Crystal structure of hexakis(dimethylformamide-κO)manganese(II) decakis(dimethylformamide)-1κ5 O,2κ5 O-[μ-octadecatungstodiphosphato(V)-κO:κO′]dimanganate(II) dimethylformamide disolvate

In the title polyoxidometalate, the Wells–Dawson-type [P2W18O62]6− polyanion bridges two MnII octahedral complexes through terminal O atoms from the belts. The crystal components are connected through numerous weak C—H⋯O hydrogen bonds to construct a three-dimensional framework.

The crystal structure of the title compound, [Mn(C 3 H 7 6À polyanion. Another Mn II ion, located on an inversion centre, is coordinated by six O atoms from the dmf ligands and forms the [Mn(dmf) 6 ] 2+ cation. The crystal components are connected through numerous weak C-HÁ Á ÁO hydrogen bonds to construct a three-dimensional network.

Chemical context
Over the past few decades, polyoxidometalates (POMs) have been considered to be interesting building blocks for the construction of organic-inorganic hybrid materials because of their nanosize, abundant topologies, controllable shapes and high negative charges (Dolbecq et al., 2010). As a result of their unique redox, catalytic, photochemical and magnetic properties, organic-inorganic hybrid POM-based materials have captured considerable attention and are applied widely in many fields such as material science, catalysis and medicine (Niu et al., 2004;Ben Khelifa et al., 2015). Herein, we report the synthesis, crystal structure and supramolecular architecture of the title compound, (1). ISSN 2056-9890

Structural commentary
The asymmetric unit of (1) consists of one half of the dinuclear complex anion [{Mn(dmf) 6À acting as a bridging ligand between the two Mn II atoms, is located about a twofold symmetry axis (Fig. 1). The Mn1 ion within this anion is coordinated by five dmf molecules through O atoms and by a terminal O atom from the belt of the Wells-Dawson-type polyanion. The coordination sphere of the Mn1 ion features a trigonal distortion with three shorter [2.137 (6), 2.143 (6) and 2.153 (6) Å ] and three longer [2.163 (5), 2.173 (6) and 2.205 (5) Å ] Mn1-O bonds. Another Mn II atom in this structure, Mn2, is located on an inversion centre and is octahedrally coordinated by six dmf molecules with the formation of the complex cation [Mn(dmf) 6 ] 2+ shown in Fig. 2. The Mn2 octahedron is characterized by a rhombic distortion with the following bond length values: 2.214 (9), 2.175 (7) and 2.134 (7) Å . The O-Mn-O bond angles in the complex ions Mn1 and Mn2 vary from 82.9 (2) to 100.0 (2) and from 84.2 (3) to 90.6 (3) , respectively, and from 169.7 (2) to 174.5 (3) for bond angles with O atoms in trans positions in the Mn1 complex. These bond length and angle values show that the octahedral coordination geometry of the Mn II ions is distorted and these values are in good agreement with literature data (Niu et al., 2004).
The two central P atoms of the POM are tetrahedrally coordinated by four bridging O atoms. The corresponding P1-O bond lengths vary from 1.528 (5) to 1.577 (5) Å (mean value 1.545 Å ) and the O-P1-O bond angles are in the range 106.5 (2) to 112.7 (2) . The W-O distances vary over a wide range: 1.700 (5)-2.384 (4) Å and the bond angles O-W-O are in the range 71.6 (2) to 103.8 (2) . These bond lengths and angles are consistent with those given in the literature for the -isomer of the Wells-Dawson-type polyanion (Dhifallah et al., 2016).

Supramolecular features
The crystal packing of the title compound is illustrated in Fig. 3. In addition to the electrostatic interactions between the ions, the structure is stabilized by numerous weak C-HÁ Á ÁO hydrogen bonds (Table 1) that organize all the structure components into a three-dimensional framework.

Synthesis and crystallization
The title compound was prepared at room temperature by dissolving successively the potassium salt K 6 [-P 2 W 18 O 62 ]Á-11H 2 O (0.606g, 0.125 mmol), synthesized by a literature method (Mbomekalle et al., 2004) and manganese(II) chloride (MnCl 2 Á4H 2 O; 0.099 g, 0.5 mmol) in dmf (25 mL) under stirring. The clear solution obtained was allowed to stand for at least one night until it took a stable color indicating that the kinetics of the reaction were complete. Yellow crystals of (1) suitable for X-ray diffraction analysis were obtained by diffusion of ethanol into the dmf solution.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were refined using a riding model with C-H = 0.93-0.96 Å and U iso (H) = 1.5U eq (C) or 1.2U eq (C). Restraints (DELU and SIMU) in SHELXL2014 (Sheldrick, 2015) were used in order to maintain a reasonable geometry and atomic displacement parameters for one DMF molecule.

octadecatungstodiphosphato(V)-κO:κO′]dimanganate(II) dimethylformamide disolvate
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 2.07 e Å −3 Δρ min = −2.08 e Å −3 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.