(2,9-Dimethyl-1,10-phenanthroline-κ2 N,N′)bis(thiocyanato-κS)mercury(II)

The asymmetric unit of the title compound, [Hg(SCN)2(C14H12N2)], contains two complex molecules in which the HgII atoms are both four-coordinated in a distorted tetrahedral configuration by two N atoms from a chelating 2,9-dimethyl-1,10-phenanthroline ligand and by two S atoms from two thiocyanate anions. The 1,10-phenanthroline ligand is slightly folded for one complex, the dihedral angle between the pyridine planes being 5.3 (1)°. In contrast it is nearly planar [0.5 (1)°] as it complexes with the other HgII atom. The thiocyanate ligands are virtually linear and the S atom is bonded to HgII with N⋯S—Hg angles ranging from 99.3 (1) to 103.5 (1)°. Despite the presence of six aromatic rings in the asymmetric unit, there are no significant intermolecular π–π contacts between phenanthroline ligands as the centroid–centroid distance of the closest contact between six-membered rings is 4.11 (1) A°.

The molecular structure of Hg(SCN) 2 (dmphen), along with the numbering scheme, is shown in Fig. 1 One of the two 2,9-dimethyl-1,10-phenanthroline ligands, the one bonded to Hg1, is folded by 5.3 (1)° while the other bonded to Hg2 is planar. Such conjugate double bond systems are expected to be planar. The probable reason comes from packing considerations. The soft Hg bonds to the soft S atom of SCNas expected. the variations in the approach angle, 99.3 (1) to 103.5 (1)° should also be attributed to packing considerations.

Experimental
The title compound was prepared by a procedure similar to that used for [CdI 2 (dmphen)] (Warad et al., 2011). A mixture of mercury thiosyanode (Hg(SCN) 2 , 50 mg, 0.16 mmol) in methanol (10 ml) and dmphen (32.8 mg, 0.16 mmol) in dichloromethane (5 ml) is stirred for 2 h at room temperature. The obtained solution was concentrated to about 1 ml under reduced pressure and mixed to 40 ml of n-hexane. This caused the precipitation of a white powder of 75 mg, (90% yield) which was filtered, dried and used for the preparation of colorless prisms of [Hg(SCN) 2 (dmphen)] by slow diffusion of nhexane into a solution of the complex in dichloromethane. All chemicals were purchased from Acros/Belgium.

Refinement
All nonhydrogen atoms were refined anisotropically. H atoms were positioned geometrically, with C-H = 0.93 and 0.96 Å for aromatic and methyl H, respectively, and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C) except for methyl groups where U iso (H)= 1.5U eq (C). prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figure 1
The title compound with displacement ellipsoids drawn at the 30% probability level. H atoms are shown as spheres of arbitary radius.

(2,9-Dimethyl-1,10-phenanthroline-κ 2 N,N′)bis(thiocyanato-κS)mercury(II)
Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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.