La4(Si5.2Ge2.8O18)(TeO3)4 and La2(Si6O13)(TeO3)2: Intergrowth of the lanthanum(III) tellurite layer with the XO4 (X=Si/Ge) tetrahedral layer

Two novel lanthanum(III) silicate tellurites, namely, La₄(Si_5.2Ge_2.8O₁₈)(TeO₃)₄ and La₂(Si₆O₁₃)(TeO₃)₂, have been synthesized by the solid state reactions and their structures determined by single crystal X-ray diffraction. The structure of La₄(Si_5.2Ge_2.8O₁₈)(TeO₃)₄ features a three-dimensional (3D) network composed of the [(Ge_2.82Si_5.18)O₁₈]⁴⁻ tetrahedral layers and the [La₄(TeO₃)₄]⁴⁺ layers that alternate along the b-axis. The germanate-silicate layer consists of corner-sharing XO₄ (X=Si/Ge) tetrahedra, forming four- and six-member rings. The structure of La₂(Si₆O₁₃)(TeO₃)₂ is a 3D network composed of the [Si₆O₁₃]²⁻ double layers and the [La₂(TeO₃)₂]²⁺ layers that alternate along the a-axis. The [Si₆O₁₃]²⁻ double layer is built by corner-sharing silicate tetrahedra, forming four-, five- and eight-member rings. The TeO₃²⁻ anions in both compounds are only involved in the coordination with La³⁺ ions to form a lanthanum(III) tellurite layer. La₄(Si_5.2Ge_2.8O₁₈)(TeO₃)₄ is a wide band-gap semiconductor.     

A gravimetric and an X-ray fluorescence method for the determination of rubidium in Rb2U(SO4)3

Chemical characterization of rubidium uranium(IV) trisulfate, Rb₂U(SO₄)₃, a new chemical assay standard for uranium requires accurate analysis of rubidium. A gravimetric and an X-ray fluorescence method (XRF) for the determination of rubidium in this compound are described. In the gravimetric method, rubidium is determined as Rb₂Na[Co(NO₂)₆].H₂O without separating uranium with a precision of the order of ±0.5%. In the XRF method, the concentration ratio of rubidium to uranium, C_Rb/C_U, is determined in the solid samples by the binary ratio method using calibration between intensity ratios (I_Rb/I_U) and concentration ratios (C_Rb/C_U). The concentration of rubidium is derived using the uranium value which is known with a precision better than ±0.05%. The XRF method has a precision better than ±0.8% for rubidium determination.     

Solid rubidium-conducting electrolytes in Rb<Subscript>1 − 2<Emphasis Type="Italic">x</Emphasis></Subscript>Me<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>AlO<Subscript>2</Subscript> systems (Me = Pb,Cd, Ca)

New highly conducting rubidium cationic solid electrolytes were synthesized on the basis of rubidium aluminates by partial substitution of Rb⁺ cations with Pb²⁺, Cd²⁺, and Ca²⁺ divalent ions and studied. All these three additives essentially increase electroconductivity of RbAlO₂ especially in the low-temperature range. The values of electroconductivity and its activation energy are close for the optimum compositions in three studied systems. The conductivity of rubidium monoaluminate is increased by the studied additives due to formation of additional rubidium vacancies by substitution 2 Rb⁺ → Me²⁺ + V′_Rb.     

Hydrothermal synthesis and structure of the first tin(II) squarate Sn2O(C4O4)(H2O)—comparison with Sn2[Sn2O2F4]

A tin(II) squarate Sn₂O(C₄O₄)(H₂O) was synthesized by hydrothermal technique. It crystallizes in the monoclinic system, space group C2/m (no. 12) with lattice parameters a=12.7380(9) Å, b=7.9000(3) Å, c=8.3490(5) Å, β=121.975(3)°, V=712.69(7) Å³, Z=4. The crystal structure determined with an R=0.042 factor, consists of [(Sn₄O₁₀)(H₂O)₂] units connected from one another in the [101] and [010] directions via squarate groups to form layers separated by Sn(II) lone pairs. This compound presents the same remarkable structural arrangement as observed in the tin-oxo-fluoride Sn₂[Sn₂O₂F₄] inorganic compound with Sn(II) lone pairs E(1) and E(2) concentrated in large rectangular-shape tunnels running along [001] direction.     

Neutron diffraction study of uranyl oxalate [UO2(C2O4)(D2O)] · 2D2O

A powdered sample of uranyl oxalate [UO₂(C₂O₄)(D₂O)] · 2D₂O (compound I) is studied using neutron diffraction. The crystals are monoclinic, space group P2₁/c, with a = 5.608(1) Å, b = 17.016(3) Å, c = 9.410(2) Å, β = 98.9369(2)°, Z = 4, R _f = 0.042, R _I = 0.054, x ² = 1.5. The main structural units of the crystals are [UO₂(C₂O₄)(D₂O)] chains. These chains, which belong to the AK⁰²M¹ (A = UO ₂ ²⁺ ) crystal-chemical group of the uranyl complexes, lie parallel to [101]. The water molecules in the crystals of I are hydrogen-bonded into zigzag chains running along [100]. Since each third oxygen atom of the chain formed of water molecules is coordinated to the uranium atom, the uranyl oxalate chains are linked into {[UO₂(C₂O₄)(D₂O)] · 2D₂O} layers that lie normal to [010]. The layers are linked into the framework through interlayer hydrogen bonds (D₂O)O-D···O (oxalate).     

catena‐Poly[[[(benzene‐1,3,5‐tricarboxylic acid)(1,10‐phenanthroline)cadmium(II)]‐μ‐oxalato] 1H‐benzotriazole solvate monohydrate]

In the title compound, [Cd(C₂O₄)(C₁₂H₈N₂)(C₉H₆O₆)]·C₆H₅N₃·H₂O, the Cd^II atom has a distorted pentagonal–bipyramidal geometry, defined by two N atoms and five O atoms from bidentate 1,10‐phenanthroline ligands, oxalate ligands and benzene‐1,3,5‐tricarboxylic acid ligands. The oxalate ligands in the asymmetric unit possess inversion symmetry. The triazole molecule is not coordinated to the Cd atom. The structure of the title compound features a one‐dimensional chain running along the crystallographic a axis, and a three‐dimensional supramolecular network is formed via aromatic π–π interactions and hydrogen‐bonding interactions.     

Synthesis, characterization, and norbornene polymerization of η-benzylnickel(II) complexes of N-heterocyclic carbenes

Neutral η¹-benzylnickel carbene complexes, [Ni(η¹-CH₂C₆H₅)(IiPr)(PMe₃)(Cl)] (3) (IiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and [Ni(η¹-CH₂C₆H₅)(SIiPr)(PMe₃)(Cl)] (4) (SIiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazolin-2-ylidene), were prepared by the reaction between [Ni(η³-CH₂C₆H₅)(PMe₃)(Cl)] and an equivalent amount of the corresponding free N-heterocyclic carbene. The preparation of η³-benzylnickel carbene complexes, [Ni(η³-CH₂C₆H₅)(IiPr)(Cl)] (5) and [Ni(η³-CH₂C₆H₅)(SIiPr)(Cl)] (6) were carried out by the abstraction of PMe₃ from 3 and 4 by the treatment of B(C₆F₅)₃. The treatment of AgX on 5 and 6 produced the anion-exchanged complexes, [Ni(η³-CH₂C₆H₅)(NHC)(X)] (7, NHC = IiPr, X = O₂CCF₃; 8, NHC = IiPr, X = O₃SCF₃; 9, NHC = SIiPr, X = O₂CCF₃; 10, NHC = SIiPr, X = O₃SCF₃). The solid state structures of 3 and 10 were determined by X-ray crystallography. The η³-benzyl complexes of IiPr (5, 7, and 8) alone, in the absence of any activators such as borate and MAO, showed good catalytic activity towards the vinyl-type norbornene polymerization. The catalyst was thermally robust and the activity increases as the temperature rises to 130 °C.     

Light induced magnetic properties of spiropyrane tris(oxalato)chromate (III) single crystals

The effect of UV light on Weiss temperature and ESR spectra in 1-isopropyl-3, 3, 5′, 6′-tetramethylspiro[indolin-2,2′-[2H]pyrano[3,2-b]pyridinium] tris(oxalato)chromate (III) (Sp₃Cr(C₂O₄)₃) has been found. Additional line has been observed in the ESR spectra of irradiated samples in “strong” magnetic fields of ~15 kOe. The analysis of angular dependences of the ESR spectra allowed a contribution of Cr³⁺ ions to magnetic properties of Sp₃Cr(C₂O₄)₃ to be determined. The zero-field splitting parameters D=0.619 cm⁻¹, E=0.024 cm⁻¹ were derived from the experimental data. The parameters were typical for Cr³⁺ in the chromium oxalate. Weiss temperature changed sign from 25 to −25 K under UV irradiation. The value of Weiss temperature and its changing cannot be explained by exchange interaction, dipole-dipole interaction or the effect of crystal field. The existence of Weiss temperature is explained by the changes in amount and spin of paramagnetic particles. The change is due to thermoactivated redistribution of electrons between chromium ions and spiropyrane molecules. Light-induced transfer of electrons is also explaining the change in sign of Weiss temperature under UV irradiation.     

Rb4O6 studied by elastic and inelastic neutron scattering: In memoriam Jean Rouxel

The black rubidium oxide Rb₄O₆ has been described to be a mixed peroxide-hyperoxide Rb₄(O₂²⁻)(O₂⁻)₂ in the literature. Previous X-ray diffraction studies on powders and single crystals, however, revealed that Rb₄O₆ crystallises like cubic Pu₂C₃ (space group I3d), and has only one crystallographically independent position for a dumbbell-shaped molecular ion. Elastic neutron scattering now shows that this structure is stable down to 5 K, and no reduction of symmetry nor ordering of the differently sized yet indistinguishable dioxygen anions takes place. The presence of the peroxide and hyperoxide anions in Rb₄O₆ at 4 K is proved by inelastic neutron scattering, resulting in two absorptions at 750 cm⁻¹ and 1130 cm⁻¹, which correspond to the stretching vibrations of O₂⁻ and O₂⁻.     

Na(H3NCH2CH2NH3)0.5[Co(C2O4)(HPO4)]: A novel phosphoxalate open-framework compound incorporating both an alkali cation and an organic template in the structural tunnels

The first open-framework metal phosphoxalate compound containing both an organic and an inorganic template in the same structure is reported. Na(H₃N⁺CH₂CH₂N⁺H₃)_0.5[Co(C₂O₄)(HPO₄)] (1) was synthesized hydrothermally via a direct metathesis reaction using the sodium salts of oxalate and phosphate in the presence of cobalt chloride and ethylenediamine dihydrochloride. The structure of 1 consists of a 3D framework built from the [Co(C₂O₄)]_n layers connected by HPO₄²⁻ group bridging two different cobalt centers between the adjacent layers. A major and a minor structural tunnels are created and occupied by the Na⁺ and H₃N⁺CH₂CH₂NH₃²⁺ ions, respectively, in the same structure. Single-crystal X-ray crystallographic data for 1 are: monoclinic, P2₁/c, a=5.8189(6), b=10.235(1), c=13.066(1) Å, β=96.671(2)°, Z=4, V=772.9(1) Å³, R=3.95% and R_w=6.37%.     

Crystal structure and cation transport properties of the layered monodiphosphates Rb6Bi4(PO4)2(P2O7)3

Single crystals of the new Bi(III) phosphates, Rb₆Bi₄(PO₄)₂(P₂O₇)₃, have been isolated and their structure has been determined by X-ray diffraction techniques. This compound crystallizes in the monoclinic space group P2₁/c with a=9.077(1)Å, b=9.268(2)Å, c=36.418(6)Å, β=95.75(1)° and Z=8. The crystal structure is made up of BiO₅ and BiO₆ polyhedra sharing the corners with PO₄ tetrahedra and P₂O₇ diphosphate groups. The structure can be described as infinite anionic layers with composition [Bi₄(PO₄)₂(P₂O₇)₃]_∞⁶⁻ parallel to the [301] plane, connected via P-O-Bi bridges to form a three-dimensional open framework. This framework delimits tunnels running along [100] and [010] directions, where the rubidium ions reside. This compound exhibits a rubidium ion conduction but with rather low conductivity value at 640 K.     

Electrochemical behavior and assembly of tetranuclear Dawson-derived sandwich compound [Cd4(H2O)2(As2W15O56)2] on 4-aminobenzoic acid modified glassy carbon electrode

The transition metal-substituted heteropolyoxoanion, Cd₄(H₂O)₂(As₂W₁₅O₅₆)₂¹²⁻ (As₄W₃₀Cd₄), is one of the trivacant Dawson derivatives. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited three steps of four-electron redox waves attributed to redox processes of the tungsten-oxo framework. Through layer-by-layer assembly, the compound was first successfully immobilized on a 4-aminobenzoic acid modified glassy carbon electrode surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)₂Cl]^2+/+ (denoted as QPVP-Os). Thus, prepared multilayer films have been characterized by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy (UV-vis). The electrocatalytic activities of the multilayer films containing As₄W₃₀Cd₄ have been investigated on the reduction of three substrates of important analytical interests, NO₂⁻, BrO₃⁻ and IO₃⁻. And with the increase of the number of As₄W₃₀Cd₄ layers, the catalytic current towards the reduction of BrO₃⁻ was enhanced and the catalytic potential shifted positively.     

Poly[bis[aquaneodymium(III)]‐μ2‐oxalato‐di‐μ4‐succinato]

In the title compound, [Nd₂(C₄H₄O₄)₂(C₂O₄)(H₂O)₂]_n, the flexible succinate anion assumes the gauche conformation and bridges the nine‐coordinate Nd atoms to generate two‐dimensional layers parallel to (010). The coordination polymer layers are linked into a three‐dimensional framework by the rigid oxalate ligands. The oxalate ions are located on a center of inversion.     

A pillared framework coordination polymer based on the Cd3(μ3‐OH) unit: poly[[(μ4‐5‐aminotetrazolato‐κ4N1:N2:N3:N4)chlorido‐μ3‐hydroxido‐(μ3‐isonicotinato‐κ3N:O:O′)dicadmium(II)] 0.14‐hydrate]

The title coordination polymer, {[Cd₂(CH₂N₅)(C₆H₄NO₂)Cl(OH)]·0.14H₂O}_n, (I), was synthesized by the reaction of cadmium acetate and N‐(1H‐tetrazol‐5‐yl)isonicotinamide in aqueous ammonia, using hydrochloric acid to adjust the pH. Under hydrothermal conditions, N‐(1H‐tetrazol‐5‐yl)isonicotinamide slowly hydrolyzes to form isonicotinic acid (Hisonic) and 5‐aminotetrazole (Hatz). The deprotonated form of isonicotinic acid (denoted isonic) acts as a bridging ligand in the structure. The polymer crystallizes in the monoclinic space group C2/m. In the structure, there is one Cd₃(μ₃‐OH) unit of C_s symmetry, with one of the Cd^II atoms and the O and H atoms located on a mirror plane. The other crystallographically independent Cd^II cation is located on an inversion centre. Each edge of the Cd₃(μ₃‐OH) isosceles triangle is bridged by an atz ligand in a μ_1,2 or μ_2,3/μ_3,4 mode. The Cd₃(μ₃‐OH) units are laced around with a belt of chloride ligands. The belts are further connected into undulating layers via weak inter‐belt Cd—Cl bonds. The two organic ligands reside across mirror planes. The construction of a three‐dimensional framework is completed by the pillaring isonic ligand. Water molecules partially occupy the voids of the framework.     

A new two‐dimensional cadmium coordination polymer with 1H‐imidazole‐4‐carboxylate and oxalate

The title compound, poly[aqua(μ₂‐1H‐imidazole‐4‐carboxylato‐κ³N³,O:O′)hemi(μ₂‐oxalato‐κ⁴O¹,O²:O^1′,O^2′)cadmium(II)], [Cd(C₄H₃N₂O₂)(C₂O₄)_0.5(H₂O)]_n, exhibits a two‐dimensional network. The Cd^II cation is coordinated to one N atom and two carboxylate O atoms from two 1H‐imidazole‐4‐carboxylate (Himc) ligands, two carboxylate O atoms from the bridging oxalate anion and one ligated water molecule; these six donor atoms form a distorted octahedral configuration. The oxalate anion lies on a centre of inversion. The Himc ligands connect the Cd^II cations to form –Cd–Himc–Cd–Himc–Cd– zigzag chains, with a Cd...Cd separation of 5.8206 (6) Å along the b direction, which are further linked by tetradentate oxalate anions to generate a two‐dimensional herringbone architecture in the ab plane. These layers are extended to form a three‐dimensional supramolecular framework via O—H...O and N—H...O hydrogen bonds and π–π stacking interactions. The solid‐state photoluminscent behaviour of the title compound has been investigated at room temperature.     

Ein neuer Zugang zu Alkalivanadaten(IV,V) Die Kristallstruktur von Rb2V3O8

A New Access to Alkali Vanadates(IV,V) Crystal Structure of Rb₂V₃O₈ By heating vanadium(V) oxide with rubidium iodide to 500°C, the vanadium experiences partial reduction and Rb₂V₃O₈ is obtained. It has the fresnoite structure. Crystal data: a = 892.29(7), c = 554.49(9) pm at 20°C, tetragonal, space group P4bm, Z = 2. X-ray crystal structure determination with 620 observed reflexions, R = 0.027. V₂O₇ units share vertices with VO₅ square pyramids, forming layers; a layer can be regarded as association product of VO²⁺ and V₂O₇^4? ions. The Rb⁺ ions between the layers have pentagonal-antiprismatic coordination.     

Mononuclear and dinuclear bromide–nitrite cadmium(II) complexes with related 1,4‐diazabicyclo[2.2.2]octane ligands

The title compounds, di‐μ‐bromido‐bis[bromido(1‐carboxymethyl‐4‐aza‐1‐azoniabicyclo[2.2.2]octane‐κN⁴)(nitrito‐κ²O,O′)cadmium(II)] dihydrate, [Cd₂Br₄(C₈H₁₅N₂O₂)₂(NO₂)₂]·2H₂O, (I), and aquabromido(1‐cyanomethyl‐4‐aza‐1‐azoniabicyclo[2.2.2]octane‐κN⁴)bis(nitrito‐κ²O,O′)cadmium(II) monohydrate, [CdBr(C₈H₁₄N₃)(NO₂)₂(H₂O)]·H₂O, (II), are two‐dimensional hydrogen‐bonded metal–organic hybrid complexes. In (I), the complex is situated on a centre of inversion so that each symmetry‐related Cd^II atom is coordinated by two bridging Br atoms, one monodentate Br atom, one chelating nitrite ligand and one organic ligand, yielding a significantly distorted octahedral geometry. The combination of O—H...O and O—H...Br hydrogen bonds produces centrosymmetric R₆⁶(16) ring motifs, resulting in two‐dimensional layers parallel to the ab plane. In contrast, the complex molecule in (II) is mononuclear, with the Cd^II atom seven‐coordinated by two bidentate nitrite groups, one N atom from the organic ligand, one monodentate Br atom and a water O atom in a distorted pentagonal–bipyramidal environment. The combination of O—H...O and O—H...Br hydrogen bonds produces R₅⁴(14) and R₃³(8) rings which lead to two‐dimensional layers parallel to the ac plane.     

Poly[[μ2‐1,3‐bis(pyridin‐4‐yl)propane](μ3‐1,4‐phenylenediacetato)cadmium]

Solvothermal reaction between Cd(NO₃)₂, 1,4‐phenylenediacetate (1,4‐PDA) and 1,3‐bis(pyridin‐4‐yl)propane (bpp) afforded the title complex, [Cd(C₁₀H₈O₄)(C₁₃H₁₄N₂)]_n. Adjacent carboxylate‐bridged Cd^II ions are related by an inversion centre. The 1,4‐PDA ligands adopt a cis conformation and connect the Cd^II ions to form a one‐dimensional chain extending along the c axis. These chains are in turn linked into a two‐dimensional network through bpp bridges. The bpp ligands adopt an anti–gauche conformation. From a topological point of view, each bpp ligand and each pair of 1,4‐PDA ligands can be considered as linkers, while the dinuclear Cd^II unit can be regarded as a 6‐connecting node. Thus, the structure can be simplified to a two‐dimensional 6‐connected network.     

Hydrothermal synthesis, structural characterization and magnetic studies of the new pillared microporous ammonium Fe(III) carboxyethylphosphonate: [NH4][Fe2(OH){O3P(CH2)2CO2}2]

The preparation by hydrothermal reaction and the crystal structure of the iron(III) carboxyethylphosphonate of formula [NH₄][Fe₂(OH){O₃P(CH₂)₂CO₂}₂] is reported. The green-yellow compound crystallizes in the monoclinic system, space group Pc(n.7), with the following unit-cell parameters: a=7.193(3) Å, b=9.776(3) Å, c=10.17(4) Å and β=94.3(2)°. It shows a typical layered hybrid organic-inorganic structure featuring an alternation of organic and inorganic layers along the a-axis of the unit cell. The bifunctional ligand [O₃P(CH₂)₂CO₂]³⁻ is deprotonated and acts as a linker between adjacent inorganic layers, to form pillars along the a-axis. The inorganic layers are made up of dinuclear Fe(III) units, formed by coordination of the metal ions with the oxygen atoms originating from the [O₃P−]²⁻ end of the carboxyethylphosphonate molecules, the oxygen atoms of the [−CO₂]⁻ end group of a ligand belonging to the adjacent layer and the oxygen atom of the bridged OH group. Each Fe(III) ion is six-coordinated in a very distorted octahedral environment. Within the dimer the Fe-Fe separation is found to be 3.5 Å, and the angle inside the [Fe(1)-O(11)-Fe(2)] dimers is ∼124°. The resulting 3D framework contains micropores delimited by four adjacent dimers in the (bc) planes of the unit cell. These holes develop along the a-direction as tunnel-like pores and [NH₄]⁺ cations are located there. The presence of the μ-hydroxo-bridged [Fe(1)-O(11)-Fe(2)] dimers in the lattice is also responsible for the magnetic behavior of the compound at low temperatures. The compound contains Fe³⁺ ions in the high-spin state and the two Fe(III) ions are antiferromagnetic coupled. The J/k value of −16.3 K is similar to those found for other μ-hydroxo-bridged Fe(III) dimeric systems having the same geometry.     

Investigations on the formation of rubidium dimolybdate via thermal decomposition of rubidium oxomolybdenum(VI) oxalate

The complex Rb₂[Mo₂O₅(C₂O₄)₂(H₂O)₂] (RMO) was prepared and characterized by means of chemical analysis and IR spectral studies. Its thermal decomposition was studied by using TG and DTA techniques. RMO loses its water between 160 and 200°C, this immediately being followed by the decomposition of anhydrous RMO, which takes place in three stages. The first two stages occur in the temperature ranges 200–220 and 220–255°, to give intermediates with tentative compositions Rb₈[Mo₈O₂₂(C₂O₄)₆] and Rb₈[Mo₈O₂₆(C₂O₄)(CO₃)], respectively, the latter then decomposing in the third stage between 255 and 340° to give the end-product, rubidium dimolybdate (Rb₂Mo₂O₇). Thed spacings for Rb₂Mo₂O₇ are given for 2θ values between 10 and 70°.