A. Assani

Silver trimagnesium phosphate bis­(hydrogenphosphate), AgMg3(PO4)(HPO4)2, with an alluaudite-like structure

The title compound, AgMg3(PO4)(HPO4)2, which has been synthesized by the hydrothermal method, has an alluaudite-like structure which is formed by edge-sharing MgO6 octahedra (one of which has symmetry 2), resulting in chains linked together by phosphate groups and hydrogen bonds. The three-dimensional framework leads to two different channels along the c axis, one of which is occupied by Ag+ ions with a square-planar coordination. The Ag+ ions are disordered over two sites in a 0.89 (3):0.11 (3) ratio. The OH groups, which point into the other type of channel, are involved in strong O—H⋯O hydrogen bonds. The title compound is isotypic with the compounds AM 3H2(XO4)(HXO4)2 (A = Na or Ag, M = Mn, Co or Ni, and X = P or As) of the alluaudite structure type.

Crystal structure of a sodium, zinc and iron(III)-based non-stoichiometric phosphate with an alluaudite-like structure: Na1.67Zn1.67Fe1.33(PO4)3

The transition-metal orthophosphate Na1.67Zn1.67Fe1.33(PO4)3 cristallizes in an alluaudite-type structure. The chains characterizing the alluaudite structure are then built up from [M 2O10] (M = Fe/Zn) units alternating with [ZnO6] octahedra. This structure is characterized by a cationic disorder in one tunnel and in the general position.

Disilver(I) trinickel(II) hydrogenphos­phate bis­(phosphate), Ag2Ni3(HPO4)(PO4)2

The title compound, Ag2Ni3(HPO4)(PO4)2, has been synthesized by the hydrothermal method. Its structure is formed by two types of chains running along the b axis. The first chain results from a linear and continuous succession of NiO6 octahedra linked to PO4 tetrahedra by a common vertex. The second chain is built up from two adjacent edge-sharing octahedra (dimers) whose ends are linked to two PO4 tetrahedra by a common edge. Those two types of chains are linked together by the phosphate groups to form polyhedral sheets parallel to the (001) plane. The three-dimensional framework delimits two types of hexagonal tunnels parallel to the a-axis direction, at (x, 1/2, 0) and (x, 0, 1/2), where the Ag atoms are located. Each silver cation is surrounded by eight O atoms. The same Ag+ coordination is found in other phosphates with the alluaudite structure, for example, AgMn3(PO4)(HPO4)2. Moreover, O—H⋯O hydrogen bonds link three PO4 tetrahedra so as to build a three-dimensional network.

A new mixed-valence lead(II) mangan­ese(II/III) phosphate(V): PbMnII2MnIII(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.

BaMnII2MnIII(PO4)3

The title compound, barium trimanganese tris(orthophosphate), was synthesized hydrothermally. Its structure is isotypic with the lead and strontium analogues AMnII 2MnIII(PO4)3 (A = Pb, Sr). Except for two O atoms on general positions, all atoms are located on special positions. The Ba and one P atom exhibit mm2 symmetry, the MnII atom 2/m symmetry, the MnIII atom and the other P atom .2. symmetry and two O atoms are located on mirror planes. The crystal structure contains two types of chains running parallel to [010]. One chain is linear and is composed of alternating MnIIIO6 octahedra and PO4 tetrahedra sharing vertices; the other chain has a zigzag arrangement and is built up from two edge-sharing MnIIO6 octahedra connected to PO4 tetrahedra by edges and vertices. The two types of chains are linked through PO4 tetrahedra into an open three-dimensional framework which contains channels parallel to [100] and [010] in which the BaII ions are located. The alkaline earth cation is surrounded by eight O atoms in the form of a slightly distorted bicapped trigonal prism.

Crystal structure of alluaudite-type NaMg3(HPO4)2(PO4).

NaMg3(PO4)(HPO4)2 crystallizes in the alluaudite-type structure. Two types of [MgO6] octahedra, one [NaO10] polyhedron, one orthophosphate and one hydrogenphosphate tetrahedron form the structural set-up.

SrMnII2MnIII(PO4)3

The title compound, strontium trimanganese tris(orthophosphate), was synthesized under hydrothermal conditions. Its structure is isotypic to that of the lead analogue PbMnII 2MnIII(PO4)3. Two O atoms are in general positions, whereas all others atoms are in special positions. The Sr and one P atom exhibit mm2 symmetry, the MnII atom 2/m symmetry, the MnIII atom and the other P atom .2. symmetry and two O atoms are located on mirror planes. The three-dimensional network of the crystal structure is made up of two types of chains running parallel to [010]. One chain is linear and is composed of alternating MnIIIO6 octahedra and PO4 tetrahedra sharing vertices; the other chain has a zigzag arrangement and is built up from two edge-sharing MnIIO6 octahedra connected to PO4 tetrahedra by edges and vertices. The two types of chains are linked through PO4 tetrahedra, leading to the formation of channels parallel to [100] and [010] in which the SrII ions are located. They are surrounded by eight O atoms in the form of a slightly distorted bicapped trigonal prism.

Crystal structure of (Na0.70)(Na0.70,Mn0.30)(Fe3+,Fe2+)2Fe2+(VO4)3, a sodium-, iron- and manganese-based vanadate with the alluaudite-type structure

The title transition metal vanadate crystallizes in an alluaudite-type structure. The chains characterizing the alluaudite structure are built up from edge-sharing [FeO6] octahedra linked together by VO4 tetrahedra.

Disilver(I) tricobalt(II) hydrogenphos­phate bis­(phosphate), Ag2Co3(HPO4)(PO4)2

Ag2Co3(HPO4)(PO4)2 contains CoO6 octahedra and phosphate groups linked to form a three-dimensional network defining tunnels parallel to the a axis that are occupied by Ag+ ions.

Dicobalt(II) lead(II) hydrogenphos­phate(V) phos­phate(V) hydroxide monohydrate

The title compound, Co2Pb(HPO4)(PO4)OH·H2O, which was synthesized under hydrothermal conditions, crystallizes in a new structure type. Except for two O atoms in general positions and two Co atoms on centres of symmetry, all other atoms in the asymmetric unit (1 Pb, 2 Co, 2 P, 8 O and 4 H) are located on mirror planes. The structure is built up from two infinite linear chains, viz. 1 ∞[CoO2/1(H2O)2/2O2/2] and 1 ∞[CoO2/1(OH)2/2O2/2], of edge-sharing CoO6 octahedra running along [010]. Adjacent chains are linked to each other through PO4 and PO3(OH) tetrahedra, leading to the formation of layers parallel to (100). The three-dimensional framework is formed by stacking along [100] of adjacent layers that are held together by distorted PbO8 polyhedra. Hydrogen bonds of the type O—H⋯O involving the water molecule are very strong, while those O atoms involving the OH groups form weak bifurcated and trifurcated hydrogen bonds.