Molybdän(VI)-fluorid-pentafluorotellurate(VI) und Molybdän(VI)-oxid-fluorid-pentafluorotellurate(VI): MoFn(OTeF5)6−n und MoOFn(OTeF5)4−n

Molybdenum(VI)fluoride-pentafluorotellurates(VI) and Molybdenum(VI)oxide-fluoridepentafluorotellurates(VI): MoF_n(OTeF₅)_6?n and MoOF_n(OTeF₅)_4?n In MoF₆ fluorine can be replaced by F₅TeO-groups by means of B(OTeF₅)₃. Rearrangement reactions and internal fluorination finally leads to MoF_n(OTeF₅)_6?n and MoOF_n(OTeF₅)_4?n.     

Nitrosyl-pentafluorotellurat(VI)

Nitrosyl pentafluorotellurate(VI) . NO+OTeF₅^? is prepared from NOCl and Hg(OTeF₅)₂. It is ionic NO+OTeF₅^? in the solid state and in acetonitrile solution, in the gaseous state however a covalent molecule ON–OTeF₅.     

Bonding information in tungsten(VI) compounds from directly bonded fluorine and fluorophenoxy subtituents

The series of compounds (FC₆H₄O)_nWF_6-n, where n = 1-6 and F is meta or para to oxygen, has been prepared and all fluorine nmr chemical shifts determined. The W-$\text{F}$, para-$\text{F}$, and meta-$\text{F}$ resonances all shift upfield as a function of n with approximate relative sensitivities of 1, 1/20, and 1/30, respectively. All chemical shifts are also found to be sensitive to molecular stereochemistry, with subtituents trans to oxygen shifted to higher field than those trans to fluorine. ¹⁹F data is also reported for the complete series (C₆H₅O)_nWF_6-n     

Antimonypentafluoroorthotellurates: Sb(OTeF5)3, Sb(OTeF5)5 and salts of Sb(OTeF5)6−

Antimony(III)pentafluoroorthotellurate has been synthesized from SbF₃ and B(OTeF₅)₃. Contrary to a previous report it is a low melting, sublimable solid (mp = 28°, bp (0.1 torr) = 68°, ¹⁹F - NMR: AB₄ spinsystem δ (A) = ?42.7, δ (B) = ?38.1, J (AB) = 186 Hz). It reacts with F₂, Cl₂ and Br₂ to give SbF₂(OTeF₅)₃, SbCl₄⁺Sb(OTeF₅)₆^? and SbBr₄⁺ Sb(OTeF₅)₆^? respectively. Interaction of Xe(OTeF₅)₂ and Sb(OTeF₅)₃ yields Sb(OTeF₅)₅, which is unstable at room temperature. Salts containing the new anion Sb(OTeF₅)₆^? have been synthesized either from Sb(OTeF₅)₅ and a corresponding pentafluoroorthotellurate e.g. Sb(OTeF₅)₅ + NMe₄⁺ OTeF₅^? = NMe₄⁺ Sb(OTeF₅)₆^?, or from SbCl₄ Sb(OTeF₅)₆^? and an appropriate chloride SbCl₄⁺ Sb(OTeF₅)₆^? + NOCl = SbCl₅ + NO⁺ Sb(OTeF₅)₆^?, or oxidatively, using a mixture of Xe(OTeF₅)₂ and Sb(OTeF₅)₅, e.g. C₆F₆ + $\text{1}\text{2}$ Xe(OTeF₅)₂ + Sb(OTeF₅)₅ = C₆F₆⁺ Sb(OTeF₅)₆^? + $\text{1}\text{2}$ Xe.     

Zur Chemie des Xenons, 1. Mitt.: Xenon(II)-bis(pentafluoro-orthotellurat), Xe(OTeF5)2

Zusammenfassung Pentafluoro-orthotellursäure, HOTeF₅, reagiert mit Xenondifluorid unter HF-Abspaltung quantitativ zu Xenon(II)-bis(pentafluoro-orthotellurat), Xe(OTeF₅)₂ (Schmp.: 35–37°C). Die Verbindung ist bis etwa 130°C thermisch stabil, oberhalb dieser Temperatur zerfällt sie hauptsächlich in Bis(pentafluorotellur)oxid, F₅TeOTeF₅, Sauerstoff und Xenon. Massenspektroskopisch konnten jedoch auch Bis(pentafluorotellur)peroxid, F₅TeOOTeF₅ und Verbindungen der allgemeinen Formel F₅Te(OTeF₄) _x OTeF₅ (x=1,2) als Zerfallsprodukte nachgewiesen werden. Röntgen-Einkristalluntersuchungen zeigen, daß Xe(OTeF₅)₂ eben (in bezug auf das TeOXeOTe-Skelett) gebaut ist und die F₅TeO-Gruppen intrans-Stellung angeordnet sind. Das Massen-, Infrarot-, Laser-Raman- und¹⁹F-KMR-Spektrum werden untersucht.

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Xenon Chemistry, I: Xe(OTeF₅)₂

Xenon(II)-bis(pentafluoro-orthotellurate), Xe(OTeF₅)₂ (M.P. 35–37°C), is formed in quantitative yield in the reaction of pentafluoro-orthotelluric acid, HOTeF₅, with Xenondifluoride. HF is evolved during the reaction. Xe(OTeF₅)₂ is thermally stable up to 130°C. Above this temperature it mainly decomposes to bis(pentafluoro-tellurium)oxide, F₅TeOTeF₅, oxygen and xenon. Mass-spectroscopically, however, bis(pentafluoro-tellurium)peroxide and compounds of the general composition F₅Te(OTeF₄) _x OTeF₅ (x=1,2) have been identified as minor decomposition products. X-ray single crystal analysis proves the TeOXeOTe entity to be planar and the F₅TeO groups intrans-position. Results of mass-, infrared-, laser-Raman- and¹⁹F-NMR-spectroscopy are given.

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Mit 1 Abbildung     

129Xe-Kernresonanzuntersuchungen von Xenonverbindungen. II. Xenon(II)-Derivate

¹²⁹-Xe-NMR Spectra of Xenon Compounds. II Xenon (II) Compounds The ¹²⁹Xe NMR Spectra of Xe(OSeF₅)₂, Xe(OTeF₅)₂, FXe–OSeF₅, FXe–OTeF₅, and F₅SeO–Xe–OTeF₅ have been measured and discussed. The mixed compounds FXe–OSeF₅, FXe–OSeF₅, FXe–OTeF₅, and F₅SeO–Xe–OTeF₅ exist only in equilibrium with the derivatives Xe(OSeF₅)₂, Xe(OTeF₅)₂ and XeF₂. Coupling of ¹²⁹Xe is observed with the fluorine directly bonded at the Xenon atom, with the equatorial fluorine atoms on selenium and tellurium. and with the tellurium isotop ¹²⁵Te.     

Oxygen-Bridged Ga2(Et)3(OTeF5)3 and the Weakly Coordinating Anions [Ga(Et)(OTeF5)3]− and [Ga(OTeF5)4]−

Salts of the weakly coordinating anions [Ga(OTeF₅)₄]⁻ as well as [Ga(Et)(OTeF₅)₃]⁻ and the neutral Ga₂(Et)₃(OTeF₅)₃ were synthesized and characterized by spectroscopic methods and single-crystal X-ray diffraction. Ga₂(Et)₃(OTeF₅)₃ was formed by treating GaEt₃ with pentafluoroorthotelluric acid (HOTeF₅) and reacted with PPh₄Cl and CPh₃Cl to [PPh₄][Ga(Et)(OTeF₅)₃] and [CPh₃][Ga(Et)(OTeF₅)₃]. In contrast, Ag[Ga(OTeF₅)₄] was prepared from AgOTeF₅ and GaCl₃ and was used as a versatile starting material for further reactions. Starting with Ag[Ga(OTeF₅)₄] the substrates [PPh₄][Ga(OTeF₅)₄] and [CPh₃][Ga(OTeF₅)₄] were formed from PPh₄Cl and CPh₃Cl.     

Enthalpies of formation of chloride fluorides and of methoxide fluorides of tungsten(VI)

Enthalpies of formation of the tungsten (VI) compounds WF₅Cl, WF₄Cl₂, WF₅(OMe), cis-WF₄(OMe)₂ and cis-WF₂(OMe)₄ are reported. Re-distribution and decomposition reactions in the chloride-fluoride and in the methoxide-fluoride series are discussed in the light of the thermochemical results.     

Stabilisation of [WF5]+ and WF5 by Pyridine: Facile Access to [WF5(NC5H5)3]+ and WF5(NC5H5)2

The enhanced reactivity of [WF₅]⁺ over WF₆ has been exploited to access a neutral derivative of elusive WF₅. The reaction of WF₆(NC₅H₅)₂ with [(CH₃)₃Si(NC₅H₅)][O₃SCF₃] in CH₂Cl₂ results in quantitative formation of trigonal-dodecahedral [WF₅(NC₅H₅)₃]⁺, which has been characterised as its [O₃SCF₃]⁻ salt by Raman spectroscopy in the solid state and variable-temperature NMR spectroscopy in solution. The salt is susceptible to slow decomposition in solution at ambient temperature via dissociation of a pyridyl ligand, and the resultant [WF₅(NC₅H₅)₂]⁺ is reduced to WF₅(NC₅H₅)₂ in the presence of excess C₅H₅N, as determined by ¹⁹F NMR spectroscopy. Pentagonal-bipyramidal WF₅(NC₅H₅)₂ was isolated and characterised by X-ray crystallography and Raman spectroscopy in the solid state, representing the first unambiguously characterised WF₅ adduct, as well as the first heptacoordinate adduct of a transition-metal pentafluoride. DFT-B3LYP methods have been used to investigate the reduction of [WF₅(NC₅H₅)₂]⁺ to WF₅(NC₅H₅)₂, supporting a two-electron reduction of W^VI to W^IV by nucleophilic attack and diprotonation of a pyridyl ligand in the presence of free C₅H₅N, followed by comproportionation to W^V.     

Transition metal compounds containing the -OTeF5 and NTeF5 groups.

The electronegative ligand OTeF₅ has been tested on the elements Ti, Mo, W, Ta, Re, Os and others. Compounds such as OMo(OTeF₅)₄, W(OTeF₅)₆, Ta(OTeF₅)₅, ReO₂(OTeF₅)₃, OsO(OTeF₅)₄ are prepared. While ReVII could be stabilized with OTeF₅, the highest oxidation state on Osmium is VI, and Iridium probably IV. OMo(OTeF₅)₄ shows a regular square pyramidal structure with apical double bonded oxygen. Chemistry on the ligand NTeF₅ is based on the synthesis of H₂NTeF₅ and R₃SiNHTeF₅¹. Other new main group derivatives are so far Cl₂NTeF₅, HClNTeF₅, OCN-TeF₅, F₃PNTeF₅, Cl₃NPTeF₅, F₂SNTeF₅ and Cl₂SeNTeF₅, the first compound with a selenium-nitrogen double bond. In the transition metal series the compounds F₄MoNTeF₅ and Cl₄WNTeF₅ (in addition to the longer known polymeric (HgNTeF₅¹) have been prepared. Both have discrete metal nitrogen double bonds.     

Molybdenum(VI) Bis(imido) Complexes: From Frustrated Lewis Pairs to Weakly Coordinating Cations

Molybdenum(VI) bis(imido) complexes [Mo(NtBu)₂(L^R)₂] (R=H 1 a ; R=CF₃ 1 b ) combined with B(C₆F₅)₃ ( 1 a /B(C₆F₅)₃, 1 b /B(C₆F₅)₃) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H−H, Si−H and O−H bonds. Cleavage of H₂ and Et₃SiH affords ion pairs [Mo(NtBu)(NHtBu)(L^R)₂][HB(C₆F₅)₃] (R=H 2 a ; R=CF₃ 2 b ) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H₂O leads to [Mo(NtBu)(NHtBu)(L^R)₂][(HO)B(C₆F₅)₃] (R=H 3 a ; R=CF₃ 3 b ). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a . Mechanistic elucidation revealed insertion of the aldehyde into the B−H bond of [HB(C₆F₅)₃]⁻. We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(L^R)₂][{PhCH₂O}B(C₆F₅)₃] (R=H 4 a ; R=CF₃ 4 b ). Catalysis occurs at [HB(C₆F₅)₃]⁻ while [Mo(NtBu)(NHtBu)(L^R)₂]⁺ (R=H or CF₃) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC).     

Formation and Crystal Structure of [(F5TeOXe)+·SO2ClF][Sb(OTeF5)6-]

Xe(OTeF₅)₂ reacts with Sb(OTeF₅)₃ under the formation of [Xe₂(OTeF₅)₃]⁺[Sb(OTeF₅)₆]^-. From SO₂ClF solution a yellow solvate [F₅TeOXe]⁺·SO₂ClF· [Sb(OTeF₅)₆]^- is formed with the crystal data: a = 1028.1(1), b = 1040.9(1), c = 1780.2(3) pm, α = 98.07(1), β = 97.68(1), γ = 105.82(1)°, space group . The O-Xe···O fragment is essentially linear (176.1(2)°), and the two Xe-O distances are quite different 197.1(4) and 242.6(4) pm.     

Darstellung und elektrochemisches Verhalten von [Nb(OTeF5)6]− und [Ta(OTeF5)6]−-Komplexen

Preparation and Electrochemistry of [Nb(OTeF₅)₆]^? and [Ta(OTeF₅)₆]^? Complexes Nb(OTeF₅)₅ and Ta(OTeF₅)₅ react with Cs[OTeF₅], [Et₄N][OTeF₅], and [(n-Bu)₄N][OTeF₅] to the corresponding Cs[M(OTeF₅)₆], [Et₄N][M(OTeF₅)₆], and [(n-Bu)₄N][M(OTeF₅)₆] complexes, (M = Nb, Ta). The electrochemical reduction of the niobium complex occurs in CH₂Cl₂ at ?0,69 V and in acetonitrile at ?0,60 V (vs. SCE). The tantalum complex is reduced in CH₂Cl₂ at ?1,52 V and in acetonitrile at ?1,42 V (vs. SCE).     

Formation of WF−6 and its dissociative products by collisional ionization

The formation of negative ions in electron transfer reactions between hyperthermal alkali atoms (Na, K) and WF₆ has been studied in the energy range 0–30 eV c.m. Relative cross sections and translational energy thresholds for ion pair formation have been measured, from which the following electron affinities (EA) and bond dissociation energies (D) have been derived: EA(WF₆) = 3.7 eV, EA(WF₅) = 1.25 eV, D(WF₅—F) = 5.1 eV, D)WF₅—F^?) = 5.4 eV, D(WF^?₅—F) = 7.6 eV. Several ion molecule reactions are discussed which result in formation of secondary fragmentation ions and WF^?₇.     

Pentafluorotellurate(VI) des fünfwertigen Iod; die Elektronegativität der Gruppen OTeF5 und OSeF5

Pentafluorotellurates of Pentavalent Iodine. Electronegativities of the OTeF₅ and OSeF₅ Groups The compounds I(OTeF₅)₅ and O=I(OTeF₅)₃ are characterized. With the help of n.m.r. spectroscopically methods it has been shown that the mixed substituted compounds F_xI(OTeF₅)_5–x and F_xI(OSeF₅)_5–x exist. The substitution behaviour of the –OTeF₅ and -OSeF₅ ligands indicate, that those groups are more electronegative than fluorine in the sence of the valence shell electron pair repulsion model. This qualitative result is indicated also by correlation of physical data of some model compounds with known values of electronegativities.     

Tungsten(VI) and Tungsten(V) Fluoride Complexes

WF₆ reacts with phosphines R₃P forming 1:1 compounds. With R=P(CH₃)₃ the coordination around the tungsten atom is capped trigonal prismatic, with R=P(CH₃)₂C₆H₅ the coordination is capped octahedral, as established by single‐crystal structure determinations: [(CH₃)₃P? WF₆]: a=752.5(21), b=945.7(24), c=629.8(18) pm. β=110.36(13)°, space group Cm, Z=2; [(CH₃)₂(C₆H₅)P? WF₆]: a=762.2(2), b=1123.5(2), c=2647.5(6) pm, space group Pbca, Z=8. [(CF₃CH₂)₂N? WF₅] reacts smoothly with P(C₆H₅)₃ forming known P(C₆H₅)₃(F)₂ and [(CF₃CH₂)₂N? WF₄? P(C₆H₅)₃], a stable, green, molecular species, identified among other methods with an crystal structure determination: a=914.9(1), b=956.0(1), c=1449.8(2) pm, α=7.642(4), β=81.648(3), γ=81.519°, space group P$\bar 1$ , Z=2.     

Fluoraustauschreaktionen an Metalltrifluorphosphin-Komplexen. IX. Zum Reaktionsverhalten von Tetrakis(trifluorphosphin)nickel(0) gegenüber Alkyl(trimethylsilyl)aminen und -amiden

Fluorine Exchange in Trifluorophosphine Metal Complexes. IX¹. (Reactions of Tetrakis(trifluorophosphine)nickel(0) with Alkyl(trimethylsilyl)amines and Amides²) Alkylaminodifluorophosphine complexes Ni(PF₃)_4-n(PF₂NHR)_n (n = 1, 2, 3) 8–11 and Me₃SiF are obtained, if alkyl(trimethylsilyl)amines NHR(SiMe₃) (R?CH₃ and n-C₄H₉) are reacted with Ni(PF₃)₄ ( 1 ). The mechanism of these peripheric reactions is discussed by assuming a four centered type intermediate. However reactions of 1 with the lithium amides LiNR(SiMe₃) (R = CH₃, C₂H₅, n-C₄H₉, and C₆H₅) yield LiF and the difluorotrimethylsilylaminophosphine complexes Ni(PF₃)_4-n[PF₂NR(SiMe₃)]_n (n = 1, 3, 4) 12–18 .     

Two Modifications of (TeO)(HAsO4) and its Dehydration Product (Te3O3)(AsO4)2 – Three more Examples of Tellurium(IV) with a Fivefold Oxygen Coordination

Two modifications of (TeO)(HAsO₄) were obtained by reacting tellurium dioxide with arsenic acid under boiling conditions (modification I, acid concentration 80 wt‐%) or under hydrothermal conditions (modification II, acid concentration 50 wt‐%). The crystal structures of the two modifications were determined from single‐crystal X‐ray data [modification I: P2₁/c, Z = 4, a = 7.4076(10), b = 5.9596(7), c = 9.5523(11) Å, β = 102.589(8)°, 2893 structure factors, 68 parameters, R[F² > 2σ(F²)] = 0.0247, wR₂(F² all) = 0.0530; modification II: P2₁/c, Z = 4, a = 6.2962(4), b = 4.7041(3), c = 13.9446(8) Å, β = 94.528(3)°, 2549 structure factors, 69 parameters, R[F² > 2σ(F²)] = 0.0207, wR₂(F² all) = 0.0462)]. Dehydration of (TeO)(HAsO₄)‐II at temperatures above 260 °C results in the formation of polycrystalline (Te₃O₃)(AsO₄)₂. Single crystals of the anhydrous product were grown either by heating stoichiometric amounts of the binary oxides TeO₂ and As₂O₅ in closed silica glass ampoules or with higher concentrated arsenic acid (80 wt‐%) under hydrothermal conditions at 220 °C. The common features in the crystal structures of (Te₃O₃)(AsO₄)₂ [P$\bar{1}$ , Z = 4, a = 6.5548(4), b = 7.6281(6), c = 15.0464(15) Å, α = 140.212(6), β = 102.418(9)°, γ = 77.346(5)°, 5718 structure factors, 146 parameters, R[F² > 2σ(F²)] = 0.0351, wR₂(F² all) = 0. 1093] and in that of the two modifications of acidic (TeO)(HAsO₄) are [TeO₅] square‐pyramids and [AsO₄] tetrahedra. In anhydrous (Te₃O₃)(AsO₄)₂ and in (TeO)(HAsO₄)‐II, a layered arrangement of the building units is found, whereas in the (TeO)(HAsO₄)‐I structure strands are formed. Different hydrogen bonding interactions are present in the two modifications of (TeO)(HAsO₄).     

19F NMR Investigations of the Reaction of B(C6F5)3 with Different Tri(alkyl)aluminum Compounds

Tris(pentafluorophenyl)borane, B(C₆F₅)₃ reacts with triethylaluminum, AlEt₃ to a mixture of Al(C₆F₅)_3−nEt_n and Al₂(C₆F₅)_6−nEt_n compounds depending on the B/Al ratio. From excess borane to excess AlEt₃ the species Al(C₆F₅)₃ → Al(C₆F₅)₂Et Al₂(C₆F₅)₄Et₂ → Al₂(C₆F₅)₃Et₃ → Al₂(C₆F₅)₂Et₄ → Al₂(C₆F₅)Et₅ are formed and differentiated by their para-F signal in ¹⁹F NMR. The reaction between B(C₆F₅)₃ and the higher aluminum alkyls, tri(iso-butyl)aluminum and tri(n-hexyl)aluminum AlR₃ (R = i-Bu, n-C₆H₁₃) is slower and requires AlR₃ excess to shift the C₆F₅ R exchange equilibria to almost complete formation of Al(C₆F₅)R₂ and BR₃. At equimolar ratio the equilibrium lies on the side of the unchanged borane together with its boranate [B(C₆F₅)₃R]⁻ anion. For tri(n-octyl)aluminum even at large Al(n-C₈H₁₇)₃ excess no C₆F₅ alkyl exchange can be observed, but boranate anions form.     

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.