2,2′-Dichloro-N,N′-[1,3-phenylenebis(methylene)]diacetamide

The complete molecule of the title compound, C12H14Cl2N2O2, is generated by a crystallographic twofold axis with two C atoms of the central benzene ring lying on the axis. In the crystal, N—H⋯O hydrogen bonds link the molecules into chains parallel to the c axis.

The complete molecule of the title compound, C 12 H 14 Cl 2 N 2 O 2 , is generated by a crystallographic twofold axis with two C atoms of the central benzene ring lying on the axis. In the crystal, N-HÁ Á ÁO hydrogen bonds link the molecules into chains parallel to the c axis.

Related literature
For the synthesis of lanthanide complexes with amide-type ligands, see: Wu et al. (2008). For a related structure, see: Yuan et al. (2010).  Table 1 Hydrogen-bond geometry (Å , ). Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL). The luminescent properties of the lanthanide complexes with amide type ligands have been investigated in our previous work (Wu et al., 2008). As part of our ongoing studies of the amide type ligands, the title compound was synthesized and characterized by X-ray diffraction.

Experimental
The complete molecule of the title compound ( Fig. 1) is generated by a crystallographic twofold axis with atoms C5 and C7 of the central phenyl group lying on the axis. All the bond lengths are comparable with those observed in a similar compound (Yuan et al., 2010). In the crystal, intermolecular N-H···O hydrogen bonds link the molecules into chains parallel to the c axis (Table 1).

Experimental
A chloroform solution containing chloroacetyl chloride (2.26 g, 0.02 mol) was added dropwise to a solution of (3-(aminomethyl)phenyl)methanamine (1.36 g, 0.01 mol) and pyridine (1.60 g, 0.02 mol) in chloroform (20 ml) under stirring on a ice-water bath. Then, the reaction mixture was stirred at room temperature for 3.5 h. A solid product was separated from the solution by suction filtration, purified by washing with water, 0.5 mol/L HCl, 0.5 mol/L NaOH and distilled water, respectively. Colourless prism crystals were obtained by slow evaporation of the acetone solution at room temperature.

Refinement
The H atoms were placed at calculated positions and refined in riding mode, with the carrier atom-H distances = 0.93 Å for aryl, 0.97 Å for methylene and 0.86 Å for the secondary amine H atoms. The U iso values were constrained to be 1.2U eq of the carrier atom for the H atoms.

Computing details
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008  The molecular structure shown with 50% probability displacement ellipsoids. Unlabelled atoms are related with the labelled ones by symmetry operation (-x, y, -z -1/2). 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 C1 0.28959 (11