Bis(μ-4-fluoro-2,6-diformylphenolato)bis[diaquanickel(II)] dichloride

In the title dinuclear nickel(II) complex, [Ni2(C8H4FO3)2(H2O)4]Cl2, synthesized by the reaction between 4-fluoro-2,6-diformylphenol and nickel(II) chloride in methanol, the coordination cation is located on an inversion center and the NiII atom adopts a slightly distorted octahedral coordination geometry. The two Ni atoms are bridged by two phenolate O atoms and the intramolecular Ni⋯Ni distance is 3.0751 (9) Å. The crystal structure is stabilized by O—H⋯Cl hydrogen bonds.

In the title dinuclear nickel(II) complex, [Ni 2 (C 8 H 4 FO 3 ) 2 -(H 2 O) 4 ]Cl 2 , synthesized by the reaction between 4-fluoro-2,6diformylphenol and nickel(II) chloride in methanol, the coordination cation is located on an inversion center and the Ni II atom adopts a slightly distorted octahedral coordination geometry. The two Ni atoms are bridged by two phenolate O atoms and the intramolecular NiÁ Á ÁNi distance is 3.0751 (9) Å . The crystal structure is stabilized by O-HÁ Á ÁCl hydrogen bonds.
Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.  Phenoxide-bridged dinuclear complexes have been extensively studied for several decades, most of them were derived from the cyclocondensation of 2,6-diformyl-4-R-phenol and alkyldiamine in the presence of metal ions (Thompson et al.,1996;Zhou et al., 2005;Raimondi et al., 2004).With short distances between the two metal ions in the complexes, they show special electrical and magnetic properties (Mohanta et al., 1998;Wang et al., 1997). Adhikary et al. reported a phenoxide-bridged dinuclear nickel(II) complex, obtained directly from the mixture of 2,6-diformyl-4-methyl-phenol and nickel(II) perchlorate (Adhikary et al., 1987). Here we report the crystal structure of a new dinuclear Ni II complex with fluorine substituent in the phenyl ring. The diference between the title complex and the one Adhikary reported is that they have different substituents in the phenyl ring and different counter-anions.

Structure Reports Online
The coordination cation consists of two 2,6-diformyl-4-flurophenolate ligands, four water molecules, two Ni II ions ( Fig.   1). The chlorine ions do not participate in coordination to the Ni atoms. Each Ni atom has a slightly distorted octahedral coordination geometry and it deviates from the equatorial plane defined by four coordinating oxygen atoms of the organic ligand by 0.0266 (4) Å. The axial positions are occupied by two water molecules with Ni-O distances of 2.057 (4) Å and 2.067 (4) Å.The Ni-O distance in the basal plane is in the range of 1.995 (4) Å -2.019 (3) Å. The presence of the two bridging phenolate O atoms gives rise to a short metal-metal contact of 3.0751 (9) Å that is slightly longer than those of binuclear nickel(II) complexes with macrocyclic phenoxo-bridging ligands (Zhou et al., 2007).
Experimental 2, 6-Diformyl-4-fluorophenol was prepared according to the literature method (Taniguchi, 1984). To a solution of 2,6-diformyl-4-fluorinphenol (1 mmol, 0.17 g) in absolute methanol (10 ml) was added a methanol solution (10 ml) containing NiCl 2 2H 2 O (1 mmol, 0.17 g). The solution was stirred vigorously for 24 h at room temperature and filtrated. The dark-green block-shaped crystals suitable for X-ray diffraction analysis were obtained by slow evaporation of solvent over a period of two weeks.

Refinement
The H atoms of water molecules were found in a difference Fourier map, and the O-H distances were restrained to 0.85 (1) Å; their temperature factor was set to 1.2U eq (O). All other H atoms were placed in calculated positions with C-H = 0.93 Å and included in the refinement in the riding-model approximation with U(H) set to 1.2U eq (C). Fig. 1. A view of the title complex, showing the labeling of the non-H atoms and 30% probability displacement ellipsoids. Atoms with the suffix (*) are generated by the symmetry operation 1-x, 1-y, 1-z.

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 > σ(F 2 ) is used only for calculating Rfactors(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.