SbF5 Research Articles

Unexpected reaction of antimony pentafluoride with a fluorinated propellane

While 1,3-dehydro-5,7-difluoroadamantane 11 reacts with SbF5 in super acid media (SO2ClF) to generate the 1,3-dehydroadamant-5,7-diyl dication 1, 1,3-dehydro-5-fluoroadamantane 12 fails to react analogously to produce the 1,3-dehydroadamant-5-yl cation 9; instead, the 3,5-difluoro-1-adamantylcation 13 is formed. We present a computational study that explains this surprising behavior by the initial addition of Sb2F10 to the propellane bond present in 12. This is computed to be highly exothermic and leads to a zwitterionic (or ion-pair) species, which in turn reacts autocatalytically with HF to produce the observed fluorinated cation 13, SbF3, and SbF6–.

Synthesis of 1-(tetrafluorophenyl)perfluoro-1-phenylethanes and their cyclization into polyfluoro-9-methylfluorenes under the action of antimony pentafluoride

The interaction of perfluoroethylbenzene with isomeric tetrafluorobenzenes in the presence of SbF5 at 25 °C, with further treatment of the reaction mixture with HF–pyridine and then with water, gives the corresponding 1-(tetrafluorophenyl)perfluoro-1-phenylethanes. 1-(2,3,4,5-Tetrafluorophenyl)perfluoro-1-phenylethane heated with SbF5 at 50–55 °C gives perfluoro-9-methylfluorene. 1-(2,3,5,6-Tetrafluorophenyl)perfluoro-1-phenylethane under similar conditions forms 1,2,3,4,5,7,8,9-octafluoro-9-(trifluoromethyl)fluorene and the corresponding 2,3,4,9-tetrahydro-1H-fluorene. In the case of 1-(2,3,4,6-tetrafluorophenyl)perfluoro-1-phenylethane, fluorene derivatives were not obtained under the action of SbF5 at 50–130 °C. The experimental data are consistent with the DFT calculations (B3LYP/6-31G*) of the energy barrier for the conrotatory electrocyclization of polyfluorinated 1,1-diphenyl-1-ethyl cations.

Isolation and Structural Characterization of Eightfold Protonated Octacyanometalates [M(CNH)8 ]4+ (M=MoIV , WIV ) from Superacids.

Octacyanometalates K4[Mo(CN)8] and K4[W(CN)8] are completely protonated in superacidic mixtures of anhydrous hydrogen fluoride and antimony pentafluoride. The resulting hydrogen isocyanide complexes [Mo(CNH)8]4+ [SbF6]− 4 and [W(CNH)8]4+ [SbF6]− 4 are the first examples of eight‐coordinate homoleptic metal complexes containing hydrogen isocyanide (CNH) ligands. The complexes were crystallographically characterized, revealing hydrogen‐bonded networks with short N⋅⋅⋅H⋅⋅⋅F contacts. Low‐temperature NMR measurements in HF confirmed rapid proton exchange even at −40 °C. Upon protonation, ν(C≡N) increases of about 50 cm−1 which is in agreement with DFT calculations.

Lewis adduct formation of hydrogen cyanide and nitriles with arsenic and antimony pentafluoride.

The reactions of hydrogen cyanide, butyronitrile, cyclopropanecarbonitrile, pivalonitrile and benzonitrile with arsenic pentafluoride and antimony pentafluoride result in the formation of 1 : 1 Lewis adducts, while malononitrile yielded both 1 : 1 and 1 : 2 Lewis adducts. All adducts were isolated and characterized by multinuclear NMR and vibrational spectroscopy, and in most cases by their X-ray crystal structures.

Formation of polyfluorofluorenes in the reactions of perfluoro-1,1-diphenylalkanes with antimony pentafluoride

Perfluoro-1,1-diphenylethane heated with SbF5 at 130 °C with further treatment of the reaction mixture with HF-pyridine and then with water, gave perfluorinated 9‐methylfluorene and 9-methyl-1,2,3,4-tetrahydrofluorene. Perfluoro-1,1-diphenylpropane under similar conditions formed perfluoro-9-ethylfluorene and perfluoro-9,9-dimethyl-1,2,3,4-tetrahydrofluorene. When perfluoroisobutylbenzene was heated with pentafluorobenzene in SbF5 medium at 130 °C, with further treatment of the reaction mixture with HF-pyridine and then with water, perfluoro-9-isopropylfluorene was obtained. Perfluorodiphenylmethane heated with SbF5, after treatment of the reaction mixture with water, gave perfluorobenzophenone; perfluorofluorene or its derivatives were not found in the mixture.

George Olah dies at 89

George A. Olah, the Donald P. and Katherine B. Loker Distinguished Professor of Organic Chemistry at the University of Southern California and the recipient of the 1994 Nobel Prize in Chemistry, has died. He was 89. Olah was a towering figure, physically and scientifically, who earned international chemistry fame 40 years ago for his novel use of “magic acid,” a concoction of antimony pentafluoride and fluorosulfonic acid that is billions of times as strong as sulfuric acid, to prepare long-lived carbocations. By extending the lifetimes of these fleeting species, Olah was able to probe them directly via spectroscopy methods. That work rapidly advanced and greatly popularized the study of reactive intermediates and organic reaction mechanisms. It ultimately led to Olah’s receipt of the Nobel Prize. In addition to research in fluorine chemistry, Olah and longtime USC colleague and scientific collaborator G. K. Surya Prakash recently focused on the chemical transformations

Experimental study on elemental behaviors in fluorination of nuclear spent fuel with flame reactor

Our proposed spent nuclear fuel reprocessing technology named FLUOREX is a hybrid system based on reprocessing technologies of fluorination and solvent extraction for light water reactor fuel. In the current research, we experimentally clarified solid–gas transfer behaviours of the fluorides in the FLUOREX process and identified the volatile and non-volatile compounds in the fluorination. We carried out a fluorination experiment for simulated spent nuclear fuel and solid separation from the UF6 gas stream. The distribution ratios of fission product elements in the experimental apparatus were evaluated. Molybdenum, Te, Nb, and Ru were volatilized by fluorination and they accompanied the UF6 gas. However, 22.9% of the Ru and 3.4% of the Nb were retained as solids in the experimental apparatus, contrary to the fact that their partial pressures in the experiment were lower than their vapor pressures. Rubidium, Sr, Zr, Ce, and Nd were completely recovered as solid fluorides, and these results agreed with the prediction based on boiling points of their fluorides. Antimony was completely recovered as a solid; nevertheless, the boiling point of antimony pentafluoride was lower than the process temperature, and that was attributed to the formation of a non-volatile antimony oxyfluoride.

Design of stereoelectronically promoted super lewis acids and unprecedented chemistry of their complexes.

A new family of stereoelectronically promoted aluminum and scandium super Lewis acids is introduced on the basis of state-of-the-art computations. Structures of these molecules are designed to minimize resonance electron donation to central metal atoms in the Lewis acids. Acidity of these species is evaluated on the basis of their fluoride-ion affinities relative to the antimony pentafluoride reference system. It is demonstrated that introduced changes in the stereochemistry of the designed ligands increase acidity considerably relative to Al and Sc complexes with analogous monodentate ligands. The high stability of fluoride complexes of these species makes them ideal candidates to be used as weakly coordinating anions in combination with highly reactive cations instead of conventional Lewis acid-fluoride complexes. Further, the interaction of all designed molecules with methane is investigated. All studied acids form stable pentavalent-carbon complexes with methane. In addition, interactions of the strongest acid of this family with very weak bases, namely, H2, N2, carbon oxides, and noble gases were investigated; it is demonstrated that this compound can form considerably stable complexes with the aforementioned molecules. To the best of our knowledge, carbonyl and nitrogen complexes of this species are the first hypothetical four-coordinated carbonyl and nitrogen complexes of aluminum. The nature of bonding in these systems is studied in detail by various bonding analysis approaches.

Ultrafast Self-Healing of Polymer toward Strength Restoration

Self-healing materials should take effect immediately following crack generation in principle, but the speed of autonomic recovery of mechanical properties through either extrinsic or intrinsic healing strategy reported so far is not that fast. Mostly, a couple of hours are taken for reaching steady state or maximum healing. To accelerate the healing process, the authors of this work make use of antimony pentafluoride as instant hardener of epoxy and successfully encapsulate the highly active antimony pentafluoride-ethanol complex in terms of hollow silica spheres. Accordingly, self-healing agent based on microencapsulated antimony pentafluoride-ethanol complex and epoxy monomer is developed. Epoxy material with the embedded healant capsules can thus be healed within a few seconds, as demonstrated by impact and fatigue tests. It is believed that the outcome presented here might help to move the self-healing technique closer to practical application, especially when the engineering significance of epoxy material is concerned.

The Existence of Hexafluoroarsenic(V) Acid

The homogeneous mixture of anhydrous hydrogen fluoride aHF and antimony pentafluoride AsF5 is known as a superacidic system. The high acidity is derived from the formation of [H2F](+) [AsF6](-). No experimental evidence exists for the existence of the free acid molecule HAsF6. The reaction of trimethylsilyl N,N-dimethylcarbamate in the binary system aHF/AsF5 led to decomposition of trimethylsilyl N,N-dimethylcarbamate at -50 °C to dimethylammonium hexafluoridoarsenate and cocrystallization of HAsF6. The single-crystal X-ray structure displays an HAsF6 molecule involved in an asymmetric hydrogen bridge to the hexafluoridoarsenate anion. As a result of the incalculable situation in the crystal lattice, the molecular structure of HAsF6 is calculated by quantum chemical structure optimization of the extreme cases of [FHF-AsF5](-) (strong hydrogen bond) and HAsF6 (no hydrogen bond) at the PBE1PBE/6-311G(3df,3pd) level of theory.

Expansion of the pentafluorobenzene ring and other skeletal transformations in the reaction of perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene) with antimony pentafluoride

The reaction of perfluoro(1-phenyl-1,2-diethyl-1,2-dihydrocuclobutabenzene) with SbF5 at 20°C, followed by treatment of the reaction mixture with water gave perfluoro {4-[1-(2-propylphenyl)propylidene]-2,5-cyclohexadien-1-one} together with perfluoro[4b,10-diethylbenzo[a]azulen-7(4bH)-one] resulting from unusual expansion of the pentafluorobenzene ring to seven-membered ring. Analogous reaction at 90°C, apart from the above compounds, afforded perfluorinated 10-ethyl- and 3,10-diethylbenzo[a]azulen-6(10H)-ones via elimination of C2F5 group from the seven-membered ring or its migration to the benzene ring.

ChemInform Abstract: Formation of Fluorene and Anthracene Derivatives in Reactions of Perfluorinated 1‐Alkyl‐1‐phenyl‐ and 1‐Alkyl‐2‐phenyl‐1,2‐dihydrocyclobutabenzenes with Antimony Pentafluoride.

AbstractThe reaction of the compounds (I) and (II) under different temperatures gives different major products and also various other derivatives as by‐products.

Synthesis and skeletal rearrangements of perfluorinated 4-alkyl- and 4-phenyl-tetralin-1-ones under the action of antimony pentafluoride

Heating of perfluorinated 1-methyl- and 1-ethyltetralins with SiO2 in an SbF5 medium at 100°C results in perfluoro-4-alkyltetralin-1-ones formation. Perfluoro-4-methyltetralin-1-one, under the action of SbF5 at 180°C with subsequent treatment of the reaction mixture with water, is converted to perfluoro-3,3-dimethylindan-1-one and perfluoro-3,4-dimethylisochromen-1-one. Perfluoro-4-ethyltetralin-1-one, under similar conditions, forms perfluoro-3-ethyl-3-methylindan-1-one, perfluoro-4-ethyl-3-methylisochromen-1-one and perfluoro-2-methyltetralin. Reaction of perfluorotetralin-1-one with pentafluorobenzene in the presence of SbF5 at 50–55°C leads to the formation of perfluoro-4-phenyltetralin-1-one, which under the action of SbF5 at 75°C isomerizes into perfluoro-3-methyl-3-phenylindan-1-one. Heating of the latter with SbF5 at 75–95°C gives, after treatment of the reaction mixture with water, perfluoro-2-(2-methylphenyl)-3-phenylpropenoic acid and perfluoro-4-methyl-3-phenylisochromen-1-one.

ChemInform Abstract: Isomerization of Perfluoro‐3,3‐diethylindan‐1‐one into Perfluoro‐1,3‐dimethyl‐4‐ethyl‐1H‐isochromen under the Action of Antimony Pentafluoride.

AbstractCompound (II) is actually isolated together with unreacted starting material (I).

Formation of fluorene and anthracene derivatives in reactions of perfluorinated 1-alkyl-1-phenyl- and 1-alkyl-2-phenyl-1,2-dihydrocylobutabenzenes with antimony pentafluoride

The reaction of perfluoro(1-methyl-1-phenyl-1,2-dihydrocyclobutabenzene) with SbF5 at 50°C, followed by hydrolysis, gave perfluoro(1-phenylindan-1-ol), while analogous reaction at 90°C afforded perfluoro[10-methylanthracen-9(10H)-one]. Perfluoro(1-methyl-2-phenyl-1,2-dihydrocyclobutabenzene) did not undergo skeletal transformations under analogous conditions, whereas at 200°C it was converted mainly into perfluoro(9-methylfluoren-9-ol). Perfluoro(1-ethyl-2-phenyl-1,2-dihydrocyclobutabenzene) reacted with SbF5 at 200°C to form perfluoro(9-ethylfluoren-9-ol) together with perfluorinated 9,9-dimethyl- and 9-ethyl-9-methyl-1,2,3,4-tetrahydro-9H-fluorenes.

Opening of the four-membered ring in perfluorinated 1-alkyl-2-phenyl- and 1-aryl-1,2-dihydrocyclobutabenzenes in the system I2-SbF5

Reactions of perfluorinated 1-phenyl-, 1-(2-ethylphenyl)-, 1-(4-ethylphenyl)-, 1-methyl-2-phenyl-, and 1-ethyl-2-phenyl-1,2-dihydrocyclobutabenzenes with iodine in antimony pentafluoride at 130°C, followed by hydroysis of the reaction mixture, resulted in the formation of perfluorinated 2-methyl-, 2-ethyl-2′-methyl-, 4-ethyl-2′-methyl-, 2-ethyl-, and 2-propylbenzophenones via opening of the four-membered ring in the initial cyclobutabenzene at the C1–C2 bond. The presence of hydrogen fluoride facilitates the process and promotes profound transformations leading to anthracene derivatives.

Investigation of the purity of antimony pentafluoride using 19F NMR

Samples of antimony pentafluoride from different syntheses as well as commercial products were investigated by 19F and 1H NMR and compared. HF was identified as impurity and SbF 6 − specie is also present. Their amounts have been correlated through a method based on 19F NMR.

The Preparation of Desflurane by the Vapor-Phase Fluorination of Isoflurane

There are several known processes for manufacturing the commercially important anaesthetic desflurane (CF3CHFOCHF2) by the catalyzed reaction of commercially available isoflurane (CF3CHClOCHF2) with hydrogen fluoride. The present available methods have the disadvantage of high catalyst usage, with consequent environmental problems, or of having to trade off low conversion against low selectivity. An alternative catalyst system was therefore sought that would avoid these problems, but would still give the benefits of a vapor-phase process and, in particular, a long catalyst life. A catalyst consisting of antimony pentafluoride supported on activated carbon has now been found to provide the basis for a novel vapor-phase process for the fluorination of isoflurane to desflurane using hydrogen fluoride. The process operates with a long catalyst life, high conversion, and high selectivity.

Isomerization of perfluoro-3,3-diethylindan-1-one into perfluoro-1,3-dimethyl-4-ethyl-1 H-isochromen under the action of antimony pentafluoride

The heating of perfluoro-3,3-diethylindan-1-one with SbF5 at 180°C after treatment of the reaction mixture with anhydrous HF afforded perfluoro-1,3-dimethyl-4-ethylisochromen, and after hydrolysis, perfluoro-1,3-dimethyl-4-ethyl-1H-isochromen-1-ol. The latter under the action of NaHCO3 converted into 5,6,7,8-tetrafluoro-1,3-bis(trifluoromethyl)-1H-isochromen-1-ol. Both isochromenols reacted with SOCl2 gave the corresponding polyfluoro-1-chloro-1H-isochromens. On dissolving isochromenols in CF3SO3H and isochromens in SbF5 perfluoro-1,3-dimethyl-4-ethylisochromenyl and 5,6,7,8-tetrafluoro-1,3-bis(trifluoromethyl)isochromenyl cations were generated which by hydrolysis were converted into the corresponding isochromenols.

Reaction of Trimethylsilylacetylenes with Antimony Pentafluoride under Matrix Isolation Conditions: Experimental and Computational Study

Reaction of trimethylsilylacetylenes Me(3)SiC≡CR with SbF(5) in the solid state was investigated using matrix isolation infrared spectroscopy and quantum-mechanical calculations. Two reaction pathways were detected. Replacement of the trimethylsilyl group with SbF(4) produces neutral antimony acetylides F(4)SbC≡CR. Acetylenic bond protonation produces silyl cation 6-R, fully bridged for R = H and SiMe(3). High total charges on the bridging SiMe(3) group and low Me(3)Si-C bond orders to acetylenic moiety, both calculated at the MP4(SDQ)/6-311G(d,p) level of theory, indicate high silyl cation character of these species.