{2,2′-[o-Phenylenebis(nitrilomethanylylidene)]diphenolato-κ4 O,N,N′,O′}nickel(II) monohydrate

The NiII atom in the title monohydrate, [Ni(C20H14N2O2)]·H2O, is coordinated within a cis-N2O2 square-planar donor set provided by the tetradentate Schiff base ligand. Overall, the molecule has a curved shape with the dihedral angle formed between the planes of the outer benzene rings being 13.92 (18)°. The water molecule was found to be disordered over two positions [ratio 0.80 (1):0.20 (1)] and the major component is linked to the complex via an O—H⋯O hydrogen bond.

The Ni II atom in the title monohydrate, [Ni(C 20 H 14 N 2 O 2 )]Á-H 2 O, is coordinated within a cis-N 2 O 2 square-planar donor set provided by the tetradentate Schiff base ligand. Overall, the molecule has a curved shape with the dihedral angle formed between the planes of the outer benzene rings being 13.92 (18) . The water molecule was found to be disordered over two positions [ratio 0.80 (1)

Related literature
For background to the catalytic potential of transition metal Schiff base complexes, see: Gupta & Sutar (2008). For the structure of the unsolvated form of the title complex. see: Radha et al. (1985); Wang et al. (2003). For our recent work in this area, see: Ghaemi et al. (2011).

Experimental
Crystal data [Ni(C 20

Comment
Schiff base complexes of transition metal ions are efficient catalysts both in homo-and hetero-geneous reactions, and the activity of these complexes varies with the type of ligand, coordination sites and metal ions (Gupta & Sutar, 2008). In continuation of work in this area (Ghaemi et al., 2011), the title complex, (I), was isolated as a monohydrate and characterized crystallographically. An unsolvated form has been characterized previously (Radha et al., 1985;Wang et al., 2003).
The Ni II atom in the complex exists within a cis-N 2 O 2 donor set defined by the tetradentate Schiff base ligand, Fig. 1 and Table 1. The respective pairs of Ni-O and Ni-N bond distances are equal within experimental error. The greatest deviation from the ideal square planar angles is seen in the N1-Ni-N2 chelate angle of 83.98 (9)°. Some minor buckling is found in the N 2 O 2 donor set with the r.m.s. deviation being 0.0548 Å. The maximum deviations from the least-squares plane are 0.0550 (10) and -0.0552 (10) Å for the N1 and N2 atoms, respectively, and the Ni atom lies 0.0002 (11) Å out of the least-squares plane. Each of the chelate rings is essentially planar. Thus, the r.m.s. deviation for the five-membered ring is 0.046 Å, and the equivalent values for the O1-and O2-containing six-membered chelate rings are 0.013 and 0.097 Å, respectively. The dihedral angle formed between the outer benzene rings is 13.92 (18)°, indicating that overall the molecule has a slightly curved shape.
The water molecule of solvation is associated with the complex molecule, forming a hydrogen bond with the O1 atom.
Disorder in the position of the water molecule precludes a detailed analysis of the supramolecular structure.
Experimental N,N'-Bis(2-hydroxybenzylidene)-o-phenylenediamine was prepared by the following procedure. To a stirred ethanolic solution (30 ml) of o-phenylenediamine (0.108 g, 1 mmol), 2-hydroxybenzaldehyde (0.244 g, 2 mmol) was added. The brightyellow solution was stirred and heated to reflux for 1 h. A yellow precipitate was obtained that was filtered off, washed with diethyl ether; yield: 75%. The title complex was obtained by the following procedure. The Schiff base ligand (0.316 g, 1 mmol) was dissolved in 20 ml e thanol. A solution of nickel(II) acetate (0.248 g, 1 mmol) in ethanol was added to the solution of ligand and the reaction mixture was refluxed for 1 h. The product washed with ethanol and air dried; yield: 85%.
Dark brown blocks of the title complex were obtained from its 5:1 acetone and methanol mixture (v/v) by slow evaporation of the solvents at room temperature over several days.

Refinement
The C-bound H-atoms were placed in calculated positions (C-H 0.93 Å) and were included in the refinement in the riding model approximation, with U iso (H) set to 1.2U equiv (C). The water molecule is disordered over two positions in a 0.80 (1):0.20 (1) ratio (from refinement). The H atoms were found for the major component only. These were very tightly supplementary materials sup-2 restrained with O-H = 0.84±0.01 Å and H···H = 1.37 + 0.01 Å; U iso (H) was set to 1.5U equiv (O). The major component forms a hydrogen bond (through the H1 atom), but the H2 atom occupies a site close to that occupied by the minor component. Fig. 1. The molecular structure of (I) showing displacement ellipsoids at the 35% probability level. Only the major component of the disordered water molecule is illustrated.

Figures
Crystal data [Ni(C 20