Cesium fluorohydrogenate, Cs(FH)2.3F

Cs(FH)_2.3F is a liquid salt exhibiting a low viscosity of 20.1 cP and a high conductivity of 86.3 mS cm⁻¹ at 25 °C, in spite of the relatively high melting point (16.9 °C). The high density of 2.82 g cm⁻³ at the liquid state is due to the heavy atomic weight and small size of cesium atom compared to the organic cations of general ionic liquids. The infrared spectroscopy indicates that this salt contains (FH)₂F⁻ as a main anionic species. The other anionic species such as (FH)₃F⁻ found in the cases of other M⁺(HF)_2.3F (M = a univalent organic cation) ionic liquid salts is not detected, suggesting its small abundance as well as the presence of neutral HF in the form of molecular and/or oligomers. The result of ¹H NMR also suggests that the anions exchange HF between them. These observations coincide with the experimental result that Cs(FH)_2.3F acts as an acid against general ionic liquid fluorohydrogenates such as EMIm(FH)_2.3F (EMIm = 1-ethyl-3-methylimidazolium) to lose HF and give Cs(FH)₂F precipitate.     

Synthesis, crystal structure, phase transition and thermal behaviour of a new dabcodiium hexaaquanickel(II) bis(sulphate), (C6H14N2)[Ni(H2O)6](SO4)2

A new dabcodiium-templated nickel sulphate, (C₆H₁₄N₂)[Ni(H₂O)₆](SO₄)₂, has been synthesised and characterised by single-crystal X-ray diffraction at 20 and −173 °C, differential scanning calorimetry (DSC), thermogravimetry (TG) and temperature-dependent X-ray powder diffraction (TDXD). The high temperature phase crystallises in the monoclinic space group P2₁/n with the unit-cell parameters: a = 7.0000(1), b = 12.3342(2), c = 9.9940(2) Å; β = 90.661(1)°, V = 862.82(3) Å³ and Z = 2. The low temperature phase crystallises in the monoclinic space group P2₁/a with the unit-cell parameters: a = 12.0216(1), b = 12.3559(1), c = 12.2193(1) Å; β = 109.989(1)°, V = 1705.69(2) Å³ and Z = 4. The crystal structure of the HT-phase consists of Ni²⁺ cations octahedrally coordinated by six water molecules, sulphate tetrahedra and disordered dabcodiium cations linked together by hydrogen bonds. It undergoes a reversible phase transition (PT) of the second order at −53.7/−54.6 °C on heating-cooling runs. Below the PT temperature, the structure is fully ordered. The thermal decomposition of the precursor proceeds through three stages giving rise to the nickel oxide.     

Coordination environment of [UO2Br4] in ionic liquids and crystal structure of [Bmim]2[UO2Br4]

The complex formed by the reaction of the uranyl ion, UO₂²⁺, with bromide ions in the ionic liquids 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][Tf₂N]) and methyl-tributylammonium bis(trifluoromethylsulfonyl)imide ([MeBu₃N][Tf₂N]) has been investigated by UV–Vis and U L_III-edge EXAFS spectroscopy and compared to the crystal structure of [Bmim]₂[UO₂Br₄]. The solid state reveals a classical tetragonal bipyramid geometry for [UO₂Br₄]²⁻ with hydrogen bonds between the Bmim⁺ and the coordinated bromides. The UV–Vis spectroscopy reveals the quantitative formation of [UO₂Br₄]²⁻ when a stoichiometric amount of bromide ions is added to UO₂(CF₃SO₃)₂ in both Tf₂N-based ionic liquids. The absorption spectrum also suggests a D_4h symmetry for [UO₂Br₄]²⁻ in ionic liquids, as previously observed for the [UO₂Cl₄]²⁻ congener. EXAFS analysis supports this conclusion and demonstrates that the [UO₂Br₄]²⁻ coordination polyhedron is maintained in the ionic liquids without any coordinating solvent or water molecules. The mean U–O and U–Br distances in the solutions, determined by EXAFS, are, respectively, 1.766(2) and 2.821(2) Å in [Bmim][Tf₂N], and, respectively, 1.768(2) and 2.827(2) Å, in [MeBu₃N][Tf₂N]. Similar results are obtained in both ionic liquids indicating no significant influence of the ionic liquid cation either on the complexation reaction or on the structure of the uranyl species.     

Low-temperature heat capacity and thermodynamic properties of crystalline carboxin (C12H13NO2S)

Carboxin was synthesized and its heat capacities were measured with an automated adiabatic calorimeter over the temperature range from 79 to 380 K. The melting point, molar enthalpy (Δ_fusH_m) and entropy (Δ_fusS_m) of fusion of this compound were determined to be 365.29±0.06 K, 28.193±0.09 kJ mol⁻¹ and 77.180±0.02 J mol⁻¹ K⁻¹, respectively. The purity of the compound was determined to be 99.55 mol% by using the fractional melting technique. The thermodynamic functions relative to the reference temperature (298.15 K) were calculated based on the heat capacity measurements in the temperature range between 80 and 360 K. The thermal stability of the compound was further investigated by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The DSC curve indicates that the sample starts to decompose at ca. 290 °C with the peak temperature at 292.7 °C. The TG-DTG results demonstrate the maximum mass loss rate occurs at 293 °C corresponding to the maximum decomposition rate.     

New synthetic and structural studies on nitroso-ortho-carboranes RCB10H10CNO and bis(ortho-carboranyl)amines (RCB10H10C)2NH (R = Ph or Me)

Improved procedures are reported for the preparation of nitroso-carboranes RCb°NO (Cb° = 1,2-C₂B₁₀H₁₀; R = Ph, Me at cage carbon C2) in 44–77% yield, and of dicarboranylamines (RCb°)₂NH in 55–65% yield by reactions between the lithio-carboranes, RCb°Li and nitrosyl chloride, NOCl, in cold mixtures of diethyl ether and either pentane (for RCb°NO) or dimethoxyethane (for (RCb°)₂NH). Deprotonation of the amines by KO^tBu in toluene in the presence of 18-crown-6, (CH₂CH₂O)₆, affords the salts [K(18-crown-6)]⁺[(RCb°)₂N]⁻. X-ray crystal structures of PhCb°NO, (PhCb°)₂NH, (MeCb°)₂NH and [K(18-crown-6)]⁺[(PhCb°)₂N]⁻ are described, and the bonding implications of their cage C…C distances (1.68, 1.80, 1.75 and 1.99 Å, respectively) are discussed. These species provide further striking examples of the remarkable capacity of the ortho-carborane cage to act as a sensitive indicator of the π-donor characteristics of ligands attached to its cage carbon atoms.     

Low-temperature single crystal X-ray diffraction and high-pressure Raman studies on [(CH3)2NH2]2[SbCl5]

The structure of bis(dimethylammonium) pentachloroantimonate(III), [(CH₃)₂NH₂]₂[SbCl₅], BDP, was studied at 15 K and ambient pressure by single-crystal X-ray diffraction as well as at ambient temperature and high pressures up to 4.87(5) GPa by Raman spectroscopy. BDP crystallizes in the orthorhombic Pnma space group with a=8.4069(4), b=11.7973(7), c=14.8496(7) Å, and Z=4; R₁=0.0381, wR₂=0.0764. The structure consists of distorted [SbCl₆]³⁻ octahedra forming zig-zag [{SbCl₅}_n]²ⁿ⁻ chains that are cross-linked by dimethylammonium [(CH₃)₂NH₂]⁺ cations. The organic and inorganic substructures are bound together by the N-H…Cl hydrogen bonds. The distortions of [SbCl₆]³⁻ units increase, partly due to the influence of the hydrogen bonds which became stronger, with decreasing temperature. The preliminary room temperature, high-pressure X-ray diffraction experiments suggest that BDP undergoes a first-order phase transition below ca. 0.44(5) GPa that destroys single-crystal samples. The transition is accompanied by changes in the intensities and positions of the Raman lines below 400 cm⁻¹.     

Effect of sintering on the ionic conductivity of garnet-related structure Li5La3Nb2O12 and In- and K-doped Li5La3Nb2O12

Garnet-structure related metal oxides with the nominal chemical composition of Li₅La₃Nb₂O₁₂, In-substituted Li_5.5La₃Nb_1.75In_0.25O₁₂ and K-substituted Li_5.5La_2.75K_0.25Nb₂O₁₂ were prepared by solid-state reactions at 900, 950, and 1000 °C using appropriate amounts of corresponding metal oxides, nitrates and carbonates. The powder XRD data reveal that the In- and K-doped compounds are isostructural with the parent compound Li₅La₃Nb₂O₁₂. The variation in the cubic lattice parameter was found to change with the size of the dopant ions, for example, substitution of larger In³⁺(r_CN6: 0.79 Å) for smaller Nb⁵⁺ (r_CN6: 0.64 Å) shows an increase in the lattice parameter from 12.8005(9) to 12.826(1) Å at 1000 °C. Samples prepared at higher temperatures (950, 1000 °C) show mainly bulk lithium ion conductivity in contrast to those synthesized at lower temperatures (900 °C). The activation energies for the ionic conductivities are comparable for all samples. Partial substitution of K⁺ for La³⁺ and In³⁺ for Nb⁵⁺ in Li₅La₃Nb₂O₁₂ exhibits slightly higher ionic conductivity than that of the parent compound over the investigated temperature regime 25-300 °C. Among the compounds investigated, the In-substituted Li_5.5La₃Nb_1.75In_0.25O₁₂ exhibits the highest bulk lithium ion conductivity of 1.8×10⁻⁴ S/cm at 50 °C with an activation energy of 0.51 eV. The diffusivity (“component diffusion coefficient”) obtained from the AC conductivity and powder XRD data falls in the range 10⁻¹⁰-10⁻⁷ cm²/s over the temperature regime 50-200 °C, which is extraordinarily high and comparable with liquids. Substitution of Al, Co, and Ni for Nb in Li₅La₃Nb₂O₁₂ was found to be unsuccessful under the investigated conditions.     

Bis(trifluoromethyl)dicarbonate, CF3OC(O)OC(O)OCF3

The synthesis of the new compound, bis(trifluoromethyl)dicarbonate, CF₃OC(O)OC(O)OCF₃, is carried out by reduction of bis(trifluoromethyl)trioxidicarbonate with excess of CO at 0 °C. The product is characterized by IR, Raman, ¹³C and ¹⁹F NMR spectroscopy and its properties are compared with those of the other members of the series CF₃OC(O)O_xC(O)OCF₃, x = 0-3. Single crystals are grown at −25 °C and the X-ray diffraction analysis shows the packing of syn-syn rotamers exhibiting C₂ symmetry. DFT calculations predict this rotamer as the most stable one and also structural and vibrational data are predicted reasonably well.     

Synthesis, heat capacity and enthalpy of formation of [Ho2(l-Glu)2(H2O)8](ClO4)4·H2O

A complex of holmium perchlorate coordinated with l-glutamic acid, [Ho₂(l-Glu)₂(H₂O)₈](ClO₄)₄·H₂O, was prepared with a purity of 98.96%. The compound was characterized by chemical, elemental and thermal analysis. Heat capacities of the compound were determined by automated adiabatic calorimetry from 78 to 370 K. The dehydration temperature is 350 K. The dehydration enthalpy and entropy are 16.34 kJ mol⁻¹ and 16.67 J K⁻¹ mol⁻¹, respectively. The standard enthalpy of formation is −6474.6 kJ mol⁻¹ from reaction calorimetry at 298.15 K.     

Thermodynamics of BaNd2Fe2O7(s) and BaNdFeO4(s) in the system BaNdFeO

Two compounds, BaNd₂Fe₂O₇(s) and BaNdFeO₄(s) in the quaternary system BaNdFeO were prepared by citrate-nitrate gel combustion route and characterized by X-ray diffraction analysis. Heat capacities of these two oxides were measured in two different temperature ranges: (i) 130-325 K and (ii) 310-845 K, using a heat flux type differential scanning calorimeter. Two different types of solid-state electrochemical cells with CaF₂(s) as the solid electrolyte were employed to measure the e.m.f. as a function of temperature. The standard molar Gibbs energies of formation of these quaternary oxides were calculated as a function of temperature from the e.m.f. data. The standard molar enthalpies of formation from elements at 298.15 K, ΔfHm° (298.15 K) and the standard entropies, Sm° (298.15 K) of these oxides were calculated by the second law method. The values of ΔfHm° (298.15 K) and Sm° (298.15 K) obtained for BaNd₂Fe₂O₇(s) are: −2756.9 kJ mol⁻¹ and 234.0 J K⁻¹ mol⁻¹ whereas those for BaNdFeO₄(s) are: −2061.5 kJ mol⁻¹ and 91.6 J K⁻¹ mol⁻¹, respectively.     

Activation of the Si-H bond of Et2SiH2 in photochemical reaction with W(CO)6: Spectroscopic characterization of intermediate W-Si compounds and the revisited crystal structure of the bis{(μ-η-hydridodiethylsilyl)tetracarbonyltungsten(I)} complex [{W(μ-η-H-SiEt2)(CO)4}2]

The photochemical reaction of W(CO)₆ with diethylsilane has been used to generate new tungsten-silicon compounds varying in stability. The initially formed η²-silane intermediate complex [W(CO)₅(η²-H-SiHEt₂)], characterized by two equal-intensity doublets with ²J_H-H = 10 Hz at δ = 5.10 (¹J_Si-H = 217 Hz) and δ = −8.05 (¹J_W-H = 38 Hz, ¹J_Si-H = 93 Hz), was detected by the ¹H NMR spectroscopy (methylcyclohexane-d₁₄, −10 °C). The η²-silane complex was converted in the dark to give more stable species. One of them was characterized by two equal-intensity proton signals observed as doublets with ²J_H-H = 5.2 Hz at δ = −8.25 and −10.39 ppm. The singlet proton resonance at δ = −9.31 flanked by ²⁹Si and ¹⁸³W satellites (¹J_Si-H = 43 Hz, ²J_Si-H = 34 Hz, ¹J_W-H = 40 Hz) was assigned to the agostic proton of the W(η²-H-SiEt₂) group in the most stable compound isolated from the photochemical reaction products in crystalline form. The molecular structure of the bis{(μ-η²-hydridodiethylsilyl)tetracarbonyltungsten(I)} complex [{W(μ-η²-H-SiEt₂)(CO)₄}₂] was established by single-crystal X-ray diffraction studies. The tungsten hydride observed in the ¹H NMR spectrum at δ = −9.31 was located in the structure at a chemically reasonable position between the W and Si atoms of the W-Si bond of the bridging silyl ligand. The reactivity of photochemically generated W-Si compounds towards norbornene, cyclopentene, diphenylacetylene, acetone, and water was studied. As was observed by IR and NMR spectroscopy, the η²-silane ligand in the complex [W(CO)₅(η²-H-SiHEt₂)] is very easily replaced by an η²-olefin or η²-alkyne ligand.     

From a 3D protonic conductor VO(H2PO4)2 to a 2D cationic conductor Li4VO(PO4)2 through lithium exchange

A new phase, Li₄VO(PO₄)₂ was synthesized by a lithium ion exchange reaction from protonic phase, VO(H₂PO₄)₂. The structure was determined from neutron and synchrotron powder diffraction data. The exchange of lithium causes a stress, leading to a change in the dimensionality of the structure from 3D to 2D by the displacement of oxygen atoms. Thus, Li₄VO(PO₄)₂ crystallizes in P4/n space group with lattice parameters a=8.8204(1) Å and c=8.7614(2) Å. It consists of double layers [V₂P₄O₁₈]_∞ formed by successive chains of VO₆ octahedra and VO₅ pyramids with isolated PO₄ tetrahedra. The lithium ions located in between the layers promote mobility. Furthermore, the ionic conductivity of 10⁻⁴ S/cm at 550 °C for Li₄VO(PO₄)₂ confirms the mobility of lithium ions in the layers. On the other hand, VO(H₂PO₄)₂ exhibits a conductivity of 10⁻⁴ S/cm at room temperature due to the presence of protons in tunnels.     

Measurement of vapor–liquid equilibria (VLE) and excess enthalpies (H) of binary systems with 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and prediction of these properties and γ using modified UNIFAC (Dortmund)

Vapor–liquid equilibria (VLE) and excess enthalpies (H^E) were measured for a variety of alkanes, alkenes, aromatics, alcohols, ketones and water in several ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM]⁺[BTI]⁻, 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [BMIM]⁺[BTI]⁻, 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [HMIM]⁺[BTI]⁻ and 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [OMIM]⁺[BTI]⁻, covering the temperature range from 323.15 to 413.15 K. The new data were used together with the already available experimental data for imidazolium compounds to fit the required group interaction parameters for modified UNIFAC (Dortmund). The results show that in the future modified UNIFAC (Dortmund) can be applied successfully also for systems with ionic liquids.     

Calorimetric study and thermal analysis of [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O (Gly: glycin)

Two solid-state coordination compounds of rare earth metals with glycin, [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O and [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 342.90 K, while [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol⁻¹ and 53.9 J K⁻¹ mol⁻¹ for [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, 1.82 kJ mol⁻¹ and 5.5 J K⁻¹ mol⁻¹ for [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.     

Vaporization of DyI3(s) and thermochemistry of the homocomplexes (DyI3)2(g) and (DyI3)3(g)

The vaporization of DyI₃(s) was investigated in the temperature range between 833 and 1053 K by the use of Knudsen effusion mass spectrometry. The ions DyI₂⁺, DyI₃⁺, Dy₂I₄⁺, Dy₂I₅⁺, Dy₃I₇⁺, and Dy₃I₈⁺ were detected in the mass spectrum of the equilibrium vapor. The gaseous species DyI₃, (DyI₃)₂, and (DyI₃)₃ were identified and their partial pressures determined. Enthalpies and entropies of sublimation resulted according to the second- and third-law methods. The following sublimation enthalpies at 298 K were determined for the gaseous species given in brackets: 274.8±8.2 kJ mol⁻¹ [DyI₃], 356.0±11.3 kJ mol⁻¹ [(DyI₃)₂], and 436.6±14.6 kJ mol⁻¹ [(DyI₃)₃]. The enthalpy changes of the dissociation reactions (DyI₃)₂=2 DyI₃ and (DyI₃)₃=3 DyI₃ were obtained as Δ_dH°(298)=193.3±5.6 and 390.3±13.0 kJ mol⁻¹, respectively.     

A tetraethylene glycol dimethylether-lithium bis(oxalate)borate (TEGDME-LiBOB) electrolyte for advanced lithium ion batteries

Tetraethylene glycol dimethylether-lithium bis(oxalate)borate (TEGDME-LiBOB) electrolyte is here studied. Electrochemical impedance spectroscopy (EIS) measurements demonstrate that the electrolyte has conductivity higher than 10^− 3 S cm^− 1 at room temperature and about 10^− 2 S cm^− 1 at 60 °C, while thermogravimetry indicates a stability extending up to 180 °C. Sweep voltammetry of the electrolyte shows anodic stability extending over 4.6 V vs. Li and cathodic peak at about 1.5 V vs. Li/Li⁺, caused by a decomposition of LiBOB salt, and following prevented by using a pre-treated Sn-C anode. Furthermore, LiFePO₄ electrode is successfully used as cathode in a lithium cell using the TEGDME-LiBOB electrolyte. The promising electrochemical results, the low cost and the very high safety level candidate the electrolyte here reported as a valid alternative to the conventional electrolyte based on fluorinated salts presently used in the lithium ion battery field.     

High-yield syntheses of [Rh7(CO)16] and [Rh14(CO)25] working in ethylene glycol solution under 1 atm of CO

The anionic rhodium carbonyl clusters [Rh₇(CO)₁₆]³⁻ and [Rh₁₄(CO)₂₅]⁴⁻ can be easily prepared by a new simple and high yield one-pot synthesis starting from RhCl₃·nH₂O dissolved in ethylene glycol and involving two steps: (i) treatment of RhCl₃·nH₂O under 1 atm of CO at 50 °C to give [Rh(CO)₂Cl₂]⁻; (ii) addition of a base (CH₃CO₂Na or Na₂CO₃) followed by reductive carbonylation under 1 atm of CO at an adequate temperature (50 °C for [Rh₇(CO)₁₆]³⁻; 150 °C for [Rh₁₄(CO)₂₅]⁴⁻). These new syntheses are more convenient than those previously reported, especially since such clusters are not accessible via silica surface-mediated reactions. This different behavior is due to the particular stabilization on the silica surface and under 1 atm of CO of an anionic carbonyl cluster, called A, which does not allow the formation of a higher nuclearity carbonyl cluster, called B, which was shown to be the key-intermediate in the synthesis of [Rh₁₄(CO)₂₅]⁴⁻ working in ethylene glycol solution. Although it was not possible to isolate crystals of A and B suitable for X-ray structural determination, a combination of cyclovoltammetry, one of the few examples so far available of the use of this technique for anionic rhodium carbonyl clusters, infrared spectroscopy and elemental analyses suggest that A and B are probably the never reported [Rh₇(CO)₁₄]⁻ and [Rh₁₅(CO)₂₈]³⁻ clusters, respectively. In particular the tentative formulation of the two clusters was carried out by a non-conventional method based on the existence of a linear correlation between carbonyl frequencies of the main band and the [(charge/Rh atoms)/CO number] ratio.     

Hydrothermal synthesis, thermal, structural, spectroscopic and magnetic studies of the Mn5−xCox(HPO4)2(PO4)2(H2O)4 (x=1.25, 2, 2.5 and 3) finite solid solution

The Mn_5−xCo_x(HPO₄)₂(PO₄)₂(H₂O)₄ (x=1.25, 2, 2.5, 3) finite solid solution has been synthesized by mild hydrothermal conditions under autogeneous pressure. The phases crystallize in the C2/c space group with Z=4, belonging to the monoclinic system. The unit-cell parameters obtained from single crystal X-ray diffraction are: a=17.525(1), b=9.0535(6), c=9.4517(7) Å, β=96.633(5) ° being R1=0.0436, wR2=0.0454 for Mn75Co25; a=17.444(2), b=9.0093(9), c=9.400(1) Å, β=96.76(1) ° being R1=0.0381, wR2=0.0490 for Mn60Co40; a=17.433(2), b=8.9989(9), c=9.405(1) Å, β=96.662(9) ° being R1=0.0438, wR2=0.0515 for Mn50Co50 and a=17.4257(9), b=8.9869(5), c=9.3935(5) Å, β=96.685(4) ° being R1=0.0296, wR2=0.0460 for Mn40Co60. The structure consists of a three dimensional network formed by octahedral pentameric entities (Mn,Co)₅O₁₆(H₂O)₆ sharing vertices with the (PO₄)³⁻ and (HPO₄)²⁻ tetrahedra. The limit of thermal stability of these compounds is, approximately, 165 °C, near to this mean temperature the phases loose their water content in two successive steps. IR spectra show the characteristic bands of the water molecules and the phosphate and hydrogen-phosphate oxoanions. The diffuse reflectance spectra are consistent with the presence of MO₆ octahedra environments in slightly distorted octahedral geometry, except for the M(3)O₆ octahedron which presents a remarkable distortion and so a higher Dq parameter. The mean value for the Dq and B-Racah parameter for the M(1),(2)O₆ octahedra is 685 and 850 cm⁻¹, respectively. These parameters for the most distorted M(3)O₆ polyhedron are 825 and 880 cm⁻¹, respectively. The four phases exhibit antiferromagnetic couplings as the major magnetic interactions. However, a small spin canting phenomenon is observed at low temperatures for the two phases with major content in the anisotropic-Co(II) cation.     

Stabilisation of heterobimetallic networks by crown ethers and hydrogen-bonding in [Ni(H2O)6][Cu3Cl8(H2O)2] · (15-crown-5)2 · 2H2O: Structure and magnetism

[Ni(H₂O)₆][Cu₃Cl₈(H₂O)₂] · (15-crown-5)₂ · 2H₂O can be conveniently prepared by the interaction of NiCl₂ · 6H₂O, CuCl₂ · 2H₂O and 15-crown-5 in water. The X-ray crystal structure reveals an ionic complex involved in a hydrogen-bonded two dimensional network with the [Ni(H₂O)₆]²⁺ and [Cu₃Cl₈(H₂O)₂]²⁻ ions sandwiched between the 15-crown-5 macrocycles. The magnetic susceptibility data (4–300 K) and magnetisation isotherms (2–5.5 K; 0–5 T) are best interpreted in terms of intra-trimer ferromagnetic coupling within the [Cu₃Cl₈(H₂O)₂]²⁻ moieties, with J ∼ 6 cm⁻¹, and antiferromagnetic coupling between the trimers, the latter mediated by H-bonding pathways. Comparisons are made to other reported quaternary ammonium salts of [Cu₃Cl₈]²⁻ and [Cu₃Cl₁₂]⁶⁻, most of which display structures that involve close stacking of such Cu(II) trimers, rather than being of the present isolated, albeit H-bonded, types.     

Phase transitions and molecular motions in [Ni(ND3)6](ClO4)2

[Ni(ND₃)₆](ClO₄)₂ has three solid phases between 100 and 300 K. The phase transitions temperatures at heating (T_C1^h=164.1 K and T_C2^h=145.1 K) are shifted, as compared to the non-deuterated compound, towards the lower temperature of ca. 8 and 5 K, respectively. The ClO₄⁻ anions perform fast, picosecond, isotropic reorientation with the activation energy of 6.6 kJ mol⁻¹, which abruptly slow down at T_C1^c phase transition, during sample cooling. The ND₃ ligands perform fast uniaxial reorientation around the Ni-N bond in all three detected phases, with the effective activation energy of 2.9 kJ mol⁻¹. The reorientational motion of ND₃ is only slightly distorted at the T_C1 phase transition due to the dynamical orientational order-disorder process of anions. The low value of the activation energy for the ND₃ reorientation suggests that this reorientation undergoes the translation-rotation coupling, which makes the barrier to the rotation of the ammonia ligands not constant but fluctuating. The phase polymorphism and the dynamics of the molecular reorientations of the title compound are similar but not quite identical with these of the [Ni(NH₃)₆](ClO₄)₂.