Synthese und Strukturuntersuchungen von Ba2H[α-FeO4W12O36] · 26 H2O

Synthesis and Structure Studies of Ba₂H[α-FeO₄W₁₂O₃₆] · 26 H₂O The heteropolyanion compound Ba₂H[α-FeO₄W₁₂O₃₆] · 26 H₂O (I) crystallizes in the tetragonal space group P4 n2 with the lattice parameters a = 12.398(6), c = 18.721(6) Å; Z = 2; D_x = 4.128 g · cm^?3. The structure was solved on a twinned crystal from 1029 observed reflections and refined to an index R of 7.6%. The calculations were done by means of a modified ORFLS-programme by Eitel and Bärnighausen. The heteropolyanion [α-FeO₄W₁₂O₃₆]^5? has the well known α-Keggin structure. The average distance of the four central oxygen atoms to the Fe^III position (0, 0, 0) is 1.84 Å. The angles ? O? Fe? O are 112.3° (4X) and 103.9 (2X), respectively, which leads to an disphenoidal distortion of the FeO₄ tetrahedron. The powder and single crystal ESR spectra of I show the anisotropy of the Fe^III fine structure transition 1/2 ? ?1/2. The Mößbauer spectra confirm the tetragonal distortion of the central FeO₄ tetrahedron (quadrupole splitting Δ ≈ 0.50 mm · s^?1).     

Coherence assembly phenomenon in the typical structures of heteropolyniobates

Crystallographic analysis has provided evidence for single cation frameworks formed from preordered cation positions in the individual building blocks (modules) constituting the basis of structures. We propose to call this phenomenon coherence assembly. According to the mechanical wave concept of the crystalline state, coherence assembly dictates the rules of mutual packing of “rigid” structural fragments. This study investigates the typical structures of heteropolyniobates: Na₁₂[Ti₂O₂][SiNb₁₂O₄₀]·4H₂O (I), menezesite Ba₂MgZr₄[BaNb₁₂O₄₂]·12H₂O (II), and the menezesite-isostructural aspedamite □₁₂(Fe³⁺,Fe²⁺)₃Nb₄·[Th(Nb,Fe³⁺)₁₂O₄₂]·(H₂O,OH)₁₂ (III).     

Untersuchung von Hydrolysereaktionen zum Aufbau von Eisen(III)‐Oxo‐Aggregaten

Investigation of the Hydrolytic Build‐up of Iron(III)‐Oxo‐Aggregates The synthesis and structures of five new iron/hpdta complexes [{Fe^III₄(μ‐O)(μ‐OH)(hpdta)₂(H₂O)₄}₂Fe^II(H₂O)₄]·21H₂O ( 2 ), (pipH₂)₂[Fe₂(hpdta)₂]·8H₂O ( 4 ), (NH₄)₄[Fe₆(μ‐O)(μ‐OH)₅(hpdta)₃]·20.5H₂O ( 5 ), (pipH₂)_1.5[Fe₄(μ‐O)(μ‐OH)₃(hpdta)₂]·6H₂O ( 7 ), [{Fe₆(μ₃‐O)₂(μ‐OH)₂(hpdta)₂(H₄hpdta)₂}₂]·py·50H₂O ( 9 ) are described and the formation of these is discussed in the context of other previously published hpdta‐complexes (H₅hpdta = 2‐Hydroxypropane‐1, 3‐diamine‐N, N, N′, N′‐tetraacetic acid). Terminal water ligands are important for the successive build‐up of higher nuclearity oxy/hydroxy bridged aggregates as well as for the activation of substrates such as DMA and CO₂. The formation of the compounds under hydrolytic conditions formally results from condensation reactions. The magnetic behaviour can be quantified analogously up to the hexanuclear aggregate 5 . The iron(III) atoms in 1 ‐ 7 are antiferromagnetically coupled giving rise to S = 0 spin ground states. In the dodecanuclear iron(III) aggregate 9 we observe the encapsulation of inorganic ionic fragments by dimeric{M₂hpdta}‐units as we recently reported for Al^III/hpdta‐system.     

Neue Heteropolyanionen des M2X2W20‐Typs mit Antimon(III) als Heteroatom

New Heteropolyanions of the M₂X₂W₂₀ Structure Type with Antimony(III) as a Heteroatom The syntheses of two new heteropolyanions of the M₂X₂W₂₀ structure type are presented. They are characterized by X‐ray structure analysis and vibrational spectra. Na₆(NH₄)₄[Zn₂(H₂O)₆(WO₂)₂(SbW₉O₃₃)₂]·36H₂O (1) is monoclinic (P2₁/n) with a = 12.873(3)Å, b = 25.303(4)Å, c = 15.975(4)Å and β = 91.99(3)°. Na₁₀[Mn₂(H₂O)₆(WO₂)₂(SbW₉O₃₃)₂]·40H₂O (2) also crystallizes in the space group P2₁/n with a = 12.892(3)Å, b = 25.219(5)Å, c = 16.166(3)Å and β = 94.41(3)°. Both polyanions are isostructural to anions of this structure type containing other heteroatoms. They are built up by two β‐B‐SbW₉ fragments, which are derived from defect structures of the Keggin anion. These subÍunits are connected by two formal WO₂ groups with further stabilization by addition of two M(H₂O)₃ groups (M = Zn^II, Mn^II, Fe^III, Co^II) leading to the M₂X₂W₂₀‐type heteropolytungstates.     

Three New Ln-Decavanadates Materials:Synthesis,Structure, and Photoluminescent Sensing for Detection of Zn2+ and Co2+

Three new compounds, [Ln(H₂O)₈]₂[V₁₀O₂₈] · 8H₂O [Ln = Ho ( 1 ), Tb ( 2 )] and [Eu(H₂O)₈]₂[V₁₀O₂₈] · 9H₂O ( 3 ), were successfully synthesized by evaporating the mixture of K₆V₁₀O₂₈ · 10H₂O and LnCl₃ · 6H₂O. Notably, three vanadates are composed of [Ln(H₂O)₈]³⁺ cation, decavanadates ([V₁₀O₂₈]^6–) anion. Meanwhile, free water molecules generate different type water clusters to connect [V₁₀O₂₈]^6– anions and coordination cations to form 3D supramolecular structure. The fluorescence measurements reveal that characteristic photoluminescence of Tb^III and Eu^III is quenched in presence of [V₁₀O₂₈]^6–, then the impacts of variational decavanadates ions concentration on the fluorescence intensities of LnCl₃ (Ln = Tb, Eu) systems and different acetate solution [M(CH₃COO)₂; M = Ni, Cr, Cu, Co, Zn] on fluorescence intensities of Ln-decavanadates (Ln = Eu, Tb) systems are investigated.     

A unique organic-inorganic hybrid FeⅢ–PrⅢ-included 2-germano-20-tungstate and its electrochemical biosensing properties

An organic-inorganic hybrid Fe^Ⅲ–Pr^Ⅲ-included 2-germano-20-tungstate [Pr（H₂O）₈]₂H₂[Fe₄（H₂O）₄（pca）₄Ge₂W₂₀O₇₂]·34H₂O（Hpca=2-pyridinecarboxylic acid）(1) was hydrothermally prepared. Its polyoxoanion comprises one tetra-Fe^Ⅲ incorporated [Fe₄（H₂O）₄（pca）₄Ge₂W₂₀O₇₂]...     

Alkalimolybdotellurate: Darstellung und Kristallstruktur von Rb6[TeMo6O24] · 10H2O und Rb6[TeMo6O24] · Te(OH)6 · 6H2O

Alkaline Molybdotellurates: Preparation and Crystal Structures of Rb₆[TeMo₆O₂₄] · 10H₂O and Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6H₂O Single crystals of Rb₆[TeMo₆O₂₄] · 10 H₂O and Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6 H₂O, respectively, were grown from aqueous solution. Rb₆[TeMo₆O₂₄] · 10 H₂O possesses the space group P1 . The lattice dimensions are a = 963.40(13), b = 972.56(12), c = 1 056.18(13) pm, α = 97.556(10), β = 113.445(9), γ = 102.075(10)°; Z = 1, 2 860 reflections, 215 parameters refined, R_g = 0.0257. The centrosymmetrical [TeMo₆O₂₄]^6? anions are stacked parallel to [010]. Rb(2) is coordinated with one exception by water molecules only. Folded chains consisting of [TeMo₆O₂₄]^6? anions and Rb(2) coordination polyhedra which are linked to pairs represent the prominent structural feature. Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6 H₂O crystallizes monoclinically in the space group C2/c with a = 1 886.4(3), b = 1 000.9(1), c = 2 126.5(3) pm, and β = 115.90(1)°; Z = 4, 3 206 reflections, 240 parameters refined, R_g = 0.0333. It is isostructural in high extent with (NH₄)₆[TeMo₆O₂₄] · Te(OH)₆ · 7 H₂O. Hydrogen bonds between Te(OH)₆ molecules and [TeMo₆O₂₄]^6? anions establish infinite strands. The [TeMo₆O₂₄]^6? anions gather around Te(OH)₆ providing channel-like voids extending parallel to [001].     

17O and 183W NMR studies of the paratungstate anions in aqueous solutions

¹⁷O (40.7 MHz) and ¹⁸³W (12.5 MHz) NMR spectra of aqueous Na₁₀[H₂W₁₂O₄₂]·27H₂O (1), Na₆[W₇O₂₄]·14H₂O (2) and (NH₄)₆[Mo₇O₂₄]·nH₂O solutions, as well as of 2, 1 and 0.1 M Na₂WO₄ and 2 M Li₂WO₄ solutions acidified up to P = 0.5, 1 and 1.14 have been measured. The composition of the W₇O₂₄^6? anion remains unchanged (2), its structure being similar to that of Mo₇O₂₄^6?183W NMR spectrum shows three resonances with the chemical shifts + 269.2, ?98.8 and ?178.9 ppm relative to WO₄^2? and intensity ratio 1:4:2. “Paratungstate A” produced during polycondensation of WO₄^2? at P ? 1.17 is identical with heptatungstate W₇O₂₄^6?. The [H₂W₁₂O₄₂]^10?183W NMR spectrum in the acidified 2 M Li₂WO₄ solution has four resonances with the chemical shifts in the range - 105–145 ppm and intensity ratio 1:2:1:2. As suggested by NMR data, the H₂W₁₂O₄₂^10? ? W₇O₂₄^6? transformations occur, which depend upon concentration and temperature.     

Solid state chemistry of polytungstic acids and their salts: II. Synthesis,properties, and structure of noncrystalline hydrogen-sodium metatungstate and powdered crystalline cesium metatungstate

A noncrystalline hydrogen-sodium metatungstate and a powdered crystalline cesium metatungstate have been prepared by a cation-exchange membrane electrolytic method and examined with UV and IR photoacoustic, thermal, conductance, and X-ray diffraction techniques. The results show that the formulas of the hydrogen-sodium metatungstate and the cesium metatungstate are Na₄H₂[H₂(W₃O₁₀)₄] · 10H₂O and Cs₆[H₂(W₃O₁₀)₄] · 9H₂O, respectively. The ionic conductivity of inner-sphere hydrogen of the complex anion [H₂(W₃O₁₀)₄]⁶⁻ is far smaller than that of the hydrogen in the outer sphere of solid state metatungstate. A single crystal of cesium metatungstate has also been prepared; it belongs to a triclinic system.     

Synthesis and characterization of new aluminium and gallium heteropoly complexes with chromium,iron, cobalt or coppercentred undecatungstate ligand

Summary Eight aluminium and gallium heteropoly undecatungstometalate complexes of general formula K_n[M(H₂O)-XW₁₁O₃₉]·nH₂O, where M=Al^III, Ga^III, and X=Cr^III, Fe^III, Co^II or Cu^II, have been prepared and characterized by elemental analysis, cation exchange i.r., u.v., x-ray powder diffraction and by thermal analyis. The compounds are stable in acidic solution. I.r., u.v. spectra and x-ray diffraction studies show that the structure of the compounds derives from the Keggin structure. Their thermostability is higher than that of the homologous dodecatungstometalates.     

Synthesis and crystal structure of KNa3[Fe3O(CH3COO)6(H2O)2]3 [α-P2W17Fe(H2O)O61]·32.5H2O

A complex of the composition KNa₃[Fe₃O(CH₃COO)₆(H₂O)₃]₃ [α-P₂W₁₇Fe(H₂O)O₆₁]·32.5H₂O (I) was obtained by interaction of FeCl₃·6H₂O and phosphotungstate K₁₀[α₂-P₂W₁₇O₆₁]·20H₂O in an acetate buffer with a yield of 52%. Compound I was characterized by single crystal X-ray phase analysis and IR spectroscopy. In the crystal structure, the Na and K cations bind [Fe₃O(CH₃COO)₆(H₂O)₃]⁺ trinuclear cations and [α-P₂W₁₇Fe(H₂O)O₆₁]⁷⁻ heteropolytungstate anions into infinite zigzag chains. Original Russian Text Copyright ? 2005 by N. V. Izarova, M. N. Sokolov, A. V. Virovets, H. G. Platas, and V. P. Fedin __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 1, pp. 149–155, January–February, 2005.     

One‐Pot Assembly of a New Mixed‐Valent Aggregate Based on Inorganic Polyoxometalate Ligands

Employing a “one‐pot” synthesis strategy, the reaction of Na₂WO₄·2H₂O, Na₂HAsO₄·7H₂O, FeCl₃·6H₂O, various Ln³⁺ ions, and hexamethylenetetramine (HMTA) in aqueous solutions with pH values ranging from 5.5 to 6.5 results in the isolation of polytungstoarsenate‐based iron aggregates, ‐K₈Na₁₄[HMTA]₄[(Fe^III₃Fe^II_0.25(OH)₃)(AsO₄)(AsW₉O₃₄)]₄·24H₂O ( 1 ) (HMTA = hexamethylenetetraamine). The polyoxoanion of 1 contains a mixed‐valent {Fe^III₁₂Fe^II(μ₃‐OH)₁₂(μ₄‐AsO₄)₄} cluster surrounded by four [B‐α‐AsW₉O₃₄]^9? units. It is the first polytungstatoarsenate‐based mixed‐valent {Fe^III₁₂Fe^II} aggregate and the largest iron cluster based on [AsW₉O₃₄]^9? ligands. The compound was characterized by elemental analyses, IR, UV/Vis absorption, and diffuse‐reflectance UV/Vis spectroscopy, TG analyses, XRPD, XPS and gel‐filtration chromatography. The electrochemical and electrocatalytical properties were also investigated. Crystal data for 1 , orthorhombic, Fddd, a = 28.156(6) Å, b = 36.003(7) Å, c = 42.126(8) Å, α = 90°, β = 90°, γ = 90°, Z = 8.     

A kinetic study on the iron(III)-promoted aquation of [Cr(C2O4)2(picolinato)]2− and [Cr(C2O4)2(2-pyridineacetato)]2− complexes

Two [Cr(C₂O₄)₂(AB)]^2– type complexes, obtained from the reaction of cis-[Cr(C₂O₄)₂(H₂O)₂]^– with the AB ligand, [AB = picolinic (pyac) or 2-pyridine-ethanoic acid (pyeac) anions], were converted into [Cr(C₂O₄)(pyac)(H₂O)₂]⁰ and [Cr(C₂O₄)(pyeac)(H₂O)₂]⁰ compounds, respectively via Fe^III-induced substitution of the oxalato ligand. The aquation products were separated chromatographically and their spectral characteristics and acid dissociation constants determined. The kinetics of the oxalato ligand substitution were studied with a 10–40 fold excess of Fe^III over [Cr^III] at [H⁺] = 0.2 M and at constant ionic strength 1.0 M (Na⁺, H⁺, Fe³⁺, ClO^– ₄). The reaction rate law is of the form: r = k _obs[Cr^III], where k _obs = kQ[Fe^III]/(1 + Q[Fe^III]). The first-order rate constants (k), preequilibria quotients (Q) and activation parameters derived from the k values have been determined. The reaction mechanism is discussed in terms of a Lewis acid catalyzed (induced) ligand substitution.     

Cyanide-bridged complexes based on dinuclear Cu(II)-M(II) [M = Pb and Cu] building blocks: Synthesis, crystal structures and magnetic properties

Four cyanide-bridged heterometallic complexes {[CuPb(L 1 )][Fe III (bpb)(CN) 2 ]} 2 ·(ClO 4 ) 2 ·2H 2 O·2CH 3 CN (1), {[CuPb(L 1 )] 2 [Fe II (CN) 6 ](H 2 O) 2 }·10H 2 O (2), {[Cu 2 (L 2 )][Fe III (bpb)(CN) 2 ] 2 }·2H 2 O·2CH 3 OH (3) and {[Cu 2 (L 2 )] 3 [Fe III (CN) 6 ] 2 (H 2 O) 2 }·10H 2 O (4) have been synthesized by treating K[Fe III (bpb)(CN) 2 ] [bpb 2-=1,2-bis(pyridine-2-carboxamido)benzenate] and K 3 [Fe III (CN)] 6 with dinuclear compartmental macrocyclic Schiff-base complexes [CuPb(L 1 )] (ClO 4 ) 2 or [Cu 2 (L 2 )]·(ClO 4 ) 2 , in which H 2 L 1 was derived from 2,6-diformyl-4-methyl-phenol, ethylenediamine, and diethylenetriamine in the molar ratio of 2:1:1 and H 2 L 2 from 2,6-diformyl-4-methyl-phenol and propylenediamine in the molar ratio of 1:1. Single crystal X-ray diffraction analysis reveals that compound 1 displays a cyclic hexanuclear heterotrimetallic molecular structure with alternating [FeⅢ (bpb)(CN) 2 ]- and [CuPb(L 1 )] 2+ units. Complex 2 is of a neutral dumb-bell-type pentanuclear molecular configuration consisting of one [Fe(CN)6] 4- anion sandwiched in two [CuPu(L 1 )] 2+ cations, and the pentanuclear moieties are further connected by the hydrogen bonding to give a 2D supramolecular framework. Heterobimetallic complex 3 is a tetranuclear molecule composed of a centrosymmetric [Cu 2 (L2)] 2+ segment and two terminal cyanide-containing blocks [FeⅢ (bpb)(CN)2 ]- . Octanuclear compound 4 is built from two [Fe(CN)6]3- anions sandwiched in the three [Cu 2 L 2 ] 2+ cations. Investigation of their magnetic properties reveals the overall antiferromagnetic behavior in the series of complexes except 2.     

NMR spectra and the structure of the guest sublattice in the monocationic forms of clinoptilolite and heulandite

The¹H NMR spectra of the hydrated monocationic forms of clinoptilolite M₆[Al₆Si₃₀O₇₂]·nH₂O (M=Li, Na, K, Cs, NH₄; n=12–22) and M ₃ ^′ [Al₆Si₃₀O₇₂]·nH₂O (M′=Mg, Ca, Sr, Ba; n=20–24) and heulandite M₈[Al₈Si₂₈O₇₂]·21H₂O (M=Na, K) are divided into three types differing in the symmetry of tensors of magnetic dipole-dipole interactions of protons in zeolite water molecules. On the basis of model calculations it is shown that water molecules in the Cs, K, and Ba forms of clinoptilolite and the K form of heulandite are ordered in structural positions. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Zeorex Ltd., Sofia. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 5, pp. 891–900, September–October, 1996. Translated by L. Smolina     

Synthesis, structure and magnetism of a S-shaped multi-iron substituted arsenotungstate containing a trivacant Keggin [B-α-AsW9O34] and a hexavacant Keggin [α-AsW6O26] fragments

A S-shaped multi-iron substituted arsenotungstate [enH₂]₂[(α-H₂As^VW₆O₂₆)Fe₃(H₂O)(B-α-H₄As^VW₉O₃₄)]₂[Fe]₂·8H₂O (1) (en=ethylenediamine) has been prepared by reaction of K₁₄[As₂^IIIW₁₉O₆₇(H₂O)]·nH₂O with Fe₂(SO₄)₃·xH₂O under hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, UV spectra, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. The skeleton of 1 consists of two asymmetric sandwich-type subunits [(α-H₂As^VW₆O₂₆)Fe₃(H₂O)(B-α-H₄As^VW₉O₃₄)]⁵⁻ linked by a di-Fe^III cluster. Moreover, magnetic susceptibility measurements demonstrate that 1 indicates the antiferromagnetic coupling interactions within Fe^III centers with the best-fitting set of parameters of J₁=−7.07 cm⁻¹, J₂=−0.45 cm⁻¹ and g=2.05, which are generated by the addition of the expressions of the molar susceptibilities of two tri-Fe^III clusters and one di-Fe^III cluster derived from for spin pairs coupled through the isotropic exchange interactions.     

Übergangsmetallkomplexe der Pyrazin-2,6-dicarbonsäure und der Pyridin-2,6-dicarbonsäure: Synthesen und Elektrochemie. Die Kristallstruktur von NH4[RuCl2(dipicH)2]

Transition Metal Complexes Containing the Ligands Pyrazine-2, 6-dicarboxylate and Pyridine-2, 6-dicarboxylate: Syntheses and Electrochemistry. Crystal Structure of NH₄[RuCl₂(dipicH)₂] The coordination chemistry of the tridentate ligand pyrazine-2, 6-dicarboxylate (pyraz-2,6 = L) with transition metals in aqueous solution has been investigated. The reaction of the ligand with metal aqua ions (1:1) affords insoluble precipitates [M^IIL(OH₂)₂] (M = Mn, Fe, Co, Ni, Cu, Zn, Cd). [TiOL(OH₂)₂], [VOL(H₂O)₂] and [UO₂L(H₂O)] were also prepared. [M^IIIL₂]^? complexes (M^III ? Fe^III, Co^III) were isolated as NH₄⁺ and P(C₆H₅)₄⁺ salts; they are strong one electron oxidants (E_1/2 = +0.602 V and +0.795 V vs. NHE, respectively). Redox potentials of analogous complexes containing pyridine- 2, 6-dicarboxylate (L′) ligands have been determined by cyclic voltammetry: [ML′₂]^1-/2?: M = V^III: -0.591 V; Cr^III: -0.712 V. It is shown that pymzine-2,6-dicarboxylate as compared to pyridine-2,6-dicarboxylate stabilizes metal complexes in low oxidation states (+II). The reaction of RuCl₃ · nH₂O with pyridine-2,6-dicarboxylic acid in aqueous solution affords the yellow-green anion [RuCl₂(L′H)₂]^?. The crystal structure of NH₄[RuCl₂(L′H)₂] has been determined. It crystallizes in the monoclinic space group P2₁/c with a = 8.812(2) Å b = 10.551(2) Å, c = 10.068(2) Å, β = 110.03(6)°, Z = 2; 2507 independent reflections; R = 0.032. The ruthenium centers are in an octahedral environment of two Cl^? ligands (trans) and two bidentate pyridine-2, 6-hydrogendicarboxylate ligands which possess each one protonated, uncoordinated carboxylic group.     

Potentiometric and spectroscopic studies of three new mixed inorganic–organic hybrid materials based on Preyssler and Wells–Dawson heteropolyoxometalates containing proline, leucine, and asparagine

Three new organic–inorganic hybrid materials based on two important heteropolyoxometalates namely Preyssler (=K_12.5H_1.5[Na(H₂O)P₅W₃₀O₁₁₀]·35H₂O) and Wells–Dawson (=K₆[P₂W₁₈O₆₂]·10H₂O) anions, namely, (Hpro)₉(Hleu)₃K₂[Na(H₂O)P₅W₃₀O₁₁₀]·25H₂O (1), (Hpro)₄(Hasp)[HP₂W₁₈O₆₂]·20H₂O (2), and (Hpro)₁₁K₃[Na(H₂O)P₅W₃₀O₁₁₀]·18H₂O (3) where pro, leu, and asp are proline, leucine, and asparagine, respectively, were prepared and identified by elemental analysis, infrared and proton nuclear magnetic resonance spectroscopies, and thermogravimetric analysis. The hybrid materials are made up of positively charged amino acids, [Na(H₂O)P₅W₃₀O₁₁₀]^14? and [P₂W₁₈O₆₂]^6? anions, and H₂O molecules of crystallization. These constituents’ fragments held together into a three-dimensional supermolecular network through non-covalent interactions. The protonation constants of the amino acids used, and Preyssler and Wells–Dawson species in all possible protonated forms, the equilibrium constants for binary systems of proline–asparagine and proline–leucine, and the stoichiometry and stability constants of the corresponding binary and ternary hybrids with Preyssler and Wells–Dawson heteropolyoxometalates in aqueous solution were investigated by potentiometric pH titration method. The stoichiometries of the most hybrid species in solution were compared with the corresponding hybrids in the solid phase, in detail.     

Die Kristallstruktur des gemischtvalenten Eisenfluoridhydrates Fe3F8 · 2 H2O

Crystal Structure of the Mixed-Valence Iron Fluorid Hydrate Fe₃F₈ · 2 H₂O Newly prepared was the red, monoclinic compound Fe₃F₈ · 2 H₂O, single crystals of which could be obtained under hydrothermal high pressure conditions (space group C2/m with a = 761.2(3), b = 750.0(1), c = 746.9(3) pm, β = 118.38(2)° and Z = 2). The X-ray structure determination (R_G = 0.0192 and 635 reflexions) yielded a framework structure, in which layers of octahedra 2[Fe^IIIF_6/2] are connected via corners of [Fe^IIF_4/2(H₂O)₂]-octahedra. The average distances in the nearly ideal octahedra are Fe^III? F = 193.0, Fe^II? F = 208.1 and Fe^II? OH₂ = 211.5 pm.