1,1′-Dimethyl-4,4′-(propane-1,3-diyl)dipyridinium tetrabromidocadmate(II)

In the cation of the title compound, (C15H20N2)[CdBr4], the dihedral angle between the two pyridine rings is 70.85 (5)°. An intermolecular π–π interaction between the pyridine rings [centroid–centroid distance = 3.900 (4) Å] is observed. The CdII atom has a distorted tetrahedral coordination.

In the cation of the title compound, (C 15 H 20 N 2 )[CdBr 4 ], the dihedral angle between the two pyridine rings is 70.85 (5) . An intermolecularinteraction between the pyridine rings [centroid-centroid distance = 3.900 (4) Å ] is observed. The Cd II atom has a distorted tetrahedral coordination.
Compound (I), as shown in Fig. 1, consists of a 1,3-bis(1-methyl-4-pyridinium)propane cation and a tetrabormocadmate anion. As result of the flexible propane chain, the two pyridine rings have seriously torsion with the dihedral angle of 70.85 (5)°. The Cd II atom is coordinated by four Br atoms to a tetrahedral divalent anion.
The mixture was stirred for 20 min at room temperature and then sealed in a Teflon-lined stainless steel autoclave with a 23 ml capacity at 428 K for 72 h. After cooling to room temperature, the filtered solution was slowly evaporates and 7 days later colourless block-shaped crystals were obtained; these were washed with deionized water, filtered, and dried in air (yield 46% based on Cd).

S3. Refinement
H atoms were placed geometrically (C-H = 0.93-0.97 Å) and refined as riding, with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C) . The highest residual electron density peak is located at 1.223 (3) Å from Cd atom.  The molecular structure of (I), with the atom-labeling scheme and 30% probability displacement ellipsoids.

Figure 2
A partial packing view of (I) along the c axis. For the sake of clarity, H atoms have been omitted.

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.