Di-μ-chlorido-bis{chlorido[2,3-dimethyl-N-(pyridin-2-ylmethylidene)aniline-κ2 N,N′]mercury(II)}

In the centrosymmetric binuclear molecule of the title complex, [Hg2Cl4(C14H14N2)2], the five-coordinated HgII ions have a distorted square-pyramidal geometry defined by two N atoms belonging to the chelating iminopyridine ligand and three Cl atoms. The benzene and pyridine rings are oriented at a dihedral angle of 56.7 (6)°. The crystal packing is stabilized by C—H⋯Cl hydrogen bonds and π–π interactions between the pyridine rings [centroid–centroid distance = 3.796 (6) Å].

In the centrosymmetric binuclear molecule of the title complex, [Hg 2 Cl 4 (C 14 H 14 N 2 ) 2 ], the five-coordinated Hg II ions have a distorted square-pyramidal geometry defined by two N atoms belonging to the chelating iminopyridine ligand and three Cl atoms. The benzene and pyridine rings are oriented at a dihedral angle of 56.7 (6) . The crystal packing is stabilized by C-HÁ Á ÁCl hydrogen bonds andinteractions between the pyridine rings [centroid-centroid distance = 3.796 (6) Å ].

Seyed Jalal Hoseyni, Mohamad Reza Talei Bavil Olyai and Behrouz Notash Comment
Schiff base metal complexes have been known since the nineteenth century. Investigation on metal-organic complexes represents one of the most active areas of material science and chemical research (Gibson et al., 2007;Gibson & Spitzmesser, 2003;Ittel et al., 2000). Schiff bases form a class of compounds with azomethin group, which are usually synthesized from the condensation of primary amines and active carbonyl groups by the elimination of water molecule.
We report herein the crystal structure of the title compound, a new mercury(II) complex. This complex was synthesized by the reaction of HgCl 2 with 2-[(2,3-dimethylphenyl)iminomethyl]pyridine in an acetonitril solution.
In the title compound ( Fig. 1), the Hg II atom is five-coordinated in a distorted squar-pyramidal geometry. The Schiff base ligand coordinates to the Hg II atom as a bidentate ligand through the N atoms of the imine group and pyridine ring.
Also two bridging and one terminal chloride anions are present in the coordination environment of the Hg II atom (Baul et al., 2004). The benzene and pyridine rings are oriented at a dihedral angle of 56.7 (6)°. Crystal packing is stabilized by intermolecular C-H···Cl hydrogen bonds (Fig. 2, Table 1) and π-π interactions between the pyridine rings [centroidcentroid distance = 3.796 (6) Å].

Experimental
For the preparation of the title compound, a solution of 2-[(2,3-dimethylphenyl)iminomethyl]pyridine (0.210 g, 1.00 mmol) in acetonitril (10 ml) was added slowly to a solution of HgCl 2 (0.271 g, 1.00 mmol) in acetonitril (10 ml) and the resulting yellow solution was stirred for 45 min at room temperature. Then the yellow precipitate was filtered and dissolved in acetonitril and left to evaporate slowly at -18°C. After a few days, yellow crystals of the title compound were isolated (yield: 0.272 g, 56.5%; m.p. 489 K).

Refinement
H atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 (CH) and 0.96 (CH 3 ) Å and with U iso (H) = 1.2(1.5 for methyl)U eq (C). The highest residual electron density was found at 0.85 Å from Hg1 atom and the deepest hole at 0.92 Å from Hg1 atom.  The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level.

Computing details
[Symmetry code: (a) 1/2-x, 3/2-y, 2-z.] 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