Poly[bis(O-ethylhydroxylaminium) [di-μ-chlorido-dichloridocadmate(II)]]

In the crystal structure of the title organic–inorganic hybrid layered perovskite, organic bilayers alternate with [CdCl4] n 2n− inorganic layers along [100].

The title compound, {(CH 3 CH 2 ONH 3 ) 2 [CdCl 4 ]} n , consists of bilayers of organic CH 3 CH 2 ONH 3 + cations and infinite [CdCl 4 ] n 2nÀ inorganic layers.It can be described as an organic-inorganic hybrid layered perovskite.In the crystal structure, the Cd II cation is situated at an inversion center and is coordinated by six chloride ions, forming a slightly distorted octahedral coordination polyhedron.By corner-sharing of the [CdCl 6 ] octahedra, infinite [CdCl 4 ] n 2nÀ inorganic layers are formed, extending parallel to (100).The inorganic layers alternate with bilayers of CH 3 CH 2 ONH 3 + cations, whereby the connection of the cationic and anionic layers is achieved through N-H� � �Cl hydrogen bonds and Coulombic interactions.

Structure description
As a class of molecular materials with the advantages of low density, mechanical flexibility, and being easy to process into thin films, organic-inorganic hybrid layered perovskite compounds have attracted a lot of attention on account of their outstanding ferroelectric, multiferroic, and semiconducting performance (Huang et al., 2018).However, it is hard to predict and design advanced materials with specific performance.One reason is the lack of understanding as to why a particular crystal structure forms (Sun et al., 2020).In this regard, it is fundamentally important to search for and study new examples of such organic-inorganic hybrid layered perovskite compounds (Yang et al., 2022).Herein, we report the synthesis and crystal structure of the title compound, (CH 3 CH 2 ONH 3 ) + 2 [CdCl 4 ] 2-, based on O-ethylhydroxylammonium cations and tetrachloridocadmate anions.
The asymmetric unit contains one Cd II cation, two chloride anions and one O-ethylhydroxylammonium cation.The Cd II cation is situated at an inversion center (Wyckoff site b) and is distorted octahedrally coordinated by six chloride anions (Fig. 1).Two medium and two long equatorial Cd-Cl1 bonds [2.6798 (5) and 2.7416 (5) A ˚, respectively], and two shorter axial Cd-Cl2 bonds [2.5384 (5) A ˚] are present.
CH 3 CH 2 ONH 3 + cations along [100] (Fig. 3).The CH 3 CH 2 ONH 3 + cation is N-H� � �Cl hydrogen-bonded to three [CdCl 6 ] octahedra with two hydrogen bonds to the axial Cl ligand, and one hydrogen bond to an equatorial ligand (Fig. 1, Table 1).The cohesion between the inverted cations in the organic bilayer is achieved through van der Waals forces.

Synthesis and crystallization
An aqueous solution (15 ml) containing stoichiometric quantities of O-ethylhydroxylammonium (5 mmol), CdCl 2 (2.5 mmol), and hydrochloric acid (5 mmol) was stirred for 15 min.The clear solution was allowed to stand at room temperature for slow evaporation.About one week later, colorless, plate-shaped crystals of (CH 3 CH 2 ONH 3 ) 2 [CdCl 4 ] were obtained in about 83% yield based on Cd.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

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.All H atoms were generated by geometrical considerations and constrained to their idealized positions.Hydrogen-bond geometry (Å, º)

Figure 2
Figure 2The organic cations and the anionic [CdCl 4 ] 2-layer (polyhedral representation) in the title compound, in a view along [100].

Figure 1 A
Figure 1A part of the crystal structure of the title compound showing the coordination around the Cd II cation, and the N-H� � �Cl hydrogen-bonding interactions (dotted lines) between the cation and the anionic layer.Displacement ellipsoids are drawn at the 50% probability level.

Table 2
Experimental details.