LiNa2AlF6: a powder structure solution

Lithium sodium aluminium fluoride was obtained as a white powder by melting a stoichiometric mixture of AlF₃, NaF and LiF at 1223 K, and then cooling to 923 K and sintering at this temperature for 4 h. The ab initio crystal structure determination was carried out using X‐ray powder diffraction techniques. The monoclinic structure of LiNa₂AlF₆ can be related to cubic elpasolite. The Li and Al atoms lie on inversion centres. The main octahedral AlF₆ structural elements are not deformed, but are rotated slightly with respect to the unit‐cell axes. The Li atoms have octahedral coordinations, whereas the Na atoms have cubo‐octahedral coordinations. The Na coordination polyhedron is distorted in comparison with that of elpasolite.     

Structural characterization of glassy phases in the system Na2O-Ga2O3-P2O5 by MAS and solution NMR and vibrational spectroscopy: II. Structure of the phosphate network

The structure of the phosphate network of glasses in the system Na2O-Ga2O3-P2O5 has been investigated as a function of the Na/Ga molar ratio and the phosphate composition corresponding to a mono, di, tri, tetra and meta phosphate stoichiometry. The glass is made of phosphate molecular groups of different lengths linked by the cations with rather ionic (Na) or more covalent (Ga) bonds except in the case of the orthophosphate composition for which we only found isolated PO4(3-) ions. The vibrational spectra are sensitive to composition variations but the band width and the couplings between the different groups prevent any quantitative determination. 31P MAS-NMR gives an in-situ information on the P environment in the glass but the signals are often large and ill defined so that the assignment is not at all straightforward. On the other hand, 31P solution NMR gives sharper signals, allowing more quantitative determinations but the dissolution process always introduces some indeterminacy on the real glass structure which can be minimized by a careful preparation of the solution.     

Mixed alkali effect and optical properties of Ni2+ doped 20ZnO+xLi2O+(30-x)Na2O+50B2O3 glasses

Optical and physical properties of Ni2+ doped 20ZnO+xLi2O+(30-x)Na2O+50B2O3 (5≤x≤25) glasses are carried out at room temperature. Powder XRD pattern of all the glass samples confirms the amorphous nature. Several physical parameters are evaluated for all the glasses with respect to the composition. The optical absorption spectra confirm the site symmetry of the Ni2+ doped glasses are near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. It is interesting to observe that the optical band gap and Urbach energies exhibit the mixed alkali effect. The FT-IR spectral investigations of Ni2+ doped glasses exhibit characteristic vibrations of BO3 and BO4 units.     

Oxygen sites and network coordination in sodium germanate glasses and crystals: high-resolution oxygen-17 and sodium-23 NMR

Sodium germanate glasses are well-studied materials in which, unlike silicates but analogous to borates, the major structural consequence of alkali addition is generally thought to involve a coordination number increase of the network-forming Ge cations. However, the nature of this change, in particular quantifying fractions of nonbridging oxygens and of five- and/or six-coordinated Ge, has remained unresolved. We present here high-resolution 17O results, including triple-quantum MAS NMR (3QMAS), on a series of crystalline model compounds that allow the definition of ranges of chemical shifts corresponding to oxygens bonded to various coordinations of Ge. These include quartz- and rutile-structured GeO2, Na4Ge9O20, Na2Ge4O9, and Na2GeO3 (germanium dioxide, sodium enneagermanate, sodium tetragermanate, and sodium metagermanate). 3QMAS spectra of Na-germanate glasses ranging from 0% to 27% Na2O clearly show the development of partially resolved peaks as alkali is added, corresponding to signals from nonbridging oxygens (in the highest Na glasses) and to oxygen bridging between one four-coordinated and one higher coordinated Ge. As in conventional models of this system, nonbridging oxygen contents are much lower than in corresponding silicates. Although we do not directly distinguish between five- and six-coordinated Ge, modeling of bridging oxygen populations and comparison with measured speciation suggest that substantial proportions of both species are likely to be present. High-field 23Na MAS NMR shows systematic decreases in mean Na-O bond distance and/or coordination number with increasing alkali content that can be compared with published results for high-temperature liquids. These results, as well as comparison of molar volumes of glasses and high-temperature liquids, suggest the possibility of significant temperature effects on liquid structure.     

Rb(GaPO4)2(OH)(H2O)·H2O: a hydrated rubidium gallium phosphate analogue of GaPO4·2H2O and leucophosphite

Crystals of the title hydrated rubidium gallium phosphate, rubidium aqua‐μ₃‐hydroxo‐di‐μ‐phosphato‐digallium hydrate, were synthesized hydro­thermally at 453 K under autogenous pressure. The solid crystallizes in the monoclinic system and its structure was determined from single‐crystal X‐ray diffraction analysis. It is similar to dihydrated gallium phosphate, GaPO₄·2H₂O, which is isostructural with the mineral leucophosphite. The structure is built up from a three‐dimensional anionic framework composed of corner‐linked octameric Ga₄(PO₄)₄(OH)₂(H₂O)₂ units. The Ga atom is in an octahedral coordination. Connection of the Ga₄P₄ species generates eight‐ring channels, in which are encapsulated the Rb⁺ cations and water mol­ecules.     

17O solid-state NMR and first-principles calculations of sodium trimetaphosphate (Na3P3O9), tripolyphosphate (Na5P3O10), and pyrophosphate (Na4P2O7)

The assignment of high-field (18.8 T) (17)O MAS and 3QMAS spectra has been completed by use of first-principles calculations for three crystalline sodium phosphates, Na 3P 3O 9, Na 5P 3O 10, and Na 4P 2O 7. In Na 3P 3O 9, the calculated parameters, quadrupolar constant ( C Q), quadrupolar asymmetry (eta Q), and the isotropic chemical shift (delta cs) correspond to those deduced experimentally, and the calculation is mandatory to achieve a complete assignment. For the sodium tripolyphosphate Na 5P 3O 10, the situation is more complex because of the free rotation of the end-chain phosphate groups. The assignment obtained with ab initio calculations can however be confirmed by the (17)O{ (31)P} MAS-J-HMQC spectrum. Na 4P 2O 7 (17)O MAS and 3QMAS spectra show a complex pattern in agreement with the computed NMR parameters, which indicate that all of the oxygens exhibit very similar values. These results are related to structural data to better understand the influence of the oxygen environment on the NMR parameters. The findings are used to interpret those results observed on a binary sodium phosphate glass.     

NaZn(H2O)2[BP2O8].H2O: a novel open-framework borophosphate and its reversible dehydration to microporous sodium zincoborophosphate N

Crystals of NaZn(H2O)2[BP2O8].H2O were grown under mild hydrothermal conditions at 170 degrees C. The crystal structure (solved by X-ray single-crystal methods: hexagonal, P6(1)22 (no. 178), a = 946.2(2), c= 1583.5(1) pm, V= 1227.8(4).10(6) pm3, Z = 6) exhibits a chiral octahedral-tetrahedral framework related to the CZP topology and contains helical ribbons of corner-linked borate and phosphate tetrahedra. Investigation of the thermal behavior up to 180 degrees C shows a (reversible) dehydration process; this leads to the microporous compound Na[ZnBP2O8].H2O, which has the CZP topology. The crystal structure of Na[ZnBP2O8].H2O was determined by X-ray powder diffraction by using a combination of simulated annealing, lattice-energy minimization, and Rietveld refinement procedures (hexagonal, P6(1)22 (no. 178), a = 954.04(2), c = 1477.80(3) pm, V= 164.88(5).10(6) pm3, Z = 6). The essential structural difference caused by the dehydration concerns the coordination of Zn2- changing from octahedral to tetrahedral arrangement.     

Isolation of two-dimensional 2:1 cation-ordered perovskite units by anion vacancy ordering in Ba6Na2Nb2P2O17

A new six-layer perovskite-related structure Ba 6Na 2Nb 2M 2O 17 (M = P, V), which consists of cubic (c) BaO 3 layers and oxygen-deficient pseudocubic (c') BaO 2 layers stacked in the sequence c'ccccc, is presented. In Ba 6Na 2Nb 2M 2O 17, two-dimensional slabs of the well-known 2:1 octahedral cation-ordered perovskite motif are isolated between layers of tetrahedral units formed by anion vacancy ordering: two consecutive NbO 6 octahedral layers are sandwiched by two single NaO 6 octahedral layers, which, in turn, connect with two isolated MO 4 tetrahedral layers. Both oxides are derived from the 2:1 ordered perovskite structure (e.g., Ba 3ZnTa 2O 9) by ordered removal of O atoms in every sixth BaO 3 layer. Both materials exhibit a relative permittivity of approximately 20-23, Q x f 0 values of approximately 7800-10600 GHz, and negative temperature coefficients of the resonant frequency of approximately -23 to -7 ppm/ degrees C.     

CRYSTAL STRUCTURE OF (NH_4)_(11)[Na(H_2O)_2P_4W_(14)O_(58)] ·12H_2O

<正> (NH4)11[Na(H2O)2P4W14O58)·12H2O, Mr = 4099. 39, triclinic, space group P1, a = 14. 376(2), b = 19.861(9), c=13. 010(3)(?) , α=104. 68(2), β=91. 37(1), γ= 104. 05(2)°, V = 3471. 1 (?)3, Z = 2, Dc=3. 922g/cm3, μ (MoKα) = 238. 274cm-1, F(000) = 3664, R = 0.0510, Rw = 0. 0665 for 9260 observed reflections with I> 3σ(I). The polyanion [Na(H2O)2P4W14O58]11- consists of two PW7O29 subunits anisostructurally, two linkage phosphorous atoms and one sodium ion with two water ligands as well. The geometries of tungsten atoms within these two subunits are almost the same as those in K12P4W14O58· 21H2O[2]. The four phosphorous atoms are in PO4 coordinations. The sodium ion locates nearly at the center of the polyanion, and is coordinated by two water molecules, five oxygen atoms of the anion and one phosphorous atom with Na-P = 3. 053(3) (?). Due to the presence of the sodium atom, the interactions between oxygen and tungsten atoms in the polyanion are somewhat weakened.     

Local structure of magnesium in silicate glasses: a 25Mg 3QMAS NMR study

We have reported the 25Mg triple-quantum magic-angle spinning (3QMAS) NMR spectra of silicate glasses. The two-dimensional spectra suggest that the magnesium ions in MgSiO3, CaMgSi2O6, Ca2MgSi2O7, Mg3Al2Si3O12, and Li2MgSi2O6 glasses are mainly in octahedral environments, although in Na2MgSi2O6, K2MgSi2O6, and K2MgSi5O12 glasses they form tetrahedral species. We discussed the coordination environments of Mg based on the field strength of competing Mg2+, Ca2+, Na+, K+, and Li+ cations, and convincingly demonstrated that there is a correlation between them. These results indicate that the two-dimensional NMR spectroscopy such as MQMAS technique is a very useful method to analyze the local environments of nonframework cations in noncrystalline solids.     

Short- and medium-range order in sodium aluminophosphate glasses: new insights from high-resolution dipolar solid-state NMR spectroscopy

The structures of sodium aluminophosphate glasses prepared by both sol-gel as well as melt-cooling routes have been extensively characterized by high-resolution solid-state 23Na, 27Al, and 31P single and double-resonance NMR techniques, including quantitative connectivity studies by 27Al <--> 31P and 23Na <--> 31P rotational echo double-resonance (REDOR) methods. Studies along four compositional lines, I: (AlPO4)x -(NaPO3)1-x, II: (Na2O)x -(AlPO4)1-x, III: (NaAlO2)x -(NaPO3)1-x, and IV: (Al2O3)x (NaPO3)1-x, reveal that the network structures of those glasses that are accessible by either preparation method are essentially identical. However, the significantly extended glass-forming ranges available by the sol-gel route facilitate exploration of the structure/composition relationships in more detail, revealing a number of interesting universal features throughout the whole glass system. Both short- and medium-range order appear to be controlled strongly by the O/P ratio of the glasses studied: Up to an O/P ratio of 3.5 (pyrophosphate composition), aluminum is predominantly six-coordinated and fully connected to phosphorus (Al(OP)6 sites). In the region 3.5 < or = O/P < or = 4.0, a dramatic structural transformation takes place, leading to the appearance of additional four- and five-coordinated aluminum species whose second coordination spheres are also entirely dominated by phosphorus. The structure of glasses with an O/P ratio of precisely 4.0 (orthophosphate) is dominated by Al(OP)4 units. As the O/P ratio increases beyond 4.0, the average extent of Al-O-P connectivity is decreased significantly. Here, new types of five- and six-coordinated aluminum units, which are only weakly connected to phosphorus, are formed, while the network modifier is attracted mainly by the phosphate units.     

Variable temperature 1H, 23Na,and 29Si MAS NMR studies on sodium silicate hydrates of composition Na2O · SiO2 · nH2O (n = 9, 6, 5): Local structure in crystals,melts, supercooled melts,and glasses

The local structure in crystals, melts, supercooled melts, and glasses of sodium silicate hydrates of composition Na₂O · SiO₂ · nH₂O (n = 9, 6, 5) is studied by variable temperature ¹H, ²³Na, and ²⁹Si MAS NMR spectroscopy. Detailed in situ investigations on the melting process of the crystalline materials reveal the importance of H₂O motion in the melting mechanism. Depending on the local coordination, crystallographically distinct Na sites show different behaviour during the melting process. Upon melting, the monomer silicate anions present in the crystalline hydrates undergo condensation reactions to oligomeric silicate anions. No recrystallization but glass formation occurs at low temperature if the melts were heated initially about 10 K above the melting point. In the glasses also oligomeric silicate anions are present with a preference for cyclotrimer species. In situ MAS NMR investigations and electric conductivity measurements of the melts, supercooled melts, and glasses suggest the distinction of three temperature ranges characterized by different local structure and dynamics of the sodium cations, water and silicate anions. These ranges comprise a glass and glass transition range A at low temperatures, an aggregation region B at intermediate temperatures, and a solution or electrolyte region C at high temperatures. In region B aggregation of sodium water complexes to hydrated polycation clusters is suggested, the dynamic behaviour of which is clearly different to that of the silicate anions, indicating that no long-lived contact ion pairs between sodium cations and silicate anions are formed.     

Dynamics of Water in NaxCoO2.yH2O

Incoherent inelastic neutron scattering experiments were performed on Na0.7CoO2 and Na0.28CoO2.1.3H2O in order to understand how the dynamics of the hydrogen-bond network of water is modified in the triangular crystalline lattice NaxCoO2.yH2O. Using quasi-elastic neutron scattering (QENS), we were able to differentiate between two types of proton dynamics: a fast process (due to water strongly bound into the sodium cobalt oxyhydrate structure during the hydration process) and a slow process (likely attributable to a collective motion). High-resolution QENS experiments, carried out on Na0.28CoO2.1.3H2O, show that, at temperatures above 310 K, the water dynamics can be well-described by a random jump diffusion model characterized by a diffusion constant equal to 0.9 x 10(-9)m2/s, which is significantly lower than the rate of diffusion for bulk water. Furthermore, our results indicate that, at room temperature, the sodium ions have no influence on the rotational dynamics of the "fast" water molecules.     

273 K下Na2CO3-Na2SO4-Na2B4O7-H2O四元体系介稳相平衡的实验研究

采用等温蒸发法研究了四元体系Na2CO3-Na2SO4-Na2B4O7-H2O在273 K时的介稳相平衡及平衡液相的密度. 利用溶解度数据绘制了该四元体系273 K下的相图. 研究结果表明, 该四元体系有异成分复盐2Na2SO4·Na2CO3形成. 相图中有2个共饱点、5条单变量曲线和4个结晶相区. 4个结晶相区分别为盐Na2CO3·10H2O, Na2SO4·10H2O, Na2B4O7·10H2O和2Na2SO4·Na2CO3的结晶区. 复盐2Na2SO4·Na2CO3同时存在于包含Na2CO3-Na2SO4-H2O三元体系的其它四元体系或高元体系中. 在273 K介稳平衡相图中, 碳酸钠以Na2CO3·10H2O形式析出; 硫酸钠以Na2SO4·10H2O的形式析出; 硼酸钠的完整分子式为Na2B4O5(OH)4·8H2O. Na2CO3对Na2B4O7有盐析作用.     

Unprecedented stabilization of cobalt(II) in a tetrahedral S2O2 environment: the use of a redox-noninnocent ligand

The reaction of Zn(II) and Co(II) with thiosalicylic acid, o-HSC6H4COOH, and its methyl ester has led to the following complexes: [Zn(SC6H4COO)] (1), (NEt4)Na[Zn(SC6H4COO)2].H2O (2), (NEt4)2Na[Co(SC6H4COO)3].2H2O (3), (NEt4)3Na3[(Co(SC6H4COO)3)2].6MeOH (4), [Zn(SC6H4COOMe)2] (5), and [Co(SC6H4COOMe)n], n = 2 (6), 3 (7). These ligands have not allowed stabilization of Co(II) in a sulfur-oxygen coordination environment. The structures of complexes 2-4 and 7 have been determined crystallographically. Those of 2-4 show significant similarities such as the behavior of the -SC6H4COO- anion as chelating ligand and the involvement of sodium ions as a structural element. Thus, the structure of the [Na(Zn(SC6H4COO)2)(H2O)]- anion in complex 2 can be described as infinite chains of consecutive [Zn(SC6H4COO)2]2- metalloligands linked by [Na(H2O)]+ centers, that of the [Na(Co(SC6H4COO)3(H2O)2)]2(4-) anion in 3 as a centrosymmetric tetranuclear Co2Na2 dimer with a (CoIII(S[symbol: see text]O)3)Na(mu-H2O)2Na(CoIII(S[symbol: see text]O)3) core, and that of the pentanuclear [Na3(Co(SC6H4COO)3)2(MeOH)6]3- anion in 4 as two dinuclear [(CoIII(S[symbol: see text]O)3)Na(MeOH)3] fragments linked to a central sodium ion, which appears to be the first structurally characterized example of a NaS6 site. The use of the o-HSC6H4COOMe ligand allowed the synthesis of [Co(SC6H4COOMe)2] (6) but not its full structural characterization. Instead, [Co(SC6H4COOMe)3] (7) was obtained and structurally characterized. It consists of mononuclear molecules containing an octahedral CoIIIS3O3 core. The selection of 2,2-diphenyl-2-mercaptoacetic acid as ligand with reductive properties has afforded the first mononuclear complex containing a CoIIS2O2 core and thus an unprecedented model for Co(II)-substituted metalloproteins containing tetrahedral MS2O2 active sites. The synthesis and full structural characterization of the isostructural complexes (NEt4)2[Zn(Ph2C(S)COO)2] (8) and (NEt4)2[Co(Ph2C(S)COO)2] (9) show that they consist of discrete [M(Ph2C(S)COO)2]2- anions, with a distorted tetrahedral coordination about the metal. In addition, the stability conferred by the ligand on the CoIIS2O2 core has allowed its characterization in solution by paramagnetic 1D and 2D 1H NMR studies. The longitudinal relaxation times of the hyperfine-shifted resonances and NOESY spectra have led to the assignment of all resonances of the cobalt complex and confirmed that it maintains its tetrahedral geometry in solution. Magnetic measurements (2-300 K) for complex 9 and 9.2H2O are in good agreement with distorted tetrahedral and octahedral environments, respectively.     

General route to three-dimensional framework uranyl transition metal phosphates with atypical structural motifs: the case examples of Cs2{(UO2)4[Co(H2O)2]2(HPO4)(PO4)4} and Cs3+x[(UO2)3CuH4-x(PO4)5].H2O

The reaction of UO2(NO3)2.6H2O with Co or Cu metal, phosphoric acid, and CsCl under mild hydrothermal conditions results in the formation of Cs2{(UO2)4[Co(H2O)2(HPO4)(PO4)4} (1) or Cs(3+x)[(UO2)3CuH(4-x)(PO4)5].H2O (2). The structure of 1 contains uranium atoms in pentagonal bipyramidal and hexagonal bipyramidal environments. The interaction of the uranyl cations and phosphate anions creates layers in the [ab] plane. The uranyl phosphate layers are joined together by octahedral Co centers wherein the Co is bound by phosphate and two cis water molecules. In addition, the Co ions are also ligated by a uranyl oxo atom. The presence of these octahedral building units stitches the structure together into a three-dimensional framework where void spaces are filled by Cs+ cations. The structure of 2 contains uranium centers in UO6 tetragonal bipyramidal and UO7 pentagonal bipyramidal geometries. The uranyl moieties are bridged by phosphate anions into sinusoidal sheets that extend into the [bc] plane and are linked into a three-dimensional structure by Cu(II). The Cu centers reside in square planar environments. Charge balance is maintained by Cs+ cations. Both the overall structures and the uranyl phosphate layers in 1 and 2 are novel.     

Synthesis, crystal structure, and solution stability of Keggin-type heteropolytungstates (NH4)6NiII0.5[alpha-FeIIIO4W11O30NiIIO5(OH2)].nH2O, (NH4)7Zn0.5[alpha-ZnO4W11O30ZnO5(OH2)].nH2O, and (NH4)7NiII0.5[alpha-ZnO4W11O30NiIIO5(OH2)].nH2O (n approximately 18)

Reaction of acidified (pH approximately 7) sodium tungstate solutions with transition metal cations (Fe(3+), Ni(2+), Zn(2+), Co(2+)) leads to the formation of transition-metal-disubstituted Keggin-type heteropolytungstates with 3d-metal ions distributed over three different positions. A detailed investigation of the synthesis conditions confirmed that the complexes could equally be obtained using aqueous solutions of either Na(2)WO(4).2H(2)O (sodium monotungstate) at pH approximately 7, Na(6)[W(7)O(24)]. approximately 14H(2)O (sodium paratungstate A), or Na(10)[H(2)W(12)O(42)].27H(2)O (sodium paratungstate B) as starting materials. Three complexes, (NH(4))(6)Ni(II)(0.5)[alpha-Fe(III)O(4)W(11)O(30)Ni(II)O(5)(OH(2))].18H(2)O, (NH(4))(7)Zn(0.5)[alpha-ZnO(4)W(11)O(30) ZnO(5)(OH(2))].18H(2)O, and (NH(4))(7)Ni(II)(0.5)[alpha-ZnO(4)W(11)O(30)Ni(II)O(5)(OH(2))].18H(2)O were isolated in crystalline form. X-ray single-crystal structure analysis revealed that the solid-state structures of the three compounds consist of four main structural fragments, namely [MO(4)W(11)O(30)M'O(5)(OH(2))](n-) (Keggin-type, alpha-isomer) heteropolytungstates, hexaquo metal cations, [M'(OH(2))(6)](2+), ammonium-water cluster ions, [(NH(4)(+))(8)(OH(2))(12)], and additional ammonium cations and water molecules. The 3d metals occupy the central (tetrahedral, M) and the peripheral (octahedral, M') positions of the Keggin anion, as well as cationic sites (M') outside of the polyoxotungstate framework. UV-vis spectroscopy, solution ((1)H, (183)W) and solid-state ((1)H) NMR, and also chemical analysis data provided evidence that the 3d-metal-disubstituted Keggin anions do not exist in solution but are being formed only during the crystallization process. Investigations in the solid state and in solution were completed by ESR, IR, and Raman measurements.     

Monitoring dehydration and condensation processes of Na2HPO4*12H2O using thermo-Raman spectroscopy

Thermal dehydration and condensation processes of disodium hydrogen phosphate dodecahydrate (Na2HPO4*12H2O) were monitored by thermo-Raman spectroscopy (TRS). Various hydrated forms Na2HPO4*12H2O, Na2HPO4*8H2O, Na2HPO4*7H2O, Na2HPO4*2H2O, Na2HPO4*H2O and Na2HPO4 were observed, followed by condensation of Na2HPO4 to sodium pyrophosphate (Na4P2O7) in a dynamic thermal process. Representative Raman spectra of all the hydrated forms Na2HPO4*12H2O, Na2HPO4*8H2O, Na2HPO4*7H2O, Na2HPO4*2H2O, Na2HPO4*H2O and Na2HPO4 were detected in both H2O and PO4(3- )regions are reported. The thermo-Raman intensity (TRI) thermogram also showed systematic loss of water in five steps of dehydration, with the differential TRI thermogram in agreement shows five dips corresponding to the five steps of dehydration, respectively. Thermogravimetry (TG) and differential thermogravimetry (DTG) are in harmony with the results of TRS, though, the two could not resolve the steps involved.     

Contribution to thermochemical studies of 0.8[xB_2O_3-(1-x)SiO_2]-0.2Na_2O glasses

Calorimetric measurements in 0.8[xB_2O_3-(1-x)SiO_2]-0.2Na_2O glasses and melts are performed in HF calorimetry at 298 K and lead borate calorimetry at 973 K,respectively.Mixing enthalpy is affected by both temperature and composition.At 298 K,the mixing enthalpies are slightly negative and components are miscible at that temperature in the whole composition range.At 973 K, the sign of the mixing enthalpies reflect the tendency to phase separation at silica-rich compositions,which is avoided for kinetic ...     

Polysulfonylamine. CLVIII [1] Kristallstrukturen von Metall‐di(methansulfonyl)amiden. 9 [2] Erhöhung der Kristallsymmetrie durch Kokristallisation: Monoklines Na[(CH3SO2)2N]·H2O und tetragonales NaK[(CH3SO2)2N]2·2H2O

Polysulfonylamines. CLVIII. Crystal Structures of Metal Di(methanesulfonyl)amides. 9. Enhancing Crystal Symmetry by Co‐crystallization: Monoclinic Na[(CH₃SO₂)₂N]·H₂O and Tetragonal NaK[(CH₃SO₂)₂N]₂·2H₂O The three‐dimensional coordination polymers NaA·H₂O ( 1 ) and NaKA₂·2H₂O ( 2 ), derived from the strong NH acid (MeSO₂)₂NH = HA, have been characterized by single crystal X‐ray diffraction at —95 °C ( 1 : monoclinic, space group C2/c, Z′ = 2; 2 : tetragonal, P4₃2₁2, Z′ = 1). The results suggest that structures with Z′ > 1 are good candidates for co‐crystallization experiments. Both packings display layer substructures built up from the multidentately coordinating anions, the aquo ligands and two kinds of chemically and/or crystallographically distinct cations, whereas cations of a third type are intercalated between the layers. All anions have the extended standard conformation of this species; 1 contains two pseudo‐C₂ symmetric A^—, 2 one pseudo‐C₂ and two crystallographically C₂ symmetric A^—. Details for structure 1 : a) The layer‐forming Na(1) and Na(3) cations are distributed over three distinctly separated planes, Na(1) occupies general positions and has a non‐octahedral O₅N environment, Na(3) resides on inversion centres that generate an octahedral O₆ coordination; b) one independent A^— is oriented vertically, the other parallel to the layer plane; c) the intercalated Na(2) ions occupy twofold rotation axes within a single plane and possess a non‐octahedral O₆ environment. Details for structure 2 : a) The layer‐forming K(1) and K(2) cations occupy twofold rotation axes within a unique plane and have chemically identically O₆N₂ coordination polyhedra approximating to hexagonal bipyramids; b) all A^— are oriented vertically to the layer plane; c) the intercalated sodium ions reside on pseudo‐inversion centres, have an octahedral O₆ environment and are distributed over two closely adjacent planes. Owing to the enhanced packing efficiency of the bimetal complex, the vertical layer repeat‐distance is reduced from 1140 pm for 1 to 720 pm for 2 . Each structure exhibits an infinite cation‐water chain that propagates in the direction of the layer stacking and contains the three independent cations.