Diaqua{2,2′-dimethoxy-6,6′-[(1E,1′E)-propane-1,3-diylbis(azanylylidene)bis(methanylylidene)]diphenolato}nickel(II)

In the molecule of the title compound, [Ni(C19H20N2O4)(H2O)2], the central NiII ion lies on a mirror plane and is surrounded by an N2O4 coordination set in the form of a distorted octahedron defined by the O atoms of two water molecules and by two phenolic O and two imine N atoms of the tetradentate Schiff base ligand. In the crystal, O—H⋯O hydrogen bonds between the water molecules and the phenolic and methoxy O atoms of neighbouring molecules lead to the formation of rods propagating parallel to [100].

In the molecule of the title compound, [Ni(C 19 H 20 N 2 O 4 )-(H 2 O) 2 ], the central Ni II ion lies on a mirror plane and is surrounded by an N 2 O 4 coordination set in the form of a distorted octahedron defined by the O atoms of two water molecules and by two phenolic O and two imine N atoms of the tetradentate Schiff base ligand. In the crystal, O-HÁ Á ÁO hydrogen bonds between the water molecules and the phenolic and methoxy O atoms of neighbouring molecules lead to the formation of rods propagating parallel to [100].

Experimental
Crystal data [Ni(C 19   Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010 (Table 1). In the molecule, the dihedral angle between the (C1-C7, N1) plane and its The resulting coordination geometry around the metal cation is comparable to that of complexes with similar Schiffbases. See, for example: Thakurta et al. (2009aThakurta et al. ( ,b,2010a. In the crystal structure of the title comound, intermolecular O-H···O hydrogen bonds between water molecules as donor groups and phenolic O and methoxy O atoms of neighbouring molecules as acceptor groups are observed ( Table   2). The hydrogen bonding interactions lead to the formation of rods propagating parallel to [100] (Fig. 2).

Experimental
The tetradentate Schiff base precursor was prepared according to the literature procedure (Sen et al., 2006). To a hot methanolic solution (20 ml) of Ni(CH 3 COO) 2 . 4H 2 O (0.248 g, 1.0 mmol), the ligand (1.0 mmol) was added, which produced immediately an intensely brown solution. The mixture was then kept at room temperature. After slow evaporation of the brown solution, dark chocolate-brown single crystals with a rectangular form were separated out in 5 days. The crystals were filtered off and washed with water and dried in air.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.93 to 0.97 Å) and were included in the refinement in the riding model approximation. The H atoms of the water molecules were located in a difference map and were refined with an O-H distances restraint of 0.85 (1) Å.

Computing details
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).   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 > σ(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.