Hexakis(dimethyl sulfoxide-κO)zinc(II) polyiodide

The title compound, [Zn{(CH3)2SO}6]I4, is a one-dimensional supramolecular polymer along a threefold rotation axis of the space group. It is built up from discrete [Zn{(CH3)2SO}6]2+ units connected through non-classical hydrogen bonds to linear I4 2− polyiodide anions (C—H⋯I = 3.168 Å). The ZnII ion in the cation has an octahedral coordination geometry, with all six Zn—O bond lengths being equivalent, at 2.111 (4) Å. The linear polyiodide anion contains a neutral I2 molecule weakly coordinated to two iodide ions.

The title compound, [Zn{(CH 3 ) 2 SO} 6 ]I 4 , is a one-dimensional supramolecular polymer along a threefold rotation axis of the space group. It is built up from discrete [Zn{(CH 3 ) 2 SO} 6 ] 2+ units connected through non-classical hydrogen bonds to linear I 4 2À polyiodide anions (C-HÁ Á ÁI = 3.168 Å ). The Zn II ion in the cation has an octahedral coordination geometry, with all six Zn-O bond lengths being equivalent, at 2.111 (4) Å . The linear polyiodide anion contains a neutral I 2 molecule weakly coordinated to two iodide ions.

Comment
Supramolecular polymers are defined as polymeric systems that extend beyond the molecule by a process of selfassembly between monomer units directed by noncovalent interactions (Huang & Scherman, 2012). These noncovalent forces, such as hydrogen bonding, coordination bonds, π-π stacking and electrostatic forces act as driving forces to construct a well defined supramolecular architectures (Fromm, 2001); however, there are a few examples where nonclassical hydrogen bonds such as C-H···I are used to construct these structures (Youm et al., 2006). Previous studies have suggested that a coordination complex with DMSO such as [Cu(DMSO) 6 ] 2+ acts as monomeric units connected through a self-assembly process with tetraiodide ions driven by weak non-classical hydrogen bonds C-H···I to form a one-dimensional supramolecular polymer (Garzón-Tovar et al., 2013). Herein we report the synthesis and structural characterization of a new supramolecular polymer.
In the title compound, [Zn{(CH 3 ) 2 SO} 6 ]I 4 , the Zn(II) ion is located on a 3-fold inversion axis being coordinated by six equidistant oxygen-bonded dimethyl sulfoxide ligands (Fig. 1) (Long et al.,1999). The two end-iodide anions build up three weak hydrogen bonds to the hydrogen atoms of the methyl groups with distances of 3.167 Å (Fig. 2) to form a one-dimensional supramolecular polymer.

Experimental
Zinc (II) chloride (1.1404 g, 8.3659 mmol) was added to a DMSO (16.506 g, 211.26 mmol) and distilled water (0.199 g, 11.1 mmol) solution. After colorless mixture was ultrasonicated for 20 min, CH 3 I (3.420 g, 24.09 mmol) was added, and ultrasonication was continued for an additional 20 min. The resulting yellow solution was kept at 20°C for 8 d, with continuous agitation. The mixture was filtered, and the filtrate was refrigerated at 4°C for 30 d, after which blue crystals with a metallic luster formed. The crystals of [Zn{(CH 3 ) 2 SO} 6 ]I 4 were filtered and dried under vacuum. The yield obtained was 0.3231 g.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Outlier data were removed using a local program based on the method of Prince and Nicholson. Refinement on F 2 for ALL reflections except for 0 with very negative F 2 or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The observed criterion of F 2 > σ(F 2 ) is used only for calculating R_factor_obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. Geometric parameters (Å, º)