{5,5′-Dihydroxy-2,2′-[(2-hydroxypropane-1,3-diyl)bis(nitrilomethanylylidene)]diphenolato}nickel(II) dihydrate

In the title complex, [Ni(C17H16N2O5)]·2H2O, the NiII ion is four-coordinated by two azomethine N and two phenolato O atoms of the tetradentate Schiff base ligand in a slightly distorted square-planar geometry. In the six-membered ring containing the metal, the azomethine N atoms and the three C atoms of the connecting 1,3-diaminopropane-2-ol, all atoms except the metal are disordered over two sets of sites with an occupacy ratio of 0.566 (3):0.434 (3). The central C atom of the major component is significantly out of the mean plane of the remaing atoms while the conformation of this ring in the minor component is noticeably different. In the crystal, O—H⋯O hydrogen bonds involving the lattice water molecules and the hydroxy groups are observed.

In the title complex, [Ni(C 17 H 16 N 2 O 5 )]Á2H 2 O, the Ni II ion is four-coordinated by two azomethine N and two phenolato O atoms of the tetradentate Schiff base ligand in a slightly distorted square-planar geometry. In the six-membered ring containing the metal, the azomethine N atoms and the three C atoms of the connecting 1,3-diaminopropane-2-ol, all atoms except the metal are disordered over two sets of sites with an occupacy ratio of 0.566 (3):0.434 (3). The central C atom of the major component is significantly out of the mean plane of the remaing atoms while the conformation of this ring in the minor component is noticeably different. In the crystal, O-HÁ Á ÁO hydrogen bonds involving the lattice water molecules and the hydroxy groups are observed.

Experimental
The Schiff base ligand, 4,4′-(1E,1′E)-(2-hydroxypropane-1,3-diyl)bis(azan-1-yl-1-ylidene) bis(methan-1-yl-1-ylidene)dibenzene-1,3-diol was prepared by condensation of 2,4-dihydroxybenzaldehyde (0.276 g, 2 mmol) and 1,3-diaminopropane-2-ol (0.090 g, 1 mmol) in methanol (25 mL). After 2 h reflux, the pale yellow solution was cooled to room temperature. The solvent was removed under reduced pressure and the Schiff-base ligand was obtained as a light-yellow liquid that was used without further purification. To prepare the complex, the Schiff base ligand (0.301 g, 1 mmol) was added to a methanolic solution (20 ml) of Ni(CH 3 COO) 2 · 4H 2 O (0.248 g, 1 mmol) which immediately produced an intensely brownish-red solution. The solution was heated to boiling and then kept undisturbed in a dark place. On cooling and after slow evaporation of the solution, dark brown plate-shaped single crystals of the complex separated out over 3 days. The crystals were filtered off and washed with water and dried in air.

Figure 1
The molecular structure of the title complex, showing displacement ellipsoids at the 50% probability level.

{5,5′-Dihydroxy-2,2′-[(2-hydroxypropane-1,3-diyl)bis(nitrilomethanylylidene)]diphenolato}nickel(II) dihydrate
Crystal data [Ni(C 17   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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.