(Mg1–xCrx)2P2O7, CaCrP2O7, SrCrP2O7 und BaCrP2O7 – Neue Diphosphate des zweiwertigen Chroms

Contributions on Crystal Chemistry and Thermal Behaviour of Anhydrous Phosphates. XXXI. (Mg_1–xCr_x)₂P₂O₇, CaCrP₂O₇, SrCrP₂O₇ and BaCrP₂O₇ – New Diphosphates of Divalent Chromium In the quasi‐binary systems A₂P₂O₇/Cr₂P₂O₇ (A = Mg, Ca, Sr, Ba) the solid solution (Mg_1–xCr_x)₂P₂O₇ as well as the new compounds CaCrP₂O₇, SrCrP₂O₇, and BaCrP₂O₇ have been synthesized and characterized for the first time. In the whole experimental range (0.01 < x < 0.94; T = 950 °C) the solid solution (Mg_1–xCr_x)₂P₂O₇ is isotypic to the pure phases β‐Mg₂P₂O₇ and β‐Cr₂P₂O₇; but no phase transition (β → α) to a low‐temperature modification, as in Mg₂P₂O₇ and Cr₂P₂O₇, was found. CaCrP₂O₇ ( A ), SrCrP₂O₇ ( B ), and BaCrP₂O₇ ( C ), phases without detectable homogenity range in the other quasi‐binary systems are not structurally related to each other, but are isotypic to the corresponding compounds containing cobalt. [( A ): P‐1, Z = 2, a = 6.312(2) Å, b = 6.499(2) Å, c = 6.916(2) Å, α = 83.12(3)°, β = 88.37(3)°, γ = 67.72(3)°, 3235 independent reflections, R1 = 0.041, wR2 = 0.112; ( C ): P‐1, Z = 2, a = 5.382(8) Å, b = 7.271(8) Å, c = 7.589(4) Å, α = 103.33(7)°, β = 89.91(9)°, γ = 93.6(1)°, 1571 independent reflections, R1 = 0.085, wR2 = 0.31]. We have reported earlier details on SrCrP₂O₇. The coordination of Cr²⁺ by oxygen is distorted octahedral in ( A) , while in the structures of ( B) and ( C) square‐pyramidal environment is found. The results of UV/VIS‐spectroscopic and magnetic measurements as well as IR‐spectra of the diphosphates are reported.     

The triple pyrophosphate Cs3CaFe(P2O7)2

The complex phosphate tricaesium calcium iron bis(diphosphate), Cs₃CaFe(P₂O₇)₂, has been prepared by the flux method. Isolated [FeO₅] and [CaO₆] polyhedra are linked by two types of P₂O₇ groups into a three‐dimensional framework. The latter is penetrated by hexagonal channels along the a axis where three Cs atoms are located. Calculations of caesium Voronoi–Dirichlet polyhedra give coordination schemes for the three Cs atoms as [8 + 3], [9 + 1] and [9 + 4]. The structure includes features of both two‐ and three‐dimensional frameworks of caesium double pyrophosphates.     

Alkaline earth metal salts of 1‐naphthoic acid

The structures of the Mg, Ca, Sr and Ba salts of 1‐naphthoic acid are examined and compared with analogous structures of salts of benzoate derivatives. It is shown that catena‐poly[[[diaquabis(1‐naphthoato‐κO)magnesium(II)]‐μ‐aqua] dihydrate], {[Mg(C₁₁H₇O₂)₂(H₂O)₃]·2H₂O}_n, exists as a one‐dimensional coordination polymer that propagates only through Mg—OH₂—Mg interactions along the crystallographic b direction. In contrast with related benzoate salts, the naphthalene systems are large enough to prevent inorganic chain‐to‐chain interactions, and thus species with inorganic channels rather than layers are formed. The Ca, Sr and Ba salts all have metal centres that lie on a twofold axis (Z′ = ) and all have the common name catena‐poly[[diaquametal(II)]‐bis(μ‐1‐naphthoato)‐κ³O,O′:O;κ³O:O,O′], [M(C₁₁H₇O₂)₂(H₂O)₂]_n, where M = Ca, Sr or Ba. The Ca and Sr salts are essentially isostructural, and all three species form one‐dimensional coordination polymers through a carboxylate group that forms three M—O bonds. The polymeric chains propagate via c‐glide planes and through MOMO four‐membered rings. Again, inorganic channel structures are formed rather than layered structures, and the three structures are similar to those found for Ca and Sr salicylates and other substituted benzoates.     

A New Type of Anionic Framework in Microporous Potassium Iron(II) Phosphate K[Fe(PO4)]

A new iron(II) orthophosphate K[Fe(PO₄)] has been obtained by hydrothermal synthesis and its crystal structure was determined by single‐crystal X‐ray diffraction: space group P2₁/n, Z = 8, a = 9.6199(10), b = 8.6756(8), c = 10.8996(13) Å, β = 115.577(8)° at 193 K, R = 0.023. Fe^II shows coordination numbers (CN) 4 (distorted tetrahedral) and CN 5 (distorted trigonal bipyramidal). The [FeO₄] and [FeO₅] units form together with the [PO₄] tetrahedra a microporous 3D para‐framework with open channels along the a and b directions. The potassium ions positioned in the channels show CN 7 and 8. The structural relations within the morphotropic row of non‐isotypic K[M(PO₄)] structures (M = Zn, Ni, Mn, Fe) are discussed on the basis of common basic structural units.     

An investigation of polyhedral deformation in two mixed‐metal diarsenates: SrZnAs2O7 and BaCuAs2O7

Two isostructural diarsenates, SrZnAs₂O₇ (strontium zinc diarsenate), (I), and BaCuAs₂O₇ [barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction. The three‐dimensional open‐framework crystal structure consists of corner‐sharing M2O₅ (M2 = Zn or Cu) square pyramids and diarsenate (As₂O₇) groups. Each As₂O₇ group shares its five corners with five different M2O₅ square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine‐coordinated M1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of the M1O₉, M2O₅ and As₂O₇ groups of known isostructural diarsenates, adopting the general formula M1^IIM2^IIAs₂O₇ (M1^II = Sr, Ba, Pb; M2^II = Mg, Co, Cu, Zn) and crystallizing in the space group P2₁/n, are presented and discussed.     

Systematische Studie zu den Koordinationseigenschaften des Guanidin‐Liganden Bis(tetramethylguanidino)propan mit den Metallen Mangan,Cobalt, Nickel,Zink, Cadmium,Quecksilber und Silber

The transition metal complexes with the ligand 1,3‐bis(N,N,N′,N′‐tetramethylguanidino)propane (btmgp), [Mn(btmgp)Br₂] ( 1 ), [Co(btmgp)Cl₂] ( 2 ), [Ni(btmgp)I₂] ( 3 ), [Zn(btmgp)Cl₂] ( 4 ), [Zn(btmgp)(O₂CCH₃)₂] ( 5 ), [Cd(btmgp)Cl₂] ( 6 ), [Hg(btmgp)Cl₂] ( 7 ) and [Ag₂(btmgp)₂][ClO₄]₂·2MeCN ( 8 ), were prepared and characterised for the first time. The stoichiometric reaction of the corresponding water‐free metal salts with the ligand btmgp in dry MeCN or THF resulted in the straightforward formation of the mononuclear complexes 1 – 7 and the binuclear complex 8 . In complexes with M^II the metal ion shows a distorted tetrahedral coordination whereas in 8 , the coordination of the M^I ion is almost linear. The coordination behavior of btmgp and resulting structural parameters of the corresponding complexes were discussed in an comparative approach together with already described complexes of btmgp and the bisguanidine ligand N¹,N²‐bis(1,3‐dimethylimidazolidin‐2‐ylidene)‐ethane‐1,2‐diamine (DMEG₂e), respectively.     

A non‐twinned polymorph of CaTe2O5 from a hydrothermally grown crystal

In contrast with the multiple twinning and/or domain formation found in the mica‐like polymorphs of CaTe₂O₅, calcium pentaoxidoditellurate(IV), that have been prepared by solid‐state reactions and for which complete structure determinations have not been successful up to now, the crystal structure of a hydrothermally grown phase was fully determined from a non‐twinned crystal. The structure is made up of alternating layers of Ca²⁺ cations and of ²_∞[Te₂O₅]²⁻ anions stacked along [100]. The lone‐pair electrons E of the Te^IV atoms are stereochemically active and protrude into channels within the anionic layer. In comparison with analogous M^IITe₂O₅ structures (M = Mg, Mn, Ni or Cu) with ditellurate(IV) anions that are exclusively made up of corner‐sharing TeO_x (x = 3–5) polyhedra resulting in flat ²_∞[Te₂O₅]²⁻ layers, the anionic layers in CaTe₂O₅ are undulating and are built of corner‐ and edge‐sharing [TeO₄] polyhedra.     

La2Si2O7 im I—Typ: Gemäß La6[Si4O13][SiO4]2 kein echtes Lanthandisilicat

I‐Type La₂Si₂O₇: According to La₆[Si₄O₁₃][SiO₄]₂ not a Real Lanthanum Disilicate In attempts to synthesize lanthanum telluride silicate La₂Te[SiO₄] (from La, TeO₂, SiO₂ and CsCl, molar ratio: 1 : 1: 1 : 20, 950 °C, 7 d) or fluoride‐rich lanthanum fluoride silicates (from LaF₃, La₂O₃, SiO₂ and CsCl, molar ratio: 5 : 2 : 3 : 17, 700 °C, 7 d) in evacuated silica tubes, colourless lath‐shaped single crystals of hitherto unknown I‐type La₂Si₂O₇ (monoclinic, P2₁/c; a = 726.14(5), b = 2353.2(2), c = 1013.11(8) pm, β = 90.159(7)°) were found in the CsCl‐flux melts. Nevertheless, this new modification of lanthanum disilicate does not contain any discrete disilicate groups [Si₂O₇]^6‐ but formally three of them are dismutated into one catena‐tetrasilicate ([Si₄O₁₃]^10‐ unit of four vertex‐linked [SiO₄]^4‐ tetrahedra) and two ortho‐silicate anions (isolated [SiO₄]^4‐ tetrahedra) according to La₆[Si₄O₁₃][SiO₄]₂. This compound can be described as built up of alternating layers of these [SiO₄]^4‐ and the horseshoe‐shaped [Si₄O₁₃]^10‐ anions along [010]. Between and within the layers the high‐coordinated La ³⁺ cations (CN = 9 ‐ 11) are localized. The close structural relationship to the borosilicates M₃[BSiO₆][SiO₄](M = Ce ‐ Eu) is discussed and structural comparisons with other catena‐tetrasilicates are presented.     

Electronic properties of polyoxometalate derivatives [(C2B9H11) M'M5O18]n‐ (M' = TiIV,MoVI, WVI; M = MoVI,WVI): Protonation,Electronic Spectra,and Redox Properties

Density functional theory is used to study the electronic structures and properties of Lindqvist‐type polyoxometalates‐supported organometallic compounds [LM'M₅O₁₈]^n– (L = [C₂B₉H₁₁]^2– (Cb), [C₅H₅]^– (Cp); M' = Ti^IV, Mo^VI, W^VI; M = Mo^VI, W^VI). [(Cb)M'M₅O₁₈]^n– are a series of novel compounds designed in this work, based on related experiment. The calculated results reveal that the Cb ligand is able to form a σ, 2π triple bond with M', which is similar to the bond character in [(Cp)M'M₅O₁₈]^n–. However, comparing with the protonation, electronic spectra and redox properties of [(Cp)M'M₅O₁₈]^n– and [M'M₅O₁₉]^n–, [(Cb)M'M₅O₁₈]^n– species show the advantageous electronic properties owning to the superior electron donating ability of the Cb ligand. © 2015 Wiley Periodicals, Inc.     

Synthesis and Characterization of the New Copper Indium Phosphate Cu8In8P4O30

The system CuO/In₂O₃/P₂O₅ has been investigated using solid state reaction between CuO, In₂O₃ and (NH₄)₂HPO₄ in silica glass crucibles at 900 °C. The powder samples were characterized by X‐ray diffraction, thermal analysis and FT‐IR spectroscopy. Orange single crystals of the new quaternary phase were achieved by the process of crystallization with mineralizers in sealed silica glass ampoules. They were then analyzed with EDX and single‐crystal X‐ray analysis in which the composition Cu₈In₈P₄O₃₀ with the triclinic space group P$\bar{1}$ (No 2) with a = 7,2429(14) Å, b = 8,8002(18) Å, c = 10,069(2) Å, α = 103,62(3)°, β = 106,31(3)°, γ = 101,55(3)° and Z = 1 was found. The three‐dimensional framework consists of [InO₆] octahedra and distorted [CuO₆] octahedra, overcaped [InO₇] prisms and [PO₄] tetrahedra, also trigonal [(CuIn)O₅] bipyramids and distorted [(CuIn)O₆] octahedra, where copper and indium are partly exchanged against each other. Cu₈In₈P₄O₃₀ exhibits an incongruent melting point at 1023 °C.     

Quervernetzung lamellarer Schichten mit Hilfe von (O–H…O)‐Wasserstoffbrücken: Strukturen von M⊕⊖N(SO2C6H4‐4‐COOH)2 (M⊕ = K⊕, Rb⊕, Cs⊕)

Structures of Ionic Di(arenesulfonyl)amides. 4. Cross‐Linking Lamellar Layers by O–H…O Hydrogen Bonds: Structures of M^⊕⊖N(SO₂C₆H₄‐4‐COOH)₂ (M^⊕ = K^⊕, Rb^⊕, Cs^⊕) Syntheses and low‐temperature X‐ray crystal structures are reported for M^IN(SO₂C₆H₄‐4‐COOH)₂, where M = K (monoclinic, space group P2₁/c, Z = 4, Z′ = 1), M = Rb (monoclinic, P2₁, Z = 4, Z′ = 2), or M = Cs (monoclinic, P2₁/c, Z = 4, Z′ = 1). The three compounds are examples of layered inorgano‐organic solids where the inorganic component is comprised of metal cations and N(SO₂)₂ groups and the outer regions are formed by the 4‐carboxy substituted phenyl rings of the folded anions. In the two‐dimensional coordination networks, K^⊕ and Cs^⊕ adopt irregular and chemically distinct [MN₁O₇] octacoordinations, whereas the independent Rb^⊕ cations attain irregular nonacoordinations of type [RbN₂O₇] or [RbO₉] respectively. The crystal packings of the compounds are governed by self‐assembly of parallel layers through exhaustive hydrogen bonding between carboxylic acid groups, resulting in a dense array of cyclic (COOH)₂ motifs within the interlamellar regions.     

Hydrothermal Synthesis and Structural Characterization of a Novel Organic—Inorganic Hybrid Compound {[Cu（2,2′—bpy）2]2—Mo8O26}

A novel organic-inorganic hybrid compound {[Cu(2,2′-bpy)2]2Mo8O26} has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group, Pna21,with a=2.4164(5),b=1.8281(4),c=1.1877(2)nm,V=5.247(2)nm^3,Z=4,and final R1=0.0331,wR2=0.0727.The structure consists of discrete {[Cu(2,2′-bpy)2]2Mo8O26} clusters,constructed from a β-octamolybdate subunit[Mo8O26]^4- covalently bonded to two [Cu(2,2′-bpy)2]^2 coordination complex cations via bridging oxo groups.In addition,the spectroscopic properties and thernal behavior of this compound have been investigated by spectroscopic techniques (UV-vis,IR,Raman and EPR spectra) and TG analysis.     

Bis(pyridine‐2,6‐dimethanol‐N,O,O′)cobalt(II) and ‐copper(II) disacchar­inate dihydrate: three‐dimensional structures with extensive hydrogen bonds and aromatic π–π‐stacking interactions

Bis­(pyridine‐2,6‐di­methanol‐N,O,O′)­cobalt(II) disaccharinate dihydrate, [Co(C₇H₉NO₂)₂](C₇H₄NO₃S)₂·2H₂O, (I), and bis­(pyridine‐2,6‐di­methanol‐N,O,O′)copper(II) disaccharinate dihydrate, [Cu(C₇H₉NO₂)₂](C₇H₄NO₃S)₂·2H₂O, (II), collectively [M(dmpy)₂](sac)₂·2H₂O (where M is Co^II or Cu^II, sac is the saccharinate anion and dmpy is pyridine‐2,6‐di­methanol), are isostructural. The [M(dmpy)₂]²⁺ cations exhibit distorted octahedral geometry in which the two neutral dmpy species act as tripodal N,O,O′‐tridentate ligands. The crystal packing is determined by hydrogen bonding, as well as by weak pyridine–saccharinate π–π‐stacking interactions.     

Comparison between various Keggin and Wells–Dawson sandwich‐type polyoxometalates in catalytic oxidation of cyclooctene and cyclohexene with hydrogen peroxide

The catalytic performance of tetra‐n‐butylammonium salts of Keggin and Wells–Dawson sandwich‐type polyoxotungstates, [M₄(PW₉O₃₄)₂]^m? and [M₄(P₂W₁₅O₅₆)₂]^n? (M = Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺), in the oxidation of cyclooctene and cyclohexene with 30% hydrogen peroxide under various conditions was investigated. In comparison, Wells–Dawson sandwich‐type polyoxometalates were found to be less active than Keggin ones. In both of them, those containing Zn and Fe gave higher conversions for different oxidation conditions. These catalysts showed very good reusability in the oxidation reaction. Copyright © 2014 John Wiley & Sons, Ltd.     

Beiträge zur Kristallchemie und zum thermischen Verhalten von wasserfreien Phosphaten. XXXIII [1] In2P2O7, ein Indium(I)‐diphosphato‐indat(III) und In4(P2O7)3 — Darstellung,Kristallisation und Kristallstrukturen

Contributions on Crystal Chemistry and Thermal Behaviour of Anhydrous Phosphates. XXXIII [1] In₂P₂O₇ an Indium(I)‐diphosphatoindate(III), and In₄(P₂O₇)₃ — Synthesis, Crystallization, and Crystal Structure Solid state reactions via the gas phase lead to the new mixed‐valence indium(I, III)‐diphosphate In₂P₂O₇. Colourless single crystals of In₂P₂O₇ have been grown by isothermal heating of stoichiometric amounts of InPO₄ and InP (800 °C; 7d) using iodine as mineralizer. The structure of In₂P₂O₇ [P2₁/c, a = 7.550(1) Å, b = 10.412(1) Å, c = 8.461(2) Å, b = 105.82(1)°, 2813 independent reflections, 101 parameter, R1 = 0.031, wR2 = 0.078] is the first example for an In⁺ cation in pure oxygen coordination. Observed distances d(In^I‐O) are exceptionally long (d_min(In^I‐O) = 2.82 Å) and support assumption of mainly s‐character for the lone‐pair at the In⁺ ion. Single crystals of In₄(P₂O₇)₃ were grown by chemical vapour transport experiments in a temperature gradient (1000 → 900 °C) using P/I mixtures as transport agent. In contrast to the isostructural diphosphates M₄(P₂O₇)₃ (M = V, Cr, Fe) monoclinic instead of orthorhombic symmetry has been found for In₄(P₂O₇)₃ [P2₁/a, a = 13.248(3) Å, b = 9.758(1) Å, c = 13.442(2) Å, b = 108.94(1)°, 7221 independent reflexes, 281 parameter, R1 = 0.027, wR2 = 0.067].     

trans‐Bis(hinokitiolato)copper(II) trans‐bis(hinokitiolato)palladium(II) cocrystals with (5/1) and (3/2) formulations

trans‐Bis(3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)copper(II) trans‐bis(3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)palladium(II) as the (5/1) and (3/2) composites [Cu(C₁₀H₁₁O₂)₂]·0.2[Pd(C₁₀H₁₁O₂)₂] and [Cu(C₁₀H₁₁O₂)₂]·0.67[Pd(C₁₀H₁₁O₂)₂], respectively, where 3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olate is the systematic name for the hinokitiolate anion (hino), are the first mixed‐metal cocrystalline products isolated from the M_x(hino)_y family of complexes. These cocrystals contain square‐planar trans‐Cu(hino)₂ and trans‐Pd(hino)₂ molecules possessing crystallographic inversion symmetry. The bulk formulation for these cocrystalline compounds is Cu_1−xPd_x(hino)₂, where x is 0.166 (4) for the (5/1) product and 0.399 (4) for the (3/2) product. This bulk formulation is simply a convenient average expression of the whole‐molecule substitutional disorder present in these compounds. The M—O bonds are in the range 1.9210 (11)–1.9453 (10) Å, the O—M—O bite angles are in the range 82.94 (4)–83.36 (4)°, and all of the hinokitiolate O atoms are involved in C—H...O hydrogen‐bonding interactions.     

Beiträge zum Koordinationsverhalten von Oxidionen in anorganischen Feststoffen. III [1] Mn2P2O7, Mn2P4O12 und Mn2Si(P2O7)2 — Kristallzüchtung,Strukturverfeinerungen und Elektronenspektren von Mangan(II)‐Phosphaten

Contributions on the Bonding Behaviour of Oxygen in Inorganic Solids. III [1] Mn₂P₂O₇, Mn₂P₄O₁₂ und Mn₂Si(P₂O₇)₂ — Crystal Growth, Structure Refinements and Electronic Spectra of Manganese(II) Phosphates By chemical vapour transport reactions in a temperature gradient single crystals of Mn₂P₂O₇ (1050 → 950 °C) and Mn₂P₄O₁₂ (850 → 750 °C) have been obtained using P/I mixtures as transport agent. Mn₂Si(P₂O₇)₂ was crystallized by isothermal heating (850 °C, 8d; NH₄Cl as mineralizer) of Mn₂P₄O₁₂ und SiO₂. In Mn₂Si(P₂O₇)₂ [C 2/c, a = 17.072(1)Å, b = 5.0450(4)Å, c = 12.3880(9)Å, β = 103.55(9)°, 1052 independent reflections, 97 variables, R1 = 0.023, wR2 = 0.061] the Mn²⁺ ions show compressed octahedral coordination (d¯_Mn—O = 2.19Å). The mean distance d¯_Mn—O = 2.18Å was found for the radially distorted octahedra [MnO₆] in Mn₂P₄O₁₂ [C 2/c, Z = 4, a = 12.065(1)Å, b = 8.468(1)Å, c = 10.170(1)Å, β = 119.29(1)°, 2811 independent reflections, 85 variables, R1 = 0.025, wR2 = 0.072]. Powder reflectance spectra of the three pink coloured manganese(II) phosphates have been measured. The spectra show clearly the influence of the low‐symmetry ligand fields around Mn²⁺. Observed d—d electronic transition energies and the results of calculations within the framework of the angular overlap model (AOM) are in good agreement. Bonding parameters for the manganese‐oxygen interaction in [Mn²⁺O₆] chromophors as obtained from the AOM treatment (B, C, Trees correction α, e_σ, e_π) are discussed.     

Magnetic Investigations and 151Eu Mössbauer Spectroscopy of MYbSi4N7 with M = Sr,Ba, Eu

The isotypic nitridosilicates MYb[Si₄N₇] (M = Sr, Ba, Eu) were obtained by the reaction of the respective metals with Si(NH)₂ in a radiofrequency furnace below 1600 °C. On the basis of powder diffraction data of MYb[Si₄N₇] Rietveld refinements of the lattice constants were performed; these confirmed the previously published single‐crystal data. The compounds contain a condensed network of corner‐sharing [N(SiN₃)₄] units. The central nitrogen thus exhibits ammonium character. Magnetic susceptibility measurements of MYb[Si₄N₇] (M = Sr, Ba, Eu) show paramagnetic behavior with experimental magnetic moments of 3.03(2), (Sr), 2.73(2) (Ba), and 9.17(2) (Eu) μ_B per formula unit. In EuYbSi₄N₇ the europium and ytterbium atoms are in stable divalent and trivalent states, respectively. According to the non‐magnetic character of the alkaline earth cations, ytterbium has to be in an intermediate valence state Yb^III‐x in the strontium and barium compound. Consequently, either a partial exchange N^3—/O^2— resulting in compositions MYb^III‐x[Si₄N_7—xO_x] or an introduction of anion defects according to MYb^III‐x[Si₄N_7—x/3□_x/3] has to be assumed. The phase width 0 ≤ x ≤ 0.4 was estimated according to the magnetic measurements. ¹⁵¹Eu Mössbauer spectra of EuYb[Si₄N₇] at 78 K show a single signal at an isomer shift of δ = —12.83(3) mm s^—1 subject to quadrupole splitting of ΔE_Q = 5.7(8) mm s^—1, compatible with purely divalent europium.     

Synthesis and Characterization of Two New Transition‐Metal Complex Salts of the Wells‐Dawson Polyanion

Two new transition‐metal (TM) complex salts of the Wells‐Dawson polyanion: [Cu(2,2′‐bpy)₃]₂[Cu(2,2′‐bpy)₂]₂[P₂W₁₈O₆₂] ( 1 ) and [2,2′‐bpy]₈[Fe(2,2′‐bpy)₃]₈[P₂W₁₈O₆₂]₄·9H₂O ( 2 ) (2,2′‐bpy = 2,2′‐bipyridine), have been synthesized under hydrothermal conditions by using pre‐prepared α‐K₆P₂W₁₈O₆₂·15H₂O as a precursor. Crystal data for compound 1 : monoclinic, space group C2/c, a = 20.722(4) Å, b = 21.988(4) Å, c = 29.614(6) Å, β = 104.32(3)°, V = 13074(5) ų, Z = 4; for compound 2 : triclinic, space group , a = 15.804(3) Å, b = 27.519(6) Å, c = 27.566(6) Å, α = 72.71(3)°, β = 89.94(3)°, γ = 89.90(3)°, V = 11447(5) ų, Z = 1. Compounds 1 and 2 have been characterized by single‐crystal X‐ray diffraction, IR spectra, thermogravimetric analysis, XPS spectra and cyclic voltammetry. The two compounds were used as solid bulk modifiers to fabricate bulk‐modified carbon paste electrodes ( 1 ‐, 2 ‐CPE). The electrochemical behaviors of 1 ‐, 2 ‐CPE have been studied in detail. The redox behavior of the parent Wells‐Dawson type cluster was maintained completely in compounds 1 and 2 .     

Poly[nickel(II)‐di‐μ‐4,4′‐bipyridyl‐κ4N:N′‐μ‐dichromato‐κ2O:O′] and poly[copper(II)‐di‐μ‐4,4'‐bipyridyl‐κ4N:N′‐μ‐dichromato‐κ2O:O′]

The novel title hybrid isomorphous organic–inorganic mixed‐metal dichromates, [Ni(Cr₂O₇)(C₁₀H₈N₂)₂] and [Cu(Cr₂O₇)(C₁₀H₈N₂)₂], have been synthesized. A non‐centrosymmetric three‐dimensional (4,6)‐net is formed from a linear chain of vertex‐linked [Cr₂O]²⁻ and [MN₄O]²⁺ (M = Ni and Cu) units, which in turn are linked by the planar bidentate 4,4′‐­bipyridine ligand through the four remaining vertices of the [MN₄O]²⁺ octahedra. There are two such three‐dimensional nets that interpenetrate with inversion symmetry.