A monoclinic polymorph of 1,2-bis[(1-methyl-1H-tetrazol-5-yl)sulfanyl]ethane (BMTTE)

The molecular and crystal structures of a monoclinic polymorph of 1,2-bis[(1-methyl-1H-tetrazol-5-yl)sulfanyl]ethane (BMTTE) are described.


Chemical context
Organic compounds such as the title compound (BMTTE) are frequently used as flexible ligands for the preparation of coordination polymers (Wang et al., 2010). A triclinic polymorph of the title compound has been described previously by Li et al., (2011). Here we describe the spectroscopic characterization and crystal structure of a new monoclinic polymorph of BMTTE, obtained by recrystallization and slow evaporation from a solution in CH 3 CN. Such compounds have been used in coordination chemistry (Zhao et al., 2008) and in materials design (Wang et al., 2009(Wang et al., , 2010.

Structural commentary
The molecule structure of the title compound, Fig. 1, shows N-N and C-S bond distances and S-C-C-S and C-S-C-C torsion angles similar to the values observed in the triclinic form (Li et al., 2011). As shown by the molecular overlap of the two polymorphs (Fig. 2), drawn with Mercury (Macrae et al., 2008), there is only a slight difference in their geometry. The tetrazole rings (N1-N4/C1 and N5-N8/C4) are inclined to one another by 5.50 (6) in the title polymorph and by 1.9 (2) in the triclinic polymorph. While there are only small differences in the geometric parameters between the two ISSN 2056-9890 polymorphic forms, they are enough to produce a different crystal packing.
As a result of these interactions, the molecules are packed very efficiently so that the Kitaigorodskii (1973) index is 72%. The crystal packing in the crystal of the triclinic polymorph is very similar, with a Kitaigorodskii index of 69% (PLATON; Spek, 2009).

Figure 1
Molecular structure of the title compound, the monoclinic polymorph of BMTTE, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Synthesis and crystallization
The title compound, (BMTTE), was synthesized by a slightly modified version of the procedure described by Li et al. (2011). 5-Mercapto-1-methyltetrazole (9.29 g, 0.08 mol) was added to a solution of sodium hydroxide (3.26 g, 0.08 mol) in EtOH (110 ml). The mixture was stirred at room temperature for one day. Dichloroethane (3.2 ml, 0.04 mol) in 6 ml of EtOH was then added dropwise and the mixture was refluxed for 18 h.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C-bound H atoms were included in calculated positions and treated as riding: C-H = 0.98-0.99 Å with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C) for other H atoms.

Figure 4
Crystal packing of the title compound, showing details of the C-HÁ Á ÁN hydrogen bonds (dashed lines, see Table 1) and examples of theinteractions (blue double-headed arrows).