Crystal structures of phosphomolybdyl salts: Pb(MoO2)2(PO4)2 and Ba(MoO2)2(PO4)2

Crystal structures of Pb(MoO₂)₂(PO₄)₂ and Ba(MoO₂)₂(PO₄)₂ were determined. Both compounds contain the molybdyl group MoO₂. The monoclinic unit-cell parameters are a = 6.353(7), b = 12.289(4), c = 11.800 Å, β = 92°56(6), and Z = 4 for the lead salt and a = 6.383(8), b = 7.142(7), c = 9.953(8) Å, β = 95°46(8), and Z = 2 for the barium salt. $\text{P2}{}_1\text{c}$ is the common space group. The R values are respectively R = 0.027 and R = 0.031 for 1964 and 1714 independent reflections. The frameworks built up by a three-dimensional network of monophosphate PO₄ and molybdyl MoO₂ groups are similar, characterized mainly by corner-sharing PO₄ and MoO₆ polyhedra. Two oxygen atoms of each MoO₆ group are bonded to the molybdenum atom only as in other molybdyl salts.     

The crystal structure of cobalt orthophosphate Co3(PO4)2

The crystal structure of cobalt orthophosphate has been refined by full-matrix least-squares procedures using automatic diffractometer data to a residual R = 0.039 (R_w = 0.058). The space group is $\text{P2}{}_{\mathrm{l}}\text{c}$, with a = 5.063(1), b = 8.361(2), c = 8.788(2) Å, and β = 121.00(2)°. Co₃(PO₄)₂ is isotypic with the previously reported γ-Zn₃(PO₄)₂ and Mg₃(PO₄)₂. Cobalt ions occupy two distinct coordination polyhedra, one five and one six-coordinated, in a ratio of two to one. The structure is described in detail.     

The crystal structure of Ca6Eu2Na2(PO4)6F2

The crystal structure of Ca₆Eu₂Na₂(PO₄)₆F₂ has been determined by single crystal X-ray diffraction. The unit cell constants are $\text{a = 9.385(2), c = 6.893(3)}\text{A}\text{?}$ and the space group is $\text{P6}{}_3\text{m}$. The structure was refined by normal full matrix least squares techniques. The final value of the refinement indicator is R = 0.065, based on 419 reflections.The structure of Ca₆Eu₂Na₂(PO₄)₆F₂ contains disordered cations in both the triangle and column positions. The occupation of the six triangle sites is $\text{1}\text{4}\text{Eu}$ and $\text{3}\text{4}\text{Ca}$ and of the four column sites $\text{1}\text{2}\text{Na}\text{,}\text{4}\text{10}\text{Ca}$, and $\text{1}\text{10}\text{Eu}$.     

The crystal structure of Cu4(PO4)2O

Cu₄(PO₄)₂O crystallizes in the space group $\text{P}\text{1}$ with a = 7.5393(8) Å, b = 8.1021(9) Å, c = 6.2764(8) Å, α = 113.65(1)°, β = 98.42(1)° and γ = 74.19(1)°. The structure was refined by full-matrix least-squares techniques using automatic diffractometer data to R = 0.046 (R_w = 0.056). Four unique copper atoms are in six, five-, and four-coordinated polyhedra which are linked together to form a three-dimensional network. The structure is best described in terms of a cubic close-packed array of oxygen atoms with one-tenth of the possible anion sites vacant.     

Crystallographic studies of the role of Mg as a stabilizing impurity in β-Ca3(PO4)2. The crystal structure of pure β-Ca3(PO4)2

β-Ca₃(PO₄)₂ crystallizes in the rhombohedral space group R3c with unit cell parameters a = 10.439(1), c = 37.375(6) Å (hexagonal setting) and cell contents of 21 [Ca₃(PO₄)₂]. The structure was refined to R_w = 0.026, R = 0.030 using 1143 X-ray intensities collected from a single crystal by counter methods. Corrections were made for absorption, secondary extinction, and anomalous dispersion.The structure is related to that of Ba₃(VO₄)₂, but has lower symmetry because of the widely different ionic sizes of Ca and Ba. Seven [Ca₃(PO₄)₂] units occupy a volume corresponding to eight [Ba₃(PO₄)₂] units. The requirement of the c glide in β-Ca₃(PO₄)₂ has been shown in the least squares refinements to be attained by disorder of one cation over two sites. This disorder has a far-reaching effect on the structure.     

The crystal structure of Ca3Cu3(PO4)4

Single crystals of Ca₃Cu₃(PO₄)₄ synthesized hydrothermally at 420°C and 55 kpsi (3.8 kbar) were found to occur in the space group $\text{P2}{}_1\text{a}$ (No. 14) with a = = 17.619(2), b = 4.8995(4), c = 8.917(1)Å, β = 124.08(1)°, and Z = 2. Full-matrix least-squares refinement of the structure using diffractometer data converged to a final anisotropic R = 0.037 (R_w = 0.046). The two calcium atoms are in six- and nine-coordination and the two copper-containing polyhedra (four- and five-coordinated) are similar to those previously found in Cu₃(PO₄)₂.     

Structure cristalline de Cu4(PO4)2O

Cu₄(PO₄)₂O is a new copper-rich phosphate. The preparation is described. The unit cell is triclinic, $\text{P}\text{1}$, with a = 7.528 Å, b = 8.090 Å, c = 6.272 Å; α = 113.68°, β = 81.56°, γ = 105.77°. The structure was solved from 1526 independent reflections using Patterson and Fourier syntheses. The final R value is 0.041 for the 1217 strongest reflections. Copper sites form a three-dimensional framework. The structure consists of homogeneous layers of copper and oxygen atoms parallel to the (012) plane. Phosphorus atoms are inserted between copper and oxygen layers.     

Cluster condensation reactions. The synthesis and crystal and molecular structure of Os6(CO)14(μ2-PPh2)2(μ3-S)3(μ4-S)

Thermal degradation of the cluster compound Os₃(CO)₈(PPh₂H)(μ₃-S)₂ (I) at 125°C leads to decarbonylation and formation of the new ligand bridged hexanuclear cluster Os₆(CO)₁₄(μ-PPh₂)₂(μ₃-S)₃(μ₄-S) (II) in 11% yield. Space Group: P$\text{1}$, No. 2, a 10.427(5), b 13.552(3), c 17.919(3) Å, α 84.87(2), β 75.41(3), γ 78.43(3)°, V 2399(2) ųZ = 2, _?calc 2.82 g cm^?3. The structure was solved by the heavy atom method and refined (3223 reflections) to the final residuals R = 0.042 and R_w = 0.036. The molecule consists of two sulfido bridged open triosmium clusters which are linked by a bridging sulfido ligand and a bridging diphenylphosphino ligand.     

Etude des equilibres solide-liquide des systems MIPO3Sm(PO3)3 (MI = Li,Na, Ag)

The M^IPO₃Sm(PO₃)₃(M^I = Li, Na, Ag) systems were studied. Differential thermal analysis and X-ray diffraction were used to investigate the liquidus and solidus relations. Three compounds LiSm(PO₃)₄, NaSm(PO₃)₄, and AgSm(PO₃)₄ were obtained which melt incongruently at 1248, 1143, and 1078 K, respectively. These compounds are isomorphous with their homologs LiLn(PO₃)₄, NaLn(PO₃)₄, AgLn(PO₃)₄ (Ln = Ce, La, Nd). They belong to the monoclinic system. The LiSm(PO₃)₄ unit cell parameters refined by least squares method are a = 16.43(3) Å, b = 7.16(1) Å, c = 9.65(3) Å, β = 125,9°(1), with the space group $\text{C2}\text{c}$ and Z = 4. NaSm(PO₃)₄ and AgSm(PO₃)₄ are isotypic; they cristallize in the $\text{P2}{}_1\text{c}$ space group, Z = 4; their unit cell parameters are, respectively, a = 12.18(1) Å, b = 13.05(1) Å, c = 7.25(5) Å, β = 126,53°(4), $\text{a = 12.25(1)}\text{A}\text{?}$, b = 13.06(1) Å, c = 7.201(9) Å, β = 126,57°(7). The ir spectra of the last two compounds indicate that these phosphates are chain phosphates.     

Crystal structure and magnetic properties of Ba2Ni3F10

Ba₂Ni₃F₁₀ is monoclinic (space group $\text{C2}\text{m}$), a = 18.542(7) Å, b = 5.958(2) Å, c = 7.821(3) Å, β = 111°92(10). Ba₂Co₃F₁₀ and Ba₂Zn₃F₁₀ are isostructural. The structure has been refined from 995 reflections by full-matrix least-squares refinement to a weighted R value of 0.048 (unweighted R, 0.047). The three-dimensional network can be described either by complex chains connected to each other by octahedra sharing corners or with an 18L dense-packing sequence. The basic unit (Ni₃F₁₀)^4? is discussed and compared to the different unit existing in Cs₄Mg₃F₁₀. Antiferromagnetic properties of Ba₂Ni₃F₁₀ (T_N = 50 K are described.     

The crystal structure of the 42-Å subcell of a layer structure with approximate composition Ba4Nb2S9

Platy crystals from the products of a mixture 4 Bas : 2 Nb : 5 S reacted at 1000°C have cell constants a = 13.754(3) Å, c = 83.73(2) Å, $\text{R}\text{3}\text{m}$. The reciprocal lattice had a pronounced subcell with dimensions a = 6.877(1) Å, c = 41.84(1) Å, same space group. Three dimensional X-ray diffraction data were collected using monochromatized Mo Kα radiation and of 5051 measured intensities 1892 were considered observed. From the set of observed intensities 611 reflections having all even indices were used to refine the crystal structure of the 42 × 7-Å subcell. The final R = 0.036 and ωR = 0.052 for the 611 observed amplitudes and R = 0.046, ωR = 0.052 for all 711 amplitudes of the subcell. The structure is based on the stacking of hexagonal BaS₃ layers with the sequence DABABDBCBCDCACAD. The D layer denotes a disordered level and occurs at $\text{z = 0,}\text{1}\text{3}$ and $\text{2}\text{3}$. The different letters for the ordered layers are based on the Ba positions in that layer. The Nb ions occupy octahedral interstices and form a unit of three face sharing octahedra parallel to c. The column is terminated above and below by disordered levels. The NbNb distances are 3.22 Å, causing displacement of Nb from the centers of the two outside octahedra. One Ba is in the center of a triangular orthobicupola formed by 12 S atoms. The other Ba is in the center of a hexagon of 6 S with 3 additional S above this layer forming $\text{1}\text{2}$ of a cuboctahedron. The lower half consists of a disordered layer of atoms. The NbS distances are 2.279, 2.433, and 2.683 Å; BaS distances vary between 3.1 and 3.5 Å. The subcell content based on the ordered structure only is Ba₁₂Nb₉S₃₆. The placement of disordered Ba and S at $\text{z = 0,}\text{1}\text{3}$, and $\text{2}\text{3}$ levels of the subcell leads to the unlikely composition Ba_16.5Nb₉S₄₂. The ordered structure most likely has a composition Ba₄Nb₂S₉, z = 36, so that the subcell composition should be Ba₁₈Nb₉S_40.5. The completely ordered structure has not been solved.     

Preparation et etude d'un oxyphosphate Fe4(PO4)2O

This compound is obtained in several ways, at 900°C, from the components of the FePO system when the oxygen pressure is made suitable, or from Fe₃(PO₄)₂ + Fe + Fe₂O₃ in a sealed tube under vacuum. It crystallizes under these latter conditions with a trace of FeCl₂. The cell is monoclinic; a = 6.564(1), b = 11.271(2), c = 9.383(2) Å, β = 103.95 (2)°, with Z = 4, group $\text{P2}{}_1\text{c}$. The structure is determined thanks to the use of a direct method and Fourier synthesis and is refined to R = 0.033. The PO₄ tetrahedra are isolated; the iron fills four crystallographic sites: three are more or less distorted octahedra, the fourth is a trigonal bipyramid. The oxyphosphate character is ascertained by the presence of some oxygen atoms connected to iron only, with, moreover, a low site potential. This compound is paramagnetic above 90°K. Its Mössbauer spectrum exhibits four doublets in good agreement with the structure; in order to identify which one corresponds to the hexahedral site, the phase Fe₃Zn(PO₄)₂O has been prepared, but its Mössbauer spectrum, in spite of the zinc affinity for the V coordination, shows that two sites are modified, which does not allow conclusions to be made.     

Crystal chemistry of the BaNbS system: A layer structure of approximate composition Ba2NbS4(S2)0.5

Black platy crystals from the product of a reaction mixture of 6BaS : 3Nb : 7S reacted at 1000°C were hexagonal with a = 6.909(4) Å, c = 49.25(2) Å, $\text{P6}{}_3\text{mmc}\text{, Z = 10}$. A pronounced subcell with a = 6.91Å, c = 5.5 Å indicated that this was a layer structure consisting of stacking of close-packed BaS₃ layers. Three dimensional X-ray diffraction data were collected from a single crystal using monochromatized MoKα radiation. From the 1535 measured reflections, 782 unique structure amplitudes were obtained of which 608 greater than 2σ(F) were used to solve the structure. The final R = 0.1065, ωR = 0.0793; for 91 reflections with l = 9n, R = 0.0397 and for the 517 reflections l ≠ 9n, R = 0.138. The structure is based on the stacking of close-packed BaS₃ layers with the sequence CBDBABDBC BCDCACDCB, where D designates a disordered layer. The disordered layers contain two crystallographically independent Ba with partial site occupancies and disordered S₂ and S ions. Nb occupy octahedral interstices and form two different arrangements; a unit consisting of 3 face-sharing octahedra and a unit of 2 face-sharing octahedra. These octahedral units are separated by the disordered layers. The NbNb distances in the chain of 3 are 3.29 Å and they are 3.57 Å in the double unit.     

K1.4P4W14O50: An odd-m member (m = 7) of the monophosphate tungsten bronze series KxP4O8(WO3)2m

The crystal structure of K_xP₄W₁₄O₅₀ (x = 1.4) has been solved by three-dimensional single crystal X-ray analysis. The refinement in the cell of symmetry $\text{A2}\text{m}$, with a = 6.660(2) Å, b = 5.3483(3) Å, c = 27.06(5) Å, and β = 97.20(2)°, Z = 1, has led to R = 0.036 and R_w = 0.039 for 2436 reflections with $\text{σ(I)}\text{I}\text{≤ 0.333}$. This structure belongs to the structural family K_xP₄O₈(WO₃)_2m, called monophosphate tungsten bronzes (MPTB), which is characterized by ReO₃-type slabs of various widths connected through PO₄ single tetrahedra. This bronze corresponds to the member m = 7 of the series and its framework is built up alternately of strands of three and four WO₆ octahedra. The structural relationships with the P₄O₈(WO₃)_2m series, called M′PTB, are described and the possibility of intergrowth between these two structures is discussed.     

Structure cristalline du phosphatoantimonate K3Sb3P2O14

K₃Sb₃P₂O₁₄ crystallizes in the rhombohedral system, space group $\text{R}\text{3}\text{m}$ with a = 7.147(1) Å, c = 30.936(6) Å, Z = 3. The structure was determined from 701 reflections collected on a Nonius CAD4 automatic diffractometer with $\text{Mo}\text{K}\text{α}$ radiation. The final R index and the weighted R_w index are 0.033 and 0.042, respectively. The structure is built up from layers of SbO₆ octahedra and PO₄ tetrahedra sharing corners. The potassium ions are situated between the (Sb₃P₂O₁₄)^3? covalent layers.     

Conductivity and Structural Investigations in Lacunary Pb6Ca2Li2(PO4)6 Apatite

Prismatic crystals of Pb₆Li₂Ca₂(PO₄)₆ were obtained by solid-state reaction. They were characterized by IR spectroscopy and chemical analyses. The structure as determined by X-ray diffraction study on single crystal revealed that the compound is isostructural to the hexagonal phase Pb₈Na₂(PO₄)₆. Crystal data for Pb₆Li₂Ca₂(PO₄)₆: space group P63/m (No. 176), a=b=9.6790(15) Å, c=7.1130(7), Z=1, R=0.039. In the compound, lithium was found to preferentially occupy the site (I) and the structure is stabilized by interactions between electron lone pairs of lead (II) ions. Electrical conductivity measured in a wide range of temperature is governed by a hopping mechanism of Li ions in tunnels.     

The crystal structure of a complex cerium(III) molybdate; Ce6(MoO4)8(Mo2O7)

Ce₆Mo₁₀O₃₉ crystallizes in the triclinic system with unit-cell dimensions (from single-crystal data) a = 10.148(5), Å, b = 18.764(6), Å, c = 9.566(5), Å, α = 103.12(7)°, β = 78.07(7)°, γ = 107.69(7)°, and space group $\text{P}\text{1}\text{, z = 2}$. The structure was solved using direct methods with 3113 countermeasured reflections (MoKα radiation), and refined using Fourier and least-squares techniques to a conventional R of 0.039 (ωR = 0.047). Ce₆Mo₁₀O₃₉ has a structure that consists of isolated MoO₄ tetrahedra together with one corner-shared pair of tetrahedra, linked to irregular eight-coordinate Ce(III) polyhedra. The average MoO distance of 1.77 Å, and average CeO distance of 2.52 Å are in good agreement with previously reported values.     

Crystal structures of NaBaCr2F9 and NaBaFe2F9: Structural correlations with other enneafluorides,particularly with KPbCr2F9

NaBaCr₂F₉ and NaBaFe₂F₉ are monoclinic (SG $\text{P2}{}_1\text{n}$, No. 14). Lattice constants are found to be a = 7.318(2) Å, b = 17.311(4) Å, c = 5.398(1) Å, β = 91.14°(3) for chromium, and a = 7.363(2) Å, b = 17.527(4) Å, c = 5.484(1) Å, β = 91.50°(5) for iron. The structures were solved from 507 and 1113 X-ray reflections, respectively, for the Cr and Fe compounds; the corresponding R_w values are 0.025 and 0.037. The network is built from tilted double cis chains of octahedra (M₂F₉)^3n?_n [M = Cr, Fe], linked by Na⁺ and Ba²⁺ ions. The structures are compared to the previously described structures, particularly KPbCr₂F₉, whose symmetry and parameters are different. The difference is analyzed first in terms of tilted octahedra, but principally in terms of bond strengths and steric activity of the Pb²⁺ lone pair. A mechanism is proposed for the transformation between the structures of NaBaCr₂F₉ and KPbCr₂F₉.     

Nd3+, Eu3+, and Gd3+ ions as local probes in the NaxSr3−2xLnx(PO4)2 and KCaLn(PO4)2 rare earth phosphates

Use of Nd³⁺, Eu³⁺, and Gd³⁺ as local structural probes allows the determination of the rare earth positions in the Na_xSr_3?2xLn_x(PO₄)₂ (Ln = La to Tb) and KCaLn(PO₄)₂ phases (Ln = rare earth). Moreover, a common feature of both series is a particularly high splitting of the excitation ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and ${}^6\text{P}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ levels of the Gd³⁺ ions.     

The crystal structure of Ba2V2O7

Ba₂V₂O₇ is triclinic with a = 13.571(3), b = 7.320(2), c = 7.306(2) Å, α = 90.09(1), β = 99.48(1), β = 99.48(1), γ = 87.32(1)°, V = 7.15.1 ų, Z = 4, and space group $\text{P}\text{1}$. The crystal structure was solved by Patterson and Fourier methods and refined by full-matrix least-squares analysis to a R_w of 0.034 (R = 0.034) using 2484 reflections measured on a Syntex $\text{P}\text{1}$ automatic four-circle diffractometer. The structure has two unique divanadate groups that are repeated by the b and c lattice translations to form sheets of divanadate groups parallel to (100). These sheets are linked by four unique Ba atoms that lie between these sheets. Ba(1) and Ba(3) are coordinated by eight oxygens arranged in a distorted biaugmented triangular prism and a distorted cubic antiprism, respectively. Ba(2) is coordinated by 10 oxygens arranged in a distorted gyroelongated square dipyramid and Ba(4) is coordinated by nine oxygens arranged in a distorted triaugmented triangular prism. These coordination numbers are substantiated by a bond strength analysis of the structure, and the variation in 〈BaO〉 distances is compatible with the assigned cation and anion coordination numbers. Both divanadate groups are in the eclipsed configuraton with 〈VO(br)〉 bond lengths of 1.821(4) and 1.824(4) Å and VO(br)V angles of 125.6(3) and 123.7(3)°, respectively. Examination of the divanadate groups in a series of structures allows certain generalizations to be made. Longer 〈VO(br)〉 bond lengths are generally associated with smaller VO(br)V angles. When VO(br)V < 140°, the divanadate group is generally in an eclipsed configuration; when VO(br)V > 140°, the divanadate group is generally in a staggered configuration. Nontetrahedral cations with large coordination numbers require more oxygens with which to bond, and hence O(br) is more likely to be three coordinate, with the divanadate group in the eclipsed configuration. In the eclipsed configuration, decrease in VO(br)V promotes bonding between O(br) and nontetrahedral cations, and hence smaller nontetrahedral cations are generally associated with smaller VO(br)V angles.