Tetraethylammonium tris(thiocyanato-κN)[tris(1H-pyrazol-1-yl-κN 2)methane]nickelate(II)

The title salt, (C8H20N)[Ni(NCS)3(C10H10N6)], consists of a tetraethylammonium cation and an anion comprising an octahedral NiII atom surrounded by three N atoms from a tripodal tris(pyrazol-1-yl)methane ligand, and three thiocyanate ligands, each bound at the N-atom end. The ligand Ni—N distances range from 2.097 (2) to 2.127 (2) Å for the tripodal ligand and from 2.045 (2) to 2.075 (2) Å for the thiocyanate ligands. The dihedral angles between the three pyrazole rings are 59.03 (12), 53.09 (10) and 67.90 (10)°.

GL gratefully acknowledges Southern Arkansas University for the financial support.

Experimental
Tris(pyrazolyl)methane ligand was synthesized according to the previously published procedure by Reger et al. (2000).
Tetraethylammonium thiocyanate and nickel trifluoromethanesulfonate were commercially available and used as received. Ni(OTf) 2 (179 mg, 0.5 mmol) was dissolved in 35 ml methanol. Tris(pyrazolyl)methane (107 mg, 0.5 mmol) was dissolved in 15 ml methanol. The ligand solution was added drop-wise to the metal containing solution with moderate stirring. Once the addition was complete, tetraethylammonium thiocyanate (0.282 g, 1.5 mmol) was added and stirred for 15 minutes. The clear solution was filtered and methanol was evaporated slowly. Blue crystals were obtained after 1 week (197 mg, 68% yield). using a range of input parameters, the present dataset was the best that could be obtained.

Refinement
In response to the low data completeness: The nature of the twinning in this structure (180° rotation about the a * axis) meant that a large number of reflections were rejected at the data reduction stage. After several attempts to eke out more usable reflections by tweaking parameters of the integration (APEX2) and of the scaling and merging (TWINABS), the present dataset was the best that we could manage. Although a complete dataset is of course always preferable, we believe that the structure solution and refinement are unambiguous, and that the model is of a reasonable quality given the unavoidable problems with this structure.
Rigid-body restraints (DELU in SHELXL97) were applied to the SCN-groups. The spherical atom scattering factor approximation is known to be particularly bad for carbon atoms involved in triple bonds.   Packing diagram of the title compound as viewed down the b axis. Hydrogen atoms are omitted to enhance clarity.

Special details
Experimental. The crystal is twinned by non-merohedry, in which twin components are related by a 2-fold rotation about the a * axis. The resulting overlap resulted in a large number of rejections during integration, scaling, merging etc. Despite many attempts using a range of input parameters, the present dataset was the best that we could manage. 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-value wR and goodness of fit S are based on F 2 . Conventional R-values R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-values based on F 2 are statistically about twice as large as those based on F, and R-values 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