Tahar Jouini

Structure cristalline de K3NbAs2O9

Abstract K3NbAs2O9 is a new compound of Mr = 503.4: orthorhombic, Pnma, a = 22.389(6), b = 5.436(1), c = 7.870(2) A, V = 957.8 A3, Z = 4, ρ = 3.495 g/cm3, Ag K α , λ = 0.5608 A, μ = 97.6 cm−1, F(000) = 1287, R = 0.050, wR = 0.046 for 661 independent reflections. The structure contains chains of AsO4 tetrahedra and NbO6 octahedra sharing corners. They are staggered and connected by NbO(5)As bridges to form «puckereda layers parallel to the bc plane. The K+ ions, located in channels communicating by the interlayer spaces, contribute mainly by holding together chains belonging to the same layer. Although the niobium atom is off-center in an “O6” octahedron and forms a short NbOaxial(1) distance and a long NbOaxial(5) distance, the hypothesis of square pyramidal coordination is rejected by showing indirectly the influence of the Nb atom on O(5) from a comparison between the AsOequatorial and the AsO(5) distances in the NbOAs bridges. The structure of β-TaH(PO4)2 (three-dimensional anion) derives from that of K3NbAs2O9 (two-dimensional) through the sharing of the homolog of O(1) between successive layers, thus locking the communication between the channels containing the H+ ions.

KNb4AsO13: Preparation et structure cristalline

Abstract KNb 4 AsO 13 : Mr = 693,64 crystallizes in the orthorhombic system, space group: Cmcm , a = 10,477(4), b = 10,312(4), c = 10,006(4)A, Z = 4. The crystal structure was refined from 760 independent reflections. The final R index and weighted R w index are 0,026 and 0,030, respectively. The three-dimensional network is constituted of infinite chains (NbO 6 NbO 6 AsO 4 ) n parallel to the a axis and linked to each other by pairs of edge-sharing octahedra. Each pair links together four infinite chains. The potassium ions occupy interconnected cavities parallel to the c axis with an occupancy rate equal to 50%.

Structure de RbAlAs2O7

Rubidium aluminium pyroarsenate, M r =374.29, triclinic, PI, a=8.233 (5), b=6.34 (2), c=6.241 (5) A, α=102.6 (1), β=103.89 (7), γ=96.7 (1) o , V=303.9 A 3 , Z=2, D m =3.9 (3) (pycnometry), D x =4.09 g cm -3 , λ(Ag Kα)=0.5608 A, μ=108.14 cm -1 , F(000)=344, T=296 K, R=0.049, wR=0.053 for 2193 reflections. The first structural investigation on a pyroarsenate is reported

AgNi3(PO4)(HPO4)2: an alluaudite-like structure.

The new title phosphate, silver trinickel phosphate bis(hydrogenphosphate), has been synthesized by the hydrothermal method. It has an alluaudite-like structure but shows some differences owing to the presence of the H atoms. The structure is isomorphous with the compounds of general formula AM(3)(XO(4))(HXO(4))(2) (A is Na or Ag, M is Co, Zn or Mn, and X is As or P), with the Ag atom, one Ni atom and one P atom lying on twofold axes.

Synthesis and structure determination of a 2D open-framework zincophosphate templated by cyclohexylamine molecules

The synthesis and crystal structure of a new bidimensional zincophosphate (ZnPO) are reported. Zn2(HPO4)2Cl2·2NC6H14 crystallizes in the monoclinic space group P21/a (n°14) with a = 8.830(3) Å, b = 9.278(3) Å, c = 26.950(9) Å, β = 90.74(3)°, V = 2207.7(1) Å3 and Z = 4. This new material consists of a 2D open-framework of corner sharing ZnO3Cl and PO3OH tetrahedra alternating with planes of protonated cyclohexylamine molecules (NC6H14)+. The organic molecules are interconnected to the framework through hydrogen bonds.

Synthesis and structure determination of a new layered zincophosphate : [H2N2C6H16]0.5[Zn2(PO4)(HPO4)(H2O)].H2O

The synthesis and crystal structure of a new microporous zincophosphate are described. [H2N2C6H16]0.5[Zn2(PO4)(HPO4)(H2O)]·H2O crystallizes in the triclinic space group P1¯ with a = 8.822(4), b = 9.236(4), c = 8.451(3) Å, α = 67.19(3), β = 91.32(3), γ = 111.10(3)°, V = 586.7(4) Å3 and Z = 2. This new material consists of infinite two-dimensional anionic layers alternated with planes containing organic diprotonated templates, N, N, N′, N′-tetramethylethylenediamine [H2N2C6H16]2+ molecules. The framework structure is built up of ZnO4, ZnO3OH2, PO4, and PO3OH tetrahedra, linked through oxygen vertices. The presence of terminal OH2 and OH groups, leads to an open structure containing four- and eight-rings. The organic molecules are interconnected to the framework through hydrogen bonds.

Structure cristalline du paraphenolammonium dihydrogenophosphate

(1–4, HOC6H4NH3)H2PO4, Mr = 206.98, Orthorhombic, P212121, a=6.155(2), b=7.514(3), c=18.704(7)A, V=865.9(1)A3, Z=4, Dm=1.57, Dx=1.59gcm−3, μ= 3.157cm−1, T=298K, R=0.037 (wR=0.027) for 868 independent reflections. The structure was determined by single crystal X-Ray diffraction. It consists of an alternate stacking of (H2PO4)− tetrahedra sheets and (HOC6H4NH3)+ cation sheets. The (H2PO4)− groups are associated to forminfinite chains (H2PO4)n with internal P-P distances of 4.554(1)A, and are connected to the organic planes thanks to strong hydrogen bonds.

Synthesis and structural characterization of the dinuclear tetrakis(guanidino) bis(2-cyanoguanidine)dicopper(II) complex

The synthesis and crystal structure of a new dinuclear complex Cu2(C2H4N4)2 (CH3N3)4 are reported. It crystallizes in the monoclinic system of space group P21/c, with a = 8,459(1) Å, b = 15,481(3) Å, c = 8,714(2) Å, β = 110,60(1)°, and Z = 2. The centrosymmetric molecular structure of Cu2(C2H4N4)2(CH3N3)4 comprises a tetrakis(guanidino)-bridged dinuclear copper(II) core with axially located cnge moities.

Rede´termination de la structure cristalline de K3NbP2O9

Abstract K3NbP2O9, Mr = 416.2, Monoclinic, P21 c, a = 5.214(2), b = 17.695(6), c = 9.751(3)A, β = 90.48(4)°, V = 899.5A3, Z = 4, ϱ = 3.07 g/cm3, MoKα, λ = 0.7107A, μ = 30.4 cm−1, F(000) = 800, R = 0.058, Rw = 0.064 for 675 independent reflections. The structure contains chains of PO4 tetrahedra and NbO6 octahedra sharing corners. They are connected by Nb O(2) P bridges to form double chains parallel to the a axis, held together by the K+ ions. The niobium atom is off-center in an “O6” octahedron so that it lies in an “O5” square pyramid. The correct coordination is shown to be 6.

Pre´paration et structure cristalline de K2Nb2As2O11

Abstract K 2 Nb 2 As 2 O 11 crystallizes in the monoclinic system, space group P21/a , with a = 10.342(6), b = 10.446(5), c = 9.971(4) A˚, β = 96.72(4)°, M = 589.86, V = 1069.8(5) A˚ 3 , Z = 4 , ϱ = 3.67 g cm −1 . The crystal structure was refined (105 variables) from 1782 independent reflections collected on a Philips PW 1100 automatic diffractometer with AgKα radiation. The final R index and weighted R w index are 0.058 and 0.056, respectively. The structure consists of NbO 6 octahedra and AsO 4 tetrahedra sharing vertices, forming infinite chains (NbO 6 AsO 4 ) ∞ parallel to the a axis. Two chains are linked together by Nb O Nb and Nb O As bonds. These double chains are connected by vertices, forming a three-dimensional network. The potassium atoms are located in tunnels parallel to the a axis.