A Unified Strategy for Arylsulfur(VI) Fluorides from Aryl Halides: Access to Ar-SOF3 Compounds

A convenient protocol to selectively access various arylsulfur(VI) fluorides from commercially available aryl halides in a divergent fashion is presented. Firstly, a novel sulfenylation reaction with the electrophilic N-(chlorothio)phthalimide (Cl-S-Phth) and arylzinc reagents afforded the corresponding Ar-S-Phth compounds. Subsequently, the S(II) atom was selectively oxidized to distinct fluorinated sulfur(VI) compounds under mild conditions. Slight modifications on the oxidation protocol permit the chemoselective installation of 1, 3, or 4 fluorine atoms at the S(VI) center, affording the corresponding Ar-SO₂F, Ar-SOF₃, and Ar-SF₄Cl. Of notice, this strategy enables the effective introduction of the rare and underexplored -SOF₃ moiety into various (hetero)aryl groups. Reactivity studies demonstrate that such elusive Ar-SOF₃ can be utilized as a linchpin for the synthesis of highly coveted aryl sulfonimidoyl fluorides (Ar-SO(NR)F).     

Study of the structure and stability of compounds PF n,n=1–5, and their anions by the density functional method

The electronic and geometrical structure of phosphorus fluorides PF_n, n = 1–5, and their singly-charged negative ions was calculated using the density functional method. Both the ground and low-lying excited states of the two series were considered. The structural parameters of neutral radicals PF₂, PF₄, and their anions were obtained for the first time. The adiabatic and vertical electron affinities (EA) of the neutral phosphorus fluorides, and the first ionization potentials of the anions were calculated. According to the calculation results, all the phosphorus fluorides have positive EA_ad, except for PF₃, which has an EA of about zero, and requires further investigation. The dissociation energies of both the neutral and negatively charged phosphorus fluorides were calculated through different channels. All the PF_n and PF _n ^– , n = 1–5, are stable in the gaseous phase. The PF^–, PF ₂ ^– , PF ₃ ^– , and PF ₅ ^– anions have excited states which are stable with respect to both the splitting off of an outer electron and to dissociation.Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2219–2232, October, 1992.     

Synthese von [SiW11O39MF]5– (M = Zr,Hf) – den ersten Heteropolyoxowolframaten mit terminal gebundenem Fluor

Synthesis of [SiW₁₁O₃₉MF]^5– (M = Zr, Hf) – the First Heteropolyoxotungstates with Terminal Bonded Fluorine The reaction of metal fluorides of Group 4 with lacunar [α-SiW₁₁O₃₉]^8– resulted in the formation of metal fluorides containing inorganic clusters. In the case of titanium all metal fluorine bonds are cleaved, while the corresponding reaction of zirconium and hafnium, respectively gave compounds having one metal fluorine bond. The new compounds contain an additional active NMR probe.     

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.     

Fluorides of Silver Under Large Compression**

The silver-fluorine phase diagram has been scrutinized as a function of external pressure using theoretical methods. Our results indicate that two novel stoichiometries containing Ag⁺ and Ag²⁺ cations (Ag₃F₄ and Ag₂F₃) are thermodynamically stable at ambient and low pressure. Both are computed to be magnetic semiconductors under ambient pressure conditions. For Ag₂F₅, containing both Ag²⁺ and Ag³⁺, we find that strong 1D antiferromagnetic coupling is retained throughout the pressure-induced phase transition sequence up to 65 GPa. Our calculations show that throughout the entire pressure range of their stability the mixed-valence fluorides preserve a finite band gap at the Fermi level. We also confirm the possibility of synthesizing AgF₄ as a paramagnetic compound at high pressure. Our results indicate that this compound is metallic in its thermodynamic stability region. Finally, we present general considerations on the thermodynamic stability of mixed-valence compounds of silver at high pressure.     

Quantum chemistry investigation of electronic structure and NMR spectral characteristics for fluorides of dialkylamidosulfoxylic acids and related compounds

The parent (H₂N? S? F) and N,N‐dialkyl‐substituted fluorides of amidosulfoxylic acid (R₂N? S? F, R?Me or R₂N?Morph) as well as the related compounds X? S? F (X?CH₃, OH, F, SiH₃, PH₂, SH, Cl) have been investigated with quantum chemical calculations at the ab initio (MP2) level of approximation. The geometries, electronic structures, molecular orbital (MO) energies and NMR chemical shift values have been calculated to evaluate the role and extent of the polarization and delocalization effects in forming of the high‐field fluorine NMR resonances within the series of interest. The δF magnitudes for all investigated fluorides of amidosulfoxylic acid as well as the δN value calculated for Me₂N? S? F are in the good agreement with the ¹⁹F and ¹⁴N NMR chemical shift values measured experimentally. For the parent compounds, H₂N? S? F and H₂N? SO₂? F, the orientation of principal axes of the magnetic shielding tensors and the corresponding principal σ_ii values along these axes have been qualitatively interpreted basing on the analysis of the MO interactions in the presence of the rotating magnetic field. Copyright © 2009 John Wiley & Sons, Ltd.     

Recent Advances in the Synthesis and Transformation of Carbamoyl Fluorides,Fluoroformates, and Their Analogues

Carbamoyl fluorides, fluoroformates, and their analogues are a class of important compounds and have been evidenced as versatile building blocks for the preparation of useful molecules in organic chemistry. While major achievements were made in the synthesis of carbamoyl fluorides, fluoroformates, and their analogues in the last half of 20^th century, an increasing number of reports have focused on using O/S/Se=CF₂ species or their equivalents as the fluorocarbonylation reagents for the direct construction of these compounds from the parent heteroatom-nucleophiles in recent years. This review mainly summarizes the advances in the synthesis and typical application of carbamoyl fluorides, fluoroformates, and their analogues by the halide exchanges and fluorocarbonylation reactions since 1980.     

Chemical processing for inorganic fluoride and oxyfluoride materials having optical functions

Chemical processing such as a sol–gel method can offer interesting and useful routes for designing and synthesizing inorganic metal fluoride and oxyfluoride materials for applications in optics and photonics. In our series of studies during the last decade, a variety of fluoride materials including alkaline earth fluorides (MgF₂, CaF₂, SrF₂ and BaF₂), rare-earth fluorides (LaF₃, NdF₃, GdF₃, etc.), rare-earth oxyfluorides (LaOF, EuOF, GdOF, Sm₄O₃F₆, Er₄O₃F₆, etc.) and complex fluorides (SrAlF₅, BaMgF₄, BaLiF₃, LiGdF₄, etc.) have been prepared, using trifluoroacetic acid as a fluorine source, in the form of nanoparticles, thin films and oxide/fluoride nanocomposites. They can be utilized as anti-reflective coatings, luminescent materials, VUV materials, IR materials, and so forth. This article summarizes fundamentals and possible applications of optically useful inorganic fluoride and oxyfluoride materials, with emphasis on porous single-layer anti-reflective coatings and visible photoluminescence of doped Eu³⁺ or Eu²⁺ ions. Furthermore, our recent results on LaF₃:Ce³⁺ and LaOF:Ce³⁺ are originally reported here.     

Concise and Additive-Free Click Reactions between Amines and CF3SO3CF3

Trifluoromethyl trifluoromethanesulfonate has proved to be an excellent reservoir of difluorophosgene and a promising click ligation for amines in the preparation of urea derivatives, heterocycles, and carbamoyl fluorides under metal- and additive-free conditions. The reactions are rapid, efficient, selective, and versatile, and can be performed in benign solvents, giving products in excellent yields with minimal efforts for purification. The characteristics of the reactions meet the requirements of a click reaction. The use of trifluoromethyl trifluoromethanesulfonate as a click reagent is advantageous over other “CO” sources (e.g., TsOCF₃, PhCO₂CF₃, CsOCF₃, AgOCF₃, and triphosgene) because this reagent is readily accessible; easy to scale up; and highly reactive, even under metal- and additive-free conditions. It is anticipated that CF₃SO₃CF₃ will be increasingly as important as SO₂F₂ as a click agent in future drug design and development.     

On Copper(I) Fluorides,the Cuprophilic Interaction,the Preparation of Copper Nitride at Room Temperature,and the Formation Mechanism at Elevated Temperatures

Our attempts to synthesize the hitherto unknown binary copper(I) fluoride have led to first successes and a serendipitious result: By conproportionation of elemental copper and copper(II) fluoride in anhydrous liquid ammonia, two copper(I) fluorides were obtained as simple NH₃ complexes. One of them presents an example of ligand‐unsupported “cuprophilic” interactions in an infinite [Cu₂(NH₃)₄]²⁺ chain with alternating Cu–Cu distances. We discovered that both copper(I) fluorides can easily be converted into Cu₃N at room temperature, just by applying a vacuum. Additionally, we investigated the formation mechanism of the classical synthesis route of Cu₃N that starts with CuF₂ and flowing NH₃ in the temperature range between ambient and 290 °C by means of thermal analysis and in situ neutron diffraction. The reaction proceeds at elevated temperatures through the formation of a blue and amorphous ammoniate Cu(NH₃)₂F₂, the reformation of CuF₂, and finally the redox reaction to form Cu₃N.     

The oxidation of 6- and 7-aryl-4(3h)-pteridinones by immobilized arthrobacter M-4 cells containing xanthine oxidase

The preparation of 6- and 7-(pX-phenyl)-4(3H)-pteridinones (X = H, CH₃, OCH₃) is described. The oxidation of these compounds by (immobilized) Arthrobacter M-4 cells containing xanthine oxidase has been studied. The oxidation monitored by uv spectroscopy usually goes fast, except for 7-(pX-phenyl)-4(3H)-pteridinones (X = CH₃, OCH₃), which are slowly oxidized. With bacterial cells immobilized in gelatine crosslinked with glutaraldehyde small laboratory-scale oxidations were carried out. Based on spectral data the products of the oxidation reactions are 6- and 7-aryllumazines.     

Expansion of the Na3MIII(Ln/An)6F30 Series: Incorporation of Plutonium into a Highly Robust and Stable Framework

Na_nMAn₆F₃₀ is an extremely versatile framework structure for incorporating tetravalent actinides (An) and cerium along with divalent or trivalent d-metals (M); moreover, the structure exhibits a high resistance to harsh chemical conditions. This extreme robustness can potentially be exploited for the sequestration of plutonium in a stable matrix; however, no Na_nMPu₆F₃₀ compounds have been reported so far. Herein, we present four new plutonium fluorides that have been prepared as single crystals by mild hydrothermal synthesis methods. Structural characterizations revealed their compositions to be Na₃AlPu₆F₃₀, Na₃FePu₆F₃₀, Na₃CoPu₆F₃₀, and Na_2.4Mn_1.6Pu₆F₃₀. Surprisingly, in the plutonium series, it was found that Co²⁺ and Mn²⁺ precursors oxidized to form Na₃Co^IIIPu₆F₃₀ and Na_2.4Mn^II/III_1.6Pu₆F₃₀, whereas the analogous reactions for cerium result in reduction of the transition metal, even when beginning with a M³⁺ precursor. While cerium is often used as a surrogate for plutonium, this work serves as an example that deviations between their chemistries do occur.     

Blue Emission of ZnGa2O4 Nanoparticles Dispersed in Fluoride Thin Films via Sol-Gel Process

Nanocomposite thin films where ZnGa₂O₄ nanoparticles were dispersed in fluorides, MgF₂ or LaF₃, were prepared by a sol-gel method using metal acetates and nitrates as starting reagents and trifluoroacetatic acid as a fluorine source. ZnGa₂O₄ and the fluorides such as MgF₂ and LaF₃ were formed simultaneously after the heat treatment of the spin-coated gel films as evidenced by X-ray diffraction. The films were transparent in the visible region. With decreasing the ZnGa₂O₄ content, absorption edges showed blue-shift. All the films exhibited a broad-band blue emission around 430 nm by ultra-violet excitation at 254 nm. The intensity of the blue emission in the PL spectra increased with decreasing the ZnGa₂O₄ content. These phenomena were attributed to the quantum size effects (the increased band-gap) and the surface effects (the increased luminescent center) in the nano-sized ZnGa₂O₄. The mechanism of the emission was discussed in view of surface states in the oxide nanoparticles.     

The room temperature preparation of metastable fluorides and potent oxidizers

The low electronegativity of an oxidation state in an anion enables high oxidation states, e.g. Ni^IV, and Ag^III, to be easily attained in liquid anhydrous HF (aHF), made basic with fluoride-ion donors. The oxidation state can be enhanced if elemental fluorine is photo-dissociated. Teflon^® valves and lines, especially transparent and kinetically stable fluorocarbon containers for the aHF solutions, provide for this. Binary fluorides that are of low solubility in aHF, can be displaced by stronger F⁻ acceptors from their high oxidation-state anions. NiF₄, NiF₃, and AgF₃, which can be made in this manner, are thermodynamically unstable with respect to loss of fluorine. The electronegativity of the oxidation state in the binary fluoride is higher than in the anion (hence the metastability) and when a strong F⁻ acceptor converts the binary fluoride into a cationic species, the electronegativity is further enhanced. Thus cationic Ag^III and Ni^IV are superior to KrF⁺, as one-electron oxidizers and are the most potent oxidizers known thus far. They are able to remove the electron from all platinum-metal hexafluoro-anions, MF₆⁻, to liberate the hexafluorides. All of this chemistry can be achieved at or below room temperature.     

Impact of Magnesium(II) on Beryllium Fluorides in Solutions Studied by 19F NMR Spectroscopy

Beryllium fluorides are widely used in protein phosphorylation studies to get stable transition state analogs or near attack conformers, which has attracted much attention. BeF₃^? is one of the optimal phosphoryl (PO₃^?) analogs for its identical geometry and charge, and Mg²⁺ naturally participates in the phosphoryl binding in biological systems. In solutions, BeF₃^? coexists with other beryllium fluorides (BeF₄^2?, BeF₂ and BeF⁺) and magnesium fluorides, and there are equilibriums between these species. In this article, ¹⁹F NMR spectroscopy was applied to the investigation of the impact of magnesium(II) on beryllium fluorides. It has been found that when Mg²⁺ was introduced into the solutions, the chemical shifts, the intensities and the line widths of ¹⁹F signals of various beryllium fluoride complexes were changed. After ionic strength correction, these effects were remarkable only for BeF₄^2? and BeF₃^?, especially BeF₄^2?, when the concentration of the fluoride ion is relatively low. Mechanism of the effects is proposed which involves ion pair formation between Mg²⁺ and beryllium fluorides.     

Matrix Isolation Spectroscopic and Relativistic Quantum Chemical Study of Molecular Platinum Fluorides PtFn (n=1–6) Reveals Magnetic Bistability of PtF4

Molecular platinum fluorides PtF_n, n=1–6, are prepared by two different routes, photo-initiated fluorine elimination from PtF₆ embedded in solid noble-gas matrices, and the reaction of elemental fluorine with laser-ablated platinum atoms. IR spectra of the reaction products isolated in rare-gas matrices under cryogenic conditions provide, for the first time, experimental vibrational frequencies of molecular PtF₃, PtF₄ and PtF₅. Photolysis of PtF₆ enabled a highly efficient and almost quantitative formation of molecular PtF₄, whereas both PtF₅ and PtF₃ were formed simultaneously by subsequent UV irradiation of PtF₄. The vibrational spectra of these molecular platinum fluorides were assigned with the help of one- and two-component quasirelativistic DFT computation to account for scalar relativistic and spin–orbit coupling effects. Competing Jahn-Teller and spin–orbit coupling effects result in a magnetic bistability of PtF₄, for which a spin-triplet (³B_2g, D_2h) coexists with an electronic singlet state (¹A_1g, D_4h) in solid neon matrices.     

Mechanochemical reactions of fluorides with hemin

Hemin has two potential sites to react with fluorides, the peripheral acid groups and the central Fe^III cation. The mechanochemical reactions of hemin with fluorides (LiF, NaF, KF, CsF, NH₄F and AgF) were monitored using X-ray diffraction (XRD), and IR and Mössbauer spectroscopies. LiF and NaF were found inert when milled with hemin, however KF, CsF, NH₄F and AgF react at both hemin sites. At the iron site Cl⁻ is replaced by F⁻ with formation of KCl, CsCl, NH₄Cl, and AgCl, as detected by XRD, while with the peripheral acid groups, fluorides collect the acidic protons to form KHF₂, CsHF₂, NH₄HF and AgHF₂. The reactions of hemin with the reactive fluorides take place first at the iron site and then at the propionic acid groups.     

Crystal Chemistry of Dichalcogenides MX2

Crystal-chemical analysis of the structures of metal (other than REE) dichalcogenides of composition X:M = 2:1 has been carried out. It is shown that there are two types of structure depending on the formal degree of metal oxidation. The first group are compounds M(X₂) containing metals in the oxidation state 2+ and covalently bonded pairs of chalcogen elements; the main structural types here are cubic (pyrite) and orthorhombic (marcasite) FeS₂. The second group involves the compounds MX₂ with metals in the formal oxidation state 4+ and chalcogenide ions X ₂ ^- ; the main structural types in this group are CdI₂, CdCl₂, MoS₂. The bond lengths M–X, X–X, and X...X are analyzed; it is shown that the high polarizability of the chalcogenide ions is reflected in shortened X...X distances. In the covalently bonded pairs X–X, the bond lengths change within the following limits: 2.03-2.30, 2.35-2.55, and 2.70-2.83 for X...X ion contacts, the minimal values are 3.07, 3.10, and 3.20 (X = S, Se, and Te, respectively).