Rate of reactions between D2O and CaxAlyOz

The rate of the reaction between D₂O and the calcium aluminum oxides Ca₃Al₂O₆, Ca₅Al₆O₁₄, CaAl₂O₄, and CaAl₄O₇ was investigated by on-line neutron diffraction powder methods at temperatures from room temperature to 100°C. The rate of the reaction increases with increasing calcium content of the compounds and with increasing temperature for each of the compounds. The crystallographic stable hydrate Ca₃Al₂(OD)₁₂ is obtained from CaAl₄O₇ and CaAl₂O₄ at temperatures above 63°C, from Ca₅Al₆O₁₄ at temperatures above 49°C, and from Ca₃Al₂O₆ at temperatures as low as 7°C.     

Ca2MgWO6 from neutron and X‐ray powder data

The room‐temperature structure of the B‐site‐ordered complex perovskite dicalcium magnesium tungstate, Ca₂MgWO₆, has been determined by simultaneous Rietveld refinement of neutron and X‐ray powder diffraction patterns. Ca₂MgWO₆ is characterized by B‐site ordering and an a⁻a⁻c⁺‐type BO₆ octahedral tilt mechanism.     

Crystal Structures and Magnetic Properties of 6H-Perovskites Ba3MRu2O9 (M=Y, In, La, Sm, Eu, and Lu)

Magnetic properties of quaternary oxides Ba₃MRu₂O₉ (M=Y, In, La, Sm, Eu, and Lu) are reported. Rietveld analyses of the X-ray diffraction data indicate that they adopt the 6H-perovskite structure and have the valence state of Ba₃M³⁺ Ru^4.5+₂O₉. All compounds are nonmetallic at least over the temperature range of 100-400 K. The magnetic susceptibilities show a broad maximum at 135-370 K except for the La compound, which shows a plateau around 22 K. In addition, another magnetic anomaly is observed at 4.5-12.5 K by the magnetic susceptibility and specific heat measurements for any compound. It is considered that this magnetic behavior is ascribed to the antiferromagnetic coupling between two Ru ions in a Ru₂O₉ dimer and to the magnetic interaction between the Ru₂O₉ dimers.     

The crystal and magnetic structures of Ca2YRuO6 and the electronic properties of the series M2+2X3+Ru5+O6 (M = Ca,Sr, Ba; X = La,Y)

Profile analysis of constant-wavelength powder neutron diffraction data has been used to refine the crystal structure of the ordered perovskite Ca₂YRuO₆. The material is monoclinic (space group $\text{P2}{}_1\text{n}$) with a disordered arrangement of calcium and yttrium on the A site and one of the B sites, such that the formula is best written as Ca_1.43Y_0.57[(Ca_0.57Y_0.43)Ru]O₆. Low-temperature neutron diffraction experiments showed that the material is a Type I antiferromagnet at 2.5 K with an ordered magnetic moment of 1.2(1)μ_B per Ru⁵⁺. It is suggested that the dominant factor in determining the electronic properties of the series M²⁺₂X³⁺Ru⁵⁺O₆ (M = Ca, Sr, Ba; X = La, Y) is the Ru-Ru separation distance.     

Ein anionischer Oxohydroxo‐Komplex mit Bismut(III): Na6[Bi2O2(OH)6](OH)2 · 4H2O

An Anionic Oxohydroxo Complex with Bismuth(III): Na₆[Bi₂O₂(OH)₆](OH)₂ · 4H₂O Colourless, plate‐like, air sensitive crystals of Na₆[Bi₂O₂(OH)₆](OH)₂ · 4H₂O are obtained by reaction of Bi₂O₃ or Bi(NO₃)₃ · 5H₂O in conc. NaOH (58 wt %) at 200 °C followed by slow cooling to room temperature. The crystal structure (triclinic, P 1¯, a = 684.0(2), b = 759.8(2), c = 822.7(2) pm, α = 92.45(3)°, ß = 90.40(3)°, γ = 115.60(2)°, Z = 1, R1, wR2 (all data), 0, 042, 0, 076) contains dimeric, anionic complexes [Bi₂O₂(OH)₆]^4— with bismuth in an ψ¹‐octahedral coordination of two oxo‐ and three hydroxo‐ligands. The thermal decomposition was investigated by DSC/TG or DTA/TG and high temperature X‐ray powder diffraction measurements. In the final of three steps the decomposition product is Na₃BiO₃.     

The crystal structures and magnetic properties of Ba2LaRuO6 and Ca2LaRuO6

Profile analysis of high-resolution, powder neutron-diffraction data was used to refine the previously reported structures of the ordered, distorted perovskites Ba₂LaRuO₆ and Ca₂LaRuO₆. Low-temperature neutron diffraction experiments showed that, at 2K, the former is a Type IIIa antiferromagnet while the latter is Type I. Both compounds have an ordered magnetic moment of $\text{μ}{}_{\mathrm{<mtext>Ru</mtext>}}\text{? 1.95μ}{}_{\mathrm{<mtext>B</mtext>}}$ per Ru⁵⁺ ion. The Néel temperature of Ba₂LaRuO₆ was determined to be 29.5K, and the covalent mixing between the ruthenium and nearest-neighbor anions is described by A²_π = 8.2 ± 1% for Ba₂LaRuO₆ and 8.6 ± 1% for Ca₂LaRuO₆. The ionic radius of a Ru⁵⁺ ion is 0.56 Å. These data are consistently interpreted within the framework of a strongly correlated, half-filled π1 band. Extension of this interpretation to the magnetic data for the perovskites CaRuO₃ and SrRuO₃ leads to a fundamental theoretical prediction.     

Synthesis, crystal structure, and magnetic properties of new layered hexagonal perovskite Ba8Ta4Ru8/3Co2/3O24

A new hexagonal perovskite-type oxide Ba₈Ta₄Ru_8/3Co_2/3O₂₄ was synthesized by the solid-state method at 1573 K and characterized by electron diffraction (ED), time-of-flight (TOF) neutron powder diffraction, and magnetic susceptibility. Structure parameters of Ba₈Ta₄Ru_8/3Co_2/3O₂₄ were refined by the Rietveld method from the TOF neutron powder diffraction data on the basis of space group P6₃/mcm and lattice parameters a=10.0075(1) Å and c=18.9248(2) Å as obtained from the ED data (Z=3). The crystal structure of Ba₈Ta₄Ru_8/3Co_2/3O₂₄ consists of 8-layered (cchc)₂ close-packed stacking of BaO₃ layers along the c-axis. Corner-shared octahedra are filled by Ta only and face-shared octahedra are statistically occupied by Ru, Co, and vacancies. Similar compounds Ba₈Ta₄Ru_8/3M_2/3O₂₄ with M=Ni and Zn were also prepared. Magnetic susceptibility measurements showed no magnetic ordering down to 5 K.     

An X-ray and neutron powder diffraction study of the Ca2+xNd8−x(SiO4)6O2−0.5x system

The variation in lattice parameters with bulk composition and preparation temperature has been determined from X-ray powder diffraction data for the system Ca_2+xNd_8?x(SiO₄)₆O_2?0.5x. The structures of two members of this system have been further refined from time-of-flight neutron powder diffraction data using the Rietveld method. Both structures belong to the $\text{P6}{}_3\text{m}$ space group and are isomorphous with natural apatite, Ca₁₀(PO₄)₆(F, OH)₂. Samples prepared at 1250°C exhibit an ordered distribution of Ca and Nd cations between two nonequivalent sites. The room temperature lattice parameters of Ca₂Nd₈(SiO₄)₆O₂ are a = 9.5291(5)Å and c = 7.0222(1) Å, while those of Ca_2.2Nd_7.8(SiO₄)₆O_1.9 are a = 9.5303(4) Å and c = 7.0147(1) Å. The composition of the latter member is believed to represent the upper limit of solid solution for this system at 1250°C.     

Über Neue Oxoruthenate vom Typ der 6 L-Perowskite: Ba3SrRu2−xTaxO9 (x = 0,8 und 1,4) mit einem Beitrag über Ba3CaRu2O9

On Novel Oxoruthenates of the 6 L-Perovskite Type: Ba₃SrRu_2?xTa_xO₉ (x = 0.8 and 1.4) with a Comment on Ba₃CaRu₂O₉ Single crystals of the phases Ba₃SrRu_2?xTa_xO₉ [(I): x = 0.8 and (II): x = 1.4] and the compound (III): Ba₃CaRu₂O₉ were prepared by a BaCl₂ flux and investigated by X-ray methods. (I)–(III) crystallizes with hexagonal symmetry space group P6 2c with lattice constants: (I) a = 6.003 Å; c = 15.227 Å; (II) a = 5.988 Å; c = 15.220 Å and (III) a = 5.891 Å; c = 14.571 Å. The crystal structures of these substances corresponds to the 6 layer perovskites with the stacking sequence (hcc)₂. All of them show a so far not described slightly distorted oxygen framework caused by the Sr²⁺ and Ca²⁺ ions.     

The crystal and magnetic structures of Ca2NdRuO6, Ca2HoRuO6, and Sr2ErRuO6

The crystal structure of Sr₂ErRuO₆ has been refined from neutron powder diffraction data collected at room temperature; space group P2₁/n, A = 5.7626(2), B = 5.7681(2), C = 8.1489(2) Å, β = 90.19(1)°. The structure is that of a distorted perovskite with a 1:1 ordered arrangement of Ru⁵⁺ and Er³⁺ over the 6-coordinate sites. Data collected at 4.2 K show the presence of long range antiferromagnetic order involving both Ru⁵⁺ and Er³⁺. The temperature dependence of the sublattice magnetizations is described. The crystal structure of Ca₂NdRuO₆ is also that of a distored perovskite (P2₁/n, A = 5.5564(1), B = 5.8296(1), C = 8.0085(1) β = 90.19(1)°. The β = 90.07(1)°) with a random distribution of Ca²⁺ and Nd³⁺ on the A site and a 1:1 ordered arrangement of Ca²⁺ and Ru⁵⁺ on the 6-coordinate B sites. The Ru⁵⁺ sublattice is antiferromagnetic at 4.2 K but there is no evidence for magnetic ordering of the Nd³⁺ ions. Ca₂HoRuO₆ is also a distorted perovskite (P2₁/n, A = 5.4991(1), B = 5.7725(1), C = 7.9381(2), β = 90.18(1)° at 4.2 K) with a cation distribution best represented as Ca_1.46Ho_0.54[Ca_0.54Ho_0.46Ru]O₆. There is no ordering among the Ca³⁺ or Ho³⁺ ions on either the A or the B sites, but the Ca/Ho ions form a 1:1 ordered arrangement with Ru⁵⁺ on the B sites. At 4.2 K the Ru⁵⁺ ions adopt a Type I antiferromagnetic arrangement but there is no evidence of long range magnetic ordering among the Ho³⁺ ions.     

Synthesis,Characterization, and Crystal Structures of Diruthenium Complexes Containing Bridging Salicylato Ligands

The thermal reaction of Ru₃(CO)₁₂ ( 1 ) with salicylic acid, in the presence of triphenylphosphine, pyridine, or dimethylsulfoxide, afforded the dinuclear complexes Ru₂(CO)₄(μ‐O₂CC₆H₄OH)₂L₂ ( 2 ) [L = PPh₃ ( 2a ). C₅H₅N ( 2b ); (CH₃)₂SO ( 2c )]. Complex 2b was further reacted with the aromatic dimmines 2,2′‐dipyridine or 1,10‐phenanthroline to give the cationic diruthenium complexes [Ru₂(CO)₂(μ‐CO)₂(μ‐O₂CC₆H₄OH)(N∩N)₂]⁺ ( 3 ) [(N∩N) = 2,2′‐dipyridine ( 3a ); 1,10‐phenanthroline ( 3b )], which were isolated as their tetraphenylborate salts. All five novel complexes were characterized spectroscopically and analytically. For 2a – 2b and 3a – 3b , single‐crystal X‐ray diffraction studies were also carried out.     

Mapping the Transformation [{RuII(CO)3Cl2}2]→[RuI2(CO)4]2+: Implications in Binuclear Water–Gas Shift Chemistry

The complete sequence of reactions in the base‐promoted reduction of [{Ru^II(CO)₃Cl₂}₂] to [Ru^I₂(CO)₄]²⁺ has been unraveled. Several μ‐OH, μ:κ²‐CO₂H‐bridged diruthenium(II) complexes have been synthesized; they are the direct results of the nucleophilic activation of metal‐coordinated carbonyls by hydroxides. The isolated compounds are [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)₂(μ‐OH)(NP^F‐Am)₂][PF₆] ( 1 ; NP^F‐Am=2‐amino‐5,7‐trifluoromethyl‐1,8‐naphthyridine) and [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)(μ‐OH)(NP‐Me₂)₂][BF₄]₂ ( 2 ), secured by the applications of naphthyridine derivatives. In the absence of any capping ligand, a tetranuclear complex [Ru₄(CO)₈(H₂O)₂(μ³‐OH)₂(μ:κ²‐C,O‐CO₂H)₄][CF₃SO₃]₂ ( 3 ) is isolated. The bridging hydroxido ligand in 1 is readily replaced by a π‐donor chlorido ligand, which results in [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)₂(μ‐Cl)(NP‐PhOMe)₂][BF₄] ( 4 ). The production of [Ru₂(CO)₄]²⁺ has been attributed to the thermally induced decarboxylation of a bis(hydroxycarbonyl)–diruthenium(II) complex to a dihydrido–diruthenium(II) species, followed by dinuclear reductive elimination of molecular hydrogen with the concomitant formation of the Ru^I? Ru^I single bond. This work was originally instituted to find a reliable synthetic protocol for the [Ru₂(CO)₄(CH₃CN)₆]²⁺ precursor. It is herein prescribed that at least four equivalents of base, complete removal of chlorido ligands by Tl^I salts, and heating at reflux in acetonitrile for a period of four hours are the conditions for the optimal conversion. Premature quenching of the reaction resulted in the isolation of a trinuclear Ru^I₂Ru^II complex [{Ru(NP‐Am)₂(CO)}{Ru₂(NP‐Am)₂(CO)₂(μ‐CO)₂}(μ₃:κ³‐C,O,O′‐CO₂)][BF₄]₂ ( 6 ). These unprecedented diruthenium compounds are the dinuclear congeners of the water–gas shift (WGS) intermediates. The possibility of a dinuclear pathway eliminates the inherent contradiction of pH demands in the WGS catalytic cycle in an alkaline medium. A cooperative binuclear elimination could be a viable route for hydrogen production in WGS chemistry.     

Lanthanide distribution in some doped alkaline earth aluminates and gallates

High-resolution neutron and synchrotron X-ray powder diffraction studies are reported for the six oxides AB₂O₄ (A=Ca²⁺, Sr²⁺ and Ba²⁺ and B=Al³⁺ and Ga³⁺). These oxides all adopt a stuffed tridymite type structure, the precise nature of which depends on both the A- and B-type cations. Bond valence calculations reveal a range of values for the various A-type cations, in all cases at least one site is significantly underbonded. Conversely the tetrahedral B-type sites invariably exhibit unexceptional bond valencies. Attempts to dope the oxides with various lanthanides to the 1% level invariably resulted in some segregation into alternate phases located at the grain boundaries. The identity of the impurity phases is presented and the importance of bond valencies in understanding this segregation is highlighted.     

Magnetic properties of quadruple perovskites Ba4LnRu3O12 (Ln=La, Nd, Sm-Gd, Dy-Lu)

Quadruple perovskites Ba₄LnRu₃O₁₂ (Ln=La, Nd, Sm-Gd, Dy-Lu) were prepared and their magnetic properties were investigated. They adopt the 12L-perovskite-type structure consisting of Ru₃O₁₂ trimers and LnO₆ octahedra. All of these compounds show an antiferromagnetic transition at 2.5-30 K. For Ba₄NdRu₃O₁₂, ferrimagnetic ordering has been observed at 11.5 K. The observed magnetic transition is due to the magnetic behavior of the Ru^4.33+₃O₁₂ trimer with S=. Magnetic properties of Ba₄LnRu₃O₁₂ were compared with those of triple perovskites Ba₃LnRu₂O₉ and double perovskites Ba₂LnRuO₆.     

An investigation of the low oxidation state chemistry of rhenium in the BaOReRe2O7 phase diagram

The first systematic survey of the BaOReRe₂O₇ phase diagram is reported, with emphasis on the reduced ternary oxides. At 800°C, the previously reported compounds Ba₃Re₂O₉, Ba₂ReO₅, and Ba₃ReO₆ were observed, all of which contain Re(VI) in ReO₆ octahedra. The stability of these phases is apparently due to ReO π-bonding in and between the octahedra. The previously unknown structure of Ba₂ReO₅ was determined by powder neutron diffraction and found to be isotypic with that of K₂VO₂F₃ (space group Pnma), with a = 7.3233(2), b = 5.7745(1), and c = 11.4124(2), Å. ReO₆ octahedra share adjacent corners to produce cis chains which are held together by 10 coordinated Ba atoms.     

Hydrogen Storage and Selective,Reversible O2 Adsorption in a Metal–Organic Framework with Open Chromium(II) Sites

A chromium(II)‐based metal–organic framework Cr₃[(Cr₄Cl)₃(BTT)₈]₂ (Cr‐BTT; BTT³⁻=1,3,5‐benzenetristetrazolate), featuring coordinatively unsaturated, redox‐active Cr²⁺ cation sites, was synthesized and investigated for potential applications in H₂ storage and O₂ production. Low‐pressure H₂ adsorption and neutron powder diffraction experiments reveal moderately strong Cr–H₂ interactions, in line with results from previously reported M‐BTT frameworks. Notably, gas adsorption measurements also reveal excellent O₂/N₂ selectivity with substantial O₂ reversibility at room temperature, based on selective electron transfer to form Cr^III superoxide moieties. Infrared spectroscopy and powder neutron diffraction experiments were used to confirm this mechanism of selective O₂ binding.     

Hydrogen Storage and Selective,Reversible O2 Adsorption in a Metal–Organic Framework with Open Chromium(II) Sites

A chromium(II)‐based metal–organic framework Cr₃[(Cr₄Cl)₃(BTT)₈]₂ (Cr‐BTT; BTT^3?=1,3,5‐benzenetristetrazolate), featuring coordinatively unsaturated, redox‐active Cr²⁺ cation sites, was synthesized and investigated for potential applications in H₂ storage and O₂ production. Low‐pressure H₂ adsorption and neutron powder diffraction experiments reveal moderately strong Cr–H₂ interactions, in line with results from previously reported M‐BTT frameworks. Notably, gas adsorption measurements also reveal excellent O₂/N₂ selectivity with substantial O₂ reversibility at room temperature, based on selective electron transfer to form Cr^III superoxide moieties. Infrared spectroscopy and powder neutron diffraction experiments were used to confirm this mechanism of selective O₂ binding.     

Al14Ba8La26.3Ru18Sr53.7O167: a variant of cubic perovskite with isolated RuO6 units

The crystal structure of the title aluminium barium lanthanum ruthenium strontium oxide has been solved and refined using neutron powder diffraction to establish the parameters of the oxygen sublattice and then single‐crystal X‐ray diffraction data for the final refinement. The structure is a cubic modification of the perovskite ABO₃ structure type. The refined composition is Ba_0.167La_0.548Sr_1.118Ru_0.377Al_0.290O_3.480, and with respect to the basic perovskite structure type it might be written as (Ba₈La_13.68Sr_34.32)(Al_13.92La_12.64Ru_18.08Sr_19.36)O_192−x, with x = 24.96. The metal atoms lie on special positions. The A‐type sites are occupied by Ba, La and Sr. The Ba atoms are located in a regular cuboctahedral environment, whereas the La and Sr atoms share the same positions with an irregular coordination of O atoms. The B‐type sites are divided between two different Wyckoff positions occupied by Ru/Al and La/Sr. Only Al and Ru occupy sites close to the ideal perovskite positions, while La and Sr move away from these positions toward the (111) planes with high Al content. The structure contains isolated RuO₆ octahedra, which form tetrahedral substructural units.     

Synthese und Struktur der basischen Erdalkalinitrate Sr2(OH)3NO3 und Ba2(OH)3NO3

Synthesis and Structure of the Basic Alkaline Earth Nitrates Sr₂(OH)₃NO₃ and Ba₂(OH)₃NO₃ Sr₂(OH)₃NO₃ and Ba₂(OH)₃NO₃ were synthesized from mixtures of freshly prepared strontium or barium hydroxides and their corresponding nitrates in evacuated quartz glass ampoules at 420 °C and 360 °C, respectively. Single crystals of Sr₂(OH)₃NO₃ were obtained in a solidified Sr(NO₃)₂ melt after subsequent heating and cooling cycles in air up to 600 °C. The crystal structure of the strontium compound was refined from single crystal and powder X‐ray data. Sr₂(OH)₃NO₃ crystallizes hexagonally in the space group (No. 189) with Z = 1 and the lattice parameters a = 6.624(2) Å and c = 3.560(1) Å (single crystal data). The powder pattern of Ba₂(OH)₃NO₃ was indexed isotypically to Sr₂(OH)₃NO₃ with the lattice parameters a = 6.9260(1) Å and c = 3.8086(1) Å, and the crystal structure was refined from powder X‐ray data. Alkaline earth ions in the structures are surrounded trigonal‐prismatically by six hydroxide ions. These prisms are sharing their trigonal faces along [001] building up columns. These columns are connected in the ab‐plane by shared edges, and form hexagonal tunnels with the nitrate groups stacked inside. Infrared and thermoanalytical data of Sr₂(OH)₃NO₃ are presented.