Bis(dicyanamido-κN)tetrakis(pyridazine-κN)nickel(II)

Reaction of nickel(II) chloride with sodium dicyanamide and pyridazine leads to single crystals of the title compound, [Ni{N(CN)2}2(C4H4N2)4], in which the NiII cation is octahedrally coordinated by two dicyanamide anions and four pyridazine ligands into a discrete complex that is located on a center of inversion.

Reaction of nickel(II) chloride with sodium dicyanamide and pyridazine leads to single crystals of the title compound, [Ni{N(CN) 2 } 2 (C 4 H 4 N 2 ) 4 ], in which the Ni II cation is octahedrally coordinated by two dicyanamide anions and four pyridazine ligands into a discrete complex that is located on a center of inversion.

Related literature
For the synthesis, structures and properties of dicyanamide coordination compounds, see: Wriedt & Nä ther (2011).

Experimental
Crystal data [Ni(C 2  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. Recently we have reported on the synthesis and characterization of paramagnetic transition metal complexes with dicyanamide as anion (Wriedt & Näther, 2011). As a part of our ongoing study in this field the crystal structure of the title compound was determined. The asymmetric unit of the title compound consits of one nickel(II) cation which is located on a center of inversion as well as one dicyanamide anion and two pyridazine ligands both in general position (Fig. 1). In the crystal structure discrete complexes are formed, in which each nickel(II) cation is coordinated by two terminal coordinated dicyanamide anions and four pyridazine ligands in a slightly distorted octahedral geometry. The Ni-N distances are in the range of 2.058 (3) Å to 2.147 (3) Å with the longer distances to the pyridazine ligands. The shortest intermolecular Ni···Ni distance amounts to 8.1796 Å.

Refinement
All H atoms were located in difference map but were positioned with idealized geometry and were refined isotropically with U eq (H) = 1.2 U eq (C) of the parent atom using a riding model with C-H = 0.95 Å.  Crystal structure of the title compund with labelling and displacement ellipsoids drawn at the 50% 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.