Polymerization of Fluorothiocarbonyl Compounds

Recently it was shown that the C[dbnd]S group in fluorothiocarbonyl compounds readily undergoes addition polymerization. This review describes polymers obtainable from such compounds as CF₂[dbnd]S, CF₃CF[dbnd]S, ClCF₂CF[dbnd]S, HCFClCF[dbnd]S, and hexafluorothioacetone. The polymerization of CF₂[dbnd]S is readily brought about in anionic systems at low temperatures, giving a high-molecular-weight poly(thiocarbonyl fluoride) with a number-average molecular weight in the range of 300,000 to 400,000. It is believed that the major portion of this polymer is composed of chains of CF₃–-S—(—CF₂S—)_n–CF[dbnd]S. Poly(thiocarbonyl fluoride) is a highly resilient elastomer in the amorphous form but suffers the disadvantage of slow crystallization at temperatures below 35°C and concomitant loss of rubbery properties. Above 175°C it depolymerizes. Fluorothioacyl fluorides also undergo anionic polymerization, but the products are logy elastomers. Copolymers of fluorothioacyl fluorides with CF₂[dbnd]S have better thermal stability but poorer resilience than poly(thiocarbonyl fluoride). Hexafluorothioacetone has been polymerized at—110°C to give a white elastomer that slowly depolymerizes at room temperature to regenerate monomer. Thiocarbonyl fluoride is also susceptible to free-radical polymerization, and in free-radical systems it copolymerizes with conventional vinyl monomers, giving a wide variety of new elastomeric products.     

Synthesis of pentafluorophenyl esters from acid fluorides and potassium pentafluorophenoxide

The reaction of potassium pentafluorophenoxide with acid fluorides has been investigated and found to yield pentafluorophenyl esters. The compounds CH₃C(O)OC₆F₅, CF₃C(O)OC₆F₅, CF(O)OC₆F₅, CF₃OOC(O)OC₆F₅, and (C₆F₅O)₂CO have been prepared. Physical and spectral data for each compound are reported.     

Synthesen und Eigenschaften von Tetrakis(perfluoralkyl)tellur Te(Rf)4 (Rf = CF3, C2F5, C2F5, C3F7, C4F9)

Synthesis and Properties of Tetrakis(Perfluoroalkyl)Tellurium Te(R_f)₄ (R_f = CF₃, C₂F₅, C₃F₇, C₄F₉) Te(CF₃)₄ is obtained from the reaction of Te(CF₃)Cl₂ with Cd(CF₃)₂ complexes as a complex with e. g. CH₃CN, DMF. It is a light and temperature sensitive hydrolysable liquid. The reaction with fluorides yields the complex anion [Te(CF₃)₄F]⁻, with fluoride ion acceptors the complex cation [Te(CF₃)₃]⁺. With traces of water an acidic solution is formed. Te(CF₃)₄ acts as a trifluoromethylation reagent. The reaction with XeF₂ gives hints for the formation of Ye(CF₃)₄F₂. Properties and NMR spectra are discussed. The much more stable complexes of Te(R_f)₄ (R_f = C₂F₅, C₃F₇, C₄F₉) are formed from the reaction of TeCl₄ with the corresponding Cd(R_f)₂ complexes.     

Oxygen difluoride

The preparation and chemical and physical properties of the oxygen fluorides (OF₂, OF, O₂F₂, OOF and O₄F₂) are reviewed. There has been speculation about the existence of other oxygen fluorides (O₃F₂, O₃F, OSF₂ and O₆F₂) but these have not been well-characterized. The first member, OF₂, is much more stable than the other oxygen fluorides, and is also less-reactive. In addition to acting as a fluorinating agent and oxidizer, OF₂ has been shown to be a source of the OF radical. Dioxygen difluoride is a powerful fluorinating agent, but if reacted under carefully controlled conditions, can be a source of the OOF radical.     

Reaktionen des fluorcyans,FCN

By reaction of cyanogen fluoride with fluorine compounds like COF₂, SF₄, SOF₄ and HF in the presence of nucleophilic catalysts the addition products CF₃NCO, CF₃NSF₂, CF₃NSOF₂ and CF₃NH₂ could be obtained together with polymer and copolymer products of FCN. By rearrangement and further reaction of intermediates also CF₃OCOF, (CF₃)₂NCOF and the hitherto unknown compounds CF₃N(CN)₂ and F₂CNCF₂NSOF₂ are formed.     

Addition of fluoroperoxides to perfluorovinylsulfur pentafluoride

The addition of CF₃OOCF₃ and SF₅OOSF₅ across the double bond in CF=CFSF₅ was studied with 1:1 addition products being observed in both cases. For CF₃OOCF₃, the product was CF₃OCF₂CF(OCF₃)SF₅, whereas for SF₅OOF₅ it was SF₅CF₂CF₂OSF₅. The different reaction paths are attributed to steric reasons.The telomerization of fluoroolefins with fluoroperoxides has been reported [1,2]. Hexafluoropropene, when telomerized with bis(trifluoromethyl) peroxide, (CF₃O)₂,[1] yielded a series of oils having the composition CF₃O(C₃F₆)_nOCF₃ where n . Similarly, hexafluoropropene reacted with bis(pentafluorosulfur) peroxide, (SF₅O)₂, [2] to yield a series of oils of the composition SF₅O(C₃F₆)_nOSF₅ where n was also equal to or larger than two. Surprisingly, in neither case was the 1:1 addition product found.During our investigation of new thermally stable high density fluorooils, the thermal and photochemical reactions of perfluorovinylsulfur pentafluoride, CF₂=CFSF₅, with the fluoroperoxides (CF₃O)₂ and (SF₅O)₂ were studied. By analogy with the previous work on C₃F₆ [1,2], the main products were higher telomers, however in the case of (CF₃O)₂ and CF₂=CFSF₅ we were able to isolate also the 1:1 addition product according to:

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The necessary CF₃O· radicals were generated either thermally at 185°C or by uv-photolysis at ambient temperature. The yields of (1) were 4% in the thermal and 8% in the photolytic reaction. Compound (l) is a clear liquid and was characterized by elemental analysis, molecular weight, and infrared and mass spectroscopy.     

Fluorination of fluoro-cyclobutene with high-valency metal fluoride

Fluorinations of 1,4,4-trifluorocyclobutene and 3,3,4,4-tetrafluorocyclobutene using high-valency metal fluorides such as CoF₃, MnF₃, AgF₂, CeF₄ and KCoF₄, and elemental fluorine were examined. In these reactions with CoF₃ and MnF₃, vic-difluorination proceeded mainly. While, 1,4,4-trifluorocyclobutene yielded 3,3,4,4-tetrafluorocyclobutene, and 3,3,4,4-tetrafluorocyclobutene yielded 1,3,3,4,4-pentafluorocyclobutene mainly in the case of AgF₂. The further fluorinated products were increased under severer conditions. Also, the plausible reaction mechanism was suggested.     

Fluorocarbon-selenium chemistry: Accomplishments and quests

The binary selenium fluorides SeF_n (n = 2, 4, 6) and Se₂F₂ are considered along with corresponding perfluorohalogenoorgano- selenium compounds with selenium in the oxydation states 1, 2, 4 and 6. For lower selenium fluorides, preparation and characterisation are emphasized. Recent results in the chemistry of SeCF₂, CF₃SeCl, CF₃SeSeCF₃, CF₃Se(O)OM and CF₃Se^VI- compounds are presented. A comparison with the corresponding sulfur chemistry is also provided.     

Kinetics and mechanism of the thermal gas‐phase oxidation of perfluorobutene‐2 in presence of trifluoromethyl hypofluorite

The oxidation of perfluorobutene‐2 (C₄F₈) initiated by trifluoromethyl hypofluorite (CF₃OF) in presence of O₂ has been studied at 323.1, 332.6, 342.5, and 352.0 K, using a conventional static system. The initial pressure of CF₃OF was varied between 4.8 and 23.6 Torr, that of C₄F₈ between 48.7 and 302.4 Torr, and that of O₂ between 51.5 and 270.4 Torr. Several runs were made in presence of 325.5–451.2 Torr of N₂. The main products were COF₂, CF₃C(O)F, and CF₃OC(O)F. Small amounts of compound containing ? CF(CF₃)? O? C(O)CF₃ group were also formed, as detected by ¹³C NMR spectroscopy. The oxidation is a homogeneous short‐chain reaction, attaining, at the pressure of O₂ used, the pseudo‐zero‐order condition with respect to O₂ as reactant. The reaction is independent of the total pressure. Its basic steps are as follows: the thermal generation of CF₃O^? radicals by the abstraction of fluorine atom of CF₃OF by C₄F₈, the addition of CF₃O^? to the alkene, the formation of perfluoroalkoxy radicals RO^? in presence of O₂, and the decomposition of these radicals via the C? C bond scission, giving products containing ? C(O)F end group and reforming RO^? and CF₃O^? radicals. The mechanism consistent with experimental results is postulated. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 532–541, 2003     

Ligandenfeld- und ESR-spektroskopische Untersuchungen zum JAHN-TELLER-Effekt des Ag2+-Ions in fluoridischer Koordination

The JAHN -TELLER Instability of Ag²⁺ in Fluoridic Coordination-EPR and Ligand Field Spectroscopic Results From the ligand field and EPR spectra of the compounds AgMe^IVF₆(Me^IV:Sn, Zr) [I]. A₂^IAgF₄ (A^I:Rb, Cs) [II] and E^II AgF₄ (E^II:Sr, Ba) [III] between 4 and 298°K could be deduced, that the fluorides [I] and [II] with unknown structures contain tetragonally elongated AgF₆-octahedra in ferro- and antiferrodistortive order respectively. While the tetragonal elongation is weak to moderate for the compounds [I] and considerable in case of the fluorides [II], the compounds [III] contain AgF₄ squares in antiferrodistortive order - in correspondence with the KBrF₄ structure. As a consequence of lower and more anisotropic k_‖- and k_?-parameters in case of Ag²⁺ compared with Cu²⁺ the d electron delocalisation within the Ag²⁺? F^? bond should be more extensive than within the Cu²⁺? F^? bond and the π anisotropy larger as well.     

Probing the Reactivity of the Potent AgF2 Oxidizer. Part 2: Inorganic Compounds

The reactivity of Ag^IIF₂ towards forty two inorganic compounds containing oxo‐ and chloro‐ ligands, has been investigated. Five families of compounds were studied: (i) binary oxides of metals and nonmetals, (ii) ternary salts of inorganic oxo acids, (iii) concentrated or anhydrous oxo‐ acids, (iv) binary and ternary chlorides and (v) oxochlorides. At low temperatures up to 200 °C AgF₂ readily oxidizes HgO, B₂O₃, PbO₂, As₂O₅, Ag₂SO₄, LiBO₂, K₂CO₃, KVO₃, Ag₂WO₄, and AgMnO₄ with concomitant oxygen evolution. In the same conditions V₂O₅, CrO₃, MoO₃, WO₃, CuO, Tl₂O₃, I₂O₅, Re₂O₇, K₂SO₄, HgSO₄, KSO₃F, KNO₃, KClO₄, KIO₄, BaCrO₄, KMnO₄ and KReO₄ resist the action of AgF₂ but many of these compounds get oxidized at higher temperatures (up to nearly 300 °C). Substantial inertness of sulfates, chromates, nitrates, perchlorates, permanganates and perrhenates suggests that one might attempt to synthesize salts of divalent silver with these anions. AgF₂ vigorously reacts with H₂SO₄ (fuming, 30% SO₃), HSO₃Cl (100%), HClO₄ (70%), and HNO₃ (fuming, 100%) at room temperature yielding salts of Ag^I and O₂; for HClO₄ and HNO₃ pre‐cooled to ?35 °C metastable perchlorate / nitrate complexes of Ag^II are obtained. Anhydrous HSO₃F behaves similar to HSO₃CF₃ (see Part 1 of this series) yielding slow methathetical conversion of AgF₂ without concomitant redox reaction. Majority of chlorides and oxochlorides studied (AgCl, AuCl₃, KAuCl₄, WCl₆, WOCl₄, MoOCl₄, MoO₂Cl₂) react with AgF₂ at temperatures below 160 °C. Reaction with SiCl₄ (in contrast to CCl₄) is violent and very exothermic at room temperature. Liquid CrO₂Cl₂ (at room temperature) and solid WO₂Cl₂ (up to 180 °C) are kinetically inert to AgF₂. We do not observe intercalation of AgF₂ with various redox—inert oxo‐ and chloro‐ Lewis bases at the experimental conditions.     

Reactions of mesomeric fluorocarbanions with acid anhydrides. Transformation of trifluoromethyl groups into fluorocarbonyl and perfluoroacyl groups

It was found that the reaction of mesomeric fluorocarbanions of the CF₃$\text{C}\text{θ}$XCOY type with benzoic anhydride leads to the loss of benzoyl fluoride and the formation of mesomeric carbanions of the FCO$\text{C}\text{θ}$XCOY type. In a similar reaction with perfluorocarboxylic acid anhydrides, besides a CF₃→COF transformation, further change of COF into COR_F is observed, leading to the formation of salts containing mesomeric anions of the R_FCO$\text{C}\text{θ}$XCOY type, which, upon acidification, give 1,1- -bis(perfluoroacyl)-2,2,2-trifluoroethanes CF₃CH(COR_F)₂ , tris- (perfluoroacyl)methanes (R_FCO)₃CH and bis(trifluoroacetyl)- acetic ester (CF₃CO)₂CHCOOMe. It has been shown that perfluoroalkyl groups in β-diketones and β,β′-triketones may hinder enolization despite their electron-attracting effect.     

Enhanced Lewis acidity by aliovalent cation doping in metal fluorides

A model regarding the generation of acidity in binary metal fluorides has been proposed and its validity has been examined for several binary fluoride systems with the general compositions MF₃/M′F₃ and MF₂/M′F₃. In accordance with this hypothesis, the binary systems (CrF₃/AlF₃, CrF₃/FeF₃ and AlF₃/VF₃) do not show acidities larger than the sum of the acidities of the component fluorides. The hypothesis predicts the generation of Lewis acidity when MF₂ is the major component (host) and generation of Brønsted acidity when MF₃ acts as the host for the MF₂/M′F₃. The experimental results (surface acidity and catalytic activity) confirmed the predictions made from this hypothesis for binary combinations MgF₂/ M′F₃ (M′=Cr, Al, Fe, V). The application of this model is discussed in terms of other parameters: ionic radii and the fluoride affinity of the metal fluorides involved.     

Chemical vapor deposition using lanthanide β-diketone chelates with difluorodichloromethane

Preparation of lanthanide fluoride and chloride films has been studied by chemical vapor deposition (CVD) using Ln(thd)₃ (Ln=lanthanide(III); thd=2,2,6,6-tetramethyl-3,5-heptanedionato ligand) and Y(thd)₃ with gas mixture systems of CF₂Cl₂ (difluorodichloromethane)/O₂ and CF₂Cl₂/H₂. Two kinds of fluorides, LnOF oxyfluoride and LnF₃ triffluoride, were obtained separately along a CVD tube at atmospheric pressure and temperature as low as 300–600°C by the reaction of Ln(thd)₃ chelates with CF₂Cl₂/O₂ gas system. The chemical characteristics of the CVD products were considered from the thermochemical point of view.     

The reaction of 1,2-diiodo-tetrafluoroethane with sulfur trioxide

As an extension of our studies on the reaction of I(CF₂CF₂)_nI (n = 2 and 3) with sulfur trioxide¹⁾, the reaction of 1,2-diiodo-tetrafluoroethane with sulfur trioxide was studied.1,2-Diiodo-tetrafluoroethane was reacted with an excess of sulfur trioxide at reaction temperature ranging from 0°C to 115°C.The products were not the expected iododifluoroacetyl fluoride and/ or oxalyl fluoride, but thermally stable derivatives with polysulfate structures.These derivaties could be converted nearly quantitatively into iododifluoroacetyl fluoride and ethyl iododifluoroacetate by potassium fluoride and by ethanol, respectively.The possible structures of these derivatives will be discussed based on these results and ¹⁹F-NMR studies.     

Catalytic Gas‐phase Fluorination of Hexachlorobutadiene to 1,2‐Dichlorotetrafluorocyclobutene over Cr/Zn‐based Catalysts

In this paper, the gas‐phase fluorination of hexachlorobutadiene (HCBD) to synthesize 1,2‐dichlorotetrafluorocyclobutene (DTB) was carried out over a series of Cr/M/Zn catalysts (M = Ni, Co, Cu, In, Al). The influence of prefluorination by different fluorinating agents (HF, 95%HF + 5%Cl₂, 95%HF + 5%O₂, CF₂O, CF₂Cl₂) on catalytic performance of Cr/Co/Zn sample was also investigated. The addition of prompters to the Cr/Zn catalyst improved remarkably its catalytic properties. The Cr/Ni/Zn catalyst exhibited the best catalytic activity (1.318 mmol/h/g) at 390 °C and the Cr/Co/Zn catalyst showed the best DTB selectivity (42.5%) at 350 °C. Compared to that of gaseous HF, the catalytic performance of the Cr/Co/Zn catalyst after treatment by HF + O₂ and CF₂O increased considerably, whereas for HF + Cl₂ and CF₂Cl₂ it showed little effect. In order to identify the different species (Cr─O, Cr─F, CrO _xF _y) present on catalysts’ surface and determine their exact role, these catalysts before and after the reaction were characterized by X‐ray photoelectron spectroscopy. It was found that the concentration of the various species was responsible for the activity and lifetime of catalysts. Moreover, a possible reaction route is proposed based upon the product distribution. The most feasible formation pathway of DTB proceeded via the cyclization of C₄Cl₄F₂ or C₄Cl₃F₃ to yield c‐C₄Cl₄F₂ and c‐C₄Cl₃F₃ followed by further the Cl/F exchange.     

Preparative Electrosynthesis of Strong Oxidizers at Boron-Doped Diamond Electrode in Anhydrous HF

The use of the boron-doped diamond electrode as a sufficiently stable electrode for electrochemical measurements/synthesis in liquid anhydrous hydrogen fluoride medium is reported. Electrooxidation of silver(I) has been studied in this solvent by using classical transient electrochemical methods and impedance spectroscopy. It has been found that faradaic currents related to silver(I) oxidation and the fluorine evolution reaction are reasonably separated at the potential scale, which allows efficient electrosynthesis of Ag^IIF₂, a powerful oxidizer. Impedance spectroscopy measurements provide insight into complex mechanism of AgF₂ formation. The procedure for electrosynthesis is provided for the first time in both galvanostatic and potentiostatic condition.     

Fluoro-ketones. II Reactions of fluorocarbon grignards and copper compounds with perfluoroalkylacid fluorides

The reactions between C₆F₅MgBr (I), p-BrC₆F₄MgBr (X), C₆F₅Cu (XXI), p-HC₆F₄Cu (XXII) and p-BrC₆F₄Cu (XV) with primary and secondary perfluoroalkylether acid fluorides were studied. The Grignard compounds react very slowly with the secondary acid halides (R_fCF(CF₃C(O)F) whereby competing reactions cause undesirable by-products and reduction of ketone yields. Primary acid halides (R_fCF₂C(O)F) react much faster with C₆F₅MgBr to give the ketone in improved yields. The organocopper compound react with either primary or secondary acid halides to give the ketone in excellent yields with no by-product formation from competing secondary reactions. Solvent, type of organometallic reagent and primary versus secondary acid fluoride are variables that influence product yield and product distribution.     

Superionic Conduction in Complex Fluorides of Antimony(III) MnSbxFy (M—Cations of an Alkali Metal, Ammonium, or Thallium, n = 1–3, and x = 1–4)

Methods of ¹⁹F NMR and impedance spectroscopy are used to investigate the internal mobility of fluoride (ammonium) ions and electrophysical characteristics of complex trivalent antimony fluorides MSb₄F₁₃, MSb₃F₁₀, MSb₂F₇, M₂Sb₃F₁₁, M₃Sb₄F₁₅, and MSbF₄ (M is an alkali cation, ammonium, thallium). The ion motion types in the cationic and anionic sublattices of the fluorides are determined at 150–500 K. The polymorphous transformations in the fluorides are usually phase transitions to a superionic state and their high ionic (superionic) conductivity (σ ≥ 10⁻⁴ to 10⁻² S cm⁻¹ at 400 K) is due to the diffusion motion of ions of fluoride, ammonium, and possibly sodium, potassium, and thallium. The high polarizability of thallium ions favors the development of high mobility of fluoride ions in the fluorides.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 560–572.Original Russian Text Copyright © 2005 by Kavun, Uvarov, Slobodyuk, Brovkina, Zemnukhova, Sergienko.