Investigation of hydrofluorides of the alkaline earth metals by the NMR method

Opalovskii, A. A.; Fedotova, T. D.; Габуда, С. П.; Ikrami, D. D.

doi:10.1007/bf00743489

Cited by 4 publications

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“…The H−F distance in the symmetric [HF 2 ] − anion of Na[HF 2 ] has been reported to be 1.1383(5) Å, [9] while the asymmetric H−F distance in SrF[HF 2 ] was reported to be 1.090(7) Å [28] . 1 H and 19 F NMR spectra taken on “SrF 2 ⋅2.5HF” were said to be essentially identical to Ca[HF 2 ] 2 [27] . The H−F distance within the [HF 2 ] − anions of “SrF 2 ⋅2.5HF” was estimated by this method to be 1.17 Å with an asymmetric position of the H atom [27] .…”

Section: Resultsmentioning

confidence: 99%

“…The crystal structure determination of Ca[HF 2 ] 2 also showed a symmetric hydrogen bond with a H−F distance of 1.1419(11) Å [20] . Additionally, the HF content of “SrF 2 ⋅ 2.5HF” was determined by titration and it was concluded that the additional 0.5 equivalents of HF belonging to “SrF 2 ⋅ 2.5HF” were not detectable by NMR spectroscopy [27] . In hindsight, it appears to us that Sr[HF 2 ] 2 may have already been obtained by these researchers.…”

Section: Resultsmentioning

confidence: 99%

“…[28] 1 H and 19 F NMR spectra taken on "SrF 2 •2.5HF" were said to be essentially identical to Ca[HF 2 ] 2 . [27] The HÀ F distance within the [HF 2 ] À anions of "SrF 2 •2.5HF" was estimated by this method to be 1.17 Å with an asymmetric position of the H atom. [27] Only for Ca[HF 2 ] 2 was this later corrected to a symmetric hydrogen bond with a HÀ F distance of 1.143 (20) Å and an F•••F distance of 2.286(4) Å.…”

Section: Resultsmentioning

confidence: 99%

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A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF₂]₂

Stene¹,

Graubner²,

Ivlev³

et al. 2022

Zeitschrift anorg allge chemie

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Single crystal X-ray diffraction shows the hydrogen bond within the [FÀ HÀ F] À anion of Sr[HF 2 ] 2 to be symmetric with HÀ F bond lengths of 1.143(5) Å and an intramolecular F•••F distance of 2.2826(18) Å. The [HF 2 ] À anion adopts crystallographic C 2symmetry, however, it is essentially linear with a FÀ HÀ F angle of 174(4)°. Solid-state quantum chemical calculations agree with the experimental findings, showing a slightly bent FÀ HÀ F angle of 177.8°. The decomposition of Sr[HF 2 ] 2 to SrF 2 and HF is endothermic by + 64 kJ/mol at room temperature. The bonding in the [FÀ HÀ F] À anion is clearly ionic both in the solid state and gas phase.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF₂]₂

Stene¹,

Graubner²,

Ivlev³

et al. 2022

Zeitschrift anorg allge chemie

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“…2) use as the initial powder for granulation barium hydrofluoride in analogy to obtaining granular sodium fluoride [5]. It is proposed that barium hydrofluoride be obtained in two ways: neutralization of barium hydroxide or its salts by a solution of hydrofluoric acid with monitoring of the pH and by interaction of liquid water-free hydrogen fluoride with powder Barium hydrofluoride is not produced commercially, so that the plan is to work out its production technology under laboratory conditions.…”

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confidence: 99%

Obtaining sorption materials based on alkali and alkaline-earth metal fluorides for separation of the azeotropic mixture UF6–HF

Fiskov¹,

Makaseev

2011

At Energy

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Methods of obtaining granular sorbents for catching and purifying volatile inorganic fluorides are examined. The results of optimizing the technology of granular lithium fluoride and approaches to obtaining pelleted barium and calcium fluorides are presented. The granules obtained gave capacity to 0.6 g HF/g sorbent while maintaining the initial structure. The initial destruction was negligible, the number of destroyed granules was the same after three sorption-desorption cycles.Absorption processes are finding wide applications for obtaining and purifying volatile inorganic fluorides in the technologies of the nuclear-fuel cycle [1]. The best known sorbent is one that is based on powdered or granular sodium fluoride -a universal absorber of many volatile inorganic fluorides. Thus, positive experience has been gained in using powered and granular lithium fluoride for deep removal of hydrogen fluoride from uranium hexafluoride. Calcium, strontium, and barium fluoride possess high selectivity to technetium and boron fluorides. Barium fluoride has a substantial (to 5 molecules) theoretical capacity for hydrogen fluoride [2]. The main physicochemical and sorption properties of these fluorides have been well studied but the absence of technologies for obtaining in a granular form and regenerating after use is impeding their industrial applications. In this connection, the search for new methods of obtaining sorbents based on fluorides of alkali and alkali-earth methods, meeting modern technological and economic production requirements, is a pressing problem.This article presents the results of production of pelleted sorbents based on lithium, calcium, and barium fluorides and their compositions, suitable for sorbtion removal of hydrogen fluoride from volatile uranium fluorides and refractory metals [3,4].The production of pelleted sorbents is based on the formation of moistened powders with the formation of a "brittle gel," formed during the hydration of NaHF 2 or NH 4 F type salts. Correspondingly, the method of obtaining sorbents includes the following operations: preparation of a mix using ammonium fluoride as the binder and pore-generator, formation on a granulator, drying of sorbent pellets in a hot air stream at 100°C, development at 150-200°C and fixing of a porous structure (sintering) at 350-400°C.The drawbacks of using ammonium fluoride as the pore-generator were revealed in the course of practical tests. Thus, the decomposition of ammonium fluoride gives rise to intense corrosion of the construction materials used for the pro-

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“…The results of the investigation of barium, strontium and calcium hydrofluorides by NMR [2,3], IR spectroscopy [4,5] and refractometry [6] have shown that their formation is due to hydrogen bonds of the type F-H... F, similarly to the alkali metal hydrofluorides [7] where the anions HF2+ 1 are present in their structure. The strength of the hydrogen bond in the series of hydrofluorides decreases from barium to calcium and with the increasing number of HF molecules present.…”

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Kinetics of the thermal decomposition of alkaline earth metal hydrofluorides

Opalovsky

Fedorov

Fedotova

1969

Journal of Thermal Analysis

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The thermal stability of alkaline earth metal hydrofluorides was studied by means of a Derivatograph. The values of the activation energy, reaction order and rate constant were determined. The comparison of the kinetic parameters of the decomposition process for the complete series of hydrofluorides studied led to a certain regularity in the differences in their thermal stabilities and its correlation with the strength of the hydrogen bond in their structure.The interaction of the alkaline earth metal fluorides with hydrogen fluoride leads to the formation of compounds of composition MeF2 9 nHF (Me = Ba, Sr, Ca) [1 ], named hydrofluorides. The results of the investigation of barium, strontium and calcium hydrofluorides by NMR [2, 3], IR spectroscopy [4, 5] and refractometry [6] have shown that their formation is due to hydrogen bonds of the type F-H... F, similarly to the alkali metal hydrofluorides [7] where the anions HF2+ 1 are present in their structure. The strength of the hydrogen bond in the series of hydrofluorides decreases from barium to calcium and with the increasing number of HF molecules present.The majority of hydrofluorides are unstable and can easily be reconverted to the corresponding fluorides by removing hydrogen fluoride. However, their thermal stability has not been thoroughly studied so far, due to the special properties of hydrofluorides and the difficulties in the experimental work with these compounds. The data reported in the literature mainly concern the thermal stability of alkali metal bifluorides MeF 9 HF [8][9][10][11]. The information on the thermal stability of the alkaline earth metal hydrofluorides is not completely available. The results of the investigation of the thermal stability of alkaline earth metal hydrofluorides are reported in this paper.The studied compounds were prepared on the basis of the data on the ternary system HF-MeF2-H20 [1]. The following reagents were used: hydrofluoric acid (of special purity); anhydrous hydrogen fluoride, purified by rectifying; metal fluorides (analytical grade). Excess hydrogen fluoride was removed in a desiccator. The compounds prepared from the aqueous solutions of HF were dried in a desiccator over phosphorus pentoxide. Some compounds were prepared by decomposing hydrofluorides of higher HF content. The compounds were analysed

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Investigation of hydrofluorides of the alkaline earth metals by the NMR method

Cited by 4 publications

References 9 publications

A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF₂]₂

A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF₂]₂

Obtaining sorption materials based on alkali and alkaline-earth metal fluorides for separation of the azeotropic mixture UF6–HF

Kinetics of the thermal decomposition of alkaline earth metal hydrofluorides

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Investigation of hydrofluorides of the alkaline earth metals by the NMR method

Cited by 4 publications

References 9 publications

A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF2]2

A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF2]2

Obtaining sorption materials based on alkali and alkaline-earth metal fluorides for separation of the azeotropic mixture UF6–HF

Kinetics of the thermal decomposition of alkaline earth metal hydrofluorides

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A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF₂]₂

A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF₂]₂