Crystal structure of (2-chloroethyl)[2-(methylsulfanyl)benzyl]ammonium chloride

In the cation of the title molecular salt, the N atom is protonated with sp 3-hybridization and has a tetrahedral geometry. In the crystal, the cations are bridged by the Cl− anions via N—H⋯Cl hydrogen bonds, forming four-centred inversion dimers with an (8) ring motif.


Chemical context
Chloroethyl-functionalized derivatives containing S-and Ndonor sites are used for the preparation of (S, N, S/Se/Te/P/As/ Sb)-type tridentate hybrid ligands by nucleophilic substitution of the chloro (Cl À ) group by RS À , ArSe À , ArTe À , Ph 2 P À , Ar 2 As À (Kumar et al., 2008a;Singh et al., 1999;Singh & Singh, 2010Kumar et al., 2008b). Metal complexes of this type of hybrid ligand are important and have found applications as catalysts in organic synthesis (Singh et al., 2013). Keeping this in mind, it was thought worthwhile to synthesise and characterise the title molecular salt. We report herein on its synthesis, by chlorination of 2-(2-methylthio)benzylamino)ethanol using thionyl chloride, and on its crystal structure.

Structural commentary
In the cation of the title molecular salt (Fig. 1), the -CH 2 -N + H 2 -CH 2 -CH 2 -Cl substituent has an extended conformation with all of the non-H atoms lying in a plane [maximum deviation = 0.032 (4) Å for atom C8]. The N1 atom is protonated with sp 3 -hybridization and has a tetrahedral geometry. The S1 atom lies in the plane of the benzene ring to which it is attached while the methyl C10 atom is displaced from the plane of the benzene ring by 1.773 (5) Å . ISSN 2056-9890 The title molecular salt was also characterised by NMR and FT-IR spectroscopy. In the proton NMR spectrum, the signals for the NCH 2 and CH 2 Cl protons gave two triplets at 3.25 and 3.9 p.p.m., respectively. The [C 10 H 15 ClSN] + cation is a secondary ammonium ion in which the N atom is protonated and hence undergoes sp 3 hybridization, resulting in a tetrahedral geometry around the N atom. This was confirmed by NMR as the iNH 2 + protons are highly deshielded and are observed as a broad singlet at 10.03 p.p.m. In the FT-IR spectrum of title salt, the N-H stretching band was observed at 1569 cm À1 .

Supramolecular features
In the crystal, the cation and anion are connected through two pairs of N-HÁ Á ÁCl hydrogen bonds. These hydrogen bonds result in the formation of four-centred inversion dimers with an R 2 4 (8) ring motif (Table 1 and Fig. 2).

Database survey
A search of the Cambridge Structural Database (Version 5.36; Groom & Allen, 2014) found no hits for similar compounds. However, tridentate (S, N, S/Se/Te)-type ligands containing the cationic part of the title salt and their Pd II and Ru II complexes have been synthesised and structurally characterized (Kumar et al., 2008a;.

Synthesis and crystallization
The synthesis of the title compound is illustrated in Fig. 3. 2-(2-Methylthio)benzylamino)ethanol (2 g, 10 mmol) was dissolved in 20 ml of dry chloroform and the solution was cooled in an ice bath. Freshly distilled SOCl 2 (3 ml, 40 mmol) dissolved in 20 ml of dry chloroform was added to it dropwise over a period of 15 min. When the addition was complete, the temperature of the reaction mixture was increased slowly and the mixture was stirred under reflux for 6 h. Thereafter, the reaction mixture was cooled and concentrated to 10 ml on a rotary evaporator, giving a light-brown solid. The solid was dissolved in 10 ml of methanol, boiled with a pinch of activated charcoal and filtered. The filtrate was treated with 20 ml of diethyl ether. It gave a white crystalline product (caution: eye and skin irritant), which was filtered, washed with diethyl ether (10 ml Â 4) and dried between the folds of filter paper. Colourless prisms of the title compound were grown in ethanol by slow evaporation of the solvent (yield: 70%; m.p.: The molecular structure of the title molecular salt, showing the atom labelling. The displacement ellipsoids are drawn at the 50% probability level. Table 1 Hydrogen-bond geometry (Å , ). Symmetry code: (i) Àx þ 1; Ày; Àz.

Figure 2
The crystal packing of the title molecular salt, viewed along the a axis. The N-HÁ Á ÁCl hydrogen bonds are shown as dashed lines (see Table 1 for details).

Figure 3
The synthesis of the title molecular salt.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The hydrogen atoms attached to atom N1 were located in a difference Fourier map. In the final cycles of refinement they were included in calculated positions, as were the C-bound H atoms, and treated as riding atoms: N-H = 0.89 Å , C-H = 0.93-0.97 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and = 1.2U eq (N,C) for other H atoms.  program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015) and PLATON (Spek, 2009).

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.73384 (17