1,4-Bis[(2-pyridylethyl)iminomethyl]benzene

In the title compound, C22H22N4, the centroid of the benzene ring is located on an inversion centre. The dihedral angle between the benzene and pyridine rings is 10.94 (5)°. The crystal structure displays weak intermolecular C—H⋯N hydrogen bonding and C—H⋯π interactions.

In the title compound, C 22 H 22 N 4 , the centroid of the benzene ring is located on an inversion centre. The dihedral angle between the benzene and pyridine rings is 10.94 (5) . The crystal structure displays weak intermolecular C-HÁ Á ÁN hydrogen bonding and C-HÁ Á Á interactions.

Comment
This work originates from our interest in developing a new class of tetradentate ligands. To the best of our knowledge, this work demonstrates the first example of neutral pyridinyldimine-based bridging ligand. The title compound might be expected to behave as a tetradentate chelating agent, in which both of the N atoms from the imine might coordinate, along with the two pyridinyl N atoms. Chakraborty et al. (1999) reported coordination of similar ligands to ruthenium whilst Haga and Koizumi (1985) reported their coordination to molybdenum. The structure of the title compound crystallized in space group P2 1 /n with Z = 2. The molecule, shown in Fig. 1, has a center of inversion at the centroid of the benzene ring and was located in special positions at Wyckoff positon a. The conformation of the molecule is best described by the dihedral angle of the central ring and pyridyl ring of 10.94 (5)°. The structure is stabilized by weak hydrogen bonds of the type C-H···N and C-H···π, the metrics of which are given in Table 1. The C-H···N intermolecular interactions, as well as C6-H6A···Ring 1 (of C10-C9-C11-C10'-C9'-C11'), connect the parallel neighbouring molecules into 2-dimentional layers. And these layers are then linked along the b axis into 3-dimentional herringbone packing via C2-H2···Ring 2 (of C1-C2-C3-C4-C5-N1) interactions, as shown in Fig.2.
The mixture was stirred at room temperature for ca 16 h. The precipitate was filtered off and washed with diethylether and dried under vacuum for 4 h affording a fine shiny white powder in 85% yield. M.p.: does not melt below 260 °C.
Recrystallization by slow diffusion of Et 2 O into a concentrated CH 2 Cl 2 of the solution gave colorless crystals suitable for X-ray structure analysis.

Refinement
All non-hydrogen atoms were refined anisotropically and all hydrogen atoms were placed in idealized positions and refined with a riding model with U iso set at 1.2 or 1.5 times U eq of their parent atoms and fixed C-H bond lengths.

Figures
Fig . 1. Molecular structure of titled compound showing the atomic numbering scheme. All non-hydrogen atoms were presented with ellipsoidal model with probability level 40%. Half of the molecule without atomic labels was generated via centre of symmetry (symmetry code: -x, -y, -z).   05, 159.45, 149.37, 138.88, 136.13, 128.21, 123.67, 121.24, 61.18, 39.61 Half sphere of data collected using SAINT strategy (Bruker, 2006). Crystal to detector distance = 50 mm; combination of φ and ω scans of 0.5°, 40 s per °, 2 iterations. 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 Rfactors(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 N1