A new organic–inorganic compound, ethylenediammonium hexachloridostannate(IV) p-anisaldehyde disolvate

This new organic–inorganic hybrid compound contains stacked sheets of ethylendiammonium cations and [SnCl6]2− anions with p-anisaldehyde molecules occupying occupying the space in between.


Chemical context
The combination of organic and inorganic components to form organic-inorganic hybrid materials has attracted considerable attention owing to the generation of new properties that are absent in type either of building block (Boopathi et al., 2017;Newman et al., 1989;Chun & Jung, 2009;Bouchene et al., 2018). Hybrid functional materials, containing both inorganic and organic components, are considered to be potential platforms for applications in extremely diverse fields, such as optics, micro-electronics, magnetism, vibrational spectroscopy, transportation, health, energy, energy storage, diagnosis, housing and the environment (Masteri-Farahani et al., 2012;Kim et al., 2020;Manser et al., 2016;Rademeyer et al., 2007). Moreover, halogenostannate hybrid compounds containing protonated amine cations have recently received considerable attention because of their interesting physical and chemical properties, such as magnetism, electroluminescence, photoluminescence and conductivity, which may lead to technological innovations (Aruta et al., 2005;Chouaib & Kamoun, 2015;Papavassiliou et al., 1999;Yin & Yo, 1998). The structures of these hybrid materials have been shown to contain contain isolated or connected chains or clusters of SnX 6 octahedra separated by amine cations (Zhou & Liu, 2012;Shahzadi et al., 2008;Liu, 2012;Diop et al., 2020). In this category of materials, the organic moieties, which balance the negative charge on the inorganic units, may also act as structure-directing agents and greatly affect the structure and dimensionality of the supramolecular framework formed (Díaz et al., 2006;Hannon et al., 2002). In the present study, we report the synthesis and structural analysis of a new organic-inorganic hybrid complex, (C 2 H 10 N 2 )[SnCl 6 ]Á2C 8 H 8 O 2 .

Structural commentary
The asymmetric unit comprises of one half of an ethylenediammonium cation, one half of a hexachlorostannate(IV) dianion, [SnCl 6 ] 2À , both of which lie on centres of inversion, and one molecule of p-anisaldehyde (Fig. 1). The environment around the tin atom in the [SnCl 6 ] 2À dianion is an almost undistorted octahedron in which the Sn-Cl bond lengths lie in the range 2.4100 (12) to 2.4322 (11) Å and the cis Cl-Sn-Cl bond angles lie in the range 89.36 (4) to 90.20 (4) . The Sn-Cl2 bond involved in hydrogen bonding is slightly longer, at 2.4322 (11) Å , than the other Sn-Cl bonds [Sn-Cl1 = 2.4100 (12)Å and Sn-Cl3 = 2.4220 (11) Å ]. These results are comparable to those reported by other research groups (van Megen et al., 2013;Ali et al., 2008;Xue & Kong 2014).

Supramolecular features
The packed crystal structure contains sheets lying parallel to the ac plane in which each [SnCl 6 ] 2À dianion is surrounded by four ethylenediammonium cations (Fig. 2). The p-anisaldehyde molecules are located in the otherwise empty space between the sheets (Fig. 3). The crystal packing of the complex is supported by N-HÁ Á ÁCl and N-HÁ Á ÁO hydrogen-bonding interactions ( Table 1). The NH 3 + groups of the ethylenediammonium cation act as the hydrogen-bonding donors. The DÁ Á ÁA distances involving the NH 3 + group and either the p-anisaldehyde molecule or the [SnCl 6 ] 2À units range from 2.763 (6) Å for N1Á Á ÁO2 iii to 3.404 (4) Å for N1Á Á ÁCl3 v . Nonclassical interactions between the p-anisaldehyde molecules and the ethylenediammonium cations, C9-H9Á Á ÁO2 vi at 2.62 Å , further serve to hold the structure together.

Database survey
Organic-inorganic hybrid compounds with structures most similar to that of the title compound include: (C 6  The atom-numbering for the asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) Àx, Ày, Àz; (ii) Àx + 1, Ày, Àz + 1.]

Synthesis and crystallization
Chemicals [p-anisaldehyde, ethylenediamine and tin(II)] were purchased from Sigma-Aldrich and were used without any further purification. The solvent use for the synthesis was ethanol (96%).
The Schiff base N,N 0 -bis(4-methoxybenzylidene)ethylenediamine was prepared by condensing p-anisaldehyde (10 g; 0.0734 mol) with ethylenediamine (2.205 g; 0.0367 mol) in ethanol (30 ml) (Fig. 4). The resulting mixture was heated under reflux for 6 h, filtered and left to evaporate at ambient temperature. (The reaction between p-anisaldehyde and ethylenediamine gave the same product whatever the proportions of reactants used). After a few days of slow evaporation, 4.511 g of crystals were obtained, corresponding to a yield of 82%. The compound was characterized by FT-IR (cm À1 : 1639.05 (C N); 1603, 1505, 1461 and 1448 (C C, aromatic); 1019 (C-O, ether).
Synthesis of the title compound 0.3 g (0.00168 mol) of N,N 0 -bis (4-methoxybenzylidene)ethylenediamine were dissolved in 30 ml of ethanol in a round-bottomed flask, followed by the addition of SnCl 2 (0.638 g; 0.00168 mol) to form a yellow solution (Fig. 5). The mixture was refluxed for 7 h at 353 K, filtered to remove Sn(OEt) 6 and Sn(OH) 2 and the resulting solution was allowed to evaporate slowly. After a few days of evaporation, lightyellow block-shaped crystals suitable for single-crystal X-ray analysis were obtained in a yield of 31%. The presence of water molecules in the solvent (EtOH, 96%) causes hydrolysis of the Schiff base and oxidation of tin(II) to tin(IV). The hydrolysis reaction leads to the formation of two molecules of p-anisaldehyde and one ethylenediammonium cation.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. (C 2 H 10 N 2 )[SnCl 6 ]Á2C 8 H 8 O 2 crystallizes in the space group P2 1 /n with the monoclinic angle, , close to 90 . The crystals formed as non-merohedral twins with about one quarter of reflections overlapping. The twin law corresponds to rotation about c*. For the crystal investigated, the relative domain sizes amounted to 0.790 (4): 0.210 (4). The structure was solved by intrinsic phasing (Sheldrick, 2015a). The twin law was identified from reflections with I obs >> I calc , and PLATON (Spek, 2020) was used to generate a suitable two-domain reflection file for twin refinement (Sheldrick, 2015b). All non-hydrogen atoms were assigned anisotropic displacement parameters. H atoms attached to C were calculated in standard geometry and treated as riding [C-H = 0.95-0.99 Å ; U iso (H) = 1.2U iso (C) or 1.5U iso (C-methyl)]. H atoms attached to N were located as local maxima in a difference-Fourier map and refined with a distance restraint N-H = 0.9 Å and an isotropic displacement parameter U iso (H) = 1.2U iso (N).  Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXT (Sheldrick 2015a); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015b); molecular graphics: PLATON (Spek, 2020); software used to prepare material for publication: SHELXL2018/3 (Sheldrick, 2015b).

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. Refinement. Refined as a two-component twin.