- Vanadium, niobium and tantalum complexes with terminal sulfur radical ligands
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Sulfur radicals terminally bound to the metal center can be considered as the one-electron reduction products of complexes with terminal sulfido ligands which serve as the reactive sites in enzymes and precursors. However, there is limited information regarding this kind of metal stabilized sulfur radical, which contrasts the more commonly known metal stabilized thiyl radical. In this work, we report the preparation of vanadium, niobium and tantalum radical complexes in the form of M(O)(S)F2 from the reactions of laser-ablated metal atoms and SOF2 in cryogenic matrixes. Combined with the results from infrared spectroscopy and density functional theory calculations, the sulfur ligand in M(O)(S)F2 is characterized to be a terminally bound radical with the unpaired electron located on the sulfur 3p orbital. Besides this radical complex, calculations also predict the existence of MF2(η2-SO) with a side-on SO ligand, but this less stable isomer is not observed as a result of high exothermicity along with its formation from metal atoms and SOF2 that is large enough to overcome the energy barrier towards the occurrence of M(O)(S)F2.
- Chen, Xiuting,Gong, Yu,Hu, Jingwen,Wei, Rui
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- Temperature-Reversible Equilibria and Exchange among Trapping Sites for SOF2 Isolated in Noble Gas Matrix
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High-resolution IR studies have been made for thionyl fluoride isolated in argon, krypton, and xenon matrices in order to probe matrix-molecule interactions and dynamics.Argon matrices show surprisingly complex site structure with at least five distinct monomer sites, whereas krypton and xenon matrices show two and three dominant trapping sites, respectively.The additional sites observed in argon are attributed to three-atom substitutional cages which are unstable in krypton and xenon matrices.The relative intensities of the various monomer sites in krypton and especially xenon change dramatically and reversibly with temperature, indicatting that the inequivalent sites are in equilibrium.In addition, the frequency positions for the various sites merge and the lines broaden as temperature is raised to give single symmetric lines in the high-temperature limit.We attribute the collapse of the site structure at elevated temperatures to a facile exchange among inequivalent sites.
- Swanson, B. I.,Jones, L. H.,Foltyn, E. M.,Asprey, L. B.
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- Rapid and column-free syntheses of acyl fluorides and peptides usingex situgenerated thionyl fluoride
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Thionyl fluoride (SOF2) was first isolated in 1896, but there have been less than 10 subsequent reports of its use as a reagent for organic synthesis. This is partly due to a lack of facile, lab-scale methods for its generation. Herein we report a novel protocol for theex situgeneration of SOF2and subsequent demonstration of its ability to access both aliphatic and aromatic acyl fluorides in 55-98% isolated yields under mild conditions and short reaction times. We further demonstrate its aptitude in amino acid couplings, with a one-pot, column-free strategy that affords the corresponding dipeptides in 65-97% isolated yields with minimal to no epimerization. The broad scope allows for a wide range of protecting groups and both natural and unnatural amino acids. Finally, we demonstrated that this new method can be used in sequential liquid phase peptide synthesis (LPPS) to afford tri-, tetra-, penta-, and decapeptides in 14-88% yields without the need for column chromatography. We also demonstrated that this new method is amenable to solid phase peptide synthesis (SPPS), affording di- and pentapeptides in 80-98% yields.
- Lee, Cayo,Sammis, Glenn M.,Thomson, Brodie J.
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p. 188 - 194
(2021/12/31)
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- Chemoselective Hydro(Chloro)pentafluorosulfanylation of Diazo Compounds with Pentafluorosulfanyl Chloride
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Pentafluorosulfanyl chloride (SF5Cl) is the most prevalent reagent for the incorporation of SF5 group into organic compounds. However, the preparation of SF5Cl often relies on hazardous reagents and specialized apparatus. Herein, we described a safe and practical synthesis of a bench-stable and easy-to-handle solution of SF5Cl in n-hexane under gas-reagent-free conditions. The synthetic application of SF5Cl was demonstrated through the unprecedented reaction with diazo compounds. The chemoselective hydro- and chloropentafluorosulfanylations of α-diazo carbonyl compounds were developed in the presence of K3PO4 or copper catalyst, respectively. These reactions provide a direct and efficient access to various α-pentafluorosulfanyl carbonyl compounds of high value for potential applications.
- Qing, Feng-Ling,Shou, Jia-Yi,Xu, Xiu-Hua
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supporting information
p. 15271 - 15275
(2021/06/08)
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- Multidimensional SuFEx Click Chemistry: Sequential Sulfur(VI) Fluoride Exchange Connections of Diverse Modules Launched From An SOF4 Hub
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Sulfur(VI) fluoride exchange (SuFEx) is a new family of click chemistry based transformations that enable the synthesis of covalently linked modules via SVI hubs. Here we report thionyl tetrafluoride (SOF4) as the first multidimensional SuFEx connector. SOF4 sits between the commercially mass-produced gases SF6 and SO2F2, and like them, is readily synthesized on scale. Under SuFEx catalysis conditions, SOF4 reliably seeks out primary amino groups [R-NH2] and becomes permanently anchored via a tetrahedral iminosulfur(VI) link: R?N=(O=)S(F)2. The pendant, prochiral difluoride groups R?N=(O=)SF2, in turn, offer two further SuFExable handles, which can be sequentially exchanged to create 3-dimensional covalent departure vectors from the tetrahedral sulfur(VI) hub.
- Li, Suhua,Wu, Peng,Moses, John E.,Sharpless, K. Barry
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supporting information
p. 2903 - 2908
(2017/03/13)
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- Syntheses of a perfluoroethanesulfonyl fluoride vinyl ether
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The target monomer, perfluoroethanesulfonyl fluoride vinyl ether 8, was obtained from the starting material, iodoperfluoroethanesulfonyl fluoride 1, through the intermediate, acyl fluoride 4. Two different synthetic routes were utilized in the conversion of 4 to 8.
- Lu, Changqing,Jiang, Wanchao,Hickman, Tom,Desmarteau, Darryl D.
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scheme or table
p. 2896 - 2898
(2011/06/17)
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- Crystal and molecular structures of the pentafluorosulfanyl compounds, SF5X (X = -NC, -CN, -NCO, -NCS and -NCCl2) by X-ray diffraction at low temperature
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A new method for the synthesis of the unstable pentafluorosulfanyl isocyanide from N-(pentafluorosulfanyl)(dichloromethanimine) was developed, thereby allowing for the study of its spectroscopic data. The structure of pentafluorosulfanyl isocyanide was determined by X-ray crystallography at 113 K. The molecule possesses an almost linear S-N-C arrangement and an unexpectedly long S-N bond. In addition, the structures of pentafluorosulfanyl cyanide, pentafluorosulfanyl isocyanate, pentafluorosulfanyl isothiocyanate, and N-(pentafluorosulfanyl)(dichloro)methanimine were determined by single crystal X-ray crystallography at low temperatures.
- Buschmann, Juergen,Lentz, Dieter,Luger, Peter,Perpetuo, Genivaldo,Preugschat, Dagmar,Thrasher, Joseph S.,Willner, Helge,Woelk, Hans-Joerg
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p. 1136 - 1142
(2008/10/09)
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- Quantitative infrared spectroscopic analysis of SF6 decomposition products obtained by electrical partial discharges and sparks using PLS-calibrations
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Infrared spectroscopy is a powerful tool for the analysis of gaseous by-products in sulfur hexafluoride gas used as an insulator in high-voltage equipment. Sparks and electrical partial discharges were generated between different point-plane configurations within a custom-made discharge chamber constructed from stainless steel and Teflon. Various electrode materials were used such as stainless steel, copper, aluminium, silver, tungsten and tungsten/copper alloy. Owing to the different electrical conditions, a wide concentration range of the decomposition products existed. The main-products found were the sulfuroxyfluorides SOF4 and SOF2, as well as HF following experiments with partial discharges and sparking with energies around 1.0 J/spark. All infrared spectra were recorded using an FTIR-spectrometer equipped with a 10 cm gas cell. Quantification was carried out using classical least-squares and partial least-squares (PLS) with multivariate spectral data from selected intervals. PLS calibration models were also optimised under the constraint of a minimum number of spectral variables with a view to developing simple photometers based on a restricted number of laser wavelengths. Standard errors of prediction obtained by cross-validation of different PLS calibration models are reported for the compounds mentioned, as well as for SF4, SO2F2 and SiF4.
- Kurte,Heise,Klockow
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p. 505 - 513
(2007/10/03)
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- Low temperature fluorination of some non-metals and non-metal compounds with fluorine
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Low temperature fluorination with elemental fluorine of elemental phosphorus, sulphur, silicon, amorphous carbon and phosphorus trichloride, phosphorus pentoxide, triphenylphosphine, hexafluorodisilane, hexachlorodisilane, hexabromodisilane, tetrasulphur tetranitride, sulphur dioxide, thionyl chloride and sulphuryl chloride has been carried out in freon-11 medium.The corresponding fluoro compounds have been isolated in near quanititative yields, purified by low temperature fractional condensation and characterised by IR spectroscopy and elemental analysis.
- Padma, D K,Kalbandkeri, R G,Suresh, B S,Bhat, V Subrahmanya
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p. 172 - 176
(2007/10/02)
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- Gas-Phase Lewis Acid-Base Interactions. An Experimental Determination of Cyanide Binding Energies from Ion Cyclotron Resonance and High-Pressure Mass Spectrometric Equilibrium Measurements
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Both ion cyclotron resonance and high-pressure mass spectrometric equilibrium techniques have been used to investigate the binding energies of anions to a variety of Lewis acids.From an analysis of the enthalpy changes associated with CN- binding it is evident that in cases of relatively weak binding considerable freedom of rotational motion of CN- in the complex may be retained.Ab initio calculations and experiment suggest that binding through both the N and C sites of CN- is nearly equally favorable in some cases.In contrast to results previously obtained for Bronsted acids which showed that CN- and Cl- bind nearly identically, the present data for Lewis acids show many cases where cyanide is much more favorably bound than chloride, a consequence of enhanced covalent binding of the CN- complexes.New Kroeger Drago parameters derived for CN- support the importance of covalent binding in cyanide adducts.Correlations of binding energy of anions to Lewis acids with the anion proton affinity show excellent linear relationships which may be used to predict binding energetics for new anions.
- Larson, J. W.,Szulejko, J. E.,McMahon, T. B.
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p. 7604 - 7609
(2007/10/02)
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- Reactivity of Chalcogen Cluster Polycations
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The chalcogen polycations S8(AsF6)2, S19(HS2O7)2, and Se4(HS2O7)2 are powerful oxidants entering into electron transfer reactions with hydrocarbons, aromatic compounds, and halides.
- Rosan, A. M.
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p. 377 - 378
(2007/10/02)
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- Some reactions of sulfonyl hypohalites with sulfur tetrafluoride
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The reactions of ClOSO2F, BrOSO2F, and ClOSO2CF3 with SF4 have been investigated. It has been found that the reactions proceed to form either trifluorosulfonium salts or covalent adducts. In the cases where the hypochlorites were used, the unusual cation SF4Cl+ can be postulated as a reactive intermediate. Characterizations of the new compounds SF3+FSO3-, SF3+CF3SO3-, cis-SF4(Cl)OSO2F, trans-SF4(Cl)OSO2F, and trans-SF4(Cl)OSO2CF3 are reported. The SF3+ salts are thermally unstable, decomposing to SF4, SOF2, and (XSO2)2O (X = F, CF3).
- O'Brien, Brian A.,DesMarteau, Darryl D.
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p. 644 - 648
(2008/10/08)
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- Gas-phase structure of dimeric tetrafluorosulfur chloroimide, (ClNSF4)2
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The geometric structure of (ClNSF4)2 was studied by gas electron diffraction. The four-membered SNSN ring is planar with the out-of-plane chlorine atoms in trans positions (C2h symmetry). The S-N bonds (1.734 (4) ?) are lengthened due to angle strain (SNS = 99.3 (0.6)°). The extremely short N-Cl bond lengths (1.638 (10) ?) are rationalized by the large SNCl bond angles (122.1 (0.7)°). Substitution effects on trans and cis S-F bond lengths of the SF4 groups are discussed.
- Oberhammer, Heinz,Waterfeld, Alfred,Mews, Rüdiger
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p. 415 - 418
(2008/10/08)
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- INTERACTION BETWEEN URANIUM PENTAFLUORIDE AND THE PENTAFLUORIDES OF VANADIUM, ARSENIC, NIOBIUM, TANTALUM, AND BISMUTH, AND THE TETRAFLUORIDE OF SULPHUR
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The interaction of UF5 with SF4, SF4O, and some Lewis-acid pentafluorides of various strengths has been studied.In anhydrous HF solutions, SF4 was shown to yield an adduct of composition 3UF5*SF4 in which both ionic and fluorine-bridged species are present.The pentafluorides of arsenic, tantalum, and niobium combine with UF5 to give adducts of composition 1.5 UF5*AsF5, UF5*2TaF5, and UF5*2NbF5, respectively.The arsenic derivative is stable at room temperature only under a pressure of AsF5, whereas the tantalum and niobium adducts decompose at higher temperature forming UF5*TaF5 and UF5*NbF5, respectively.Vibrational spectroscopic study of the pentafluoride adducts of UF5 has shown that they consist of covalent fluorine-bridged species.Uranium pentafluoride is fluorinated at room temperature by VF5 and by BiF5 in anhydrous HF.
- Holloway, John H.,Staunton, Garry M.,Rediess, Klaus,Bougon, Roland,Brown, David
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p. 2163 - 2166
(2007/10/02)
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- The Reaction of S2NAsF6 with Halogens: Preparation and X-Ray Crystal Structure of Bis(difluorothio)nitronium Hexafluoroarsenate(V), (SF2)2NAsF6; Preparation of (SBr)2NAsF6, and Vibrational Spectrum and Normal-co-ordinate Analysis of the (SX)2N+ (X=Cl or Br) Cations
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Solutions of S2NAsF6 in liquid SO2 react with elemental chlorine and bromine yielding (SX)2NAsF6 (X=Cl or Br), essentially quantitatively.No reaction was detected with iodine.The vibrational spectrum of (SBr)2N+ was similar to that of (SCl)2N+ of known structure, implying a similar structure for the bromine derivative.This conclusion was supported by a normal-co-ordinate analysis of (SX)2N+.The analysis was consistent with some positive interaction between the halogen atoms in (SX)2N+, possibly accounting for the cis planar geometry of these cations.Attempts to prepare (SF)2NAsF6 were unsuccessful.However, (SF2)2NAsF6 was synthesised by the reaction of S2NAsF6 and XeF2 in liquid SO2F2, essentially quantitatively.The structure of (SF2)2NAsF6 was determined by X-ray diffraction.The crystals are orthorhombic with a=14.909(1), b=9.843(4), c=12.113(1) Angstroem, and Z=8.The structure was refined in space group Pbca to a conventional R factor of 0.076 for 902 independent reflections with I>2?(I).It consists of discrete (SF2)2N+ and AsF6- with some cation-anion interactions.The (SF2)2N+ cation has approximate C2γ symmetry with essentially eclipsed fluorine-sulphur bonds as viewed along the sulphur-sulphur axis.The average S-N and S-F distances are 1.551(10) and 1.523(8) Angstroem, and the average FSF and FSN bond angles are 94.0(5) and 100.2(6) deg.The SNS bond angle is 121.1(6) deg.The vibrational spectrum of (SF2)2NAsF6 is reported.
- Brooks, Wendell V. F.,MacLean, Gregory K.,Passmore, Jack,White, Peter S.,Wong, Chi-Ming
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p. 1961 - 1968
(2007/10/02)
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- Some chemistry of difluorodiazine
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Difluorodiazine undergoes reaction with some sulfur oxides and sulfur and phosphorus fluorides and oxyfluorides. These reactions are characterized by fluorination or fluorination with oxygen elimination. The quantitative syntheses of difluoramidosulfuryl fluoride, FSO2NF2, and pentafluorosulfur difluoramine, SF5NF2, and a high yield preparation of sulfuryl bromide fluoride, FSO2Br, are given. The isomerization of trans-N2F2 was accomplished at a temperature lower than formerly described.
- Lustig, Max
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p. 104 - 106
(2008/10/08)
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