Phosphorus Pentafluoride Research Articles

Ring-Opening Polymerization of a Benzylated 1,6-Anhydro-β-d-talopyranose and Synthesis of a New Polysaccharide, (1→6)-α-d-Talopyranan

1,6-Anhydro-2,3,4-tri-O-benzyl-β-d-talopyranose (1) was synthesized and polymerized to compare its polymerizability with that of other benzylated 1,6-anhydrohexopyranoses reported previously. In methylene chloride at −60 °C, phosphorus pentafluoride as the initiator gave stereoregular polymers (2) with number-average molecular weights (Mn) of 9500−19 600. The polymerizability was analyzed based on the configuration of the hydroxyl groups and conformational change of the pyranose ring during polymerization. The monomer reactivity ratios resulting from copolymerization with 1,6-anhydro-2,3,4-tri-O-benzyl-β-d-glucopyranose (4) were also compared. The present monomer 1 required a large amount of the initiator for polymerization. 31P NMR results of polymerization suggested that considerable amounts of the initiator coordinated with not only the oxygen of the 1,6-anhydro ring of the monomer but also those of the polymer. This additional coordination of the initiator with the polymer oxygens is expected to decrease the initiation efficiency. Debenzylation resulted in a new stereoregular polysaccharide, (1→6)-α-d-talopyranan (3).

Ring‐opening polymerization of benzylated 1,6‐anhydro‐β‐D‐lactose and specific biological activities of sulfated (1→6)‐α‐D‐lactopyranans

AbstractA new anhydro disaccharide monomer, 1,6‐anhydro‐2,3‐di‐o‐benzyl‐4‐o‐(2′,3′,4′,6′‐tetra‐o‐benzyl‐β‐D‐galactopyranosyl)‐β‐D‐glucopyranose (benzylated 1,6‐anhydro lactose (LSHBE)), was synthesized from D‐lactose to investigate the polymerizability and biological activities of the resulting branched polysaccharides. The ring‐opening polymerization of LSHBE was carried out with phosphorus pentafluoride as a catalyst under high vacuum to give a stereoregular benzylated (1 → 6)‐α‐D‐lactopyranan. The molecular weights of poly(LSHBE)s increased with an increase in the amount of CH2Cl2 solvent, and polymerization temperatures were affected in both molecular weights and yields of the polymers. The copolymerization of LSHBE with benzylated 1,6‐anhydro‐β‐D‐glucopyranose (LGTBE) gave the corresponding copolysacchrides having different proportions of lactose and glucose units in good yields. After debenzylation to recover hydroxyl groups and then sulfation, sulfated homopoly(lactose)s and copoly(lactose and glucose)s were obtained. Sulfated homopoly(lactose)s had moderate anti‐HIV (EC50 = 5.9 and 1.3 μg/mL) and blood anticoagulant activities (AA = 18 and 13 unit/mg), respectively. Sulfated copoly(lactose and glucose) having 15 mol % lactose units gave high anti‐HIV and blood anticoagulant activities of 0.3 μg/mL and 54 unit/mg, respectively. These biological results suggest that the distance between branched units on the main chain plays an important role in the anti‐HIV and blood anticoagulant activities. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 913–924, 2009

Berry Pseudorotation Mechanism for the Interpretation of the 19F NMR Spectrum in PF5 by Ab Initio Molecular Dynamics Simulations

For the first time, theoretical evidence that confirms the importance of the Berry pseudorotation process in the interpretation of the 19F NMR spectrum of phosphorus pentafluoride (PF5) is presented. Ab initio molecular dynamics simulations have been performed to generate a large number of configurations used for NMR parameter computations at the density functional theory level. Two different temperatures were set to highlight the effect of pseudorotation process on the NMR spectrum. Average 19F chemical shifts and spin-spin coupling constants calculated for the five fluorine atoms converge towards the NMR equivalence of the five atoms when the Berry pseudorotation mechanism is accounted for.

Qualitative quantum dynamics with allowance for Berry pseudorotation in XPF4 and PF5 molecules: II. The PF5 molecule

The purpose of this study is to construct a rigorous qualitative description of internal quantum dynamics of the phosphorus pentafluoride molecule PF5 with allowance for its transitions of the Berry pseudorotation type between twenty independent energetically equivalent equilibrium configurations. As the first step toward the solution of this very complicated problem, a significantly simpler problem is considered of internal dynamics of an XPF4 molecule in which the Berry pseudorotation connects only two independent equivalent equilibrium configurations. In this study, the methods based on the currently developed concept of the symmetry-group chain are employed, which allow one to describe the internal dynamics without resorting to equations of motion.

Ring-opening polymerization of new 1,6-anhydro-β- d-glucosamine derivatives

New 1,6-anhydro-glucosamine monomers having amino protecting groups at C2 positions; i.e. 1,6-anhydro-3,4-di- O-benzyl-2-( N,N-cyclo (1,2-bis(dimethylsilyl)ethylamino)-2-deoxy-β- d-glucopyranose (A2NSG), 1,6-anhydro-3,4-di- O-benzyl-2-hexamethyleneimino-2-deoxy-β- d-glucopyranose (A2NHG) and 1,6-anhydro-3,4-di- O-benzyl-2-( N,N-dibenzylamino)-2-deoxy-β- d-glucopyranose (A2NBG), were synthesized in order to investigate the effects of the 2-amino groups on cationic ring-opening polymerizations. When phosphorus pentafluoride and antimony pentachloride were used as initiators, the A2NSG monomer gave polymers having number-average molecular weights ofM¯ n = 4.1 × 10 3 and 3.4 × 10 3 (P¯D n = 13 and 8), respectively. The resulting polymers had positive specific rotations ranging from[α] 25 d = +33.1 °to+44.1 ° and the Cl signal in the 13C NMR spectra appeared as a single peak around 100 ppm, which suggested that the polymers had 1,6-α stereoregularity. The A2NHG monomer gave polymers in low yields, and the A2NBG monomer had no polymerizability. These results suggest that the ring-opening polymerization of 1,6-anhydro-glucosamine monomers depends on both electron withdrawal and steric hindrance of the 2-amino protecting groups.

Absolute oscillator strengths for the valence and inner (P 2p,2s) shell photoabsorption, photoionization, and ionic photofragmentation of PF 3

Absolute oscillator strengths (cross-sections) for the photoabsorption of phosphorus pentafluoride (PF 5) have been measured for the first time in the valence and phosphorus 2p discrete regions using high-resolution (0.0–0.1 eV fwhm), dipole ( e, e) spectroscopy. Long-range data (10–300 eV) have also been obtained at lower resolution (1 eV fwhm), from which the absolute oscillator strength scale has been determined using the valence-shell Thomas-Reiche-Kuhn sum-rule. The accuracy of the present measurement has been tested using the S(−2) sum rule normalization. Evaluation of the S(−2) sum using the presently reported absolute photoabsorption oscillator strength data gives a dipole polarizabilit for PF 5 in good agreement with the experimental value. The photoionization efficiencies, photoion branching ratios, and absolute partial oscillator strengths for molecular and dissociative photoionization have also been determined for PF 5 by dipole ( e, e+ion) coincidence spectroscopy from the first ionization threshold up to and above the phosphorus 2p edge.

Reaction mechanisms of phosphorus fluorides: An ab initio study

Reaction mechanisms of phosphorus fluorides may be analyzed on the basis of the coordination model of reaction mechanisms. Some of the intermediates and mechanistic details arising out of such an analysis have been investigated by ab initio molecular orbital calculations. The rapid equilibrium between five- and six-coordinate phosphorus fluorides, and exchange of axial and equatorial fluorines in PF 5, is investigated by calculating the structures of adducts of phosphorus pentafluoride, i.e. D-PF 5 where D = NH 3, H 2O, CH 3F, HF, PF 5 and PF 6. Bond cleavage in phosphorus fluorides is investigated by calculating the structure of a fluorine-bridged anion P 2F 11 −. A reaction pathway is proposed for the fluoride-catalyzed oxidation of phosphorus (III) to phosphorus(V) fluorides which involves the known species PF 3, PF 4 −, PF 4 and PF 5.

Acid generation in the thermal decomposition of diaryliodonium salts

Diphenyliodonium tetrafluoroborate and diphenyliodonium hexafluorophosphate have been found to generate up to two equivalents of hydrogen fluoride per equivalent of the iodonium salt by pyrolysis at 239°C in the neat state and at 150°C in the presence of anisole or nitrobenzene. The formation of hydrogen fluoride is presumed to arise by dissociation of hydrogen tetrafluoroborate or hydrogen hexafluorophosphate initially formed, due to the high temperatures, thus giving rise also to the Lewis acids boron trifluoride and phosphorus pentafluoride, respectively. A detailed analysis of the volatile organic products of the decomposition of the diphenyliodonium salts was also carried out. Many products were identified in all of the cases studied. For example, the neat decomposition of diphenyliodonium tetrafluoroborate afforded benzene, fluorobenzene, iodobenzene, the three isomeric iodobiphenyls, biphenyl, three isomeric terphenyls, and one or more of the diiodobiphenyls, iodoterphenyls, and polyaromatics. Among the iodobiphenyls, the ortho and para isomers were found to predominate over the meta isomer. The terphenyl isomers did not exhibit this ortho, para selectivity. It was significant that decomposition of the diaryliodonium salts in anisole suspension did not afford methoxybiphenyls or iodomethoxybiphenyls. An interpretation of these results is presented. © 1996 John Wiley & Sons, Inc.

N-Halogeno compounds part 17. Precursors of NF-TEDA reagents: quaternary salts of 1,4-diazabicyclooctane containing fluoro-anions, and their Lewis acid-Lewis base adducts with boron trifluoride, phosphorus pentafluoride and sulphur trioxide

Methods are described for the synthesis of 1-alkyl-4-aza-1-azoniabicyclo[2.2.2]octane salts [R +N(CH 2CH 2) 3NX − (R = CH 3, CH 2Cl, C 2H 5, CF 3CH 2, n-C 8H 17; X − = CF 3SO 3 −, BF 4 −, PF 6 −)] and of related 1:1 adducts Lewis acids [X − R +N(CH 2CH 2) 3N +LA − (R = CH 3, CH 2Cl; X − = CF 3SO 3 −, BF 4 −, PF 6 −; LA = BF 3, PF 5, SO 3)] used in the development of site-selective electrophilic fluorinating agents of the 1-alkyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane class (Selectfluor tm reagents). Detailed NMR data ( 1H, 19F, 13C, 11B, 31P) for the salts and their adducts are listed.

Acid generation in the thermal decomposition of diaryliodonium salts

Diphenyliodonium tetrafluoroborate and diphenyliodonium hexafluorophosphate have been found to generate up to two equivalents of hydrogen fluoride per equivalent of the iodonium salt by pyrolysis at 239°C in the neat state and at 150°C in the presence of anisole or nitrobenzene. The formation of hydrogen fluoride is presumed to arise by dissociation of hydrogen tetrafluoroborate or hydrogen hexafluorophosphate initially formed, due to the high temperatures, thus giving rise also to the Lewis acids boron trifluoride and phosphorus pentafluoride, respectively. A detailed analysis of the volatile organic products of the decomposition of the diphenyliodonium salts was also carried out. Many products were identified in all of the cases studied. For example, the neat decomposition of diphenyliodonium tetrafluoroborate afforded benzene, fluorobenzene, iodobenzene, the three isomeric iodobiphenyls, biphenyl, three isomeric terphenyls, and one or more of the diiodobiphenyls, iodoterphenyls, and polyaromatics. Among the iodobiphenyls, the ortho and para isomers were found to predominate over the meta isomer. The terphenyl isomers did not exhibit this ortho, para selectivity. It was significant that decomposition of the diaryliodonium salts in anisole suspension did not afford methoxybiphenyls or iodomethoxybiphenyls. An interpretation of these results is presented. © 1996 John Wiley & Sons, Inc.

Ring-Opening Polymerization of a 1,4-Anhydro Xylose Derivative Having an Azido Group and Synthesis of Stereoregular 3-Amino-3-deoxy-(1→5)-α-d-xylofuranan

A new 1,4-anhydro pentose monomer having an azido group, 1,4-anhydro-3-azido-2-O-benzyl-3-deoxy-α-d-xylopyranose (A3ABX), was synthesized by benzylation of 1,4-anhydro-α-d-ribopyranose at the C2 hydroxyl group and subsequent trifluoromethylsulfonylation at the C3 hydroxyl group, followed by SN2 replacement of the trifluoromethylsulfonyl group with the azido group with lithium azide. Ring-opening polymerization of A3ABX was attempted with Lewis acid catalysts such as boron trifluoride etherate, phosphorus pentafluoride, and antimony pentachloride at different temperatures between −60 and −20 °C. Boron trifluoride etherate catalyst gave a polymer with a positive specific rotation and with a single C1 absorption at 99 ppm in the 13C NMR spectrum, indicating that the resulting polymer had a stereoregular 1,5-α furanosidic structure. When the polymerization was carried out by antimony pentachloride at −60 °C, the polymer obtained had a negative specific rotation and the C1 absorption shifted downfield to around 107 ppm, suggesting that the polymer might be composed of a 1,5-β furanosidic unit. Reduction of the azido group to an amino group and the benzyl group to a hydroxyl group gave 3-amino-3-deoxy-(1→5)-α-d-xylofuranan. The structural analysis of the polysaccharides was performed by means of high-resolution 1H and 13C NMR spectroscopies including the two-dimensional spectra of H−H COSY, NOESY, and FGHMQC.

Syntheses of Polysaccharides Having Various Contents of Carboxyl Groups by Ring-Opening Copolymerization

Polysaccharides having various contents of carboxyl group precursors were synthesized by ring-opening copolymerization of 1,6-anhydro-2,4-di-O-benzyl-3-O-1-(methoxycarbonyl)ethyl-β-D-glucopyranose (1) with tri-O-benzyl-levoglucosan (2) with phosphorus pentafluoride as catalyst in methylene chloride at −60°C. The monomer reactivity ratios calculated by Kelen–Tudos method were r1=0.77 and r2=0.71. Birch reduction with lithium metal was quite effective for the deprotection of both methyl ester and benzyl ether groups of the polymer.

1,4-Difluoro-1,4-diazoniabicyclo [2.2.2] octane salts

1,4-Difluoro-1,4-diazoniabicyclo [2.2.2] octane salts, F− +N(CH 2CH 2) 3N + −F 2X − ( 2) where X − = BF 4 −, PF 6 −, FSO 3 −, CF 3SO 3 −, have been synthesised by direct fluorination of 1:1 or 1:2 Lewis acid adducts of 1,4-diazabicyclo[2.2.2]octane with boron trifluoride, phosphorus pentafluoride or sulfur trioxide, and of 1,4-bis(trimethylsilyl)-1,4-diazoniabicyclo[2.2.2]octane ditriflate, respectively, in cold acetonitrile. The bis(tetrafluoroborate) salt ( 2; X − = BF 4 − has also been obtained via fluorination of 1-heptafluoro- n-butyryl-1,4-diazo-niabicyclo[2.2.2]octane-trifluoromonoborane tetrafluoroborate.

MOLECULAR STRUCTURES OF PCl4F, PCl3F2, PCl2F3, AND PF5: INFRARED AND LOW - TEMPERATURE RAMAN VIBRATIONAL SPECTRA

Abstract Molecular structures of PCl4F, PCl3F2, PCl2F3, and PF5 are derived from vapor-state infrared spectra (2000-250 cm−1) and low-temperature liquid-state Raman displacements (Δv = 50–1200 cm−1) together with qualitative polarization measurements. All of the compounds appear to have a basic trigonal bipyramidal framework. The spectra of PCl4F are best interpreted in terms of a C3v structure in which the fluorine atom occupies an axial site; in PCl3F2 (D 3h point group) the fluorine atoms also assume axial positions. For PCl2F3, the symmetrical D 3h structure is shown to be incorrect. Available evidence supports the. C2v structure in which the fluorine atoms appear in one equatorial and two axial sites. Phosphorus pentafluoride is found to have a regular trigonal bipyramidal structure. Complete vibrational assignments are made in terms of the normal modes and thermodynamic functions are evaluated for PCl5, PCl3F2 and PF5.

Optical properties of hydrogenated amorphous silicon films doped with fluorinated gases

Doped amorphous silicon films were prepared by plasma-enhanced chemical vapour deposition of silane and hydrogen mixtures, using phosphorus pentafluoride (PF 5) and boron trifluoride (BF 3) as dopant precursors. The films were studied by UV-vis spectroscopy and their photo and dark conductivity were measured, the latter as a function of temperature. The optical gap of the n-type samples, doped with PF 5, diminished as the concentration of this gas in the plasma was increased. However, the optical gap of p-type samples, doped with BF 3, did not show any appreciable optical gap decrease as the concentration of BF 3 was varied from 0.04% to 4.7%. The dark conductivity of the p-type films at these extremes of the doping range were 7.6 × 10 −10 and 3.5 × 10 −1 Ω −1 cm −1, respectively.

Theoretical study of the harmonic and anharmonic force fields of phosphorus pentafluoride

Abstract The harmonic force field of PF 5 is calculated at the ab initio SCF (self-consistent field) level and at the correlated MP2 level (second-order Moller-Plesset perturbation theory) using triple-zeta basis sets with multiple polarization functions (up to f functions at phosphorus). The ab initio results support the validity of a previous harmonic force field which has been refined with respect to experimental data while constraining certain off-diagonal force constants to scaled SCF values. The anharmonic force field of PF 5 is obtained from ab initio SCF calculations. The theoretical anharmonic spectroscopic constants agree reasonably well with the experimental data that are available. Many unknown spectroscopic constants are predicted.

Darstellung und Reaktionen von zweikernigen Platin(II)-Komplexen; Einkristall-Röntgenstrukturanalyse eines Tetrakis(difluorphosphonato)-Palladat(II)-Komplexes / Preparation and Reactions of Binuclear Platinum(II) Complexes. Single Crystal X-Ray Diffraction Study of a Tetrakis(difluorophosphonato)palladate(II) Complex

o-Methylbenzyldifluorophosphite 2 was obtained by the reaction of o-methylbenzyltrimethyl silyl ether 1 with chlorodifluorophosphine PF2Cl. The reaction of 2 with the palladium(II) complex 3 led to the tetrakis(difluorophosphonato)palladate(II) complex 7. The X-ray structure analysis of 7 confirmed the nearly exact square planar structure at the metal atom of the tetrakis(difluorophosphonato)palladate(II) dianion. Minimal deviations from the ideal geometry at palladium and phosphorus are mainly the result of thermal motion or disorder phenomena in the crystal. In the reaction of the platinum(II) complex 8 with chlorodifluorophosphine the binuclear tetrakis(chlorodifluorophosphine)platinum(II)chloro complex 9 was obtained. In acetonitrile, 9 was cleaved to form the mononuclear complex 10. Similar results were obtained in the oxidative addition reactions of the platinum(0) complex 11 with sulfuryl chloride fluoride, 12, sulfuryl fluoride, 13, and phosphorus pentafluoride. Tetrakis-(triphenylphosphine)-μ-dichlorodiplatinum(II) hexafluorophosphate 14 was isolated. In acetonitrile the mononuclear acetonitrile-bis(triphenylphosphine)chloroplatinum(II) hexafluorophosphate complex 15 was isolated.

Chemical synthesis of a comb-shaped, branched stereoregular polysaccharide, 4- O-α- d-mannopyranosyl-(1 → 6)-α- d-mannopyranan

4- O-α- d-Mannopyranosyl-(1 → 6)-α- d-mannopyranan ( 7) was prepared via ring-opening polymerization of 1,6-anhydro-2,3-di- O-benzyl-4- O-(2,3,4,6-tetra- O-benzyl-α- d-mannopyranosyl)-β- d-mannopyranose ( 5) using phosphorus pentafluoride as initiator in dichloromethane at −60°C, followed by debenzylation. Compound 5 was obtained via glycosidation of 1,6-anhydro-2,3- O-isopropylidene-β- d-mannopyranose ( 1) with 2,3,4,6-tetra- O-benzyl-1- O-trichloroacetimidoyl-α- d-mannopyranose ( 2) using p-toluenesulfonic acid as catalyst and subsequent transformation of the protecting groups of the resulting 1,6-anhydro-4- O-(2,3,4,6-tetra- O-benzyl-α- d-mannopyranosyl)-2,3- O-isopropylidene-β- d-mannopyranose ( 3).

Quasi-heterogeneous combustion of phosphorus in fluorine

The combustion of red phosphorus in fluorine under conditions of outside-diffusion inhibition at temperature range 300–623 K and total pressure up to 5.0 MPa was studied. At the present conditions the combustion has a quasi-heterogeneouse nature. The high temperature in the reaction surface layer of red phosphorus heats the deep phosphorus layers, where a red-to-white modification transition of phosphorus occurs because that there is no access of fluorine. The allotropic change of phosphorus modification in the deep layers results in the change of kinetic characteristics of the reaction: the fluorination rate sharply increases after achieving of certain degree of conversion, that is untypical for topochemical reactions. The product of phosphorus fluorination depending on the process conditions may be phosphorus pentafluoride or trifluoride or mixture of these substances. The kinetic characteristics of phosphorus fluorination by molecular fluorine in the wide range of temperatures and pressures under outside-diffusion inhibition conditions had been studied. The diffusion coefficients of reactants and gaseous reaction products and the optimal conditions of synthesis of phosphorus penta- and trifluorides had been determined.

Pure rotational spectrum of phosphorus pentafluoride observed by microwave Fourier transform spectroscopy

Pure rotational transitions of PF 5 (phosphorus pentafluoride) in the vibrational ground state have been measured in the frequency range of 9–25 GHz for the first time. The transitions are forbidden in the rigid rotor limit but become weakly allowed due to a small dipole moment induced by centrifugal distortion. They obey the selection rule Δ k = ±3. The extremely weak absorption lines in the static gas have been recorded with a pulsed microwave Fourier transform spectrometer. Q-branch series for K = ∥ k∥ = 1, 2, 3, and 5 in the lower state have been identified with J ranging from 45 to 94. The series J 6←3 has been found to split into A 1 and A 2 states under the influence of sextic and octic centrifugal distortion nondiagonal in K. In a weighted least-squares fit, the molecular constants ( A- B), D JK , D K , H JK , h 3, and h 3 J have been simultaneously determined from the measured transition frequencies. Combining the difference ( A- B) of the rotational constants with the result for B from recent high-resolution infrared spectra has provided a value for A. A complete r 0 structure has been determined from the rotational constants A and B. It agrees with previous electron diffraction studies and with ab initio calculations. The tensorial constant θ x xx which measures the induced dipole moment has been estimated by comparing the transitions of PF 5 with the “forbidden” transitions of OPF 3. No indication of a splitting larger than the present linewidth of 50 kHz has been found which may be attributed to the Berry pseudorotation.