Synthesis and properties of sulfur cyanide trifluoride,SF3CN,sulfur dicyanide difluoride,SF2(CN)2, and sulfinyl cyanide fluoride,FS(O)CN

Sulfur cyanide trifluoride, SF₃CN, and sulfur dicyanide difluoride, SF₂(CN)₂, have been prepared by metathesis between sulfur tetrafluoride, SF₄, and trimethyl silyl cyanide, (CH₃)₃SiCN, at – 30°C. Treatment of SF₃CN with freshly sublimed selenium dioxide, SeO₂, lead to sulfinyl cyanide fluoride, FS(O)CN. IR, Raman, ¹⁹F-NMR, uv and mass spectra of the novel compounds are presented as well as some physical and chemical properties.     

The role of the sulfur 3d orbitals in bond formation in sulfur-containing compounds

The role of the sulfur 3d orbitals in bond formation is discussed by taking into account the influence of the environment on the orbitals of the sulfur atom in the molecules. The calculation results of a series of prototype molecules containing sulfur such as SF₂ SF₄, NSF₃, SF₀, H₂S are reported. It is convincingly shown that in highly electronegative environment the energy levels of the sulfur 3d orbitals are reduced to the vicinity of those of the ligand valence orbitals and their spatial distributions are contracted to the bonding area, and therefore they can participate in bond formation to a certain extent, which is enhanced by the formation of the d-p π back bonds. It seems that the result reported in this paper is helpful for the solution of the long-standing debate about the sulfur 3d orbital participation in bond formation.     

Chiral substituierte Schwefelfluoride

Chirally Substituted Sulfur Fluorides The compounds CF₃? CFCl? SF₃, (CF₃? CFCl)₂SF₂, and CF₃? CFCl? SOF were prepared and their ¹⁹F-nmr spectra fully analysed. In CF₃? CFCl? SF₃ the chiral carbon atom leads to a splitting of the two axial fluorine atoms on sulfur. (CF₃? CFCl)₂SF₂ exists in a dl-form with equivalent (sulfur)-F atoms and a meso form with non-equivalent (sulfur)-F atoms. CF₃? CFCl? SOF exists in two diastereomeric forms.     

Untersuchung von Schwefel-Fluor-Verbindungen durch Codestillation und Cosublimation im Cady-Rohr

Zusammenfassung Das Trennverfahren der quantitativen Codestillation und Cosublimation ist zur Untersuchung von Schwefel-Fluor-Verbindungen eingesetzt worden, die vorwiegend Schwefel in niedriger Oxidationsstufe enthalten. Die neue Technik, die sich ideal für die Analyse luftempfindlicher und korrosiver Gasmischungen eignet, ermöglichte die Trennung kleiner Stoffmengen von SOF₂, SSF₂, FSSF und SF₃SF durch Destillation und die Charakterisierung dieser Stoffe durch ihre Dampfdrücke sowie die sich daraus ergebenden thennodynamischen Daten der Verdampfung bei sehr niedrigen Drücken. Mischungen aus SF₃SF und FSSF sowie FSSF und SSF₂ verhalten sich beim Sieden ideal, SSF₂ und SF₄ bilden ein azeotropes Gemisch mit SF₄ im Überschuß. SF₆ kann von den weniger flüchtigen Schwefelfluoriden durch Cosublimation leicht abgetrennt werden und als Standard für die Bestimmung von Stoffmengen und molaren Massen durch Verflüchtigung im Stickstoff- und Argonstrom dienen.Die Auswertung der Daten, die bei der Sublimation des Trifluorosulfoniumtetrafluoroborates, SF ₃ ⁺ BF ₄ ^– im Cady-Rohr erhalten wurden, bewiesen, daß die Flüchtigkeit dieser Verbindung auf ihre Dissoziation in SF₄ und BF₃ zurückzuführen ist.

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Investigation of sulfur fluorine compounds by codistillation and cosublimation in the Cady tube

Summary The separation concept of quantitative codistillation and cosublimation has been used to investigate sulfur fluorine compounds with sulfur in a lower oxidation state. The new technique, which is ideally suited to analyse air sensitive and corrosive gas mixtures, enabled the separation of small quantities of SOF₂, SF₄, SSF₂, FSSF and SF₃SF by distillation, and to characterize these compounds through their vapour pressures and thermodynamic data of vaporization at low pressures. Mixtures of FSSF and SF₃SF, and, FSSF and SSF₂ behave ideally on boiling, whereas SSF₂ and SF₄ form an azeotropic system with SF₄ in excess. SF₆ can easiliy be separated from the less volatile sulfur fluorides by cosublimation and may be used as a standard for the estimation of the amount of substances and molar masses through volatilization in nitrogen and argon. The evaluation of data obtained through the sublimation of trifluorsulfonium tetrafluoroborate in the Cady tube proved that the votalization process is caused by the dissociation of SF ₃ ⁺ BF ₄ ^– to yield SF₄ and BF₃.

     

Lewis Acid Behavior of SF4: Synthesis,Characterization, and Computational Study of Adducts of SF4 with Pyridine and Pyridine Derivatives

Sulfur tetrafluoride was shown to act as a Lewis acid towards organic nitrogen bases, such as pyridine, 2,6‐dimethylpyridine, 4‐methylpyridine, and 4‐dimethylaminopyridine. The SF₄?NC₅H₅, SF₄?2,6‐NC₅H₃(CH₃)₂, SF₄?4‐NC₅H₄(CH₃), and SF₄?4‐NC₅H₄N(CH₃)₂ adducts can be isolated as solids that are stable below ?45 °C. The Lewis acid–base adducts were characterized by low‐temperature Raman spectroscopy and the vibrational bands were fully assigned with the aid of density functional theory (DFT) calculations. The electronic structures obtained from the DFT calculations were analyzed by the quantum theory of atoms in molecules (QTAIM). The crystal structures of SF₄?NC₅H₅, SF₄?4‐NC₅H₄(CH₃), and SF₄?4‐NC₅H₄N(CH₃)₂ revealed weak S?N dative bonds with nitrogen coordinating in the equatorial position of SF₄. Based on the QTAIM analysis, the non‐bonded valence shell charge concentration on sulfur, which represents the lone pair, is only slightly distorted by the weak dative S?N bond. No evidence for adducts between quinoline or isoquinoline with SF₄ was found by low‐temperature Raman spectroscopy.     

Synthesis and Characterization of 2‐Pyridylsulfur Pentafluorides

Current approaches to prepare SF₅‐substituted heterocycles during the synthesis of targeted heterocyclic compounds require the use of SF₅‐functionalized aryl or alkyne reagents or SF₅Cl as a source of the SF₅ functional group. Herein we report that excess oxidative fluorination of 2,2′‐dipyridyl disulfide with a KF/Cl₂/MeCN system leads to the formation of thirteen new 2‐pyridylsulfur chlorotetrafluorides (2‐SF₄Cl‐pyridines). These molecules are found to undergo further chlorine–fluorine exchange reactions by treatment with silver(I) fluoride enabling ready access to a series of ten new substituted 2‐pyridylsulfur pentafluorides (2‐SF₅‐pyridines). This is the first preparatively simple and readily scalable example of the transformation of an existing heterocyclic sulfur functionality to prepare SF₅‐substituted heterocycles.     

Strukturen von SF5-substituierten Metallkomplexen

Structures of SF₅-substituted Metal Complexes Crystal and molecular structure of [(CO)₆Co₂(F₅S? C?C? SF₅)], [(CO)₄Co? CH₂? SF₅] and [(CO)₅Mn? S? CF?N? SF₅] are reported. Whereas the first two complexes are formed as expected, the latter one is the product of an unclear reaction pathway. In decomposition reactions of [(CO)₄Co? CH₂? SF₅] and [(CO)₅Mn? CH₂? SF₅] H₂C?SF₄ is produced. This allows a one step preparation of this elusive, simplest alkylidine sulfur tetrafluoride.     

Kinetics of Sulfur Oxide, Sulfur Fluoride, and Sulfur Oxyfluoride Anions with Ozone

Rate constants and product branching ratios were measured for eleven sulfur oxide, sulfur fluoride, and sulfur oxyfluoride anions reacting with O₃. The SO^– ₂ ion reacts rapidly to form –O^– ₃, SO^– ₃, and e^–. The temperature dependence of the branching ratio shows more reactive detachment and less SO^– ₃ formation at higher temperature. SO^– ₃ reacts with O₃, forming SO^– ₄ at 1/3 to 1/4 of the collisional rate from 200 to 500 K, respectively. At 300 K, SF^– ₆ charge transfers to O₃ at 20% of the collisional rate. F₂SO^– ₂ reacts with O₃ at a few percent of the collision rate, forming both O^– ₃ and FSO^– ₃; The ion F₃SO^– reacts slowly with O₃ to form F₃SO^– ₂. The ions SO^– ₄, SF^– ₅, FSO^– ₂, FSO^– ₃, F₃SO^–, and F₅SO^– are unreactive with O₃. A trend is noted relating the ion reactivity with the coordination of the central sulfur atom, i.e., the number of S–F bonds plus two times the number of S=O bonds. Only ions with a sulfur coordination of 4 or 6 are reactive, although the reaction rate constants are generally small. The reactivity trends appear to be partially explained by spin conservation. These reactions are all sufficiently slow, so O₃ reactions should not play a major role in SF₆/O₂ discharges. All ions studied have been found to be unreactive with O₂.     

Mass spectrometric study of SF6-N2 plasma during etching of silicon and tungsten

The reaction products in the SF₆-N₂ mixture rf plasma during reactive ion etching of Si and W have been measured by a mass spectrometric method. Two kinds of cathode materials were used in this work; they were stainless steel for the Si etching, and SiO₂ for the W etching. The main products detected in the etching experiments of Si and W included SF₄, SF₂, SO₂, SOF₂, SOF₄, SO₂F₂, NSF, NF₃, N₂F₄, N_xS_y, NO₂, and SiF₄. In the W etching with the SiO₂ cathode, additional S₂F₂, N₂O, and WF₆ molecules were also obtained. The formation reactions about the novel NSF compound and the sulfur oxyfuorides were discussed.     

Calculated structures of thiopyrylium-S-fluoride and S-trifluoride and attempts of their preparation

Structures and energies of cyclo-C₅H₅SF and cyclo-C₅H₅SF₃ have been calculated. In both cases the 2- and 4-CF-isomers are more stable than the SF and SF₃ isomers. The fluxional behavior of the sulfur bonded fluorides has been calculated also. In cyclo-C₅H₅SF an ellipsoidal rotation of the sulfur bonded fluorine atom is observed with a barrier of a few kcal mol⁻¹. In sulfur bonded cyclo-C₅H₅SF₃ the (Turnstile) rotation is predicted to occur without noticeable barrier, in agreement with previous work.Attempts to isolate the sulfur bonded isomers failed entirely: always 2 or 4-carbon-fluorides were obtained for cyclo-C₅H₅SF. The acyclic SF₅⁻ carrying precursors for the synthesis of cyclo-C₅H₅SF₃ failed in crucial steps of the reactions.     

Inorganic volatile fluorides obtained from electrical decomposition of sulfur hexafluoride in a quartz tube

Recent investigations on sulfur hexafluoride decomposition have shown the need of a rapid and efficient method for the qualitative and quantitative analysis of the reaction products. An analytical method for characterizing the gas mixture obtained from the decomposition of sulfur hexafluoride in a quartz reactor submitted to an r.f. discharge, is presented. A combination of gas-chromatographic, mass spectrometric and infrared spectrophotometric techniques has shown the presence of SF₆, SO₂F₂, SOF₄, SOF₂, SiF₄ and F₂ in the gas mixtures examined. For quantitative purposes a gas-chromatographic method has been found to be most suitable.     

A molecular orbital study of bond energies in compounds of sulfur and fluorine

CNDO/2 molecular orbital theory is employed in a study of the binding energies of the molecules SF, SF₂, SF₄, SF₆, their cations and anions, and of the molecules SSF₂, FSSF and S₂F₁₀. Computed energies, when rescaled according to energy partitioning concepts, compare favorably with available experimental data. Ionization energies and electron affinities are calculated for SF, SF₂, SF₄ and SF₆.

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Zusammenfassung Mit Hilfe der CNDO/2 Theorie werden die Bindungsenergien der SF, SF₂, SF₄ und SF₆ Moleküle, von deren positiven und negativen Ionen und von SSF₂, FSSF und S₂F₁₀ berechnet. Die berechneten Energien stimmen gut mit experimentellen Daten überein, wenn sie nach Energieaufteilungsprinzipien wiederberechnet werden. Ferner werden die Ionisierungsenergien und Elektronenaffinitäten für SF, SF₂, SF₄ und SF₆ angegeben.

     

Electron scattering and dissociative attachment by SF6 and its electrical-discharge by-products

Discrete electron-molecule processes relevant to SF₆ etching plasmas are examined. Absolute, total scattering cross sections for 0.2–12-eV electrons on SF₆, SO₂, SOF₂, SO₂F₂, SOF₄, and SF₄, as well as cross sections for negative-ion formation by attachment of electrons, have been measured. These are used to calculate dissociative-attachment rate coefficients as a function ofE/N for SF₆ by-products in SF₆.     

Experimental investigation and simulation of hollow fiber membrane process for SF6 recovery from GIS

In this present study, polyethersulfone hollow fiber membrane was used to recover sulfur hexafluoride (SF₆) from gas‐insulated switchgear (GIS). SF₆, N₂ pure gas and mixed gas (12.5 vol.% of SF₆) experiment was initiated to observe permeation behavior according to temperature and pressure difference and retentate flow rate. Scanning electron microscopy was used to investigate the morphological characteristics and the structure of asymmetric hollow fibers. The permeation rates of SF₆ and N₂ were measured by the variable pressure method. As a result, permeance of N₂ was 9.5–16.3 GPU, and selectivity of N₂/SF₆ was 10.5–13.3. Moreover, the concentration of SF₆ in the retentate stream reached to 99.2% by the control of the operating condition. Based on the experimental results, tree‐stage membrane process was designed using simulation program. As a result, demanded membrane area reduced about 74% according to operating condition difference. Copyright © 2013 John Wiley & Sons, Ltd.     

Novel sulfur-nitrogen-fluorine compounds : synthesis and properties of SF5NHF,SF5NClF and SF4NF

Using reactions developed for the synthesis of CF₂NF, CF₃NClF and CF₃NHF from ClCN, F₃SN can now be converted in high yield to the analogous sulfur compounds, SF₄NF, SF₅NClF and SF₅NHF. N-fluorotetrafluorosulfurimine is the simplest sulfur(VI) imine and is a rigid molecule. Details on the synthesis and properties of these novel compounds will be presented.     

Die Kristallstruktur des SF5−-Anions

Crystal Structure of the SF₅^?-Anion The carbanion SF₅? C(CF₃)₂^? decomposes slowly forming SF₅^?, and (CF₃)₂C?C(CF₃)₂. The pentafluorosulfates(IV) grow in large crystals which are stable for prolonged times in presence of a SF₄ vapour pressure. Crystal structure analysis of Rb⁺SF₅^? (Pbnm, a = 776.1(14), b = 990.3(5), c = 614.1(3) pm, Z = 4) revealed the SF₅^? anion in the expected square pyramidal structure. The axial bond is 15.9 pm shorter than the average equatorial bonds. The sulfur atom is located below the equatorial fluorine atoms. Pure Cs⁺SF₅^?-crystals seem to be notoriously twinned. Accidentally we isolated a double salt (Cs⁺)₆(SF₅^?)₄ (HF₂^?)₂ (P4 b2, a = 1031.7(15), c = 627.6(9) pm, Z = 1). Herein the anion SF₅^? has the same structure as in Rb⁺SF₅^?.     

Nucleophilic Activation of Sulfur Hexafluoride by N-Heterocyclic Carbenes and N-Heterocyclic Olefins: A Computational Study

Sulfur hexafluoride (SF₆) is considered as a potent greenhouse gas, whose effective degradation is challenging. Here we report a computational study on the nucleophilic activation of sulfur hexafluoride by N-heterocyclic carbenes and N-heterocyclic olefins. The result shows that the activation of SF₆ is both thermodynamically and kinetically favorable at mild condition using NHOs with fluoro-substituted azolium and sulfur pentafluoride anion being formed. The Gibbs free energy barrier during the activation of SF₆ has a linear relationship with the energy of HOMO of substrates, which could be a guideline for applying those compounds that feature higher energy in HOMO to activate SF₆ in high efficiency.     

The reactions of iminosulfur difluorides and chlorine monofluoride

The reactions of perfluoroalkyl- and perfluoroacyl-iminosulfur difluorides with chlorine monofluoride result in the preparation of perfluoroalkyldichloroamines and a new class of compounds N,N-dichloroperfluoroamides, R_fC(O)NCl₂, via the elimination of SF₄. The amides, FC(O)NCl₂ and CF₃C(O)NCl₂, in addition to 1,2-bis-(dichloroamino)tetrafluoroethane, Cl₂NCF₂CF₂NCl₂, are reported and characterized. The reactions of CIF with other sulfur(IV) imines proceed in an analogous manner to form perfluoroalkyl-dichloroamines via the elimination of the corresponding sulfur(IV) fluoride.     

Data on the formation and decomposition of bis(pentafluorosulfur) trioxide,bis(pentafluorosulfur) dioxide,bis(pentafluorosulfur) monoxide and of the radicals SF5O2 and SF5O. A review of earlier kinetic investigations

A method is described for the preparation of pure bis(pentafluorosulfur) trioxide. The mechanisms of formation and decomposition of SF₅O₃SF₅ and SF₅O₂SF₅ are described by reference to previous kinetic studies. The dissociation energies of these oxides and of the radicals SF₅O₂ and SF₅O are given and some reactions of SF₅·, SF₅O·, and SF₅O₂· are described.