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1.  Li0.5Al0.5Mg2(MoO4)3  
The title compound, lithium/aluminium dimagnesium tetra­kis­[orthomolybdate(VI)], was prepared by a solid-state reaction route. The crystal structure is built up from MgO6 octa­hedra and MoO4 tetra­hedra sharing corners and edges, forming two types of chains running along [100]. These chains are linked into layers parallel to (010) and finally linked by MoO4 tetra­hedra into a three-dimensional framework structure with channels parallel to [001] in which lithium and aluminium cations equally occupy the same position within a distorted trigonal–bipyramidal coordination environment. The title structure is isotypic with LiMgIn(MoO4)3, with the In site becoming an Mg site and the fully occupied Li site a statistically occupied Li/Al site in the title structure.
PMCID: PMC3884375  PMID: 24426975
2.  MnBa2(HPO4)2(H2PO4)2  
Crystals of manganese(II) dibarium bis­(hydrogenphosphate) bis­(dihydrogenphosphate), MnBa2(HPO4)2(H2PO4)2, were obtained by hydro­thermal synthesis. The title compound is isotypic with its CdII and CaII analogues. The structure is built up of an infinite {[Mn(HPO4)2(H2PO4)2]4−}n chain running along [100], which consists of alternate MnO6 octa­hedra and [PO4] tetra­hedra, in which the centrosymmetric MnO6 octa­hedra share their four equatorial O-atom corners with tetra­hedral [PO3(OH)] groups and their two axial apices with tetra­hedral [PO2(OH)2] groups. These chains are held together by BaO9 coordination polyhedra, developing into a three-dimensional structure. The O—H⋯O hydrogen bonds additionally stabilize the structural set-up. Due to the ionic radius of Mn2+ being much smaller than those of Ca2+ and Cd2+, this may imply that their adopted structure type has a great tolerance for incorporating various ions and the exploitation of more diverse compounds in the future is encouraged.
PMCID: PMC3379057  PMID: 22719278
3.  Distrontium trimanganese(II) bis­(hydro­gen­phosphate) bis­(ortho­phosphate) 
The title compound, Sr2Mn3(HPO4)2(PO4)2, was synthesized under hydro­thermal conditions. In the structure, one of two Mn atoms is located on an inversion centre, whereas all others atoms are located in general positions. The framework structure is built up from two types of MnO6 octa­hedra (one almost undistorted, one considerably distorted), one PO3OH and one PO4 tetra­hedron. The centrosymmetric MnO6 octa­hedron is linked to two other MnO6 octa­hedra by edge-sharing, forming infinite zigzag chains parallel to [010]. The PO3OH and PO4 tetra­hedra connect these chains through common vertices or edges, resulting in the formation of sheets parallel to (100). The Sr2+ cation is located in the inter­layer space and is bonded to nine O atoms in form of a distorted polyhedron and enhances the cohesion of the layers. Additional stabilization is achieved by a strong inter­layer O—H⋯O hydrogen bond between the PO3OH and PO4 units. The structure of the title phosphate is isotypic to that of Pb2Mn3(HPO4)2(PO4)2.
PMCID: PMC3793668  PMID: 24109255
4.  Redetermination of the low-temperature polymorph of Li2MnSiO4 from single-crystal X-ray data 
Crystals of dilithium manganese(II) silicate were grown under high-temperature hydro­thermal conditions in the system LiOH—MnO2—SiO2. The title compound crystallizes in the βII-Li3PO4 structure type. The coordination polyhedra of all cations are slightly distorted tetra­hedra (m symmetry for MnO4 and SiO4), which are linked by corner-sharing to each other. The vertices of the tetra­hedra point to the same direction perpendicular to the distorted hexa­gonal close-packed (hcp) array of O atoms within which half of the tetra­hedral voids are occupied by cations. In comparison with the previous refinement from powder X-ray data [Dominko et al. (2006 ▶). Electrochem. Commun. 8, 217–222], the present reinvestigation from single-crystal X-ray data allows a more precise determination of the distribution of the Li+ and Mn2+ cations, giving a perfectly site-ordered structure model for both Li+ and Mn2+.
PMCID: PMC3435565  PMID: 22969438
5.  KPr(PO3)4  
Single crystals of the title compound, potassium praseodymium(III) polyphosphate, were obtained by solid-state reaction. The monoclinic non-centrosymmetric structure is isotypic with all other KLn(PO3)4 analogues from Ln = La to Er, inclusive. The crystal structure of these long-chain polyphosphates is built up from infinite crenelated polyphosphate chains of corner-sharing PO4 tetra­hedra with a repeating unit of four tetra­hedra. These chains, running along [100], are arranged in a pseudo-tetra­gonal rod packing and are further linked by isolated PrO8 square anti­prisms [Pr—O = 2.3787 (9)–2.5091 (8) Å], forming a three-dimensional framework. The K+ ions reside in channels parallel to [010] and exhibit a highly distorted coordination sphere by eight O atoms at distances ranging from 2.7908 (9) to 3.1924 (11) Å.
PMCID: PMC3007571  PMID: 21588081
6.  Li3Al(MoO2)2O2(AsO4)2  
Single crystals of trilithium(I) aluminium(III) bis­[dioxidomolybdenum(VI)] dioxide bis­[arsenate(V)], Li3AlMo2As2O14, have been prepared by solid-state reaction at 788 K. The structure consists of AsO4 tetra­hedra, AlO6 octa­hedra and Mo2O10 groups sharing corners to form a three-dimensional framework containing channels running respectively along the [100] and [010] directions, where the Li+ ions are located. This structure is compared with compounds having (MX 2O12)n chains (M = Mo, Al and X = P, As) and others containing M 2O10 (M = Mo, Fe) dimers.
PMCID: PMC2968439  PMID: 21582037
7.  A two-dimensional organic–inorganic hybrid compound, poly[(ethylenediamine)tri-μ-oxido-oxidocopper(II)molybdenum(VI)] 
A new organic–inorganic two-dimensional hybrid compound, [CuMoO4(C2H8N2)], has been hydro­thermally synthesized at 443 K. The unit cell contains layers composed of CuN2O4 octa­hedra and MoO4 tetra­hedra. Corner-sharing MoO4 and CuN2O4 polyhedra form CuMoO4 bimetallic sites that are joined together through O atoms, forming an edge-sharing Cu2Mo2O4 chain along the c axis. The one-dimensional chains are further linked through bridging O atoms that join the Cu and Mo atoms into respective chains along the b axis, thus establishing layers in the bc plane. The ethyl­enediamine ligand is coordinated to the Cu atom through its two N atoms and is oriented perpendicularly to the two-dimensional –Cu—O—Mo– layers. The average distance between adjacent layers, as calculated by consideration of the closest and furthest distances between two layers, is 8.7 Å. The oxidation states of the Mo and Cu atoms of VI and II, respectively, were confirmed by bond-valence sum calculations.
PMCID: PMC2959353  PMID: 21200997
8.  NaAg2Mo3O9AsO4  
The title compound, sodium disilver arsenatotrimolybdate, Na0.93 (1)Ag2.07 (1)Mo3AsO13, was prepared by a solid-state reaction. In the crystal structure, isolated AsO4 tetra­hedra share corners with groups of three edge-sharing MoO6 octa­hedra. This arrangement leads to the formation of anionic 1 ∞[Mo3AsO13]n ribbons extending parallel to [100]. The three metal sites show occupational disorder by AgI and NaI cations, each with a different Ag:Na ratio. The metal cations are situated in the space between the ribbons and are surrounded by terminal O atoms of the ribbons in the form of distorted MO7 polyhedra (M = Ag, Na) for distances < 3.0 Å. The title compound shows weak ionic conductivity. Structural relationships between different compounds in the quaternary systems M–Sb–P–O, M–Nb–P–O and M–Mo–As–O (M is Ag or an alkali metal) are also discussed.
PMCID: PMC2983299  PMID: 21587345
9.  β-Xenophyllite-type Na4Li0.62Co5.67Al0.71(AsO4)6  
The title compound, tetrasodium lithium cobalt aluminium hexa­(orthoarsenate), was synthesized by a solid state reaction route. In the crystal structure, Co2+ ions are partially substituted by Al3+ in an octa­hedral environment [M1 with site symmetry 2/m; occupancy ratio Co:Al = 0.286 (10):0.714 (10)]. The charge compensation is ensured by Li+ cations sharing a tetra­hedral site with Co2+ ions [M2 with site symmetry 2; occupancy ratio Co:Li = 0.690 (5):0.310 (5)]. The anionic unit is formed by two octa­hedra and three tetra­hedra linked only by corners. The CoM1M2As2O19 units associate to an open three-dimensional framework containing tunnels propagating along the a-axis direction. One Na+ cation is located in the periphery of the tunnels while the other two are situated in the centres: all Na+ cations exhibit half-occupancy. The structure of the studied material is compared with those of various related minerals reported in the literature.
PMCID: PMC3790335  PMID: 24098157
10.  Zn1.86Cd0.14(OH)VO4  
The title compound, dizinc cadmium hydroxide tetraoxido­vanadate, Zn1.86Cd0.14(OH)VO4, was prepared under low-temperature hydro­thermal conditions. It is isostructural with Zn2(OH)VO4 and Cu2(OH)VO4. In the crystal structure, chains of edge-sharing [ZnO6] octahedra are inter­connected by VO4 tetra­hedra (site symmetries of both V atoms and their coordination polyhedra are .m.) to form a three-dimensional [Zn(OH)VO4]2− framework with channels occupied by Zn and Zn/Cd cations adopting trigonal–bipyramidal and distorted octa­hedral coordinations, respectively. Zn1.86Cd0.14(OH)VO4 is topologically related to adamite-type phases, and descloizite- and tsumcorite-type structures.
PMCID: PMC3011449  PMID: 21589202
11.  A new mixed-valence lead(II) mangan­ese(II/III) phosphate(V): PbMnII 2MnIII(PO4)3  
The title compound, lead trimanganese tris(orthophosphate), has been synthesized by hydro­thermal methods. In this structure, only two O atoms are in general positions and all others atoms are in the special positions of the Imma space group. Indeed, the atoms in the Wyckoff positions are namely: Pb1 and P1 on 4e (mm2); Mn1 on 4b (2/m); Mn2 and P2 on 8g (2); O1 on 8h (m); O2 on 8i (m). The crystal structure can be viewed as a three-dimensional network of corner- and edge-sharing PO4 tetra­hedra and MnO6 octa­hedra, building two types of chains running along the b axis. The first is an infinite linear chain, formed by alternating MnIIIO6 octa­hedra and PO4 tetra­hedra which share one vertex. The second chain is built up from two adjacent edge-sharing octa­hedra (MnII 2O10 dimers) whose ends are linked to two PO4 tetra­hedra by a common edge. These chains are linked together by common vertices of polyhedra in such a way as to form porous layers parallel to (001). These sheets are bonded by the first linear chains, leading to the appearance of two types of tunnels, one propagating along the a axis and the other along b. The PbII ions are located within the inter­sections of the tunnels with eight neighbouring O atoms in form of a trigonal prism that is capped by two O atoms on one side. The three-dimensional framework of this structure is compared with similar phosphates such as Ag2Co3(HPO4)(PO4)2 and Ag2Ni3(HPO4)(PO4)2.
PMCID: PMC3772398  PMID: 24046541
12.  The type IV polymorph of KEu(PO3)4  
Single crystals of KEu(PO3)4, potassium europium(III) polyphosphate, were obtained by solid-state reactions. This monoclinic form is the second polymorph described for this composition and belongs to type IV of long-chain polyphosphates with general formula A I B III(PO3)4. It is isotypic with its KEr(PO3)4 and KDy(PO3)4 homologues. The crystal structure is built of infinite helical chains of corner-sharing PO4 tetra­hedra with a repeating unit of eight tetra­hedra. These chains are further linked by isolated EuO8 square anti­prisms, forming a three-dimensional framework. The K+ ions are located in pseudo-hexa­gonal channels running along [01] and are surrounded by nine O atoms in a distorted environment.
PMCID: PMC2972142  PMID: 21578546
13.  Penta­ammonium hepta­sodium bis­[penta­kis(μ2-oxido)deca­oxido­bis­(μ5-phosphato)penta­molybdenum(VI)] henicosa­hydrate 
The title compound, (NH4)5Na7[Mo5P2O23]2·21H2O, was prepared under atmospheric conditions in aqueous solution at room temperature. The structure contains the [Mo5P2O23]6− heteropolyoxometallate anion, which has been previously reported a number of times with a variety of differing counter-cations. Each anion is built up of five MoO6 octa­hedra sharing an edge and forming a ring which is closed by common corners of the terminal octa­hedra. The rings are closed on both sides by two asymmetric PO4 tetra­hedra, sharing three corners with three MoO6 octa­hedra. The anions are chiral and the two independent anions in the asymmetric unit were arbitarily chosen with the same chirality, but the centrosymmetric crystal contains both enanti­omers. The structure can alternatively be described as a succession of layers parallel to (101), formed by the [Mo5P2O23]6− anions and linked by sodium chains. Water mol­ecules and ammonium ions fill the remaining space and ensure the cohesion through extensive N—H⋯O and O—H⋯O hydrogen bonding.
PMCID: PMC2983582  PMID: 21580198
14.  Dicobalt copper bis­[orthophosphate(V)] monohydrate, Co2.39Cu0.61(PO4)2·H2O 
In an attempt to hydro­thermally synthesize a phase with composition Co2Cu(PO4)2·H2O, we obtained the title compound, Co2.39Cu0.61(PO4)2·H2O instead. Chemical analysis confirmed the presence of copper in the crystal. The crystal structure of the title compound can be described as a three- dimensional network constructed from the stacking of two types of layers extending parallel to (010). These layers are made up from more or less deformed polyhedra: CoO6 octa­hedra, (Cu/Co)O5 square pyramids and PO4 tetra­hedra. The first layer is formed by pairs of edge-sharing (Cu/Co)O5 square pyramids linked via a common edge of each end of the (Cu/Co)2O8 dimer to PO4 tetra­hedra. The second layer is undulating and is built up from edge-sharing CoO6 octa­hedra. The linkage between the two layers is accomplished by PO4 tetra­hedra. The presence of water mol­ecules in the CoO4(H2O)2 octa­hedron also contributes to the cohesion of the layers through O—H⋯O hydrogen bonding.
PMCID: PMC2979060  PMID: 21578990
15.  The aluminoarsenate K1.8Sr0.6Al3(AsO4)4  
The title compound, potassium strontium trialuminium tetra­arsenate, was prepared by solid-state reaction. The structure consists of AlO6 octa­hedra (site symmetries 2.. and 2/m) and two AsO4 tetra­hedra (.2. and m..) sharing corners and edges to form a two-dimensional structure parallel to (010). The cations are occupationally disordered and are located in the interlayer space. For both types of cations, distorted coordination polyhedra are observed.
PMCID: PMC3344283  PMID: 22590049
16.  Cubic ZrW1.75Mo0.25O8 from a Rietveld refinement based on neutron powder diffraction data 
The solid solution in the system Zr–Mo–W–O with composition ZrW1.75Mo0.25O8 (zirconium tungsten molybdenum octa­oxide) was prepared by solid-state reactions as a polycrystalline material. Its structure has cubic symmetry (space group P213) at room temperature. The structure contains a network of corner-sharing ZrO6 octa­hedra (.3. symmetry) and MO4 (M = W, Mo) tetra­hedra (.3. symmetry). Along the main threefold axis of the cubic unit cell, the MO4 tetra­hedra are arranged in pairs forming M 2O8 units in which the M1O4 tetra­hedra have larger distortions in terms of bond distances and angles than the M2O4 tetra­hedra. These units are disordered over two possible orientations, with the M—Oterminal vectors pointing to the [111] or [ ] directions. The reversal of the orientations of the M 2O8 units results from the concerted flips of these units. The time-averaged proportions of flipped and unflipped M 2O8 units were determined and the fraction of unflipped M 2O8 units is about 0.95. The order degree of the M 2O8 unit orientation is about 0.9. During the reversal process, the M-atom site has a migration about 0.93 Å, one of the O-atom sites has a 0.25 Å migration distance, whereas two other O-atom sites migrate marginally (≃ 0.08 Å). The results prove the constraint strategy to be a reasonable approach based on the ratcheting mechanism.
PMCID: PMC2977542  PMID: 21583728
17.  A triclinic polymorph of dicadmium divanadate(V) 
The title compound, Cd2V2O7, was obtained under hydro­thermal conditions. Different from the known monoclinic form, the new polymorph of Cd2V2O7 has triclinic symmetry and is isotypic with Ca2V2O7. The building units of the crystal structure are two Cd2+ cations, with coordination numbers of six and seven, and two V atoms with a tetra­hedral and a significantly distorted trigonal–pyramidal coordination environment, respectively. Two VO5 pyramids share an edge and each pyramid is connected to one VO4 tetra­hedron via a corner atom, forming an isolated V4O14 8− anion. These anions are arranged in sheets parallel to (-211) and are linked through the Cd2+ cations into a three-dimensional framework structure.
PMCID: PMC3884238  PMID: 24454014
18.  RbCuFe(PO4)2  
A new iron phosphate, rubidium copper(II) iron(III) bis­(phosphate), RbCuFe(PO4)2, has been synthesized as single crystals by the flux method. This compound is isostructural with KCuFe(PO4)2 [Badri et al. (2011 ▶), J. Solid State Chem. 184, 937–944]. Its structure is built up from Cu2O8 units of edge-sharing CuO5 polyhedra, inter­connected by FeO6 octa­hedra through common corners to form undulating chains that extend infinitely along the [011] and [01-1] directions. The linkage of such chains is ensured by the PO4 tetra­edra and the resulting three-dimensional framework forms quasi-elliptic tunnels parallel to the [101] direction in which the Rb+ cations are located.
PMCID: PMC3793670  PMID: 24109257
19.  An ortho­rhom­bic polymorph of the ultraphosphate YP5O14  
Single crystals of yttrium penta­phosphate(V), YP5O14, were obtained by solid-state reaction. The ortho­rhom­bic title compound belongs to the family of ultraphosphates and is the second polymorph of this composition. It is isotypic with its Ho and Er analogues. The structure contains two bridging Q 2-type PO4 tetra­hedra and one branching Q 3-type PO4 tetra­hedron, leading to infinite ultraphosphate ribbons running along the a axis. The coordination polyhedron around the Y3+ cation may be described as distorted bicapped trigonal-prismatic. The YO8 polyhedra are isolated from each other. They are linked by corner-sharing to the O atoms of six Q 2-type and of two Q 3-type PO4 tetra­hedra into a three-dimensional framework.
PMCID: PMC2968816  PMID: 21582306
20.  Redetermination of AgPO3  
Single crystals of silver(I) polyphosphate(V), AgPO3, were prepared via a phospho­ric acid melt method using a solution of Ag3PO4 in H3PO4. In comparison with the previous study based on single-crystal Weissenberg photographs [Jost (1961 ▶). Acta Cryst. 14, 779–784], the results were mainly confirmed, but with much higher precision and with all displacement parameters refined anisotropically. The structure is built up from two types of distorted edge- and corner-sharing [AgO5] polyhedra, giving rise to multidirectional ribbons, and from two types of PO4 tetra­hedra linked into meandering chains (PO3)n spreading parallel to the b axis with a repeat unit of four tetra­hedra. The calculated bond-valence sum value of one of the two AgI ions indicates a significant strain of the structure.
PMCID: PMC3052054  PMID: 21522230
21.  Ba2Sb4GeS10  
The title quaternary compound, dibarium tetra­anti­mony germanium deca­sulfide, Ba2Sb4GeS10, crystallizes in a novel three-dimensional ∞ 3[Sb4GeS10]4− network structure, which is composed of triangular pyramidal SbS3 (site symmetry m..), distorted SbS5 (m..) polyhedra and regular GeS4 (-4..) tetra­hedra. The SbS3 and SbS5 units are connected with each other through corner- and edge-sharing, forming a Sb4S10 layer in the ab plane. The GeS4 tetra­hedra further bridge two neighbouring Sb4S10 layers, forming a three-dimensional ∞ 3[Sb4GeS10]4− network. The Ba2+ cation (..2) is located between two Sb4S10 layers and is coordinated by ten S atoms with Ba—S bond lengths in the range 3.2505 (9)–3.4121 (2) Å.
PMCID: PMC3647782  PMID: 23723748
22.  β-Nd2Mo4O15  
The title compound, dineodymium(III) tetra­molybdate(VI), has been prepared by a flux technique and is the second polymorph of composition Nd2Mo4O15. The crystal structure is isotypic with those of Ce2Mo4O15 and Pr2Mo4O15. It features a three-dimensional network composed of distorted edge- and corner-sharing NdO7 polyhedra, NdO8 polyhedra, MoO4 tetra­hedra and MoO6 octa­hedra.
PMCID: PMC3011581  PMID: 21589208
23.  The γ-polymorph of AgZnPO4 with an ABW zeolite-type framework topology 
The γ-polymorph of the title compound, silver zinc orthophos­phate, was synthesized under hydro­thermal conditions. The structure consists of ZnO4, PO4 and AgO4 units. The coord­ination spheres of ZnII and PV are tetra­hedral, whereas the AgI atom is considerably distorted from a tetra­hedral coordination. Each O atom is linked to each of the three cations. An elliptic eight-membered ring system is formed by corner-sharing of alternating PO4 and ZnO4 tetra­hedra, leading to a framework with an ABW-type zeolite structure. The framework encloses channels running parallel to [100] in which the Ag cations are located, with Ag⋯Ag contacts of 3.099 (3) Å. This short distance results from d 10⋯d 10 inter­actions, which play a substantial role in the crystal packing. The structure of γ-AgZnPO4 is distinct from the two other polymorphs α-AgZnPO4 and β-AgZnPO4, but is isotypic with NaZnPO4-ABW, NaCoPO4-ABW and NH4CoPO4-ABW.
PMCID: PMC3009017  PMID: 21588789
24.  Undeca­europium hexa­zinc dodeca­arsenide 
The title compound, Eu11Zn6As12, crystallizes with the Sr11Cd6Sb12 structure type (Pearson’s symbol mC58). The complex monoclinic structure of the first arsenide to form with this type features chains made of corner-sharing ZnAs4 tetra­hedra, separated by Eu atoms. There are a total of 15 unique positions in the asymmetric unit. Except for one Eu atom with site symmetry 2/m, all atoms are located on mirror planes. An usual aspect of the structure are some Zn—As distances, which are much longer than the sum of the covalent radii, indicating weaker inter­actions.
PMCID: PMC2983538  PMID: 21580200
25.  Ni2Sr(PO4)2·2H2O 
The title compound, dinickel(II) strontium bis­[ortho­phosphate(V)] dihydrate, was obtained under hydro­thermal conditions. The crystal structure consists of linear chains ∞ 1[NiO2/2(OH2)2/2O2/1] of edge-sharing NiO6 octa­hedra ( symmetry) running parallel to [010]. Adjacent chains are linked to each other through PO4 tetra­hedra (m symmetry) and arranged in such a way to build layers parallel to (001). The three-dimensional framework is accomplished by stacking of adjacent layers that are held together by SrO8 polyhedra (2/m symmetry). Two types of O—H⋯O hydrogen bonds involving the water mol­ecule are present, viz. one very strong hydrogen bond perpendicular to the layers and weak trifurcated hydrogen bonds parallel to the layers.
PMCID: PMC3011770  PMID: 21589209

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