Crystal structure of 2-[bis(benzylsulfanyl)methyl]-6-methoxyphenol

The title compound is an example of an ortho-vanillin-based functionalized dithioether, which could be useful as a potential chelating ligand or bridging ligand for coordination chemistry. Its crystal structure was determined at 100 K. Both weak intramolecular O—H⋯O and intermolecular O—H⋯S hydrogen bonding can be observed.

In the context of our research interest in the assembly of molecular cluster compounds and coordination polymers by complexation of ArSCH 2 SAr or dithiolane-and dithianebased thiaheterocycles (Chaabé ne et al., 2016;Knauer et al., 2020;Knorr et al., 2014;Raghuvanshi et al., 2017Raghuvanshi et al., , 2019Schlachter et al., 2018) , we have developed novel functionalized dithio ether compounds such as ferrocenyl thioethers ISSN 2056-9890 bearing a substituent at the -carbon atom linking the two -SR groups. With the idea of designing a functionalized thioacetal ligand bearing additional harder O-donor sites along with the two soft S-donor sites, we chose 2-hydroxy-3-methoxybenzaldehyde (ortho-vanillin) as the starting material. This hydroxylated aldehyde is present in the extracts and essential oils of many plants. Several papers describe also its use (in its deprotonated vanillinato form or as a Schiff base-derived ligand) in coordination chemistry (Andruh, 2015;Kırpık et al., 2019;Yu et al., 2011). Its reaction with 2 equivalents of benzyl mercaptan affords the targeted dithioacetal 2-hydroxy-3methoxyphenyl[bis(benzylthio)]methane, 1, which was isolated in high yield as a crystalline solid.
This acyclic thioacetal contains, in addition to the benzylic thio ether groups and the methoxy group prone to ligate metal centres, a phenolic hydroxyl group, which may allow additional interactions through hydrogen bonding.

Supramolecular features
In the crystal, there is an O-HÁ Á ÁS hydrogen bond between the H2 atom of the phenolic hydroxyl group and the S1 atom of a neighbouring molecule with distances [H2Á Á ÁS1 = 2.44 (2) Table 1 Hydrogen-bond geometry (Å , ).
Cg1 is the centroid of the C2-C7 ring.

Figure 2
A view of the crystal packing of the title compound. For clarity, H atoms have been omitted. The intramolecular O1Á Á ÁH2 contacts are shown as dashed lines. For clarity, only H atoms involved in these interactions are presented. The intermolecular contacts are shown in Fig. 3.

Figure 1
The molecular structure of 1 with displacement ellipsoids drawn at the 50% probability level.  Table 1). This O2-H2Á Á ÁS1 interaction results in the formation of chains running along the b-axis direction.
The benzylic methylene group on sulfur atom S2 interacts with the -cloud of the phenyl part of the vanillin unit through a C-HÁ Á Á interaction (Table 1). The second phenyl ring of the dithiane unit also exhibits a C-HÁ Á Á interaction: the second methylene group on sulfur atom S1 interacts with a phenyl carbon. The third C-HÁ Á Á contact is between adjacent vanillin units.  Laskar et al., 2013). It is noteable that in most of these examples, the intermolecular contacts are noticeably stronger than those of 1.

Synthesis and crystallization
The reaction scheme for the synthesis of the title compound is illustrated in Fig. 4 Synthesis of 1.

Figure 3
Intermolecular contacts for compound 1. Symmetry codes as in Table 1. added to a flask at 273 K. The mixture was stirred for 60 min at room temperature. After the reaction was complete, the resulting mixture was neutralized with 10% aq NaHCO 3 (10 mL) and extracted with dichloromethane (3 Â 10 mL). The combined extracts were washed with H 2 O (3 Â 20 mL) and dried over Na 2 SO 4 . Evaporation of the solvent in vacuo gave a solid product, which was further purified by column chromatography. The product was obtained as a white solid, Yield: 83% (430 mg). X-ray quality crystals were obtained by keeping a dichloromethane:hexane (1:1)

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were positioned geometrically (C-H = 0.95-1.00 Å ) and refined using a riding model, with U iso (H) = 1.2U eq (C) for CH 2 and CH hydrogen atoms and U iso (H) = 1.5U eq (C-methyl). The phenolic proton H2 was refined independently.

Funding information
LK thanks the Fonds der Chemischen Industrie for a doctoral fellowship. We are grateful to the region of Franche-Comté for funding a postdoctoral fellowship for A. .

2-[Bis(benzylsulfanyl)methyl]-6-methoxyphenol
Crystal data 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.