Ga-Ga bonding and tunnel framework in the new Zintl phase Ba3Ga4Sb5

A new Zintl phase Ba₃Ga₄Sb₅ was obtained from the reaction of Ba and Sb in excess Ga flux at 1000°C, and its structure was determined with single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group Pnma (No. 62) with a=13.248(3) Å, b=4.5085(9) Å, c=24.374(5) Å and Z=4. Ba₃Ga₄Sb₅ has a three-dimensional [Ga₄Sb₅]⁶⁻ framework featuring large tunnels running along the b-axis and accommodating the Ba ions. The structure also has small tube-like tunnels of pentagonal and rhombic cross-sections. The structure contains ethane-like dimeric Sb₃Ga-GaSb₃ units and GaSb₄ tetrahedra that are connected to form 12- and 14-membered tunnels. Band structure calculations confirm that the material is a semiconductor and indicate that the structure is stabilized by strong Ga-Ga covalent bonding interactions.     

Gallium substitutions as a means to stabilize alkaline-earth and rare-earth metal pnictides with the cubic Th3P4 type: Synthesis and structure of A7Ga2Sb6 (A=Sr, Ba, Eu)

Three new compounds—Sr_7.04(2)Ga_1.94(2)Sb₆, Ba_7.02(3)Ga_1.98(3)Sb₆ and Eu_7.04(3)Ga_1.90(3)Sb₆—have been synthesized from reactions of the corresponding elements using gallium as a metal flux. Their crystal structures (space group I4¯3d (No. 220), Z=2 with unit cell parameters: a=9.9147(9) Å for the Sr-compound; a=10.3190(9) Å for the Ba-compound; and a=9.7866(8) Å for the Eu-compound) have been established by single-crystal X-ray diffraction. The structures are best described as Ga-stabilized derivatives of the hypothetical Sr₄Sb₃, Ba₄Sb₃ and Eu₄Sb₃ phases with the cubic Th₃P₄ type. Such an inclusion of interstitial Ga atoms in this atomic arrangement results in the formation of isolated [Ga₂Sb₆]¹⁴⁻ fragments, isoelectronic and isostructural with the [Sn₂Te₆]⁶⁻ anions in the K₃SnTe₃ type, and allows for the attainment of a charge-balanced electron count. In that sense, the Sr₄Sb₃, Ba₄Sb₃ and Eu₄Sb₃ binaries, which are expected to be electron-deficient and are currently unknown, can be “turned” into Sr₇Ga₂Sb₆, Ba₇Ga₂Sb₆ and Eu₇Ga₂Sb₆, whose structures are readily rationalized following the Zintl concept.     

Eu7Ga6Sb8: A Zintl phase with Ga-Ga bonds and polymeric gallium antimonide chains

The Zintl phase Eu₇Ga₆Sb₈ was obtained from a direct element combination reaction at 900°C. It crystallizes in the orthorhombic space group Pbca (No. 61) with a=15.6470(17) Å, b=17.2876(19) Å, c=17.9200(19) Å, and Z=8. In Eu₇Ga₆Sb₈, the anionic framework forms infinite chains of [Ga₆Sb₈]¹⁴⁻ which are arranged side by side to make a sheet-like arrangement but without linking. The sheets of chains are separated by Eu²⁺ atoms and also within the sheet, Eu²⁺ atoms fill the spaces between two chains. The chain is made up of homoatomic tetramers (Ga₄)⁶⁺ and dimers (Ga₂)⁴⁺ connected by Sb atoms. The compound is a narrow band-gap semiconductor with E_g∼0.6 eV and satisfies the classical Zintl concept. Extended Hückel band structure calculations confirm that the material is a semiconductor and suggest that the structure is stabilized by strong Ga-Ga covalent bonding interactions. Magnetic susceptibility measurements for Eu₇Ga₆Sb₈ show that the Eu atoms are divalent and the compound has an antiferromagnetic transition at 9 K.     

La3Pd4Zn4 and La3Pt4Zn4 with a different coloring of the Gd3Cu4Ge4-type structure

Abstract  

The intermetallic zinc compounds La₃Pd₄Zn₄ and La₃Pt₄Zn₄ were synthesized by induction melting of the elements in sealed tantalum tubes. The structures were refined from X-ray single-crystal diffractometer data: Gd₃Cu₄Ge₄ type, Immm, a = 1,440.7(5), b = 743.6(2), c = 419.5(2) pm, wR ₂ = 0.0511, 353 F ² for La₃Pd₄Zn₄; and a = 1,439.9(2), b = 748.1(1), c = 415.66(6) pm, wR ₂ = 0.0558, 471 F ² for La₃Pt₄Zn₄ with 23 variables per refinement. The palladium (platinum) and zinc atoms build up a three-dimensional polyanionic [Pd₄Zn₄] (260–281 pm Pd–Zn) and [Pt₄Zn₄] (260–279 pm Pt–Zn) network in which the lanthanum atoms fill cavities of CN 14 (6 Pd/Pt + 8 Zn for La1) and CN 12 (6 Pd/Pt + 6 Zn for La2), respectively. The copper position of the Gd₃Cu₄Ge₄ type is occupied by zinc and the two crystallographically independent germanium sites by palladium (platinum), a new coloring pattern for this structure type. Within the [Pd₄Zn₄] and [Pt₄Zn₄] the Pd2 and Pt2 atoms form Pd2–Pd2 (291 pm) and Pt2–Pt2 (296 pm) dumbbells. The structures of La₃Pd₄Zn₄ and La₃Pt₄Zn₄ are discussed with respect to the prototype Gd₃Cu₄Ge₄ and the Zintl phase Sr₃Li₄Sb₄. Temperature-dependent magnetic susceptibility measurements indicate diamagnetism for La₃Pt₄Zn₄ and Pauli paramagnetism for La₃Pd₄Zn₄.     

Syntheses, crystal structures and spectroscopic properties of KEu[AsS4], K3Dy[AsS4]2 and Rb4Nd0.67[AsS4]2

Three rare earth compounds, KEu[AsS₄] (1), K₃Dy[AsS₄]₂ (2), and Rb₄Nd_0.67[AsS₄]₂ (3) have been synthesized employing the molten flux method. The reactions of A₂S₃ (A = K, Rb), Ln (Ln = Eu, Dy, Nd), As₂S₃, S were accomplished at 600 °C for 96 h in evacuated fused silica ampoules. Crystal data for these compounds are: 1, monoclinic, space group P2₁/m (no. 11), a = 6.7276(7) Å, b = 6.7190(5) Å, c = 8.6947(9) Å, β = 107.287(12)°, Z = 2; 2, monoclinic, space group C2/c (no. 15), a = 10.3381(7) Å, b = 18.7439(12) Å, c = 8.8185(6) Å, β = 117.060(7)°, Z = 4; 3, orthorhombic, space group Ibam (no. 72), a = 18.7333(15) Å, b = 9.1461(5) Å, c = 10.2060(6) Å, Z = 4. 1 is a two-dimensional structure with ²_∞[Eu(AsS₄)]⁻ layers separated by potassium cations. Within each layer, distorted bicapped trigonal [EuS₈] prisms are linked through distorted [AsS₄]³⁻ tetrahedra. Each Eu²⁺ cation is coordinated by two [AsS₄]³⁻ units by edge-sharing and bonded to further two [AsS₄]³⁻ units by corner-sharing. Compound 2 contains a one-dimensional structure with ¹_∞[Dy(AsS₄)₂]³⁻ chains separated by potassium cations. Within each chain, distorted bicapped trigonal prisms of [DyS₈] are linked by slightly distorted [AsS₄]³⁻ tetrahedra. Each Dy³⁺ ion is surrounded by four [AsS₄]³⁻ moieties in an edge-sharing fashion. For compound 3 also a one-dimensional structure with ¹_∞[Nd₀.₆₇(AsS₄)₂]⁴⁻ chains is observed. But the Nd position is only partially occupied and overall every third Nd atom is missing along the chain. This cuts the infinite chains into short dimers containing two bridging [As₄]³⁻ units and four terminal [AsS₄]³⁻ groups. 1 is characterized with UV/vis diffuse reflectance spectroscopy, IR, and Raman spectra.     

Lanthanum Gallium Tin Antimonides LaGaxSnySb2

A series of quaternary lanthanum gallium tin antimonides LaGa_xSn_ySb₂ was elaborated to trace the structural evolution between the known end members LaGaSb₂ (SmGaSb₂-type) and LaSn_ySb₂ (LaSn_0.75Sb₂-type). Five members of this series were characterized by single-crystal X-ray diffraction. For low Sn content, the Sn atoms disorder with Ga atoms in zigzag chains to form solid solutions LaGa_1-ySn_ySb₂ (0≤y≤0.2) adopting the SmGaSb₂-type structure, as exemplified by LaGa_0.92(3)Sn_0.08Sb₂ and LaGa_0.80(3)Sn_0.20Sb₂ (orthorhombic, space group D⁵₂−C222₁,Z=4). For higher Sn and lower Ga content, there is a segregation in which the Sn atoms appear in chains of closely spaced partially occupied sites as in the parent LaSn_0.75Sb₂-type structure whereas the Ga atoms remain in zigzag chains as in the parent SmGaSb₂-type structure. This feature is observed in the structures of LaGa_0.68(4)Sn_0.31(3)Sb₂, LaGa_0.62(3)Sn_0.32(3)Sb₂, and LaGa_0.43(3)Sn_0.39(3)Sb₂ (orthorhombic, space group D¹⁷_2h−Cmcm,Z=4). The last example illustrates that the combined Ga/Sn content can be substoichiometric (x+y<1). These compounds have a layered nature, with the chains of Ga or Sn atoms residing between ²_∞[LaSb₂] slabs.     

Formation of [Cp2TiSbMe2]2, [Cp2TiSb(SiMe3)2]2 and [Cp2TiCl]2·2Mes4Sb2

Reactions of [Cp₂Ti(btmsa)] (btmsa = bis(trimethylsilyl)acetylene) with R₄Sb₂ (R = Me, Me₃Si) give [Cp₂TiSbMe₂]₂ (1) or [Cp₂TiSb(SiMe₃)₂]₂ (2) respectively. [Cp₂TiCl]₂·2Mes₄Sb₂ (3) is serendipitously formed from [Cp₂Ti(btmsa)] and Mes₂SbH containing NH₄Cl traces.     

Synthesis, structure and physical properties of the new Zintl phases Eu11Zn6Sb12 and Eu11Cd6Sb12

Reported are the syntheses, crystal structure determinations from single-crystal X-ray diffraction, and magnetic properties of two new ternary compounds, Eu₁₁Cd₆Sb₁₂ and Eu₁₁Zn₆Sb₁₂. Both crystallize with the complex Sr₁₁Cd₆Sb₁₂ structure type—monoclinic, space group C2/m (no. 12), Z=2, with unit cell parameters a=31.979(4) Å, b=4.5981(5) Å, c=12.3499(14) Å, β=109.675(1)° for Eu₁₁Zn₆Sb₁₂, and a=32.507(2) Å, b=4.7294(3) Å, c=12.4158(8) Å, β=109.972(1)° for Eu₁₁Cd₆Sb₁₂. Their crystal structures are best described as made up of polyanionic and ribbons of corner-shared ZnSb₄ and CdSb₄ tetrahedra and Eu²⁺ cations. A notable characteristic of these structures is the presence of Sb-Sb interactions, which exist between two tetrahedra from adjacent layers, giving rise to unique channels. Detailed structure analyses shows that similar bonding arrangements are seen in much simpler structure types, such as Ca₃AlAs₃ and Ca₅Ga₂As₆ and the structure can be rationalized as their intergrowth. Temperature-dependent magnetization measurements indicate that Eu₁₁Cd₆Sb₁₂ orders anti-ferromagnetically below 7.5 K, while Eu₁₁Zn₆Sb₁₂ does not order down to 5 K. Resistivity measurements confirm that Eu₁₁Cd₆Sb₁₂ is poorly metallic, as expected for a Zintl phase.     

Nb28Ni33.5Sb12.5, a New Representative of the X-phase

The first ternary compound in the Nb–Ni–Sb system, Nb₂₈Ni_33.5Sb_12.5, has been synthesized and its structure has been determined by single-crystal X-ray diffraction methods. Nb₂₈Ni_33.5(2)Sb_12.5(2) adopts the X-phase structure type (orthorhombic, space group Pnnm, Z=1, a=13.2334(5) Å, b=16.5065(7) Å, c=5.0337(2) Å), which belongs to the set of tetrahedrally close-packed (TCP) structures adopted by many intermetallic compounds. Typical of such TCP structures, the atoms reside in sites of high coordination number, with Ni and Sb in CN12 and Nb in CN14, -15, and -16 sites. The relative importance of various metal–metal bonding interactions is discussed on the basis of extended Hückel band structure calculations. Nb₂₈Ni_33.5Sb_12.5 displays metallic behavior with a room-temperature resistivity of 2.3×10⁻⁴ Ω cm.     

Ternary Antimonide EuSn3Sb4 and Related Metallic Zintl Phases

The ternary Zintl compound europium tin antimonide, EuSn₃Sb₄, has been synthesized at 900°C in the presence of a tin flux, and its structure has been determined by single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group D¹⁶_2h-Pnma with a=9.954(2), b=4.3516(7), c=22.650(4) Å, and Z=4 at 22°C. EuSn₃Sb₄ is isostructural to SrSn₃Sb₄; it possesses channels defined by an anionic framework of shared SnSb₄ tetrahedra, SnSb₃ trigonal pyramids, and Sb–Sb zigzag chains, and it is filled by Eu²⁺ cations. Resistivity measurements indicate weakly metallic behavior for ASn₃Sb₄ (A=Eu, Sr) and the structurally related Ba₂Sn₃Sb₆. The anisotropic metallic nature of these compounds is explained through extended Hückel band structure calculations.     

The Crystal Structures of the Strontium Gallates Sr10Ga6O19 and Sr3Ga2O6

The crystal structures of Sr₁₀Ga₆O₁₉ and Sr₃Ga₂O₆ have been characterized using X-ray diffraction techniques. In the case of Sr₁₀Ga₆O₁₉, the structure was determined from a single crystal diffraction data set collected at room conditions and refined to a final R index of 0.061 for 3471 observed reflections (I>2 σ(I)). The compound is monoclinic with space group C12/c1 (a=34.973(4) Å, b=7.934(1) Å, c=15.943(2) Å, β=103.55(1)°, V=4300.7(6) ų, Z=8, D_calc=4.94 g/cm³, μ(MoKα)=32.04 mm⁻¹) and can be classified as an oligogallate. It is the first example of an inorganic compound where six [TO₄]-tetrahedra of only one chemical species occupying the tetrahedral centres are linked via bridging oxygen atoms to form [T₆O₁₉] groups. The hexamers are not linear, but highly puckered. Eleven symmetrically different Sr cations located in planes parallel (100) crosslink between the oligo-groups. They are coordinated by six to eight oxygen ligands. The structure of Sr₃Ga₂O₆ has been refined from powder diffraction data using the Rietveld method (space group Pa , a=16.1049(1), V=4177.1(1) ų, Z=24, D_calc=4.75 g/cm³). The compound is isostructural with tricalcium aluminate and contains highly puckered, six-membered [Ga₆O₁₈]¹⁸⁻ rings. The rings are linked by strontium cations having six to nine nearest oxygen neighbors.     

The new silver(I)thioantimonate(III) [C4N2H14][Ag3Sb3S7] and a new structural variant of the silver(I)thioantimonate(III) [C2N2H9]2[Ag5Sb3S8] both synthesized under solvothermal conditions

The novel silver(I)thioantimonates(III) [C₄N₂H₁₄][Ag₃Sb₃S₇] (I) (C₄N₂H₁₂=1,4-diaminobutane) and [C₂N₂H₉]₂[Ag₅Sb₃S₈] (II) (C₂N₂H₈=ethylenediamine) were synthesized under solvothermal conditions using AgNO₃, Sb, S and the amines as structure directing molecules. Both compounds crystallize as orange needles with lattice parameters a=6.669(1) Å, b=30.440(3) Å, c=9.154(1) Å for I (space group Pnma), and a=6.2712(4) Å, b=15.901(1) Å, c=23.012(2) Å, β=95.37(1)° for II (space group P2₁/n). In both compounds the primary building units are trigonal SbS₃ pyramids, AgS₃ triangles and AgS₄ tetrahedra. In I the layered [Ag₃Sb₃S₇]²⁻ anion is constructed by two different chains. An [Sb₂S₄] chain running along [100] is formed by vertex sharing of SbS₃ pyramids. The second chain contains a Ag₃SbS₅ group composed of the AgS₄ tetrahedron, two AgS₃ units and one SbS₃ pyramid. The Ag₃SbS₅ units are joined via S atoms to form the second chain which is also directed along [100]. The layered anion is then obtained by condensation of the two individual chains. The organic structure director is sandwiched by the inorganic layers and the shortest inter-layer distance is about 6.4 Å. In II the primary building units are linked into different six-membered rings which form a honeycomb-like layer. Two such layers are connected via Ag-S bonds of the AgS₄ tetrahedra giving the final undulated double layer anion. The structure directing ethylenediamine cations are located in pairs between the layers and a sandwich-like arrangement of alternating anionic layers and organic cations is observed. The inter-layer separation is about 5.4 Å. Both compounds decompose in a more or less complex manner when heated in an argon atmosphere. The optical band gaps of about 1.9 eV for the two compounds proof the semiconducting behavior. For II the conductivity was measured with impedance spectroscopy and amounts to σ_295K=7.6×10⁻⁷ Ω⁻¹ cm⁻¹. At 80 °C the conductivity is significantly larger by one order of magnitude.     

Dy5Ni0.66Bi2.34 and Lu5Ni0.56Sb2.44 – Substitution derivatives with the orthorhombic Yb5Sb3-type structure. Magnetocaloric effect of Dy5Ni0.66Bi2.34

Dy₅Ni_0.66Bi_2.34 and Lu₅Ni_0.56Sb_2.44 were synthesized by arc-melting and were found to adopt an orthorhombic Yb₅Sb₃-type structure. Cell parameters are a = 12.075(2), b = 9.165(2), c = 8.072(1) Å for Dy₅Ni_0.66Bi_2.34 and a = 11.6187(9), b = 8.933(1) and c = 7.8377(6) Å for Lu₅Ni_0.56Sb_2.44. Dy₅Ni_0.66Bi_2.34 undergoes a step-like ferromagnetic transition around 66 K. Magnetocaloric effect in terms of the magnetic entropy change, ΔS, reaches −3.73 J/kg K at 75 K for Dy₅Ni_0.66Bi_2.34.     

Hydrothermal Synthesis and Crystal Structure of [(CH3NH3)1.03K2.97]Sb12S20·1.34H2O

A novel thioantimonate(III) [(CH₃NH₃)_1.03K_2.97]Sb₁₂S₂₀·1.34H₂O was synthesized hydrothermally. It crystallizes in space groupP , witha=11.9939(7) Å,b=12.8790(8) Å,c=14.9695(9) Å,α=100.033(1)°,β=99.691(1)°,γ=108.582(1)°,V=2095.3(2) ų, andZ=2. The structure is determined from single crystal X-ray diffraction data collected at room temperature and refined toR(F)=0.037. In the crystal structure, each Sb(III) atoms has short bonds (2.37–2.58 Å) to three S atoms. The pyramidal [SbS₃] groups share common S atoms forming two types of centrosymmetric [Sb₁₂S₂₀] rings with the same topology. These rings are interconnected by weaker Sb–S bonds (2.92–3.29 Å) into 2-dimensional layers. Adjacent layers are parallel with K⁺and CH₃NH⁺₃ions and H₂O molecules located between them. Variation of bond valence sums calculated for the Sb(III) cations is found to be correlated with the coordination geometry. This is interpreted as due to the stereochemical activity of their lone electron pairs.     

Sr11Cd6Sb12: a new Zint1 compound with infinite chains of pentagonal tubes

A new Cd-containing transition metal Zintl phase, Sr₁₁Cd₆Sb₁₂, was obtained from a direct element combination reaction using the Sn flux method. Its structure was determined using single-crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2/m with a=32.903(3) Å, b=4.7666(5) Å, c=12.6057(13) Å, β=109.752(2)°, and Z=2. Sr₁₁Cd₆Sb₁₂ has a one-dimensional infinite chain structure consisting of double pentagonal tubes, where Sr²⁺ cations reside both within two tubes and between the infinite chains of tubes. The anionic framework [Cd₆Sb₁₂]²²⁻ has features similar to those of Eu₁₀Mn₆Sb₁₃. The difference in Eu₁₀Mn₆Sb₁₃ is that its double pentagonal tubes are further condensed to form two-dimensional layers.     

Supramolecular pseudometallacycles in a nickel compound with 4,4-diaminodiphenylmethane: Synthesis and structure of {Ni[(CH2(C6H4NH2)2]2(NO3)2(H2O)2}

The [Ni(DDM)₂(NO₃)₂(H₂O)₂] complex (DDM is 4,4-diaminodiphenylmethane [CH₂(C₆H₄NH₂)₂]) is synthesized, and its structure is determined. The crystals are triclinic, space group P , a = 5.846(1) ?, b = 9.450(2) ?, c = 13.390(3) ?, α = 105.63(3)°, β = 98.13(3)°, γ = 105.84(3)°, V = 666.6(2) ?³, ρ_calcd = 1.553 g/cm³, Z = 2. The Ni(II) ion (in the inversion center) is bound to a distorted octahedral array formed by the nitrogen atoms of the primary amino groups of the DDM molecules and the oxygen atoms of the monodentate nitrato groups and water molecules (Ni(1)-N(3) 2.119(2) ?, Ni(1)-O(1) 2.122(2) ?, Ni(1)-O(w) 2.047(2) ?, angles at the Ni atoms vary in the 85.08(9)°–94.92(9)° interval). The structure contains supramolecular metallacycles formed by the O(w)-H…N(2) hydrogen bonds between the coordinated H₂O molecules and the terminal amino groups of DDM. The metallacycles are joined by the Ni²⁺ ions into infinite chains running in the [111] direction. Original Russian Text ? Yu.V. Kokunov, V.V. Kovalev, Yu.E. Gorbunova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 11, pp. 1838–1843.     

Determination of heat capacities of PbCrO4(s), Pb2CrO5(s), and Pb5CrO8(s)

Abstract  

Heat capacities of PbCrO₄(s), Pb₂CrO₅(s), and Pb₅CrO₈(s) were measured by differential scanning calorimetry. The measured heat capacities as a function of temperature are expressed as C _p <PbCrO₄> J K⁻¹ mol⁻¹ = 150.37 + 27.74 × 10⁻³ T − 2.80 × 10⁶ T ⁻² (T = 300–750 K), C _p <Pb₂CrO₅> J K⁻¹ mol⁻¹ = 194.55 + 76.09 × 10⁻³ T − 4.64 × 10⁶ T ⁻² (T = 300–700 K), and C _p  <Pb₅CrO₈> J K⁻¹ mol⁻¹ = 323.35 + 184.80 × 10⁻³ T − 5.48 × 10⁶ T ⁻² (T = 300–600 K). From the measured heat capacity data, thermodynamic functions such as enthalpy increments, entropies, and Gibbs energy functions were derived.     

The lanthanoid polyantimonides with the ideal compositions Pr5Sb12 and Nd5Sb12 crystallizing with a new structure type and Ho2Sb5 with Dy2Sb5-type structure

The title compounds were isolated in well-crystallized form from samples with a substantial excess of antimony, annealed at temperatures slightly below the melting point of that element. Their crystal structures were determined from single-crystal diffractometer data. Pr_9-xSb_21-y and Nd_9-xSb_21-y crystallize with a new monoclinic structure type, Pearson symbol mS(62-5.4), space group Cm, Z=2 with a=2859.1(4) pm, b=426.3(1) pm, c=1356.1(2) pm, β=95.52(1)°, R=0.034 for 4351 structure factors and 188 variable parameters for Pr_9-xSb_21-y and a=2845(2) pm, b=424.7(8) pm, c=1345.9(9) pm, β=95.42(7)°, R=0.069 for 2928 F values and 188 variables for Nd_9-xSb_21-y. Of the 30 atomic sites, three show fractional occupancy corresponding to the compositions Pr_8.303(5)Sb_20.03(1) and Nd_8.30(2)Sb_19.98(9), respectively. A model for the order of occupied atomic sites with a tripled b-axis is proposed resulting in the ideal compositions Pr₅Sb₁₂ and Nd₅Sb₁₂. The holmium compound Ho₂Sb₅ has a Dy₂Sb₅-type structure: mP28, P2₁/m, a=1301.8(3) pm, b=414.9(1) pm, c=1451.1(2) pm, β=102.14(1)°, R=0.028 for 2573 F values and 86 variables. In both structure types most rare earth atoms have nine antimony neighbors forming tricapped trigonal prisms. The coordination polyhedra of the antimony atoms show a great variety, with a trigonal prism of rare earth atoms as one extreme case. The other extreme coordination of an antimony atom is a distorted octahedron formed by six antimony atoms. The differences and similarities of both structures are discussed. Chemical bonding within the antimony polyanions is analyzed on the basis of an extended Zintl-Klemm concept using bond-length-bond-strength relationships.     

Hydro(solvo)thermal synthesis and structural characterization of a new organically templated gallophosphate: [H3N(CH2)2NH3]1/2·[Ga5 (PO4)4(OH)4]

A new three-dimensional open-framework gallophosphate: [H₃N(CH₂)₂NH₃]_1/2·[Ga₅ (PO₄)₄(OH)₄] has been prepared by hydro(solvo)thermal synthesis in presence of ethylenediamine (en) as structure-directing agent. Its structure was determined by means of single-crystal X-ray diffraction analysis with the following crystal data: monoclinic space group C2/m, a=10.1604(9) Å, b=12.0085(15) Å, c=7.1892(7) Å, β=90.797(6)°, V=877.08(16) Å³, Z=2, R₁=0.0264, wR₂=0.0764. The total numbers of measured reflections and unique reflections were 3508 and 1300, respectively. It is built up from a new secondary building unit (SBU) Ga₄P₄O₂₀(OH)₄, in which Ga atoms exhibit distorted trigonal bipyramidal coordination and P atoms are in tetrahedral coordination. The SBU Ga₄P₄O₂₀(OH)₄ are linked into a layer by bridge oxygen atoms. The GaO₄(OH)₂ octahedra link the layers into a three-dimentional framework. Diprotonated ethylenediamine was found in the channel of the framework. The material was characterized by IR spectroscopy, ¹H NMR spectra, thermogravimetric and differential thermal analyses and elemental analysis.     

Synthesis and study of (CN3H6)2[(UO2)2(C2O4)(SeO3)2] by IR spectroscopy and X-ray diffraction

Single crystals of (CN₃H₆)₂[(UO₂)₂(C₂O₄)(SeO₃)₂] were synthesized and studied by IR spectroscopy and X-ray diffraction. The compound crystallizes in the triclinic system with the unit cell parameters a = 7.1169(12) ?, b = 7.4874(10) ?, c = 8.9748(14) ?, α = 88.243(6)°, β = 74.546(6)°, γ = 81.445(6)°, space group P[`1]P\bar 1, Z = 1, R = 0.0304. The main structural units of the crystals are layers of the [(UO₂)₂(C₂O₄)(SeO₃)₂]²⁻ composition; the layers belong to the crystal chemical group A ₂ K ⁰² T ₂³ (A = UO₂²⁺ K ⁰² = C₂O₄²⁻, T ³ = SeO₃^–) of uranyl complexes. Uranium-containing complex groups are linked by electrostatic interactions and a network of hydrogen bonds with CN₃H₆⁺ guanidinium ions to form a three-dimensional framework.