Tetraaquatetramanganese(II) catena-[germanodihydroxidodi(hydrogenphosphate)diphosphate]

The title compound, Mn4(H2O)4[Ge(OH)2(HPO4)2(PO4)2], was synthesized by the solvothermal method. Its crystal structure is isotypic with the iron and cobalt analogues [Huang et al. (2012 ▶). Inorg. Chem. 51, 3316–3323]. In the crystal structure, the framework is built from undulating manganese phosphate sheets parallel to (010) interconnected by GeO6 octahedra (at the inversion center), resulting in a three-dimensional network with eight-membered ring channels into which all the protons point. The undulating manganese phosphate sheet consists of zigzag manganese octahedral chains along [10-1], built from MnO4(OH)(OH2) octahedra and MnO5(OH2) octahedra by sharing their trans or skew edges, which are interconnected by PO3(OH) and PO4 tetrahedra via corner-sharing. The crystal structure features extensive O—H⋯O hydrogen-bonding interactions.

The asymmetric unit of the title compound consists of two distinct Mn atoms, one Ge atom, and two crystallographically independent P atoms ( Figure 1). Mn1 is surrounding by four O atoms, an OH-group, and a H 2 O molecule forming a distorted octahedron Mn1O 4 (OH)(OH 2 ) with bond distances of 2.159-2.207 Å. Mn2 adopt a nearly regular octahedral coordination to five O atoms and a water molecule with bond distances ranging from 2.176 to 2.224 Å.
Ge atom coordinates to four O-atoms in the equatorial plane with shorter bond lengths of 1.846-1.871 Å and two hydroxyl groups in trans-position with longer distance of 1.913 Å. Both P atoms are in tetrahedral coordination with bond lengths of 1.526-1.573 Å. All the bond lengths and angles of the title compound are similar to those of the known germanophosphates (Huang et al., 2012;Liu, Yang, Wang et al., 2008;Liu, Yang, Zhang et al., 2008;Zhao et al., 2009).
The mixture was transferred into a Teflon-lined stainless steel autoclave (internal volume of 15 mL) and heated at 423K for 7 days under static conditions. After the autoclaves cooling to room temperature, the products were filtered off and washed by distilled water for several times and dried in air. Finally light-pink block-shaped crystals were obtained. It is needed to note that the products often contain a minor impurity of GeO 2 . Many efforts have been made to get pure phase.

sup-2
Acta Cryst. (2012). E68, i37-i38 However, even the pure phase was obtained but the yield is so low that not enough for further characterization. Thus only single crystal X-ray diffraction of the title compound was carried out.

Refinement
Originally, all hydrogen positions were located from the difference Fourier map and refined by applying the constraint of displacement parameters as 0.05 eÅ 3 and a bond distance of d(O-H) = 0.82 (1)Å. After the refinement, O8-H5 turned out to have no acceptor atom. Therefore, the H5 position was calculated geometrically and fixed without applying further refinement.  (Brandenburg, 2005) and ATOMS (Dowty, 2004); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and

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. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness 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 threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) 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.