Bis(5-methylpyrazine-2-carboxylato-κ2 N,O)nickel(II)

In the title complex, [Ni(C6H5O2N2)2], the NiII atom is situated on an inversion centre and is coordinated in a square-planar geometry by four O atoms and two N atoms of the chelating ligands.

In the title complex, [Ni(C 6 H 5 O 2 N 2 ) 2 ], the Ni II atom is situated on an inversion centre and is coordinated in a squareplanar geometry by four O atoms and two N atoms of the chelating ligands.
We gratefully acknowledge the Scientific Research Program Single-crystal analysis shows the complex crystallizes in monoclinic space group P2 1 /c and exists as a two-dimensional geometry. As shown in Figure 1, Ni1 is four-coordinated by two oxygen atoms and two nitrogen atoms from two mpca − ligands, displaying a square planar coordination geometry with Ni1-O1 = 1.947 (3) Å and Ni1-N1 = 1.977 (4) Å. The weak coordiantion between Ni1 and O2, which from the adjacent mpca − igand, result in the formation of a distorted octahedral geometry for nickle atom (Ni1-O2=2.509 (2) Å). Then the complex is further extend into a two-dimensional layer structure, see Figure 2.

Experimental
A mixture of NiCl 2 ·6H 2 O (0.238 g, 1 mmol), Hmpca (0.304 g, 1 mmol) and distilled H 2 O (6 ml) was sealed in a 15 ml Teflon-lined stainless steel vessel, which was heated at 120°C for 3 days and then cooled to room temperature at a rate of 5°C/h. Red crystals were obtained, washed with ethanol (yield 43% based on Ni).

Refinement
The H atoms of C atoms were positioned geometrically and refined with a riding model, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C). The water H atoms were located in difference Fourier maps, and were refined with distance restraints of O-H = 0.85±0.02 Å and H ··· H = 1.39±0.02 Å.

Bis(5-methylpyrazine-2-carboxylato-κ 2 N,O)nickel(II)
Crystal data [Ni(C 6  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.34 e Å −3 Δρ min = −1.37 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.