Crystal structure of hexakis(dimethyl sulfoxide-κO)manganese(II) diiodide

The title salt consists of isolated octahedrally shaped [Mn(DMSO)6]2+ cations (DMSO is dimethyl sulfoxide) and two I− anions, held together through weak C—H⋯I interactions.


Chemical context
Tridentate pincer ligands coordinating either through two P and one N atom (PNP-type) or through two P and one C atom (PCP-type) have multifarious applications in catalysis, synthetic chemistry or molecular recognition (Szabo & Wendt, 2014). Although these ligands play an important role in coordination chemistry, studies of pincer complexes of firstrow transition metals are rather scarce (Murugesan & Kirchner, 2016). During a current project to prepare the first manganese(II) PNP-type pincer complexes (Mastalir et al., 2016) according to the reaction scheme presented in Fig. 1, we obtained instead the title salt, [Mn(DMSO) 6 ]I 2 (DMSO is dimethyl sulfoxide), and report here its crystal structure.

Structural commentary
The Mn 2+ cation is bound to the O atoms of six DMSO molecules that are arranged in an octahedral configuration around the metal cation (Fig. 2). The deviation from the ideal octa-hedral coordination are minute, with cis O-Mn-O angles ranging from 85.8 (2) to 93.8 (2) and trans angles from 176.3 (2) to 178.2 (2) . The averaged Mn-O bond length of 2.17 (2) Å is in perfect agreement with that of the related perchlorate salt [Mn (DMSO)

Supramolecular features
The isolated complex [Mn(DMSO) 6 ] 2+ molecules are stacked into rows extending parallel to [100] whereby the rows are arranged in a distorted hexagonal rod packing. The iodide counter-anions are located between the rows and, apart from Coulomb interactions, are linked to the complex cations through weak C-HÁ Á ÁI interactions (  The structures of the molecular and ionic entities in the title salt, showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level and, for clarity, the H atoms have been omitted. Table 1 Hydrogen-bond geometry (Å , ).

Synthesis and crystallization
All manipulations were performed under an inert atmosphere of argon by using Schlenk techniques or in a MBraun inert-gas glove box. The solvents were purified according to standard procedures. Anhydrous MnI 2 was purchased from Sigma-Aldrich and was used without further purification. The synthesis of the PNP-ligand was performed according to literature procedures (Benito-Garagorri et al., 2006). The title manganese salt was formed in the course of the targeted synthesis of an Mn II PNP-complex (Fig. 1). Anhydrous MnI 2 (93 mg, 0.50 mmol) and the PNP-ligand (115 mg, 0.33 mmol) were stirred in 7 ml tetrahydrofuran for one h. 2 ml of DMSO were added and the solution filtrated over celite. The clear colourless solution was layered with 15 ml diethyl ether and was left for 7 days. Colourless crystals of the title compound were obtained as the only solid reaction product.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Close inspection of the diffraction pattern revealed twinning by non-merohedry with one domain rotated by 180 about [100]. Intensity statistics showed 1583 reflections belonging to domain 1 only (mean I/ = 7.5), 1583 reflections to domain 2 only (mean I/ = 7.2) and 4780 reflections to both domains (mean I/ = 7.5). The presence of two domains with equal scattering volume was confirmed by the refinement (refinement as a two-component twin using an HKLF-5 file). The refined Flack parameter (Flack, 1983) of 0.10 (2) revealed additional twinning by inversion. The maximum remaining electron density is found 1.30 Å from atom H2C and the minimum remaining electron density 1.06 Å from atom I1.   (2) Computer programs: APEX2 and SAINT-Plus (Bruker, 2014), SHELXS97 (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), Mercury (Macrae et al., 2006) and publCIF (Westrip, 2010 Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT-Plus (Bruker, 2014); data reduction: SAINT-Plus (Bruker, 2014); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: publCIF (Westrip, 2010). 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 2-component twin.