Synthesis of functionalized fluorine-containing hyperbranched poly(aryl ether ketones) for optical applications

Hyperbranched poly(aryl ether ketones) with terminal fluorine atoms (OH: F = 0.48: 1.00) or hydroxyl groups (OH: F = 2.02: 1.00) have been obtained through the polycondensation of bis(4,4′-dihydroxydiphenyl-2,2-hexafluoropropane) with 1,3,5-tris[4-(4-fluorobenzoyl)phenoxy]benzene in tetramethylene sulfone. Both polymers have M _n = (7.1?7.3) × 10³ and M _w = (8.4?8.8) × 10³ and are transparent in the near-IR region, in particular, at 1.30 and 1.55 μm.     

Sterically encumbered poly(arylene ether)s containing spiro‐annulated substituents: Synthesis and thermal properties

Four novel 2‐trifluoromethyl‐activated bisfluoro monomers have been synthesized successfully using a Suzuki‐coupling reaction of 3‐trifluoromethyl‐4‐fluoro phenyl boronic acid with 2,7‐dibromofluorene with varied pendants. Four monomers were converted to a series of fluorene‐based poly(arylene ether)s with pendants by nucleophilic displacement of the fluorine atoms on the terminal benzene ring with 4,4′‐hexafluoroisopropylidenediphenol. The polymers obtained by displacement of the fluorine atoms, exhibit weight‐average molecular weight up to 9.89 × 10⁴ g/mol in GPC. Thermal analysis studies indicated that these polymers did not show melting endotherms but did show relatively high T_g values up to 270 °C in DSC and outstanding thermal stability up to 532 °C for 5% weight loss in TGA in a nitrogen atmosphere. The polymers are soluble in a wide range of organic solvents: THF, CHCl₃, NMP, DMAc, DMF, toluene and EAc, and so forth, at room temperature. Transparent and flexible films were easily prepared by solution casting from chloroform solution of each of the polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Constitution moléculaire d' α,ω-difluoro-μ-oxo-poly(méthylphosphanoxy diméthylsilanes): Mise en evidence d'une forte tendance à l'alternance régulière des centres siliciés et phosphorés à l'equilibre

The purpose of this study was to gain a closer knowledge of the molecular constitution of the linear fluorine-terminated oxygen-bridged methylphosphanoxy/dimethylsilane polymers, for example, to find evidence for preferential sorting (or, on the contrary, for random scattering) of the substituents and building units. The title polymers were prepared by reaction of MeP(O)F₂ with cyclic dimethylsiloxanes (Me₂SiO)_n (n = 3 or 4). An equilibrium is reached in the redistribution of fluorine vs. bridging oxygen atoms among the phosphorus and silicon-based centers, and among the resulting building units, after about 2 months at 120°C. The excellent resolution of the ¹H-NMR spectra (Fig. 2), even at 60 MHz, allowed identification of seventeen different fragments (Table II). Nineteen equilibrated samples of varied overall compositions (R = F/(Si + P); R′ = P/(Si + P)) have been analyzed (Table IV), and their molecular constitution is described by a set of four basic constants. The fundamental features which govern the structure of these polymers are as follows. (a) The regular (Si-O-P) alternation of the two different centers, which is thermodynamically favored, as shown by the linkage constant K₀ = [Si-O-Si][P-O-P]/[Si-O-P]² ? 10⁴, which describes the sorting of the silicon and phosphorus atoms on the bridging oxygens, and which deviates by four orders of magnitude from its random value of 0.25. (b) A somewhat surprising lack of preferential distribution of fluorine and oxygen between the two centers (K_I = [MeP(O)F₂][Me₂SiO_1/2]₂/[Me₂SiF₂]-[MeP(O)(O_1/2)₂]) differs little from (a), which contrasts with the preferential affinity of fluorine for silicon and oxygen for phosphorus (K_I ? 10⁷) that was found when F atoms and OCH₃ groups were exchanged between the same centers. (c) The sorting of the fluorine atoms and oxygen bridges on each center, to give neso molecules and the terminal and medium building units, resulting in a slight preference for the formation of the terminal units, as expressed by      

Synthesis and Characterization of Novel Poly(Arylene Ether)s from 4,4′‐Thiodiphenol

Four novel perfluoroalkylated poly(arylene ether)s have been synthesized successfully using four perfluoroalkyl‐activated bisfluoro monomers. These polymers are synthesized through nucleophilic displacement of the fluorine atoms on the benzene ring with 4,4′‐thiodiphenol and are named as 1a, 1b, 1c and 1d, respectively. The polymers obtained by displacement of the fluorine atoms exhibit weight‐average molar masses up to 3.9×10⁴ g · mol^?1 in Gel permeation chromatography. These poly(arylene ether)s showed very high thermal stability up to 548°C for 10% weight loss in TGA under nitrogen and high glass transition temperature (T_g) up to 178°C in DSC depending on the repeat unit structures. The glass transition temperatures taken as peak in tan δ in DMA measurements are in good agreement with the DSC T_g values. All the polymers synthesized are soluble in a wide range of organic solvent such as CHCl₃, CHCl₂, THF, NMP, DMF and toluene. Transparent thin films of these polymers cast from THF exhibited tensile strengths up to 72 MPa, modulus up to 1.69 GPa with low elongation at break depending on their exact repeating unit structures. Rheological properties showed ease of processability of these polymers with no change in melt viscosity with temperature.     

Ca(AsF3)(AsF6)2: the first alkaline earth metal cation coordinated to AsF3

Ca(AsF₃)(AsF₆)₂ was prepared by the reaction of CaF₂ with excess AsF₅ in AsF₃ solvent. The compound crystallizes in an orthorhombic crystal system, space group Pnma, with a =1034.9(4) pm, b = 1001.7(4) pm and c = 1088.4(4) pm, V = 1.1283(8) nm³ and Z = 4. Calcium is coordinated to eight fluorine atoms, with six fluorine atoms located at the corners of a regular trigonal prism originating from six AsF₆ units. Two rectangular faces of the trigonal prism are capped by fluorine atoms from two fluorine bridged AsF₃ molecules. For the first time, AsF₃ is shown to serve as a bridging ligand to two metal cations, with bridging distances of F(AsF₃)-Ca = 241.1 and 243.2 pm. It was found, again for the first time, that the bridging As-F distances are shorter (172.4 and 173.1 pm) than the terminal As-F distance (184.5 pm). The Raman spectrum shows vibrational modes that are readily assigned to AsF₃ and AsF₆⁻.     

Solvothermal Synthesis,Crystal Structure,and Photocatalytic H2 Evolution of two CuII Coordination Polymers Based on Keggin Polyoxotungstates

Two new Cu^II coordination polymers based on α‐Keggin polyoxotungstates, [Cu₂(dpa)₂(H₂O)₂(GeW₁₂O₄₀)] · 0.5CH₃COOH ( 1 ) and [Hdpa][Cu₂(dpa)₂(4,4′‐bipy)(H₂O)₂(PW₁₀V₂O₄₀)] ( 2 ) (dpa = 2,2′‐dipyridylamine, 4,4′‐bipy = 4,4′‐bipyridine), were obtained by solvothermal reactions in glacial acetic acid and characterized by elemental analysis, IR spectroscopy, TG analysis, X‐ray powder diffraction, and single‐crystal X‐ray diffraction. Compound 1 exhibits a 1D two‐rowed chain constructed from [GeW₁₂O₄₀]^4– anions coordinated with [Cu(1)(dpa)]²⁺ and [Cu(2)(dpa)(H₂O)₂]²⁺ fragments by four terminal oxygen atoms. Compound 2 exhibits a 2D layered structure constructed from [PW₁₀V₂O₄₀]^5– anions coordinated with [Cu(dpa)(4,4′‐bipy)_0.5(H₂O)]²⁺ fragments by four terminal oxygen atoms. Furthermore, the electrochemical properties of 1 and the photocatalytic hydrogen production of 1 and 2 were investigated.     

Three new zinc(II) complexes constructed by biphenyl-2,2′,6,6′-tetracarboxylic acid: Effect of solvents and terminal ligands

Interaction of biphenyl-2,2′,6,6′-tetracarboxylic acid (H₄bta) and Zn(II) ions in DMF led to the formation of a one-dimensional coordination polymer, while in the presence of 1,10-phenanthroline and 1H,1′H-2,2′-biimidazole as terminal ligands in H₂O, analogous interactions induced the generation of two-dimensional layers with (6, 3) topology. The bta ligands in these three coordination polymers adopt η⁴,μ₂-tetradentate, η⁵,μ₄-pentadentate and η⁴,μ₄-tetradentate coordination modes, respectively, and the corresponding angles of two benzene rings of bta ligands are 70.52, 83.81 and 73.35°, in accordance with the coordination modes and steric hindrance effect of the terminal ligands.     

X-ray photoelectron spectroscopy as detection tool for coordinated or uncoordinated fluorine atoms demonstrated on fluoride systems NaF,K2TaF7, K3TaF8, K2ZrF6, Na7Zr6F31 and K3ZrF7

While systems K₃TaF₈ and K₃ZrF₇ were prepared by modified molten salt method modified wet pathway was used for reproducible preparation of Na₇Zr₆F₃₁. Its congruently melting character was demonstrated on simultaneous TG/DSC measurements and XRD patterns. X-ray photoelectron spectroscopy was applied for identification of differently bonded fluorine atoms in series of compounds NaF, K₂TaF₇, K₃TaF₈, K₂ZrF₆, Na₇Zr₆F₃₁ and K₃ZrF₇. Three different types of fluorine atoms were described qualitatively and quantitatively. Uncoordinated fluorine atoms (F⁻) provide signals at lowest binding energies, followed by signals from terminally coordinated fluorine atoms (M–F) and then bridging fluorine atoms (M–F–M) at highest energy. Based on XPS F 1s signals assigned to fluorine atoms in compounds with correctly determined structure it was suggested that fluorine atoms in K₃ZrF₇ have partially bridging character.     

The transformation of Sn(ND3)2F4 into Sn(ND2)2F2. Synthesis and neutron crystal structure determination of Sn(ND2)2F2

Diamido-difluoro-tin Sn(ND₂)₂F₂ can be produced by ammonolysis from (NH₄)₂SnF₆ at 633 K. The compound is a product formed from Sn(ND₃)₂F₄ during the ammonolysis reaction. Sn(ND₂)₂F₂ isostructural with Sn(NH₂)₂F₂ crystallizes in space group C2/m with lattice constants a = 1072.92(7), b = 325.97(1) pm, c = 505.79(4) pm and β = 105.713(6) ° (V = 170.28(1) ·10⁶ pm³) containing two formula units per unit cell. Data refinement by the Rietveld method of neutron time-of-flight data collected at POLARIS yields a weighted profile R-value R_wp = 0.022. Tin is octahedrally coordinated by two fluorine atoms and four amido groups. The octahedra are connected to one-dimensional chains by edge sharing. The ND₂ groups are in the bridging position whilst the fluorine atoms are terminal. Nearly linear (175.2(4) °) and angular (134.35(8) °) N-D···F hydrogen linkages connect the chains.     

Effects of fluorine substituent on properties of cyclometalated iridium(III) complexes with a 2,2′-bipyridine ancillary ligand

Cationic cyclometalated Ir(III) complexes (Ir1-Ir5) with fluorine-substituted 2-phenylpyridine (ppy) derivatives as C^N cyclometalating ligands and 2,2′-bipyridine (bpy) as the ancillary ligand, have been synthesized and fully characterized. The influences of the number and the position of fluorine atoms at the cyclometalating ligands on the photophysical, electrochemical and oxygen sensing properties of the Ir(III) complexes have been investigated systematically. The introduction of fluorine on the C^N cyclometalating ligands of the complexes results in blue-shifts of the maximum emission wavelengths, and increases in the photoluminescence quantum yields (Φ_PL), phosphorescence lifetimes and energy gaps, compared to the non-fluorinated [Ir(ppy)₂(bpy)]⁺PF₆^? (Ir0). Among them, 2-(2,4-difluorophenyl)pyridine-derived Ir4 shows the maximum blue-shift (514 nm vs. 575 nm for Ir0) and the highest Φ_PL (50.8% vs. 6.5% for Ir0). The complex Ir3 with 2-(4-fluorophenyl)-5-fluoropyridine as C^N ligand exhibits the highest oxygen sensitivity and excellent operational stability in 10 cycles within 4000 s.     

Synthesis and monolayer properties of double-chained phosphatidylcholines containing perfluoroalkyl groups of different length

A series of double-chained phosphatidylcholines (PCs), 1,2-dioctadec-9′-ynoyl-sn-glycero-3-phosphocholine analogs containing perfluoroalkyl moieties (CF₃, C₂F₅, n-C₄F₉ or n-C₈F₁₇) as the terminal segment in two hydrophobic chains, 1a-d, were synthesized. Equilibrium spreading pressures of these fluorinated PCs at the air-water interface were measured as an indication of monolayer stability, in order to obtain the minimal fluorine content in PC molecule efficient to exhibit monolayer stabilizing effect. The monolayer stability sigmoidally increased with the fluorine content in PC molecule and subsequently leveled off above a certain fluorine content, i.e., n-C₄F₉ moiety, at 25 °C. Under this condition, the replacement of at least five hydrogen atoms at the terminal hydrophobic segment in double-chained PC molecule by fluorine atoms, i.e., CF₃CF₂ moiety, is required to exhibit the monolayer stabilizing effect, whereas further fluorination of double-chained PC (F(CF₂)_n; n > 4) has a minor effect on the monolayer stability.     

Synthesis and characterization of partially fluorinated stearolic acid analogs: Effect of their fluorine content on the monolayer at the air-water interface

Novel stearolic acid analogs (i.e., 9-octadecynoic acid analogs: 1a-d) containing the shorter perfluoroalkyl groups, CF₃, C₂F₅, n-C₃F₇ or n-C₄F₉ group were synthesized. Equilibrium spreading pressures (π_es) of their monolayers at the air-water interface were measured in order to demonstrate how the fluorine content has an effect on the stability of the fatty acid monolayers. As the fluorine content in stearolic acid molecule increased, its melting points was lowered indicating the solid bulk phase of stearolic acid became thermally unstable, while its monolayer stability evaluated by π_e at 25 °C, dramatically increased and subsequently leveled off above a certain fluorine content. Under this condition, the replacement of at least five hydrogen atoms at the terminal hydrophobic segment in stearolic acid molecule by fluorine atoms (CF₃CF₂ group) was required to alter the bulk property of stearolic acid and exhibit the stabilization of monolayers, whereas further fluorination of stearolic acid had a minor effect on the monolayer stability. This behavior suggests the terminal fluorinated hydrophobic segment exclusively controls the interfacial stability of fatty acid monolayers.     

Homo- and copoly(arylene ether ketones) with side hydroxyl groups

The polycondensation of 2-β-oxyethyl-3,3-bis(4-oxyphenyl)phthalimidine with 4,4′-difluorobenzophenone proceeding via the nucleophilic substitution of the activated halogen atom in aryl halide has been studied. Conditions ensuring formation of noncrosslinked high-molecular-mass homo- and copoly(arylene ether ketones) containing side alcoholic hydroxyl groups (4,4′-difluorobenzophenone: a mixture of bisphenols: K₂CO₃: Na₂CO₃ = 1: 1: 1: 0.05) have been established. The polymers have M _w = (20–88.7) × 10³ and show good solubility in organic solvents; their onset temperatures of softening are in the range 195–250°C. Polymer films cast from solution are characterized by a breaking strength of 78–109 MPa.     

Synthesis and characterization of fluorine‐containing polybenzimidazole for proton conducting membranes in fuel cells

Two new kinds of fluorine‐containing polybenzimidazoles (PBI), poly(2,2′‐(tetrafluoro‐p‐phenylene)‐5,5′‐bibenzimidazole) and poly(2,2′‐tetradecafluoroheptylene‐5,5′‐bibenzimidazole), were synthesized by condensation polymerization of 3,3′‐diaminobenzidine and perfluoroterephthalic acid (or perfluoroazelaic acid), with polyphosphoric acid as solvent. Thermogravimetric analysis results show that the fluorine‐containing polymers synthesized exhibit promising thermal stability. The film‐forming properties of the fluorine‐containing polymers are improved over nonfluorinated PBI. The introduction of fluorine into the backbone of the polymers has significant positive affection on their chemical oxidation stability demonstrated by Fenton test. Compared with poly(2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole)/phosphoric acid (PA) composite membrane, the resulting fluorinated membranes with a same PA doping level exhibit better flexibility and higher proton conductivity. The maximum proton conductivity gained is 3.05 × 10^?2 S/cm at 150 °C with a PA doping level of 7. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2115–2122, 2010     

Constitution moléculaire d'α,ω-difluoropolydiméthyl-N-méthylsilazanes. Equilibres obtenus par une réaction de redistribution

Unlike the α,ω-dihalogenopolydimethylsiloxanes, the α,ω-dichloropolydimethyl-N-methylsilazanes show a net preference for cyclic species with respect to linear structures at equilibrium. The aim of this study is to evaluate the perturbations in the molecular constitution of these α,ω-dihalogenopolydimethyl-N-methylsilazanes resulting from the substitution of the terminal chlorine atoms by fluorine atoms. This polymeric family was prepared by reacting (CH₃)₂SiF₂ with nonamethylsilazane [(CH₃)₂SiNCH₃]₃. The redistribution of the fluorine atoms with the bridging methylimino groups reached an equilibrium after about 5 months' heating at 150°C for all the samples prepared. The relative abundance of the various molecular species and fragments at equilibrium was deduced from the quantitative analysis of the proton nuclear magnetic resonance (NMR) spectra. The molecular constitution at equilibrium is described by two constants. The first, K = [neso] [middles in chains]/[terminal moieties]² = (2.8 ± 0.8) 10^?2, shows that the presence of terminal fluorine atoms is unfavorable to the formation of short chains. On the other hand, the trimeric cyclic species [(CH₃)₂SiNCH₃]₃ are found to be highly favored (K°₃ = 550 ± 100 mole/liter). These observations further confirm that the equilibrium constants which control the noncyclic part of polymeric families depend little on the functionality of the substituents exchanged [for example, on changing from ? N(CH₃)₂ to ? NCH₃? ] when the reorganization heat order is one.     

Supramolecular host–guest coordination systems: [(G+)(Me3E)3MII(CN)6]∞ as ion exchangers,where (G+=Me3E,Et4N or stp), (E=Sn or Pb) and (M=Fe or Ru)

A number of 3D-coordination polymers, constructed via [^dM(CN)₆] building blocks and (Me₃E) connecting units, have been prepared and characterized by X-ray powder diffraction and different spectroscopic methods. 1-Methyl-4-(4′-R-styryl) or (2′-R-styryl) pyridinium cations (stp) have been successfully encapsulated within the expandable wide channels of the 3D-coordination polymers by tribochemical or ion exchange reactions producing novel molecular composites. Apart from 6, [(4′-OCH₃-stp)(Me₃Sn)₃Fe^II(CN)₆–MeOH]_∞ which exhibits thermochromic behaviour, the molecular composites [(stp)_x(Me₃E)₃Fe^III_1–xFe^II_x(CN)₆]_∞, 1–12 are mixed valence materials exhibiting localized interaction between the mixed valence iron. The results indicated an ion charge transfer interaction between the guest stp-cations and the host matrix. The molecular composites [(stp)(Me₃E)₃ M^II(CN)₆]_∞, 13–18 are due to the facile readiness of the coordination polymers [(Me₃E)₄M(CN)₆]_∞ and [(Et₄N)(Me₃Sn)₃Fe(CN₆)]_∞ to ion exchange.     

Polymeric organosilicon systems 14. Synthesis and some properties of alternating polymers composed of a dithienylene group and a mono-, di- or tri-silanylene unit

Poly[5, 5′ - (dimethylsilylene) - 2, 2′ - dithienylene] (4a), poly[5, 5′ -(methylphenylsilylene)-2, 2′ -dithienylene] (4b), poly[5, 5′ -(1, 1, 2, 2-tetramethyldisilanylene)-2, 2′ -dithienylene] (4c), poly[5, 5′-(1, 2-dimethyl-1, 2-diphenyldisilanylene)-2, 2′ -dithienylene] (4d), poly[5, 5′-(1, 2, 2, 2-tetramethyldisilanylene)-2, 2′-dithienylene] (4e), and poly[5, 5′-(1, 1, 2, 2, 3, 3 - hexamethyltrisilanylene) - 2, 2′ -dithienylene] were synthesized by dehalogenative coupling of the respective bis(2-bromothienyl)- substituted mono, di- and tri-silanes with magnesium in the presence of a catalytic amount of a nickel(II) complex in 16–99% yields. The polymers thus obtained are light-yellow solids and soluble in common organic solvents. Molecular weights, M_w, of the polymers were measured and found to be 7800–35 000 by gel-permeation chromatography relative to polystyrene standards. The photochemical properties of the polymers (4a–4d) having silylene and disilanylene units were investigated. Only poly[5, 5′-(1, 2-dimethyl-1, 2-diphenyl-disilanylene)-2, 2′-dithienylene] (4d) was found to be photoactive, but the others were inactive. When the thin solid films prepared from the polymers 4a–4e by spin-coating were exposed to antimony(V) fluoride in vacuo, the films became conducting; their conductivities were determined to be 10^?2 – 10^?3 S cm^?1 by the four-probe method.     

Reaction of F atoms with dichloromethane by modulated molecular beam mass spectrometry

The reaction of atomic fluorine with dichloromethane has been studied by the diffusion cloud in a flow technique. Fluorine atoms were generated through F₂ dissociation in a high-frequency discharge. The reaction products were detected mass spectrometrically, applying the technique of focusing the paramagnetic component of the molecular beam in an inhomogeneous magnetic field to detect radical species. Cl atoms and CHCl₂ and CF₃ free radicals have been identified among the reaction products. The initial step was shown to be hydrogen atom abstraction. The room temperature rate constant of this reaction was found to be k₀ = (1.51 ± 0.28) X 10^?11 cm³/s. The rate constant of the secondary reaction of fluorine atoms with dichloromethyl radicals, which is suggested to produce mainly HCl, was evaluated as 3 X 10^?10 cm³/s.     

Copper(II) and cadmium(II) isothiocyanate coordination polymers with 4,4′‐bi‐1,2,4‐triazole

The coordination polymers catena‐poly[[[(4,4′‐bi‐1,2,4‐triazole‐κN¹)bis(thiocyanato‐κN)copper(II)]‐μ‐4,4′‐bi‐1,2,4‐triazole‐κ²N¹:N^1′] dihydrate], {[Cu(NCS)₂(C₄H₄N₆)₂]·2H₂O}_n, (I), and poly[tetrakis(μ‐4,4′‐bi‐1,2,4‐triazole‐κ²N¹:N^1′)bis(μ‐thiocyanato‐κ²N:S)tetrakis(thiocyanato‐κN)tricadmium(II)], [Cd₃(NCS)₆(C₄H₄N₆)₄]_n, (II), exhibit chain and two‐dimensional layer structures, respectively. The differentiation of the Lewis acidic nature of Cu^II and Cd^II has an influence on the coordination modes of the triazole and thiocyanate ligands, leading to topologically different polymeric motifs. In (I), copper ions are linked by bitriazole N:N′‐bridges into zigzag chains and the tetragonal–pyramidal CuN₅ environment is composed of two thiocyanate N atoms and three triazole N atoms [basal Cu—N = 1.9530 (18)–2.0390 (14) Å and apical Cu—N = 2.2637 (15) Å]. The structure of (II) contains two types of crystallographically unique Cd^II atoms. One type lies on an inversion center in a distorted CdN₆ octahedral environment, with bitriazole ligands in the equatorial plane and terminal isothiocyanate N atoms in the axial positions. The other type lies on a general position and forms centrosymmetric binuclear [Cd₂(μ‐NCS‐κ²N:S)₂(NCS)₂] units (tetragonal–pyramidal CdN₄S coordination). N:N′‐Bridging bitriazole ligands link the Cd centers into a flat (4,4)‐network.     

Metallorganische lewis-säuren; metallkomplexe mit schwach koordinierten anionischen liganden: XIII. Nachweis der koordination von tetrafluoroborat in carbonylmolybdän- und -wolfram-komplexen durch 19F- und 31P-NMR-spektroskopie

In the tetrafluoroborato complexes (η⁵-C₅H₅)(CO)₂LMFBF₃ (M = Mo, W; L = CO, PPh₃, P(OPh)₃) and (η⁵-C₉H₇)(CO)₃WFBF₃ the coordinated fluorine atom and the terminal F atoms of the BF₄ ligand can be distinguished by their ¹⁹F NMR signals. ¹⁹F and ³¹P NMR spectra of (η⁵-C₅H₅)(CO)₂P(OPh)₃WFBF₃ allow to establish cis → trans isomerization at elevated temperatures as well as rapid rotation of the coordinated BF₄ ligand.