Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C6(CH3)62+

In contrast to the well‐known 2‐norbornyl cation, the structure of which was a matter of long debate until its pentacoordinated nature was recently proven by an X‐ray structure, the pentagonal‐pyramidal dication of hexamethylbenzene has received considerably less attention. This species was first prepared by Hogeveen in 1973 at low temperatures in magic acid (HSO₃F/SbF₅), for which he proposed a non‐classical structure (containing a hexacoordinated carbon) based on NMR spectroscopy and reactivity studies, but no X‐ray crystal structure has been reported. C₆(CH₃)₆²⁺ can be obtained through the dissolution of hexamethyl Dewar benzene epoxide in HSO₃F/SbF₅ and crystallized as the SbF₆⁻ salt upon addition of excess anhydrous hydrogen fluoride. The crystal structure of C₆(CH₃)₆²⁺ (SbF₆⁻)₂⋅HSO₃F confirms the pentagonal pyramidal structure of the dication. The apical carbon is bound to one methyl group (distance 1.479(3) Å) and to the five basal carbon atoms (distances 1.694(2)–1.715(3) Å).     

Intramolecular Fluorocyclizations of Unsaturated Carboxylic Acids with a Stable Hypervalent Fluoroiodane Reagent

A new class of fluorinated lactones was prepared by the intramolecular fluorocyclizations of unsaturated carboxylic acids by using the stable fluoroiodane reagent in combination with AgBF₄. This unique reaction incorporates a cyclization, an aryl migration, and a fluorination all in one step. The fluoroiodane reagent, prepared easily from fluoride, can also be used without a metal catalyst to give moderate yields within just 1 hour, thus demonstrating that it is a suitable reagent for developing new ¹⁸F‐labelled radiotracers for PET imaging.     

Ionic mobility and electrophysical properties of solid solutions in PbF<Subscript>2</Subscript>–SbF<Subscript>3</Subscript> and PbF<Subscript>2</Subscript>–SnF<Subscript>2</Subscript>–SbF<Subscript>3</Subscript> systems

Ionic mobility and electrical conductivity of solid solutions with fluorite structure, obtained with solid-state approach in PbF₂–SbF₃ and PbF₂–SnF₂–SbF₃ systems, are studied by 19F NMR and electrochemical impedance spectroscopy methods. The 19F NMR spectra parameters, types of ion motions in the fluoride sublattice, and the ionic conductivity magnitude are shown to be determined by the temperature and fluoride concentration in the solid solutions. The solid solution specific conductivity in the PbF₂–SbF₃ and PbF₂–SnF₂–SbF₃ systems at 420–450 K is as high as ~10^–2 S/cm, which allows accounting the solid solutions as a base for preparation of functional materials.     

Some properties of polyfluoroacyl- and polyfluoroacetonyl fluorosulfates

Conclusions Polyfluoroacyl fluorosulfates are decomposed by the action of KF, SbF₅ and its mixtures with HSO₃F with the formation of the corresponding acyl fluorides. Pentafluoroacetonyl fluorosulfate reacts with SbF₅ to form hexafluoroacetone; the fluoride ion causes decomposition of 3-chlorotetrafluoroacetonyl fluorosulfate to chlorodifluoroacetyl fluoride.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1368–1372, June, 1987.     

The preparation and 119Sn mössbauer spectra of [Sn2F3] [MF6] (M  As,Sb)

Tin(II) fluoride reacts with Lewis acids, AsF₅ and SbF₅, in a 2:1 ratio, to give salts of the [Sn₂F₃⁺] cation. Reaction of SnF·MF₆ with SnF₂ in liquid SO₂ also produces the [Sn₂F₃] [MF₆] salt. Tin-119 Mössbauer data are presented and compared with those for SnF₂, SnF·MF₆ and Sn(SbF₆)₂.     

Silver-silver(I) system in superacid mixtures HF+SbF5

An electrochemical study of silver in superacid medium HF+SbF₅ shows that Ag is not oxidized and that the couple Ag/Ag(I) may be used as a reference electrode in mixtures of HF and SbF₅ containing 30% of SbF₅ (by weight). From potentiometric measurements with a silver electrode, it is shown that AgSbF₆ is slightly soluble and the solubility product is determined (log(K_s/mol²l^?2)=1.1). Evidence for the strong acidity of SbF₅ is demonstrated and it is shown that there are no polymers (such as Sb₂F₁₁^?) in the concentration range 0–3 M of SbF₅.     

Preparation and application of porous calcium fluoride—a novel fluorinating reagent and support of catalyst

A novel material, porous calcium fluoride (PCF) with more than 60 m²/g surface area, was prepared by the reaction of soda lime (SL) with anhydrous hydrogen fluoride (AHF), and its application as a fluorinating reagent and support of catalyst was investigated.     

Reaktion von Lanthanfluorid mit Halogenalkanen

Reactions of Lanthanum Fluoride with Halogenoalkanes Reactions are reported on lanthanum fluoride as a fluorinating reagent and as a catalyst for the fluorination and dismutation of halogenoalkanes. Carbon tetrachloride, monofluorotrichlormethane, and chloroform are partially fluorinated by lanthanum fluoride. In the presence of HF, lanthanum fluoride acts as catalyst the fluorine transfer to CCl₄, CHCl₃ and C₂F₃Cl₃. Monofluorotrichloromethane, difluorodichloromethane, and trifluorotrichloroethane dismutate on lanthanum fluoride. Results on the thermal decomposition of the above-mentioned fluorochloroalkanes are communicated.     

The synthesis and vibrational spectra of the antimony(V)fluoride-fluorosulfates SbF3(SO3F)2, SbF4(SO3F) and Sb2F9(SO3F)

The synthesis of the title compounds by a variety of routes is described. These routes involve the oxidation of antimony(III)fluoride by bis(fluorosulfuryl)peroxide and the use of non-statistical ligand redistribution reactions. Complex formation with ClO₂SO₃F leads to ClO₂[SbF_n(SO₃F)_6-n], with n=3 or 4. Polarized Raman data and low temperature infrared data are reported. All antimony(V)fluoride-fluorosulfates are found to have fluorosulfate bridges with SbF₃(SO₃F)₂ and SbF₄(SO₃F) being polymers. Ionic formulations for the ClO⁺₂ complexes are again based on vibrational spectra.     

Hydrolysis of antimony(III) fluoride complexes

Vibrational and ¹⁷O NMR spectroscopy in combination with quantum chemical calculations are used to investigate the hydrolysis of antimony(III) fluoride complexes. A hydrolytic decomposition of SbF₃ and [SbF₄]^? is accompanied by oligomerization with the formation of edge-and corner-connected dimers ([Sb₂O₂F₄]^2?, [Sb₂OF₈]^4?) and trimers ([Sb₃O₃F₆]^3?, [Sb₃OF₉]^2?) with bridging oxygen atoms. The hydrolysis of [SbF₄]^? is also characterized by the presence in the solution of a discrete cation of [SbF₅]^2? which is least hydrolized. Only a partial isomorphic substitution of fluoride ion by hydroxide one is possible, which is reflected in the composition of K₂Sb(OH)_xF_5?x (x = 0.3) crystals isolated from the fluoride aqueous solution.     

Composes d'addition entre les pentafluorures d'uranium et d'antimoine,preparation des composes UF5. n SbF5 (n = 1 ou2)

The adduct UF₅.2SbF₅ has been obtained from the reaction of UF₅ with SbF₅ and the reaction of UF₆ with SbF₅ in the presence of freon 114. From this preparation and also from studies on UF₆, SbF₅ solutions, the fluorinating properties of UF₆ were found to be enhanced by the presence of SBF₅. An x-ray diffraction study has shown that crystals of UF₅.2SbF₅ are monoclinic, space group P2₁/c, with unit cell dimensions a = 8.036(3) Å ; b = 14.112(13) Å ; c = 10.028(17) Å ; β = 96.91(7)°.The adduct UF₅.SbF₅ is obtained by thermal decomposition of UF₅.2SbF₅.     

Stabilization of [WF5]+ by Bidentate N‐Donor Ligands

Transition‐metal hexafluorides do not exhibit fluoride‐ion donor properties in the absence of donor ligands. We report the first synthesis of donor‐stabilized [MF₅]⁺ derived from a transition‐metal hexafluoride via fluoride‐ion abstraction using WF₆(L) (L=2,2′‐bipy, 1,10‐phen) and SbF₅(OSO) in SO₂. The [WF₅(L)][Sb₂F₁₁] salts and [WF₅(1,10‐phen)][SbF₆]?SO₂ have been characterized by X‐ray crystallography, Raman spectroscopy, and multinuclear NMR spectroscopy. The reaction of WF₆(2,2′‐bipy) with an equimolar amount of SbF₅(OSO) reveals an equilibrium between [WF₅(2,2′‐bipy)]⁺ and the [WF₄(2,2′‐bipy)₂]²⁺ dication, as determined by ¹⁹F NMR spectroscopy. The geometries of the cations in the solid state are reproduced by gas‐phase geometry optimizations (DFT‐B3LYP), and NBO analyses reveal that the positive charges of the cations are stabilized primarily by compensatory σ‐electron donation from the N‐donor ligands.     

The Crucial Role of Sb2F10 in the Chemical Synthesis of F2

The purely chemical synthesis of fluorine is a spectacular reaction which for more than a century had been believed to be impossible. In 1986, it was finally experimentally achieved, but since then this important reaction has not been further studied and its detailed mechanism had been a mystery. The known thermal stability of MnF₄ casts serious doubts on the originally proposed hypothesis that MnF₄ is thermodynamically unstable and decomposes spontaneously to a lower manganese fluoride and F₂. This apparent discrepancy has now been resolved experimentally and by electronic structure calculations. It is shown that the reductive elimination of F₂ requires a large excess of SbF₅ and occurs in the last reaction step when in the intermediate [SbF₆][MnF₂][Sb₂F₁₁] the addition of one more SbF₅ molecule to the [SbF₆]⁻ anion generates a second tridentate [Sb₂F₁₁]⁻ anion. The two tridentate [Sb₂F₁₁]⁻ anions then provide six fluorine bridges to the Mn atom thereby facilitating the reductive elimination of the two fluorine ligands as F₂.     

The preparation and characterisation of some new binary fluorides of antimony

Antimony pentafluoride acts as a useful oxidising agent towards many non-metals, giving interesting cations, and in the process is itself reduced. It would be helpful to know what the reduced products are, and under what conditions they are formed. Therefore, SbF₅ and the known SbF₅·SbF₃⁽¹⁾ in AsF₃ solution were reduced by iodine and/or PF₃ giving crystals of the new adduct, (SbF₃)₆(SbF₅)₅ [Monoclinic, a = 11.638(1), b = 8.995(1), c = 16.723(3) ā, β = 106.81(1)°, P2₁/c]; (SbF₃)₅(SbF₅)₃ [Orthorhombic, a = 19.187(9), b = 15.890(2), c = 15.713(3) ā, Pnma] and (SbF₃)₃SbF₅ [Monoclinic, a = 10.895(3), b = 10.941(3), c = 4.772(1) ā, β = 96.66(3)°, P2₁/m]. (SbF₃)₃SbF₅ seemed to be the most reduced adduct, no evidence was obtained for (SbF₃)_n(SbF₅) n > 3, under these conditions. The (SbF₃)₆(SbF₅)₅ adduct has a Raman spectrum identical to that reported by Gillespie⁽²⁾ and coworkers for an adduct of approximate composition SbF₃·SbF₅ and has a very different structure to that of (SbF₃)₆(SbF₆)₅ reported by Edwards.⁽³⁾ The crystal structures of the new adducts will be discussed and the cations they contain compared with those found in SbF₃·SbF₅⁽¹⁾ and (SbF₅)₆(SbF₅)₅⁽³⁾ (Edward's form).     

Reaction of Perfluorobenzocyclobutene with Excess Pentafluorobenzene in SbF<Subscript>5</Subscript>

The reaction of perfluorobenzocyclobutene with excess pentafluorobenzene in SbF₅, followed by hydrolysis, gave a mixture of perfluoro-1,3,3-triphenyl-1,3-dihydro-2-benzofuran-1-ol, perfluoro-1,1,2-triphenylbenzocyclobuten- 5-one, and perfluoro-4-(2,2-diphenylbenzocyclobuten-1-ylidene)cyclohexa-2,5-dien-1- one. When the reaction mixture was treated for a long time with Olah’s reagent (HF–pyridine), isomeric perfluoro-9,10-diphenyl-1,4-, -1,10-, -2,9-, and -9,10-dihydroanthracenes were formed and were converted to perfluoro-9,10-diphenylanthracene by the action of SbF₅.     

Homoleptic [M(XeF2)6] cations of copper(II) and zinc(II)—Syntheses and crystal structures of [M(XeF2)6](SbF6)2 (M = Cu, Zn)

[Cu(XeF₂)₆](SbF₆)₂ crystallizes in the rhombohedral symmetry with a = 1003.6(2) pm, c = 2246.5(12) pm at 200 K and Z = 3, space group (No. 148). [Zn(XeF₂)₆](SbF₆)₂ is isostructural to [Cu(XeF₂)₆](SbF₆)₂ with a = 1007(2) pm and c = 2243(6) pm. The structures are characterized by isolated homoleptic [M(XeF₂)₆]²⁺ (M = Cu, Zn) cations and of [SbF₆]⁻ octahedra.Reactions of M(SbF₆)₂ (M = Cu, Zn) with XeF₂ in anhydrous hydrogen fluoride (aHF) and reactions of MF₂ with Xe₂F₃SbF₆ in aHF always yield a mixture of [M(XeF₂)₆](SbF₆)₂, Xe₂F₃SbF₆ and MF₂.     

The solution thermochemistry of antimony pentafluoride and some fluoroantimonates

From hydrolysis and solution measurements the enthalpies of formation of SbF₅(?), LiSbF₆(s), NaSbF₆(s), KSbF₆(s), CsSbF₆(s), AgSbF₆(s), and SbF₆^?aq. are estimated to be ?1324 ± 12, ?2062 ± 5, ?2060 ± 6, ?2080 ± 3, ?2082 ± 15, ?1653 ± 3, and ?1789 ± 4 kJ mol^?1 respectively. Less precise estimates of the enthalpies of formation of O₂SbF₆ and of CsSb₃F₁₆ are also given. From the results the fluoride ion affinity of SbF₅, the single ion hydration enthalpy of SbF₆^? (g), and the charge distribution within the SbF₆^? ion have been calculated.     

(η3-allyl)palladium(II) catalysts for the addition polymerization of norbornene derivatives with functional groups

Cycloaliphatic polyolefins with functional groups were prepared by the Pd(II)-catalyzed addition polymerization of norbornene derivatives. Homo- and copolymers containing repeating units based on bicyclo[2.2.1] hept-5-en-2-ylmethyl decanoate (endo/exo-ratio = 80/20), bicyclo[2.2.1]hept-5-ene-2-carboxylic acid methyl ester (exo/endo = 80/20), bicyclo[2.2.1]hept-5-ene-2-methanol (endo/exo = 80/20), and bicyclo[2.2.1]hept-5-ene-2-carboxylic acid (100% endo) were prepared in 49–99% yields with {(η³-allyl)Pd(BF₄)} and {(η³-allyl)Pd(SbF₆)} as catalysts. The catalyst containing the hexafluoroantimonate ion was slightly more active than the tetrafluoroborate based Pd-complex.     

19F NMR Study of Antimony(III) Fluoride Complexes in Solution

The state of SbF₃, Sb₃O₂F₅, MSb₃F₁₀, MSb₂F₇, M₃Sb₄F₁₅, MSbF₄, and M₂SbF₃, as well as HF and MF (M = Na, K, Rb, Cs, NH₄, and Tl), in a 0.25 M aqueous solution at room temperature was studied by ¹⁹F NMR. It is found that chemical shifts of the ¹⁹F NMR signals (relative to CFCl₃) for the compounds under investigation vary in the 73.3–157.5 ppm range. For the Sb(III) fluoride complexes, chemical shifts in the ¹⁹F NMR spectra vary in the 73.3–85.5 ppm range (relative to CFCl₃). Although the crystals of Sb(III) fluoride complexes contain different polyhedra that are joined in different ways, the NMR spectra of all compounds under study show one narrow signal. The spectra of aqueous solutions of Sb(III) fluoride complexes do not contain signals of free fluoride ions and oxofluoride Sb₃O₂F₅.     

Donor-Stabilised [SbF4]+: SbF5 as a Fluoride-Ion Donor

Antimony pentafluoride is a strong Lewis acid and fluoride-ion acceptor that has not previously demonstrated any discreet fluoride-ion donor properties. The first donor-stabilised [SbF₄]⁺ cations were prepared from the autoionisation of SbF₅ in the presence of bidentate N-donor ligands 2,2’-bipyridine (bipy) and 1,10-phenanthroline (phen) as their [SbF₆]⁻ salts. The [SbF₄(N−N)][Sb₂F₁₁] (N−N=bipy, phen) salts were synthesised by the addition of one equivalent of SbF₅⋅SO₂ to [SbF₄(N−N)][SbF₆] in liquid SO_2. The salts show remarkable stability and were characterised by Raman spectroscopy and multinuclear NMR spectroscopy. The crystal structures of [SbF₄(phen)][SbF₆] ⋅ 3CH₃CN and [SbF₄(phen)][SbF₆] ⋅ 2SO₂ were determined, showing distorted octahedral cations. DFT calculations and NBO analyses reveal that significant degree of electron-pair donation from N to Sb stabilizes [SbF₄]⁺ with the Sb−N bond strength being approximately two thirds of that of the Sb−F bonds in these cations and the cationic charge being primarily ligand-centred.