Ferey Gerard

Crystal structure determination of the hydrated gallium phosphate GaPO4·2H2O, analog of variscite

Abstract The crystal structure of the hydrated gallium phosphate, GaPO4·2H2O, analog of variscite, has been determined by means of single-crystal X-ray diffraction characterisation. The structure is built from the connection of PO4 tetrahedra with GaO4(H2O)2 octahedra. The 3D framework consists of the stacking of 63 nets and is related to the topologies of metavariscite, the polymorphs of silica (tridymite, cristobalite) and zeolite Li-A(BW). A formation pathway of the hydrated gallium phosphate with leucophosphite structural type is proposed from that of the variscite one. Crystal data: Mr = 200.72 g mol−1 , orthorhombic, space group Pbca (no. 61), a = 9.9260(1) A, b = 8.6189(1) A, c = 9.7622(1) A, V = 835.17(2) A3, Z = 8, R1(F) = 0.0361, wR2(F2) = 0.0922 for 1255 reflections with I > 2σ(I).

Hydrothermal synthesis and structure determination of [VF(PO4), N2C2H9] and [Ti(OH)(PO4), N2C2H9], two M(III) phosphates with the ULM-11 bidimensional topology

Abstract [V III F(PO 4 ), en ] and [Ti III (OH)(PO 4 ), en ] ( en = ethylenediamine) are two new layered compounds isostructural with ULM-11. Both were synthesized hydrothermally (453 K, 3 days for ULM-11 (V III ) and 453 K, 28 days for ULM-11 (Ti III )). Structures were determined by single-crystal X-ray diffraction (V III sample) or powder X-ray diffraction (Ti III sample). Both compounds crystallize in the monoclinic system (space group P 2 1 / c ) with cell parameters at 293 K: a = 9.2272 (3) A, b = 7.3532 (2) A, c = 9.8496 (2) A, β = 101.315 (1) °, V = 655.30 A 3 , Z = 4 for the vanadium phase and a = 9.265 (1) A, b = 7.329 (1) A, c = 9.911 (1) A, β = 100.89 (1) °, V = 660.90 A 3 , Z = 4 for the titanium compound. In both lamellar structures, layers consist of chains of MO 3 X 2 N octahedra (M = V, Ti and X = F, OH) related together via PO 4 tetrahedra. One amino group of the diamine is directly bound to the metallic center (via the N atom) while the protonated second amino group points at the interlayer space interacting with terminal P-O groups by strong hydrogen bonds.