Samarium,Europium, and Gadolinium Complexes with 4-(2,1,3-Benzothiadiazol-4-ylamino)pent-3-en-2-onate

Russian Journal of Coordination Chemistry - New lanthanide complexes with 4-(2,1,3-benzothiadiazol-4-ylamino)pent-3-en-2-onate (L–) [Ln(L)3] are synthesized using two methods: by the reaction...     

First determination of volume changes and enthalpies of the high-pressure decomposition reaction of the structure H methane hydrate to the cubic structure I methane hydrate and fluid methane

Pressure-temperature (P-T) conditions of the decomposition reaction of the structure H high-pressure methane hydrate to the cubic structure I methane hydrate and fluid methane were studied with a piston-cylinder apparatus at room temperature. For the first time, volume changes accompanying this reaction were determined. With the use of the Clausius-Clapeyron equation the enthalpies of the decomposition reaction of the structure H high-pressure methane hydrate to the cubic structure I methane hydrate and fluid methane have been calculated.     

Unexpected Product of the Reaction of Iron(II) Dichloroclathrochelate with the [Fe2(μ-S)2(CO)6]2– Cluster Dianion: Synthesis and X-ray Diffraction Structure of the First Cage Complex with Thiol Groups Inherently Bonded to a Macrobicyclic Framework

Russian Journal of Coordination Chemistry - An attempt to prepare a hybrid clusteroclathrochelate by nucleophilic substitution of iron(II) dichloroclathrochelate by substitution of its chlorine...     

Direct measurement of stoichiometry of the structure <Emphasis Type="Italic">H</Emphasis> argon gas hydrate synthesized at high pressure

For the first time the composition of a high-pressure gas hydrate has been studied analytically. The experimentally determined composition of the argon hydrate of hexagonal structure III (structure H) is Ar· (3.27±0.17)H₂O, with the hydrate being stable in the range of pressures 460–770 MPa. The new results confirm the reliability of previous results based on the refinement of argon hydrate structures using neutron powder diffraction data and help to elucidate the evolution of hydrate structures in Ar-H₂O system under high pressures.     

Phase Diagram of the Benzene–Dinitratotetrapyridinecopper(II) (Guest–Host) System and Thermodynamic Parameters for the Hostβ2Guest Clathrate Dissociation

In the first part of the work, thephase diagram of the benzene -ndash;[CuPy⁴(NO³)²] system has beendetermined in the -100 to +200 °C temperaturerange using DTA and solubility techniques. The onlycompound found in the system is the[CuPy⁴(NO³)²] 2C⁶H⁶clathrate. It is stable up to a temperature of+104.2(5) °C at which it melts incongruently togive liquid and the solid [CuPy⁴(NO³)²]host phase. At 146.1(5) °C exfoliation into twoliquid phases is observed, with the composition of themonotectic point being close to that of the clathrate.In the second part of the work, thermodynamicparameters of the clathrate dissociation have beendetermined from benzene vapour pressure strainmeasurements. For the process1/2 [CuPy⁴(NO³)²]2C⁶H⁶(solid) = 1/2 [CuPy⁴(NO³)²] (solid) +C⁶H⁶ (gas) H° = 45.3(3) kJ/mole; S₂₉₈° = 126(1) J/(mole K); G₂₉₈° = 7.7(5) kJ/mole.     

The Formation and Stability of the [FePy3Cl3]· Py Clathrate in the Pyridine–Iron(III) Chloride System: Phase Diagram and Solid–Gas Equilibria Study

The phase diagram of the pyridine–iron(III) chloride system has been studied for the 223–423 K temperature and 0–56 mass-% concentration ranges using differential thermal analysis (DTA) and solubility techniques. A solid with the highest pyridine content formed in the system was found to be an already known clathrate compound, [FePy₃Cl₃]·Py. The clathrate melts incongruently at 346.9 ± 0.3 K with the destruction of the host complex: [FePy₃Cl₃]·Py_(solid)=[FePy₂Cl₃]_(solid) + liquor. The thermal dissociation of the clathrate with the release of pyridine into the gaseous phase (TGA) occurs in a similar way: [FePy₃Cl₃]·Py_(solid)=[FePy2Cl₃]_(solid) + 2 Py_(gas). Thermodynamic parameters of the clathrate dissociation have been determined from the dependence of the pyridine vapour pressure over the clathrate samples versus temperature (tensimetric method). The dependence experiences a change at 327 K indicating a polymorphous transformation occurring at this temperature. For the process in the range 292–327 K, ΔH =70.8 ± 0.8 kJ/mol, ΔS =197 ± 3 J/(mol K), ΔG =12.2 ± 0.1 kJ/mol; in the range 327–368 K, ΔH =44.4 ± 1.3 kJ/mol, ΔS =116 ± 4 J/(mol K), ΔG =9.9 ± 0.3 kJ/mol.     

New data on phase diagram and clathrate formation in the system water–isopropyl alcohol

The phase diagram of the binary system isopropyl alcohol–water was investigated by means of differential thermal analysis and powder X-ray diffraction. Two incongruently melting polyhydrates with the compositions close to the molar ratio of isopropanol to water 1:5 were found. The melting point of one of the polyhydrates is ?49.6 °C, the melting point of the second one is within the range ?38.8 to ?30.6 °C. Assumptions concerning the structure of each compound were made on the basis of powder X-ray diffraction data.     

Calorimetric measurements of sodium chloride dihydrate (hydrohalite)

Calorimetric measurements of sodium chloride dihydrate NaCl·2H₂O (mineral name hydrohalite) were carried out with using DSC. Heat capacity from 190 to 250 K was measured and found to increase from 109 to 137 J mol^?1 K^?1. The enthalpy of formation of hydrohalite from solid ice and halite at 273.15 K was derived from the thermal effect of melting/decomposition in DSC measurements and found to be close to ??1.8 kJ mol^?1. The same DSC results show clearly that the upper temperature limit for the existence of hydrohalite is several degrees greater than the current value of 273.15 K accepted for the peritectic decomposition of hydrohalite. The phase diagram of the NaCl–H₂O system needs correction.

     

Preparation of fine powders by clathrate-forming freeze-drying: a case study of ammonium nitrate

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