Crystal structure and Hirshfeld surface analysis of bis[(ethoxymethanethioyl)sulfanido](N,N,N′,N′-tetramethylethane-1,2-diamine)mercury(II)

In the crystal, molecules are linked by weak C—H⋯S hydrogen bonds, forming a two-dimensional supramolecular architecture.


Chemical context
Xanthates (dithiocarbonates) attract the interest of many researchers in the field of coordination chemistry owing to their antidotal, antioxidant and antitumor activities (Shahzadi et al., 2009;Perluigi et al., 2006;Larsson & Oberg, 2011). These ligands exhibit different coordination modes such as monodentate, isobidentate or anisobidentate. Cellulose xanthate has been used for the separation of alcohols by the chromatographic method (Friebolin et al., 2004). It has been reported that metal xanthates exhibit cytotoxic activity on human cancer cells and have the ability to inhibit both DNA and RNA viruses in vitro (Efrima & Pradhan, 2003). Mercury represents one of the most toxic heavy metals found in solid and liquid waste from oil refineries and the mining industry. We report herein the synthesis and crystal structure of a new Hg II xanthate containing N,N,N 0 ,N 0 -tetramethylethylenediamine, including the results of a Hirshfeld surface analysis.

Structural commentary
The asymmetric unit of the title complex ( Fig. 1) comprises one Hg II ion, one half N,N,N 0 ,N 0 -tetramethylethylenediamine ligand and one ethylxanthate ligand. The Hg II ion is coordinated by two N atoms of the N,N,N 0 ,N 0 -tetramethylethylenediamine ligand and two S atoms from two ethylxanthate xanthate ligands in a distorted tetrahedral environment. The Hg-N and Hg-S bond lengths (Table 1) are 2.531 (8) and 2.416 (3) Å , respectively, whereas the bond angles around the central Hg II ion are in the range 73.8 (3)-149.91 (18) . The bond lengths and angles of the HgN 2 S 2 coordination units correspond to those in the structures of mixed-ligand Hg II coordination compounds (see Database survey). The C1-O1 and C2-O1 bond lengths are 1.355 (11) to 1.460 (12) Å , respectively, although all of the C-O bonds show single-bond character. In the {S 2 C} section of the xanthate ligands, the C1-S1 distance is 1.727 (9) Å , which is typical of a single bond, whereas the C1 S2 distance of 1.633 (10) Å is typical of a carbon-to-sulfur double bond. The C-N and C-C bond lengths in the N,N,N 0 ,N 0 -tetramethylethylenediamine ligand are normal (Qadir et al., 2020).

Supramolecular features
In the crystal, there is a weak intermolecular hydrogen bonding (Table 2) between S atoms and the H atoms of the methylene groups [C4-H4BÁ Á ÁS1 (x À 1 2 , y À 1 2 , Àz + 3 2 )]. Fig. 2 illustrates the two-dimensional wave-like structure extending in the ab plane formed by hydrogen-bonding interactions in [Hg(C 3 H 5 S 2 O 1 ) 2 (tmeda)].  , 1996) and [HgCl 2 (C 6 H 16 N 2 )] (ZZZAJM; Htoon & Ladd, 1976). In BATXOJ, the coordination geometry is distorted tetrahedral with the independent Hg-S distances being 2.413 (5) and 2.842 (5) Å . The range of S-Hg-S angles is 81.8 (2)-150.8 (3) with the wider angle involving the more tightly bound S1 atoms. In EKODAK, the corresponding mercury complex adopts a severely distorted tetrahedral configuration defined by the two monodentate selenolate and chelating tmeda ligands. The Hg-N bond lengths are in the range 2.573 (17)-2.601 (18) Å . In POTJOY, intermolecular C-HÁ Á ÁS hydrogen bonds are important in the crystal packing. Similarly, the molecules are connected to each other via C-HÁ Á ÁS hydrogen bonds in the title complex. In TEVQAM, the Hg-N and Hg-S bond lengths are 2.54 and 2.34 Å , respectively, comparable to those in the title compound.

Hirshfeld surface analysis
A Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) was carried out using CrystalExplorer17.5 (Turner et al., 2017) to quantify the various intermolecular interactions. The Hirshfeld surface mapped over d norm is illustrated in Fig. 3 and the associated two-dimensional fingerprint plots in Fig. 4

Figure 2
Two-dimensional wave-like structure extending in the ab plane formed by hydrogen-bonding interactions in [Hg(C 3 H 5 S 2 O 1 ) 2 (tmeda)].

Synthesis and crystallization
Potassium ethylxanthate (4 mmol, 0.64 g) in hot ethanol (10 mL) was added to a hot solution of Hg(CH 3 CO 2 ) 2 (2 mmol, 0.64 g) in ethanol (10 mL) under stirring. The formed precipitate was filtered off, washed with water and airdried. The precipitate was suspended in hot ethanol (10 mL) and tetramethylethylenediamine (2 mmol, 0.23 g) was added under stirring. The colour changed to dark brown. The precipitate was filtered off and dried and then recrystallized from ethanol. Brown rods were formed.

Figure 3
Hirshfeld surface mapped with d norm .

Bis[(ethoxymethanethioyl)sulfanido](N,N,N′,N′-\ tetramethylethane-1,2-diamine)mercury(II)
Crystal data [Hg(C 3 H 5 OS 2 ) 2 (C 6 H 16 N 2 )] M r = 559.18 Orthorhombic, Pbcn a = 12.235 (7)  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.