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).     

Synthesen und Schwingungsspektren der homoleptischen Acetonitrilkomplex-Kationen [Au(NCCH3)2]+, [Pd(NCCH3)4]2+, [Pt(NCCH3)4]2+ und des Adduktes CH3CN · SbF5. Kristallstrukturen der Salze [M(NCCH3)4][SbF6]2 · CH3CN,M = Pd,Pt

The Syntheses and Vibrational Spectra of the Homoleptic Metal Acetonitrile Cations [Au(NCCH₃)₂]⁺, [Pd(NCCH₃)₄]²⁺, [Pt(NCCH₃)₄]²⁺, and the Adduct CH₃CN · SbF₅. The Crystal and Molecular Structures of [M(NCCH₃)₄][SbF₆]₂ · CH₃CN, M = Pd or Pt Solvolyses of the homoleptic metal carbonyl salts [M(CO)₄][Sb₂F₁₁]₂, M = Pd or Pt, in acetonitrile leads at 50 °C both to complete ligand exchange for the cations as well as to a conversion of the di-octahedral anion [Sb₂F₁₁]^– into [SbF₆]^– and the molecular adduct CH₃CN · SbF₅ according to: [M(CO)₄][Sb₂F₁₁]₂ + 7 CH₃CN → [M(NCCH₃)₄][SbF₆]₂ · CH₃CN + 2 CH₃CN · SbF₅ + 4 CO M = Pd, Pt The monosolvated [M(NCCH₃)₄][SbF₆]₂ · CH₃CN are obtained as single crystals from solution and are structurally characterized by single crystal x-ray diffraction. Both salts are isostructural. The cations are square planar but the N–C–C-sceletial groups of the ligands depart slightly from linearity. The new acetonitrile complexes as well as [Au(NCCH₃)₂][SbF₆] and the adduct CH₃CN · SbF₅ are completely characterized by vibrational spectroscopy.     

Metal (II) hexafluoroarsenates: Thermal decomposition studies on the adducts MF2·2AsF5 (M = Mg,Ca, Sr,Mn, Co,Ni, Cd,Hg, Pb), 2MF2·3AsF5 (M = Fe,Cu, Zn) and MF2·AsF5 (M = Ag,Sn)

Thermal studies have shown that metal(II) hexafluoro-arsenates of the types MF₂·2AsF₅ ( M = Mg, Ca, Sr, Mn, Co, Ni, Cd, Hg, Pb), 2MF₂·3AsF₅ (M = Fe, Cu, Zn) and MF₂·AsF₅ (M = Ag, Sn), prepared by the reaction of metal difluorides with AsF₅ in anhydrous HF at room temperature, decompose when heated in an argon atmosphere. In all cases AsF₅ is given off. For some of the adducts the decompositions proceed in one or more steps to give the original difluorides, but for others, the decompositions overlap one another. The greatest range of intermediate stoicheiometries results from the decompositions of the MF₂·2AsF₅ type adducts in which the metal difluoride content is a minimum. In decompositions of adducts of this type as many as three different intermediates, 2MF₂·3AsF₅, MF₂·AsF₅ and 2MF₂·AsF₅, may be observed.     

THE METASTABLE PARTIALLY POSITIVELY CHARGED Se6 MOLECULE: PREPARATION,CHARACTERISATION AND X-RAY CRYSTAL STRUCTURE OF [Ag2(Se6)(SO2)2][Sb(OTeF5)6]2, [Ag2Se6][AsF6]2 AND [AgSe6][Ag2(SbF6)3]

Reactions designed to give Se₆[Sb(OTeF₅)₆]₂ by the reaction of Se₂Br₂, 4Se, and 2Ag[Sb(OTeF₅)₆] lead to products that include [Ag₂(Se₆)(SO₂)₂][Sb(OTeF₅)₆]₂(1). The distorted cubic (Ag₂Se₆ ²⁺) _n consists of a Se₆ molecule bicapped by two silver cations (local D_3d sym.). Reactions of AgMX₆ (M = As, Sb) with selenium in liquid SO₂ yielded crystals of [Ag₂Se₆][AsF₆]₂ (2) and [AgSe₆][Ag₂(SbF₆)₃] (3). Both salts contain stacked arrays of [AgSe₆]⁺ half-sandwich cationic units. [Ag₂Se₆][AsF₆]₂ in addition contains stronger, linear Se─Ag─Se horizontal linkages between the vertically stacked cationic columns. [AgSe₆][Ag₂(SbF₆)₃] features a remarkable three-dimensional [Ag₂(SbF₆)₃]^? anion held together by strong Sb─F···Ag contacts between component Ag⁺ and SbF₆ ^? ions. Hexagonal channels through this honeycomb-like anion are filled by the stacked [AgSe₆ ⁺]_x.     

Preparation of CuAsF6 and Ni[AsF6]2.2SO2

Arsenic pentafluoride reacts with excess copper in sulphur dioxide to give CuAsF₆. A similar reaction with elemental nickel yields Ni(AsF₆)₂.2SO₂, the structure of which is discussed. The X-ray powder diffraction photograph of CuAsF₆ was indexed on a rhombohedral unit cells a = 5.49±.01Å, α = 55.7±.1°, V = 105.4ų, Z = 1, and is of the same structural type as LiSbF₆ showing that the cuprous ion is octahedrally surrounded by fluorines. Comparison of the unit cell volume of CuAsF₆ with other structurally similar hexafluoroarsenate salts shows that the effective volume of cuprous ion is small indicating substantial anion-cation interaction. Arsenic pentafluoride reacts with Monel in the presence of sulphur dioxide give a mixtures of CuAsF₆ and Ni[AsF₆]₂.2SO₂.     

The Protonation of Acetamide and Thioacetamide in Super­acidic Solutions: Crystal Structures of [H3CC(OH)NH2]+AsF6– and [H3CC(SH)NH2]+AsF6–

Acetamide and thioacetamide react with the superacid solutions HF/MF₅ (M = As, Sb) under formation of the corresponding salts [H₃CC(OH)NH₂]⁺MF₆^– and [H₃CC(SH)NH₂]⁺MF₆^– (M = As, Sb), respectively. The reaction of DF/AsF₅ with acetamide and thioacetamide lead to the corresponding deuterated salts [H₃CC(OD)ND₂]⁺AsF₆^– and [H₃CC(SD)ND₂]⁺AsF₆^–, respectively_. The salts are characterized by vibrational and NMR spectroscopy, and in the case of [H₃CC(OH)NH₂]⁺AsF₆^– and [H₃CC(SH)NH₂]⁺AsF₆^– also by single‐crystal X‐ray analyses. The [H₃CC(OH)NH₂]⁺AsF₆^– ( 1 ) salt crystallizes in the triclinic space group P$\bar{1}$ with two formula units per unit cell, and the [H₃CC(SH)NH₂]⁺AsF₆^– ( 2 ) salt crystallizes in the monoclinic space group P2₁/c with four formula units per unit cell. In both crystal structures three‐dimensional networks are observed which are formed by intra‐ and intermolecular N–H ··· F and O–H ··· F or S–H ··· F hydrogen bonds, respectively. For the vibrational analyses, quantum chemically calculated spectra of the cations [H₃CC(OH)NH₂ · 3HF]⁺ and [H₃CC(SH)NH₂ · 2HF]⁺ are considered.     

Reaction of PF5·CH3CN with sulfide

Nitriles react with PF₅ and also with AsF₅, SbF₅ forming 1:1-adducts. Using C₂Cl₃F₃ as a solvent is of advantage for this reaction. PF₅·CH₃CN and [N(C₂H₅)₄]SH give [N(C₂H₅)₄][P₂S₂F₈] with a sulfur double bridge and hexafluorophosphate in acetonitrile [1]. In case of AsF₅·CH₃CN a salt with the anion [AsF₅NHCSCH₃]^? has been isolated [2]. Following products have been confirmed in a reaction mixture of PF₅·CH₃CN and SH^? in acetonitrile by NMR (³¹P and ¹⁹F): [PF₆]^?, [F₅PSPF₅]^2?,

, F₄PSH, F₃PS, HPS₂F₂, [PS₂F₂]^?, [F₅PNC(SH)CH₃]^?, [F₅PNHCSCH₃]^?, [F₅PSH]^?. With a ratio PF₅·CH₃CN: SH^? = 2:1 the S-bridge-complexes are prefered whereas in case of a ratio 1:1 the non-bridged P-complexes are the main products.     

Diaryldichalcogenide radical cations

One-electron oxidation of two series of diaryldichalcogenides (C₆F₅E)₂ (13a–c) and (2,6-Mes₂C₆H₃E)₂ (16a–c) was studied (E = S, Se, Te). The reaction of 13a and 13b with AsF₅ and SbF₅ gave rise to the formation of thermally unstable radical cations [(C₆F₅S)₂]˙⁺ (14a) and [(C₆F₅Se)₂]˙⁺ (14b) that were isolated as [Sb₂F₁₁]^– and [As₂F₁₁]^– salts, respectively. The reaction of 13c with AsF₅ afforded only the product of a Te–C bond cleavage, namely the previously known dication [Te₄]²⁺ that was isolated as [AsF₆]^– salt. The reaction of (2,6-Mes₂C₆H₃E)₂ (16a–c) with [NO][SbF₆] provided the corresponding radical cations [(2,6-Mes₂C₆H₃E)₂]˙⁺ (17a–c; E = S, Se, Te) in the form of thermally stable [SbF₆]^– salts in nearly quantitative yields. The electronic and structural properties of these radical cations were probed by X-ray diffraction analysis, EPR spectroscopy, and density functional theory calculations and other methods.     

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.     

Preparation and Characterization of Protonated Fumaric Acid

Fumaric acid was reacted with the binary superacidic systems HF/SbF₅ and HF/AsF₅. The O,O'-diprotonated [C₄H₆O₄]²⁺([MF₆]^–)₂ (M = As, Sb) and the O-monoprotonated [C₄H₅O₄]⁺[MF₆]^– (M = As, Sb) species are formed depending on the stoichiometric ratio of the Lewis acid to fumaric acid. The colorless salts were characterized by low-temperature vibrational spectroscopy. In case of the hexafluoridoantimonates single-crystal X-ray structure analyses were carried out. The [C₄H₆O₄]²⁺([SbF₆]^–)₂ crystallizes in the monoclinic space group C2/c with four formula units per unit cell and [C₄H₅O₄]⁺[SbF₆]^– crystallizes in the triclinic space group P1 with one formula unit per unit cell. The protonation of fumaric acid does not cause a notable change of the C=C bond length. The experimental data are discussed together with quantum chemical calculations of the cations [C₄H₆O₄ · 4 HF]²⁺ and [C₄H₆O₄ · 2 H₂CO · 2 HF]²⁺.     

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.     

The Simultaneous Oxidation of Tellurium and Transition Metals by AsF5 – Syntheses and Crystal Structures of [M(SO2)6](Te6)[AsF6]6 (M = Ni,Zn) and [Cd(SO2)2][AsF6]2

The reactions of elemental nickel and tellurium and of ZnTe with excess AsF₅ in liquid SO₂ yield [M(SO₂)₆](Te₆)[AsF₆]₆ (M = Ni, Zn) as orange crystals. The crystal structure determinations (triclinic, , M = Ni: a = 1632.59(2), b = 1795.06(1), c = 1822.97(2) pm, α = 119.11(4), β = 90.78(4), γ = 106.28(4)°, V = 4408.24(8)·10⁶pm³, Z = 4) show the two compounds to be isotypic. The structures are made up of discrete [M(SO₂)₆]²⁺ complexes, Te₆⁴⁺ clusters and octahedral [AsF₆]^? ions. In the [M(SO₂)₆]²⁺ complexes the metal ions are surrounded octahedrally by six SO₂ molecules bound via the O atoms. The Te₆⁴⁺ polycations are of trigonal prismatic shape with short Te–Te bonds within the triangular faces (270 pm) and long Te–Te bonds along the edges parallel to the pseudo C₃ axes of the prisms (312 pm). The arrangement of the ions is related to the Li₃Bi structure type. [M(SO₂)₆]²⁺ complexes and Te₆⁴⁺ polycations together form a distorted cubic closest packing with all tetrahedral and octahedral interstices filled by [AsF₆]^? ions. The analogous reaction starting from CdTe did not yield a compound containing simultaneously [Cd(SO₂)_n]²⁺ complexes and tellurium polycations but instead Te₆[AsF₆]₄ · 2 SO₂ besides [Cd(SO₂)₂][AsF₆]₂ were obtained. It crystallizes isotypically to [Mn(SO₂)₂][AsF₆]₂ (Mews, Zemva, 2001) (orthorhombic, Fdd2, a = 1534.96(3), b = 1812.89(3), c = 892.28(3) pm, V = 2483·10⁶ pm³, Z = 4).     

Ring Opening Reactions of β-Propiolactam in Superacidic Media

The reaction of β-propiolactam in the superacidic systems HF/MF₅ (M=Sb, As) led to the formation of monoprotonated 3-aminopropanoyl fluoride in the form of [C(O)F(CH₂)₂NH₃][SbF₆] and [C(O)F(CH₂)₂NH₃][AsF₆]. In the presence of traces of water, the diprotonated species β-alanine [C(OH)₂(CH₂)₂NH₃][AsF₆]₂ was synthesized for the first time. All salts were characterized by low-temperature infrared and Raman spectroscopy. Additionally, single-crystal X-ray analyses were conducted in the case of [C(O)F(CH₂)₂NH₃][SbF₆] and [C(OH)₂(CH₂)₂NH₃][AsF₆]₂. By using SO₂ instead of HF as the solvent, the salt [C(OH)₂(CH₂)₂NHSO][SbF₆]₂ was obtained, and single-crystal X-ray analysis of this salt containing a thionylimide moiety was conducted. For the formation of these open-chain compounds, an acyl cationic species as intermediate is assumed, which is formed from N-protonated β-propiolactam. Quantum chemical calculations at the B3LYP/aug-cc-pVTZ and MP2/aug-cc-pVTZ levels of theory were carried out to gain a better understanding of the formation and the structural properties of protonated β-propiolactam.     

Reactions of Manganese(II) Fluoride in the Superacidic Systems HF/SbF5 and HF/GeF4 – Crystal Structure of Mn(SbF6)2 and Vibrational Spectra of MnGeF6

Mn(SbF₆)₂ was prepared from MnF₂ and SbF₅ in aHF (anhydrous HF) and single crystals were obtained from the respective solution. The compound crystallises in the triclinic space group P 1 (No. 2) with a = 517.3(2) pm, b = 554.9(2) pm, c = 888.2(2) pm, α = 73.98(3)°, β = 89.17(2)°, γ = 62.54(2)° and Z = 1. MnGeF₆ was prepared from MnF₂ and GeF₄ in aHF and by metathetical reaction between solutions of K₂GeF₆ in aHF and Mn(AsF₆)₂ in aHF. Attempt to isolate Mn(GeF₅)₂ prepared by metathetical reaction between solutions of XeF₅GeF₅ in aHF and Mn(AsF₆)₂ in aHF failed, although some slight evidences for its existence were obtained. Vibrational data of MnGeF₆ are in agreement with lowering of the symmetry of GeF₆^2– from O_h to C_3i because of the site symmetry effects.     

Synthese,Struktur und Phasenumwandlung von Te4[AsF6]2·SO2

Synthesis, Crystal Structure, and Solid State Phase Transition of Te₄[AsF₆]₂·SO₂ The oxidation of tellurium with AsF₅ in liquid SO₂ yields Te₄²⁺[AsF₆^—]₂ which can be crystallized from the solution in form of dark red crystals as the SO₂ solvate. The crystals are very sensitive against air and easily lose SO₂, so handling under SO₂ atmosphere or cooling is required. The crystal structure was determined at ambient temperature, at 153 K, and at 98 K. Above 127 K Te₄[AsF₆]₂·SO₂ crystallizes orthorhombic (Pnma, a = 899.2(1), b = 978.79(6), c = 1871.61(1) pm, V = 1647.13(2)·10⁶pm³ at 297 K, Z = 4). The structure consists of square‐planar Te₄²⁺ ions (Te‐Te 266 pm), octahedral [AsF₆]^— ions and of SO₂ molecules which coordinate the Te₄ rings with their O atoms in bridging positions over the edges of the square. At room temperature one of the two crystallographically independent [AsF₆]^— ions shows rotational disorder which on cooling to 153 K is not completely resolved. At 127 K Te₄[AsF₆]₂·SO₂ undergoes a solid state phase transition into a monoclinic structure (P112₁/a, a = 866.17(8), b = 983.93(5), c = 1869.10(6) pm, γ = 96.36(2)°, V = 1554, 2(2)·10⁶ pm³ at 98 K, Z = 4). All [AsF₆]^— ions are ordered in the low temperature form. Despite a direct supergroup‐subgroup relationship exists between the space groups, the phase transition is of first order with discontinuous changes in the lattice parameters. The phase transition is accompanied by crystal twinning. The main difference between the two structures lies in the different coordination of the Te₄²⁺ ion by O and F atoms of neighbored SO₂ and [AsF₆]^— molecules.     

Fluoride-fluorosulfates of arsenic (V) and arsenic (III)

The synthesis of AsF₃(SO₃F)₂ by the reaction AsF₃ + S₂O₆F₂→AsF₃(SO₃F)₂ is described. Various alternate routes leading to similar arsenic (V) fluoride-fluorosulfates are discussed. All materials are clear, viscous, strongly associated liquids of the general formula AsF_n(SO₃F)_5?n, with n ranging from about 2 to 4. The presence of fluorosulfate bridges is ascertained by IR and Raman spectra.The spectroscopic investigation is also extended to arsenic (III) fluoride- fluorosulfates.     

pH determination in anhydrous hydrogen fluoride and superacid media by means of the chloranil electro-chemical indicator system

The electro chemical systems of chloranil (quinone/semiquinone and semiquinone/hydroquinone) are shown to be usable as pH indicators in anhydrous hydrogen fluoride and in the superacid mixtures HF + MF_n (where MF_n = PF₅, BF₃, TaF₅, NbF₅, AsF₅ and SbF₅). The combined use of both hydrogen and chloranil electrodes has allowed the establishment of a complete potential-pH diagram of chloranil in the whole acidity range of HF. The quinone/semiquinone system can be used at very high acidity levels (solutions of AsF₅ or SbF₅) where the hydrogen electrode does not function correctly. A new value of the autoprotolysis constant of HF is reported (K_i = [H⁺. [F^-] = 10^-13.7 mol² l^-2) and compared with earlier values. The equilibrium constants of acid-base systems of the quinone (Q/QH⁺) and hydroquinone (QH₂/QH₃⁺ and QH²⁺₄) forms of chloranil, and the disproportionation constant of the semiquinone (QH₂⁺ form are also reported. The indicator system allows the acidity levels reached in HF to be placed on an R(H) scale (where R(H) = 0 corresponds to pH = 0 in aqueous solution). These levels were found to lie between R(H) = -14.2 for 1 M KF solution and R(H) = -27.9 for 1 M SbF₅ (i.e. 18% by weight).     

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.     

Pentafluorsulfanylamine und Sulfanylammonium-Salze

Pentafluorosulfanylamines and Sulfanylammonium Salts . From the addition of HF to sulfurtetrafluorideimides N-alkylpentafluorosulfanylamines RNHSF₅(2a, 2b: R=CH₃, C₂H₅) are obtained in quantitative yield. N, N-dialkylpentafluorosuIfanylamines Et₂NSF₅(5a) and pip-SF₅ (5b) are isolated from the reaction of the appropriate sulfurdifluoronitridearnides NSF₂NR₂ and HF/SF₄. Protonation of the amines with the superacidic system HF/AsF₅ gives stable pentafluorosulfanyl-ammonium salts SF₅NHRR′_. AsF₆ (12: R = R′ = CH₃; 14: R=R′=H; 10: R=CH₃, R′ = H). Under the same conditions the adduct AsF₅· NSF₂CF(CF₃)₂ (15) forms a cation with hexacoordinated sulfur (trans-H₃NSF₄CF(CF₃)₂^?AsF₆⁶: 16), while with Asp₅ · NSF₂NMe₂ (17) the reaction stops at tetracoordination (HNSF₂NMe₂⁺AsF₆ : 18).