Synthesis and crystal structure of (E)-2-benzyl-1,3-diphenylisothiouronium iodide

The title compound, a salt form of (E)-2-benzyl-1,3-diphenylisothiouronium iodide, was prepared by the reaction of 1,3-diphenylthiourea and benzyl iodide. In the crystal, N—H⋯I hydrogen bonds link the components into [100] chains.


Chemical context
Isothiouronium salts containing an R-S-C-(NHR) 2 + moiety have been investigated as their hydrogen-bonding motifs for molecular recognition of anions (Yeo & Hong, 1998;Kubo et al., 2000;Kato et al., 2004;Nguyen et al., 2009;Nguyen & Kim, 2010) and as organocatalysts (Nguyen & Kim, 2011, 2012Lee et al., 2018;Kang et al., 2019). The isothiouronium group could enhance the acidity of their NH groups compared with thiourea and therefore be used as prospective alternative for thiourea. In addition, the chemical modification of the isothiouronium skeleton is readily performed using alkylation reactions of thiourea. As part of our work in this area, the synthesis and single-crystal structure of the title molecular salt, C 20 H 19 N 2 S + ÁI À are reported herein.

Supramolecular features
In the crystal, the cations and anions are linked by almost linear N-HÁ Á ÁI hydrogen bonds (Fig. 2

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at at the 30% probability level.

Synthesis and crystallization
1,3-Diphenylthiourea (4.4 mmol) was added to a solution of benzyl iodide (13.2 mmol) in dry dichloromethane at room temperature. The reaction mixture was then stirred for 24 h and concentrated in vacuo. The residue was purified via flash chromatography (hexane:ethyl acetate = 8:2), to give a the title compound as a yellow solid (1.14 g, yield 58%

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were positioned geometrically (C-H = 0.94-0.98 Å , N-H = 0.80 Å ) and refined using a riding model withU iso (H) = 1.2U eq (carrier).  program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2020); software used to prepare material for publication: SHELXTL ( (Sheldrick, 2008)). Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.