95 Å and U iso (H) = 1.2U eq (C).

[2-({2-[(2-Azanidylbenzylidene)amino]benzylidene}amino)-4-chlorophenolato]nickel(II)
Crystal data 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 was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 sigma(F 2 ) is used only for calculating Rfactor (gt).