Bis(methanol-1κO)tetra-μ-pyridazine-1:2κ4 N:N′;2:3κ4 N:N′-di-μ-thiocyanato-1:2κ2 N:N;2:3κ2 N:N-tetrathiocyanato-1κ2 N,3κ2 N-trinickel(II) methanol tetrasolvate

Reaction of an excess nickel(II) thiocyanate with pyridazine leads to single crystals of the title compound, [Ni3(NCS)6(N2C4H4)4(CH3OH)2]·4CH3OH. The crystal structure consists of trimeric discrete complexes, in which two NiII cations are coordinated by two terminal and one μ-1,1 bridging thiocyanato anions, one methanol molecule and two bridging pyridazine ligands, whereas the central NiII atom is coordinated by two μ-1,1 bridging anions as well as four bridging pyridazine ligands. The asymmetric unit consists of two crystallographically independent Ni cations, one of which is located on a center of inversion, as well as three crystallographically independent thiocyanato anions, two pyridazine ligands and three independent methanol molecules in general positions. Two of the solvent molecules do not coordinate to the metal atoms and are located in cavities of the structure. The discrete complexes are linked by intermolecular O—H⋯O and O—H⋯S hydrogen bonding into layers parallel to the bc plane.

Reaction of an excess nickel(II) thiocyanate with pyridazine leads to single crystals of the title compound, [Ni 3 (NCS) 6 -(N 2 C 4 H 4 ) 4 (CH 3 OH) 2 ]Á4CH 3 OH. The crystal structure consists of trimeric discrete complexes, in which two Ni II cations are coordinated by two terminal and one -1,1 bridging thiocyanato anions, one methanol molecule and two bridging pyridazine ligands, whereas the central Ni II atom is coordinated by two -1,1 bridging anions as well as four bridging pyridazine ligands. The asymmetric unit consists of two crystallographically independent Ni cations, one of which is located on a center of inversion, as well as three crystallographically independent thiocyanato anions, two pyridazine ligands and three independent methanol molecules in general positions. Two of the solvent molecules do not coordinate to the metal atoms and are located in cavities of the structure. The discrete complexes are linked by intermolecular O-HÁ Á ÁO and O-HÁ Á ÁS hydrogen bonding into layers parallel to the bc plane.

Related literature
For the background to this work and the synthesis of bridging thiocyanato coordination compounds, see: Boeckmann & Nä ther (2010, 2011Wö hlert et al. (2011). For structures of related trinuclear complexes, see: Wriedt & Nä ther (2009) ;Yi et al. (2006). For a description of the Cambridge Structural Database, see: Allen (2002  Data collection: X-AREA (Stoe & Cie, 2008); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2011); software used to prepare material for publication: XCIF in SHELXTL. The structure determination of the title compound was performed within a project on the synthesis of transition metal coordination compounds in which the metal centers are linked by bridging anionic ligands (Boeckmann & Näther (2010, 2011Wöhlert et al. (2011)). Within this project we reported on two modification of a trinuclear complex based on nickel(II) thiocyanate and pyridazine (Wriedt & Näther (2009)). In further investigations we have reacted nickel(II) thiocyanate with pyridazine in methanol which results in the formation of single-crystals of the title compound, which were characterized by single-crystal X-ray diffraction. The asymmetric unit of the title compound consists of two nickel(II) cations, one of them is located on a center of inversion, three thiocyanato anions, two pyridazine ligands and three methanol molecules all of them located in general position (Fig. 1). In the crystal structure two crystallographic independent nickel(II) cations are present. Ni1 is coordinated by two terminal N-bonded and one µ-1,1 bridging thiocyanato anions, one methanol molecule and two bridging pyridazine ligands in a slightly distorted octahedral geometry (Tab. 1). Ni2 is coordinated by two µ-1,1 bridging thiocyanato anions and four pyridazine ligands and the coordination environment can also be described as a sligthly distorted octahedron (Tab. 1). The nickel(II) cations are connected through µ-1,1 bridging thiocyanato anions and the two µ 2 -N,N pyridazine ligands into trimeric units. The Ni-N distances are in range of 2.025 (3) Å to 2.133 (3) Å with angles between 86.53 (12) ° to 180 ° (Tab. 1). The intramolecular Ni···Ni distances amount to 3.3349 (4) Å. The crystal structure contains additional methanol molecules located in cavities of the structure which are not coordinated to the metal cations. These methanol molecules are linked by intermolecular O-H···O and O-H···S hydrogen bonding to the metal complexes forming layers which are parallel to the b-c plane ( Fig. 2 and Tab. 2). It must be noted that according to a search in the CCDC database (CONQUEST Ver. 1 12.2010) (Allen, 2002) a trinuclear complex with cobalt(II) thiocyanate and pyridazine was reported by Yi et al. (2006).

Experimental
Nickel(II) thiocyanate (Ni(NCS) 2 ) and pyridazine were obtained from Alfa Aesar. All chemicals were used without further purification. 0.5 mmol (87.0 mg) and 0.125 mmol (9.1 µL) pyridazine were reacted in 0.5 ml methanol. Green single crystals of the title compound were obtained after two days.

Refinement
All H atoms were located in difference map but were positioned with idealized geometry and were refined isotropic with U iso (H) = 1.2 U eq (C) (1.5 for methyl H atoms) using a riding model with C-H = 0.95 for aromatic and 0.98 Å for methyl H atoms. The O-H H atoms were located in difference map, their bond lengths set to ideal values of 0.84 Å and afterwards they were refined using a riding model with U iso (H) = 1.5 U eq (O). SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2011); software used to prepare material for publication: XCIF in SHELXTL (Sheldrick, 2008).

Figure 1
Crystal structure of the title compound with labeling and displacement ellipsoids drawn at the 30% probability level.

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.

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