Aqua[1-(pyrazin-2-yl)ethanone oximato-κ2 N,N′][1-(pyrazin-2-yl)ethanone oxime-κ2 N,N′](thiocyanato-κN)nickel(II)

In the title complex, [Ni(C6H6N3O)(NCS)(C6H7N3O)(H2O)] or [Ni(mpko)(SCN)(mpkoH)(H2O)] [where mpkoH = 1-(pyrazin-2-yl)ethanone oxime], the NiII cation is in a slightly distorted octahedral geometry, being coordinated in the equatorial plane by four N atoms from two different mpkoH ligands, one of which is deprotonated, and by one N atom from a thiocyanate anion and one O atom from a water molecule in the axial positions. There is an intramolecular O—H⋯O hydrogen bond involving the oxime units of the two ligands. In the crystal, a three-dimensional supramolecular architecture is formed by O—H⋯O and O—H⋯N hydrogen bonds.

In the title complex, [Ni(C 6

H 6 N 3 O)(NCS)(C 6 H 7 N 3 O)(H 2 O)] or [Ni(mpko)(SCN)(mpkoH)(H 2 O)]
[where mpkoH = 1-(pyrazin-2-yl)ethanone oxime], the Ni II cation is in a slightly distorted octahedral geometry, being coordinated in the equatorial plane by four N atoms from two different mpkoH ligands, one of which is deprotonated, and by one N atom from a thiocyanate anion and one O atom from a water molecule in the axial positions. There is an intramolecular O-HÁ Á ÁO hydrogen bond involving the oxime units of the two ligands. In the crystal, a three-dimensional supramolecular architecture is formed by O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds.

Experimental
Crystal data [Ni(C 6    In the past decades, much attention has been paid to the design and synthesis of oximes complexes. Oximes can be feasibly synthesized by the Schiff base condensation of an aldehyde or ketone with hydroxylamine. To date, various oximate ligands as bridging ligands have been extensively explored for their great ability to form homo-and heterometallic polynuclear complexes, which can transmit magnetic exchange efficiently (Radek et al. 1999(Radek et al. , 2001. Among oximate bridging ligands, R-substituted-pyridyloximes, (py)C(R)NOH, salycylaldoximes and R-saoH 2 play an outstanding role to generate a great variety of polynuclear complexes which not only have aesthetically pleasing structures, but also possess interesting magnetic properties of single molecule magnet (SMM) and single chain magnet (SCM) behavior (Escuer et al., 2010;Spini, 1973).
The title compound, Fig. 1, is a new nickel complex obtained by the reaction of nickel chloride hexahydrate with mpkoH (methyl pyrazine-2-yl ketoxime) in CH 3 OH solution. The Ni II cation is in a slightly distorted octahedral geometry.
The equatorial plane is defined by four N atoms from two mpkoH ligands -one of which is deprotonated, while the axial positions are occupied by one N atom from a SCNanion and one water O atom. There is an intramolecular O-H···O hydrogen bond (Table 1) involving the the oxime moieties of the two ligands.
In the crystal a three-dimensional supramolecular architecture is formed by O-H···O and O-H···N hydrogen bonds ( Fig. 2 and Table 1).

Experimental
The title complex was prepared by the addition of nickel chloride hexahydrate (23.9 mg, 0.1 mmol) to a CH 3 OH solution of methyl pyrazine-2-yl ketoxime (28 mg, 0.2 mmol); the pH was adjusted to 8 with 1M KSCN. Slow evaporation of the solvent gave red block-like crystals of the title compound, suitable for X-ray analysis, after several days at room

Refinement
The OH and water H atoms were located in a difference Fourier map. All except one of the water H atoms [H1W; constrained to be 0.82 Å with U iso (H) = 1.5U eq (O)], were freely refined. The C-bound H atoms were placed in calculated positions and refined as riding atoms: C-H = 0.93 and 0.96Å for CH and CH 3 H atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for CH 3 H atoms and = 1.2 for other H atoms.    Table 1 for details).

κN)nickel(II)
Crystal data [Ni(C 6 (9) Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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.