Crystal structure of bis(diisopropylammonium) cis-diiodidobis(oxolato-κ2 O 1,O 2)stannate(IV)

The packing of the title molecular salt features N—H⋯O and bifurcated N—H⋯(O,O) hydrogen bonds, which generate [10-1] chains.

In the title compound, ( i Pr 2 NH 2 ) 2 [SnI 2 (C 2 O 4 ) 2 ], which was prepared by reacting ( i Pr 2 NH 2 + ) 2 ÁC 2 O 4 2À with SnI 4 in a 2:1 molar ratio in a mixed ethanolacetonitrile solvent, the Sn atom is coordinated by two chelating oxalate ions and two iodide ions, with the latter in a cis configuration. In the crystal, the cations are linked to the anions by N-HÁ Á ÁO and bifurcated N-HÁ Á Á(O,O) hydrogen bonds, generating [101] chains.

Chemical context
As a result of their numerous applications (treatment of cancer, fertilizers, PVC stabilizers, catalysts or reaction intermediates), organotin compounds have been studied for many years (Christie et al., 1979;Seik & Kumar Das, 1993;Ramaswamy et al., 2008;Reichelt & Reuter, 2014). As a continuation of our work on organotin compounds (Diop et al., 2002(Diop et al., , 2003Sarr et al., 2013), we now describe the synthesis and crystal structure of the title compound, (I).

Supramolecular features
In the crystal of (I), the oxalate ions accept hydrogen bonds from the protonated cations: each cation forms one simple N-HÁ Á ÁO hydrogen bond and one asymmetric bifurcated (2) Fig. 2. The packing also features some weak C-HÁ Á ÁO interactions but the main inter-chain interactions are van der Waals forces as shown in Fig. 3.

Synthesis and crystallization
The title compound was obtained in mixed solvents of ethanol/ acetonitrile (50/50) by the reaction of bis(diisopropyl-   The molecular structure of (I), with displacement ellipsoids depicted at the 50% probability level and N-HÁ Á ÁO hydrogen bonds shown as dashed lines.  ammonium) oxalate ( i Pr 2 NH 2 ) 2 ÁC 2 O 4 (0.20 g; 0.63 mmol) with tin(IV) iodide (SnI 4 ) (0.20 g; 0.32 mmol) in a 2:1 molar ratio. The yellow solution obtained was stirred for 1 h and then filtered. Yellow prisms of (I) were obtained by slow solvent evaporation of the filtrate after two weeks.
The bands at 3039 and 1698 cm À1 in the IR spectrum of (I) are assigned respectively to the stretching and deformation vibrations N-H and N-H while the broad band at 1676 and those at 1369, 1237 cm À1 are attributed to the asymmetric and symmetric vibrations of the oxalate -CO 2 groups. The shape of the band at 1676 cm À1 may be due to a superposition of several bands, which may correlate with the different hydrogen-bonding patterns of the oxalate O atoms. The IR spectrum is available in the supporting information.

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H distances of 0.98-1.00 Å and an N-H distance of 0.91 Å . All displacement parameters of H atoms U iso (H) were set to 1.2U eq (C,N) or 1.5U eq (Cmethyl).

Bis(diisopropylammonium) cis-diiodidobis(oxolato-κ 2 O 1 ,O 2 )stannate(IV)
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.