NMR investigation of certain hydrated fluorosilicates

Proton and fluorine NMR were investigated in the temperature range 90–425 °K in the hexahydrated fluorosilicates of Zn, Cu, Mn, Co, and Ni and in the tetrahydrated CuSiF6 to obtain information about the internal motions in these solids. Second moment transitions were observed at widely different temperatures for the different substances, and these are ascribed to the onset of reorientation of the M(H2O) and SiF octahedra. The correlation frequency and the potential barrier hindering the motion were calculated in all the cases. Apart from the narrowing taking place at higher temperatures, the Co salt showed a change in the line structure at 248 °K, where a phase transition was reported from magnetic susceptibility measurements. Studies on the single crystals of ZnSiF6 • 6H2O and NiSiF6 • 6H2O showed that there are three nonequivalent p-p vectors, and after the transition they all become equivalent, with the M(H2O) octahedron reorienting about the fourfold axes. ©1973 The American Institute of Physics

Investigations on the preparation, oxidation and reduction reactions of thiophosphoryl fluoride

Pure thiophosphoryl fluoride has been prepared by the fluorination of thiophosphoryl chloride by sodium fluoride in acetonitrile medium. Oxidation of this phosphoryl fluoride by acidified chloramine-T ruptures the phosphorus-sulphur bond and oxidises the sulphur present to the hexavalent state. Anhydrous hydrogen iodide reduces the sulphur to hydrogen sulphide and phosphorus to the trivalent state.

Thermal decomposition of sulphur hexafluoride

Abstract is not available.

Thiophosphoryl fluoride and phosphoryl fluoride as initiators for the polymerisation of tetrahydrofuran

Thiophosphoryl fluoride and phosphoryl fluoride have been found to initiate the polymerisation of tetrahydrofuran. The living polymer formed has a high molecular weight of the order of a million and the density is found to be between 0.98 - 1.02 g/cc. A cationic mechanism for the polymerisation has been proposed.

A New Method for the Preparation of Sulphuryl Chloro Fluoride

It has been observed that a suspension of sodium fluoride in boiling acetonitrile could be used for the preparation of fluorine compounds such as silicon tetrafluoride [1], thiophosphoryl fluoride [2], sulphur tetrafluoride [3,4], and fluorocyclophosphazenes [5]. This method, when adopted for the fluorination of sulphuryl chloride [6], it is observed that a mixture of sulphuryl fluoride and sulphuryl chloro fluoride is obtained. On the other hand, when lead fluoride is substituted for sodium fluoride, pure sulphuryl chloro fluoride is evolved. Based on this observation, a new method has been standardised for the preparation of a pure sample of sulphuryl chlorofluoride by fluorinating sulphuryl chloride by lead fluoride in acetonitrile medium.

Pyridinium poly(hydrogen fluoride)- a reagent for the preparation of hexafluorophosphates

Pyridinium poly(hydrogen fluoride) has been found to be an efficient and versatile reagent for the preparation of hexafluorophosphates. Pyridinium hexafluorophosphate has been prepared by the reaction between phosphorus (V) halides (POCl3, POBr3, PSCl3, PCl5, PBr5) and pyridinium poly(hydrogen fluoride). This in turn is used to prepare the hexafluorophosphates of ammonium, sodium, potassium, rubidium and cesium in good yield and high purity.

Reaction of thiophosphoryl fluoride with metals and metal oxides

Abstract is not available.

NMR investigation of certain hydrated fluorosilicates

Proton and fluorine NMR were investigated in the temperature range 90–425 °K in the hexahydrated fluorosilicates of Zn, Cu, Mn, Co, and Ni and in the tetrahydrated CuSiF6 to obtain information about the internal motions in these solids. Second moment transitions were observed at widely different temperatures for the different substances, and these are ascribed to the onset of reorientation of the M(H2O)₆²⁺ and SiF₆^2- octahedra. The correlation frequency and the potential barrier hindering the motion were calculated in all the cases. Apart from the narrowing taking place at higher temperatures, the Co salt showed a change in the line structure at 248 °K, where a phase transition was reported from magnetic susceptibility measurements. Studies on the single crystals of ZnSiF6 · 6H2O and NiSiF6 · 6H2O showed that there are three nonequivalent p-p vectors, and after the transition they all become equivalent, with the M(H2O)₆²⁺ octahedron reorienting about the fourfold axes.

Hydrolysis of thiophosphoryl fluoride

The hydrolysis of thiophosphoryl fluoride has been studied both in acid and alkaline medium. The products are phosphate, fluoride and varying amounts of sulphide, sulphite, thiosulphate and elemental sulphur depending on experimental conditions. The probable mode of formation of the different sulphur species has been explained on the basis of sulphur in a higher oxidation state in the thiophosphoryl fluoride molecule.

NMR study of internal motions in certain iron group fluosilicates

NMR study of ferrous fluosilicate hexahydrate indicated the presence of motion of both proton and fluorine nuclei. Only a single narrow line was observed for protons for any arbitrary orientation of a single crystal with respect to the applied magnetic field. This can be interpreted in terms of a phase-correlated flip motion of the interproton vectors between two disordered orientations or in terms of a hindered rotation of the Fe(H2O) 6 octahedron about the fourfold axes, together with the flip motion. The fluorine second moment indicated that the SiF6 octahedron also is undergoing reorientation. The temperature variation of the powder linewidth showed a transition around 195°K and led to rather low values for the potential barriers hindering the motions. No significant temperature variation of the linewidth was observed for hexahydrated cobalt fluosilicate in the temperature range between 90°K and room temperature. Similar observations in a powder sample of tetrahydrated copper fluosilicate also showed the presence of internal motions. The linewidth transition in this case took place at about 220°K and was found to be rather abrupt. The potential barrier for the motion was found to be relatively high.

An ultraviolet photoelectron spectroscopic study of BF3–donor complexes

He i spectra of strong n–v type adducts of BF3 with H2O, CH3OH, (C2H5)2O, and CH3CN as well as of weak complexes of BF3 with NO and H2S are reported along with assignments based on MO calculations. The energy of the fluorine orbitals of BF3 is shown to be shifted in proportion to the strength of the donor–acceptor interaction. BF3 seems to form a contact pair with CS2.

A comparative study of superconducting LaBa2Cu3O7−δ and La3−xBa3+xCu6O14+δ

Based on X-ray diffraction and electron microscopy it is shown that oxides of the general formula La Ba2Cu3O7−δ become tetragonal when δ deviates slightly from 0. This tetragonal structure is similar to that of La3−xBa3+xCu6O14+δ, with a cubic perovskite subcell and triple periodicity. Electron micrographs of these tetragonal oxides show 90° microdomains. Orthorhombic LaBa2Cu3O7−δ with high Tc (not, vert, similar77 K) is found only when δ reverse similar, equals 0; this sample is subject to formation of twins. Fluorine substitution seems to favor superconductivity.

A New Method for the Preparation of Sulphuryl Chloro Fluoride

It has been observed that a suspension of sodium fluoride in boiling acetonitrile could be used for the preparation of fluorine compounds such as silicon tetrafluoride [1], thiophosphoryl fluoride [2], sulphur tetrafluoride [3,4], and fluorocyclophosphazenes [5]. This method, when adopted for the fluorination of sulphuryl chloride [6], it is observed that a mixture of sulphuryl fluoride and sulphuryl chloro fluoride is obtained. On the other hand, when lead fluoride is substituted for sodium fluoride, pure sulphuryl chloro fluoride is evolved. Based on this observation, a new method has been standardised for the preparation of a pure sample of sulphuryl chlorofluoride by fluorinating sulphuryl chloride by lead fluoride in acetonitrile medium.

Use of metastable equilibria for determination of Gibbs energy of solids

Attempts are made to measure activities of both components of a binary alloy (A�B) at 650 K using a solid-state galvanic cell incorporating a new composite solid electrolyte. Since the ionic conductivity of the composite solid electrolyte is three orders of magnitude higher than that of pure CaF2, the cell can be operated at lower temperatures. The alloy phase is equilibrated in separate experiments with flourides of each component and fluorine potential is measured. The mixture of the alloy (A�B) and the fluoride of the more reactive component (BF2) is stable, while (A�B) + AF2 mixture is metastable, Factors governing the possible use of metastable equilibria have been elucidated in this study. In the Co�Ni system, where the difference in Gibbs energies of formation of the fluorides is 21.4 kJ/mol, emf of the cell with metastable phases at the electrode is constant for periods ranging from 90 to 160 ks depending on alloy composition. Subsequently, the emf decreases because of the onset of the displacement reaction. In the Ni�Mn system, measurement of the activity of Ni using metastable equilibria is not fully successful at 650 K because of the large driving force for the displacement reaction (208.8 kJ/mol). Critical factors in the application of metastable equilibria are the driving force for displacement reaction and diffusion coefficients in both the alloy and fluoride solid solution.