Synthesis and Biological Evaluation of CF3Se-Substituted α-Amino Acid Derivatives

Several CF₃Se-substituted α-amino acid derivatives, such as (R)-2-amino-3-((trifluoromethyl)selanyl)propanoates ( 5 a / 6 a ), (S)-2-amino-4-((trifluoromethyl)selanyl)butanoates ( 5 b / 6 b ), (2R,3R)-2-amino-3-((trifluoromethyl)selanyl)butanoates ( 5 c / 6 c ), (R)-2-((S)-2-amino-3-phenylpropanamido)-3-((trifluoromethyl)selanyl)propanoates ( 11 a / 12 a ), and (R)-2-(2-aminoacetamido)-3-((trifluoromethyl)selanyl)propanoates ( 11 b / 12 b ), were readily synthesized from natural amino acids and [Me₄N][SeCF₃]. The primary in vitro cytotoxicity assays revealed that compounds 6 a , 11 a and 12 a were more effective cell growth inhibitors than the other tested CF₃Se-substituted derivatives towards MCF-7, HCT116, and SK-OV-3 cells, with their IC₅₀ values being less than 10 μM for MCF-7 and HCT116 cells. This study indicated the potentials of CF₃Se moiety as a pharmaceutically relevant group in the design and synthesis of novel biologically active molecules.     

Metal/Fluorocarbon Pyrolants: VI. Combustion Behaviour and Radiation Properties of Magnesium/Poly(Carbon Monofluoride) Pyrolant

The performance of poly(carbon monofluoride) (PMF) (synonym: graphite fluoride) (CF_x)_n, ( 1 ) as oxidizer in a fuel rich Mg based pyrolant (ξ(Mg)=0.45) is investigated. The radiance [W sr⁻¹] under both static and dynamic conditions, the spectral radiant exitance [W cm⁻² μm⁻¹], the linear burn rate [mm s⁻¹] and the mass consumption rate [g s⁻¹ cm⁻²] have been determined. Calculations for enthalpy of anaerobic and aerobic combustion [kJ g⁻¹] and for the equilibrium composition of the combustion products as well as combustion temperature are given. A mechanism for the reaction is discussed. The combustion product from Mg/(CF_x)_n surprisingly reveals the formation of single walled carbon nanotubes (SWCNT) and “carbon nano carpet rolls” (CNCR). For part V see Ref. [1].     

Convenient Modular Syntheses of Fluorous Secondary Phosphines and Selected Derivatives

Reactions of the fluorous primary phosphines R_fn(CH₂)₂PH₂ [R_fn=(CF₂)_n−1CF₃; n=6, 8, 10] and R_fn′CHCH₂ [(n′=6, 8, 10) (1 : 1; THF, reflux) in the presence of AIBN give the title compounds [R_fn(CH₂)₂][R_fn′(CH₂)₂]PH [n/n′=6/6 ( 4 , 55%), 8/8 ( 5 , 58%), 10/10 ( 6 , 53%), 8/6 ( 7 , 52%), 10/8 ( 8 , 51%)] as low-melting white solids on up to 10-g scales. The chiral tertiary phosphine [R_f6(CH₂)₂][R_f8(CH₂)₂][R_f10(CH₂)₂]P ( 9 ) is similarly prepared from 7 and R_f10CHCH₂ in the presence of VAZO (neat, 100 °C; 67%). The reaction of 5 and THF⋅BH₃ yields the phosphine borane 5 ⋅BH₃ (95%). Additions of triphosgene [(CCl₃O)₂CO] to 5 or R_f8(CH₂)₂PH₂ give [R_f8(CH₂)₂]₂PCl or R_f8(CH₂)₂PCl₂, which are characterized in situ. The CF₃C₆F₁₁/toluene partition coefficients of 4 – 9 increase with the number and lengths of the R_fn segments.     

Atom Economic Ruthenium‐Catalyzed Synthesis of Bulky β‐Oxo Esters

Ruthenium complexes with the formulae Ru(CO)₂(PR₃)₂(O₂CPh)₂ [ 6a – h ; R=n‐Bu, p‐MeO‐C₆H₄, p‐Me‐C₆H₄, Ph, p‐Cl‐C₆H₄, m‐Cl‐C₆H₄, p‐CF₃‐C₆H₄, m,m′‐(CF₃)₂C₆H₃] were prepared by treatment of triruthenium dodecacarbonyl [Ru₃(CO)₁₂] with the respective phosphine and benzoic acid or by the conversion of Ru(CO)₃(PR₃)₂ ( 8e – h ) with benzoic acid. During the preparation of 8 , ruthenium hydride complexes of type Ru(CO)(PR₃)₃(H)₂ ( 9g , h ) could be isolated as side products. The molecular structures of the newly synthesized complexes in the solid state are discussed. Compounds 6a – h were found to be highly effective catalysts in the addition of carboxylic acids to propargylic alcohols to give valuable β‐oxo esters. The catalyst screening revealed a considerably influence of the phosphine′s electronic nature on the resulting activities. The best performances were obtained with complexes 6g and 6h , featuring electron‐withdrawing phosphine ligands. Additionally, catalyst 6g is very active in the conversion of sterically demanding substrates, leading to a broad substrate scope. The catalytic preparation of simple as well as challenging substrates succeeds with catalyst 6g in yields that often exceed those of established literature systems. Furthermore, the reactions can be carried out with catalyst loadings down to 0.1 mol% and reaction temperatures down to 50 °C.

     

Preparation and properties of plasma-deposited films with surface energies varying over a wide range

Polymer surfaces have been modified by chemical reaction or thin film deposition using a capacitatively coupled plasma RF-discharge system. This has allowed the production of a graded, reproducible series of surfaces with surface energies ranging from low to high. Three gases, hexafluoroethane (C₂F₆), perfluoropropane (C₃F₈), and hexafluoropropene (CF₃CF?CF₂), were used to prepare the low-energy surfaces. Ethylene oxide (C₂H₄O) was used to prepare the higher energy surfaces. Intermediate values of surface energy were obtained by using gas mixtures of perfluoropropane and ethylene oxide. The plasma-deposited films were characterized by ESCA and contact-angle studies. In the low-energy range, the critical surface tension (γ_c) values of the films prepared were found to be lower than those for Teflon. For the higher energy surfaces, values up to about 45 dyn/cm were obtained. Addition of oxygen to the plasma permitted the production of films with still higher γ_c values. ESCA studies indicate that, under the reaction conditions used, C₃F₈ and CF₃CF?CF₂ form a fluoropolymer deposit on glass that is at least 100 Å thick. For the same reaction parameters, C₂F₆ resulted in more etching and deposition of a much thinner film.     

Polystyrene with trifluoromethyl units: Monomer reactivity ratios,thermal behavior,flammability, and thermal degradation kinetics

Chemical modification based on incorporation of flame retardants (FR) into the polymer backbone was used in order to reduce polystyrene flammability. 3‐(trifluoromethyl)styrene (StCF₃) and 3,5‐bis(trifluoromethyl)styrene (St(CF₃)₂) were applied as reactive FR. Copolymers were synthesized with different feed ratios and it gave series of copolymers with various amounts of StCF₃ and St(CF₃)₂ (5–50% mol/mol of St). Glass transition temperature (T_g) and thermal stability of obtained (co)polymers were determined from differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Kinetic parameters such as the thermal decomposition activation energy (E) and frequency factor (A) were estimated by Ozawa and Kissinger models. Pyrolysis combustion flow calorimeter (PCFC) was applied as a tool for assessing the flammability of the synthesized (co)polymers. Relative reactivity ratios were determined by applying the conventional linearization Jaacks method (r_St = 1.34_, r_StCF3 = 0.54), (r_St = 0.47_, r_St(CF3)2 = 0.13). The results suggest that incorporation of fluorinated styrenes into PSt enchance flame retardance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42839.     

Dinuclear Rhodium Complexes Containing the Diyne 1,4-C6H4(C≡CH)2 and the Isomeric Bisvinylidene 1,4-C6H4(CH=C:)2 as Bridging Units

The reaction of [RhCl(PiPr₃)₂] ( 1 ) with 1,4-C₆H₄(C≡CH)₂ at 0°C leads almost quantitatively to the formation of the bis(alkyne) complex [(PiPr₃)₂ClRh-(HC≡C₆H₄-C≡CH)RhCl(PiPr₃)₂] (2). At elevated temperatures (THF, 60°C) it rearranges to give the isomeric bis(vinylidene) complex [(PiPr₃)₂ClRh-(=C=CH-C₆H₄-CH=C=)RhCl(PiPr₃)₂] (3). A one-pot synthesis of 3 is also described. Treatment of either 2 or 3 with pyridine affords the bis(alkynyl)dihydrido compound [(PiPr₃)₂(py)Cl(H)Rh(-C≡C-C₆H₄-C≡C-)Rh(H)Cl(py)(PiPr₃)₂] ( 4 ) in which both metal centers are octahedrally coordinated. Whereas the reaction of 2 with NaC₅H₅ produces the complex C_sH₅(PiPr₃)Rh(HC≡C-C₆H₄-C≡CH)Rh(PiPr₃)C₅H₅ ( 7 ), the bis(vinyl-idene) isomer C₅H₅(PiPr₃)Rh(=C=CH-C₆H₄-CH=C=)Rh(PiPr₃)C₅H_s ( 8 ) is obtained from 4 and NaC₅H₅. Electrophiles preferably attack the Rh=C bonds of 8 and thus on protonation with CF₃CO₂H the bis(vinyl) complex C₅H₅(PiPr₃)(CF₃CO₂)-Rh(Z,Z-CH=CH-C₆H₄-CH=CH)Rh(O₂CCF₃)(PiPr₃)C₅H_s ( Z-9 ) is formed. In acetone solution, it rearranges to give the E isomer. Reaction of 8 with sulfur affords the bis(thioketene) complex C₅H₅(PiPr₃)Rh(≡²-C,S; η²-C,S-S=C=CH-C₆H₄-CH=C=S)-Rh(PiPr₃)C₅H₅ ( 12 ), for which only one diastereomer is observed. All attempts to prepare mononuclear rhodium compounds containing the diyne HC≡C-C₆H₄-G≡CH or the isomeric vinylidene: C=CH-C₆H₄-G≡CH as ligand failed.     

Surface analysis of cotton fabrics fluorinated in radio‐frequency plasma

Cotton fabrics were treated by radio‐frequency plasma with tetrafluoromethane (CF₄) and hexafluoropropene (C₃F₆) gases under different exposure times, pressures, and power levels. The hydrophobicity and water repellency were analyzed with measurements of the cosine of the contact angle (cos θ) and wet‐out time. The hydrophobicity was enhanced with treatments of both gases. X‐ray photoelectron spectroscopy (XPS) revealed increases in the surface fluorine content of 1–2% for CF₄ plasma and of 2.3–7.8% for C₃F₆ plasma. The relative chemical composition of the C_1s spectra after CF₄ and C₃F₆ plasma treatments showed increases in the relative amounts of ? C? O? C? and fluorocarbon groups (? CF, ? CF₂, and ? CF₃), whereas peak areas for ? COH and ? COOH decreased. The hydrophobicity was enhanced by the increase in the fluorine content and fluorocarbon groups. C₃F₆ plasma treatment resulted in higher hydrophobicity than CF₄ plasma treatment according to not only cos θ and wet‐out measurements but also XPS analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2038–2047, 2003     

Polymerization of [2,5-bis(trifluoromethyl)phenyl]acetylene and polymer properties

Summary [2,5-Bis(trifluoromethyl)phenyl]acetylene [BTFPA; HCCC₆H₃-2, 5-(CF₃)₂]polymerized with W, Mo, and Nb catalysts to produce methanol-insoluble polymers in high yields. The poly(BTFPA) produced by the W(CO)₆-based catalyst at 30 °C was soluble in p-(CF₃)₂C₆H₄, and had relatively high molecular weight ([]=0.352 dL/g in p-(CF₃)₂C₆H₄). The main chain of the polymer was composed of alternating double bonds, and the polymer was a dark brown solid. The temperature at which the weight loss of the polymer started was higher than 300 °C. The polymerization behavior and polymer properties for BTFPA are compared with those for phenylacetylene and [o-(trifluoromethyl)phenyl]acetylene.     

Enhanced Hydrogenation Activity and Recycling of Cationic Rhodium Diphosphine Complexes through the Use of Highly Fluorous and Weakly‐Coordinating Tetraphenylborate Anions

The effect of the nature of the anion on the performance of ionic rhodium catalysts has received little attention. Herein it is shown that the use of highly fluorous tetraphenylborate anions can enhance catalyst activity in both conventional and fluorous media. For hydrogenation catalysts of the type [Rh(COD)(dppb)][X] {COD=1,5‐cis,cis‐cyclooctadiene; dppb=1,4‐bis(diphenylphosphino)butane; X=BF₄⁻ ( 1a ), [BPh₄]⁻ ( 1b ), [B{C₆H₄(SiMe₃)‐4}₄]⁻ ( 1c ), [B{C₆H₃(CF₃)₂‐3,5}₄]⁻ ( 1d ), [B{C₆H₄(SiMe₂CH₂CH₂C₆F₁₃)‐4}₄]⁻ ( 1e ), [B{C₆H₄(C₆F₁₃)‐4}₄]⁻ ( 1f ) and [B{C₆H₃(C₆F₁₃)₂‐3,5}₄]⁻ ( 1 g )} the activity towards the hydrogenation of 1‐octene in acetone increased in the order 1c < 1b < 1e < 1a < 1d ~ 1f < 1g with 1g being twice as active as the commonly applied 1a . Despite the fluorophilic character introduced by the substituted tetraarylborate anions, the presence of some perfluoroalkyl‐substituents in the cation was still required for achieving high partition coefficients. Therefore, [Rh(COD)(Ar₂PCH₂CH₂PAr₂)][X] {Ar=C₆H₄(SiMe₂CH₂CH₂C₆F₁₃)‐4, X=[B{C₆H₃(C₆F₁₃)₂‐3,5}₄]⁻ ( 3f ); Ar=C₆H₄(SiMe(CH₂CH₂C₆F₁₃)₂)‐4 and X=[B{C₆H₄(C₆F₁₃)‐4}₄]⁻ ( 2g )} were prepared, which were active in the hydrogenation of 1‐octene, 2g even more so than 3f . Both these highly fluorous catalysts could be recycled with 99% efficiency through fluorous biphasic separation, whereas the corresponding BF₄⁻ complex of 2g ( 2a ) did not show any affinity for the fluorous phase.     

The system iron(II)/mpzbpy mediates the H2O2 oxidation of cyclohexane and cyclooctene and the aerobic oxidative cleavage of ascorbic acid to oxalate

The iron complex generated in situ from Fe(CF₃SO₃)₂ and the new tridentate N ligand mpzbpy (mpzbpy stands for 6-(3,5-dimethylpyrazol-1-ylmethyl)-6′-methyl-2,2′-bipyridine) mediates the room temperature oxidation of cyclohexane to cyclohexanol and cyclohexanone, and the epoxidation of cyclooctene to cyclooctene oxide. X-ray diffraction studies of single crystals obtained by reaction of iron(II) triflate with mpzbpy in methanol in the presence of ascorbic acid reveals the formation of a dinuclear complex, namely [Fe₂(mpzbpy)₂(C₂O₄)(CF₃SO₃)₂] (1), where two iron(II) ions are bridged by an oxalato dianion originating from the oxidative cleavage of ascorbic acid. Magnetic susceptibility measurements of 1 show that the two metallic centres are weakly antiferromagnetically coupled, with a J value of −1.74(1) cm⁻¹.     

Synthesis and Properties of Fully Triphenylamine-based Polyamides Bearing 3,5-bis(Trifluoromethyl) and/or 3,5-dimethyl Substituents on the Pendent Phenyl Units

Four new fully triphenylamine-based polyamides coded as polyamide (CF₃,CF₃), polyamide (CF₃,CH₃), polyamide (CH₃,CF₃), and polyamide (CH₃,CH₃) were synthesized by the phosphorylation polyamidation reaction from various combinations of 3,5-bis(trifluoromethyl)-4′,4″-dicarboxytriphenylamine, 3,5-dimethyl-4′,4″-dicarboxytriphenylamine, 3,5-bis(trifluoromethyl)-4′,4″-diaminotriphenylamine, and 3,5-dimethyl-4′,4″-diaminotriphenylamine. All the polyamides were amorphous and readily soluble in many common organic solvents and could be solution-cast into transparent, flexible, and strong films with good mechanical properties. They had useful levels of thermal stability associated with high glass-transition temperatures of 268–287°C and 10?wt%-loss temperatures in excess of 500°C. Cyclic voltammograms of the film of polyamide (CH₃,CH₃) on the indium-tin oxide-coated glass substrates exhibited two oxidation redox couples with E_1/2 around 0.82 and 1.29?V vs. Ag/AgCl in tetrabutylammonium perchlorate/acetonitrile solution, accompanied by a color change from pale yellow neutral state to dark green oxidized state. The CF₃-substituted polyamides displayed a higher oxidation potential and less electrochemical stability as compared to the CH₃-substituted analogues.     

Electrochemical study of β-diketonatobis(triphenylphosphite)rhodium(I) complexes

The electrochemical behaviour of the series of ten [Rh(RCOCHCOR′)(P(OPh)₃)₂] complexes with R, R′ = CF₃, CF₃ (1), CF₃, CH₃ (2), CF₃, Ph (C₆H₅) (3), CF₃, Fc (ferrocenyl = (C₅H₅)Fe(C₅H₄)) (4), CH₃, Ph (5), CH₃, CH₃ (6), Ph, Ph (7), Fc, CH₃ (8), Fc, Ph (9) and Fc, Fc (10) were studied in acetonitrile containing 0.100 mol dm⁻³ tetra-n-butylammonium hexafluorophosphate as supporting electrolyte utilizing a glassy carbon working electrode. Results are consistent with Rh(I) being first oxidized in an electrochemically irreversible two-electron transfer process at peak anodic potentials ranging E_pa(Rh) = 0.124–0.881 V vs. Fc/Fc⁺. For the ferrocene-containing complexes (4), and (8)–(10) the rhodium oxidation was followed by the electrochemically reversible oxidation of the ferrocenyl group in a one-electron transfer process at a slightly more positive potential. Relationships were established between the electrochemical quantity E_pa(Rh) and kinetic parameter log k₂ as well the sum of experimental group electronegativities (Gordy Scale) of the R and R′ groups (χ_R + χ_R′), the Hammett σ values (σ_R + σ_R′) and the Lever ligand parameter E_L for the [Rh(RCOCHCOR′)(P(OPh)₃)₂] complexes: E_pa(Rh) (vs. Fc/Fc⁺/V) = 0.31 (χ_R + χ_R′)–1.09 = 0.56 (σ_R + σ_R′) + 0.28 = S_M (ΣE_L) + (I_M − 0.66 V) = −0.23 log k₂ − 0.03 (k₂ = second order rate constant for the oxidative addition of methyl iodide to rhodium). A profound shift of E_pa(Rh) to a more positive potential was observed for Rh(I) substrates containing β-diketonato ligands with increasing electronegative substituents R and R′. An exponential dependence of E_pa(Rh) on the pK_a of the β-diketone was obtained.     

Correlation between heats of immersion and limiting capacitances in porous carbons

Based on more than 80 carbons, the paper shows that immersion calorimetry into benzene, water and carbon tetrachloride can be used to assess with a good accuracy the limiting capacitance C_o at low current densities in both acidic (2 M H₂SO₄) and aprotic (1 M tetraethyl ammonium tetrafluoroborate in acetonitrile) electrolytic solutions. The enthalpies of immersion Δ_iH(C₆H₆) and Δ_iH(H₂O) provide information on C_o-acidic, where both the surface area and the oxygen content play a role. On the other hand, in the case of the organic electrolyte the oxygen content has only a small influence and C_o-aprotic is directly related to Δ_iH(C₆H₆) and Δ_iH(CCl₄). Carbon tetrachloride has a critical dimension (0.65 nm), which is close to the size of the (C₂H₅)₄N⁺ ion (0.68 nm) and therefore Δ_iH(CCl₄) provides better information in the case of carbons with small micropores. The advantage of this approach lies in the fact that immersion calorimetry, in itself a useful tool for the structural and the chemical characterization of carbons, can also be used to evaluate directly the gravimetric capacitances of these solids at low current densities.     

Effect of CsF-concentration on electrolytic conductivity, viscosity and anodic reaction of nickel electrode in (CH3)3N-CsF–HF system at room temperature

In order to increase the formation ratio of perfluorotrimethylamine, (CF₃)₃N, to overall anode gas in electrolytic production using Ni anode, mixed melts of (CH₃)₃N·mHF + CsF·2.3HF were used as electrolytes at room temperature. The ionic conductivity of the mixed melts decreased with an increase in the CsF concentration, whereas the viscosity of the mixed melts increased with increasing the CsF concentration. AC impedance and XRD analysis revealed that the presence of CsNi₂F₆ in the oxidized layer formed on the Ni anode after electrolysis. The gas evolved at the Ni anode was composed of (CF₃)₃N, (CF₃)₂CHF₂N, CF₃(CHF₂)₂N, (CHF₂)₃N, CF₄, NF₃, CHF₃, C₂HF₅, and C₂F₆. The best ratio of (CF₃)₃N to the overall anode gas (52.11%) was obtained in the electrolyte of (CH₃)₃N·5.0HF + 50 wt% CsF·2.3HF mixed melt at 20 mA cm⁻².     

Alkyne Metatheses in Transition Metal Coordination Spheres: Convenient Tungsten‐ and Molybdenum‐Catalyzed Syntheses of Novel Metallamacrocycles

Reactions of (CO)₅Re(Br), (η⁵‐C₅H₅)Ru(Cl)(PPh₃)₂, and [Pt(μ‐Cl)(C₆F₅)(S(CH₂CH₂‐)₂)]₂ with the alkyne‐containing phosphine Ph₂P(CH₂)₆C≡CCH₃ give the bis(phosphine) complexes fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 5 ), (η⁵‐C₅H₅)Ru(Cl)(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 6 ), and trans‐(Cl)(C₆F₅)Pt(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 7 ). Alkyne metatheses with the catalyst (t‐BuO)₃W(≡C‐t‐Bu) (10–15 mol %, chlorobenzene, 80 °C) give the seventeen‐membered metallamacrocycles fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 8 ), (η⁵‐C₅H₅)Ru(Cl)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 9 ), and trans‐(Cl)(C₆F₅)Pt(PPh₂(CH₂)₆CC(CH₂)₆P Ph₂) ( 10 ). ³¹P NMR analyses show 90–75% conversions to 8 – 10 (59–47% isolated after chromatography). The identity of 8 was confirmed by a crystal structure, and 10 was hydrogenated over Pd/C to fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 12 , 87%), which was crystallographically characterized earlier. A catalyst derived from Mo(CO)₆/4‐chlorophenol effects a slower conversion of 7 to 10 at 140 °C. In the case of 5 , a mer, trans isomer of 8 is isolated ( 11 , 44%), as established by NMR and IR data. In 10 – 12 , the diphosphines span trans positions. These results, together with previous examples involving group VIII metallocenes, establish the wide viability of the title reaction.     

One Dimensional Structure of Zn(II) Metal Organic Framework (MOF) Assembled Rapidly at Room Temperature: Structural,Thermal Study,and Luminescent Properties

One-dimensional structure of Zinc(II) metal organic framework ([Zn₂(C₁₀H₈N₂)₃(NO₃)₄]_∞) has been synthesized at room temperature and structurally characterized by elemental analysis, thermogravimetric analysis, and single-crystal X-ray diffraction. The five-coordinated Zn(II) complex exhibits trigonal bipyramidal coordination geometry. The Zn(II) ion is stabilized by three-connected nodes to form 1D ladder structure. The 1D chain is further connected to each other via hydrogen bonding to form 2D structure. Disordered CH₂Cl₂ solvent molecules were trapped in the pores. The luminescent and thermal properties have been also investigated. In addition, the activation thermodynamic parameters, ΔE^*, ΔH^*, ΔS^* and ΔG^* are calculated from the DTA curves using Coats–Redfern method.     

Surface modification of Teflon® PFA with vacuum UV photo-oxidation

Surface modification of poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) with vacuum UV (VUV) photo-oxidation using radiation from excited Ar atoms downstream from an Ar microwave (MW) plasma shows: (1) an improvement in wettability as observed by water contactangle measurements; (2) surface roughening; (3) incorporation of oxygen as C=O, CF—O—CF₂ and CF₂—O—CF₂ moieties and (4) enhancement of the CF—O—C _n F_2n+1 concentration. Adhesion measurements of Cu sputter coated onto the photo-oxidized PFA surface results in failure within the PFA (cohesive failure) and not at the Cu–PFA interface.     

Multinuclear Metal Carbonyl Alkoxide and Aryloxide Derivatives as Models for Metal Carbonyls Adsorbed on Metal Oxide Supports

The synthesis and characterization of two tungsten carbonyl dimers containing bridging alkoxide or aryloxide ligands are described. The crystal and molecular structures of [PPN]₂[W₂(CO)₈(OCH₂CF₃)₂], 1, and [Et₄N]₃[W₂(CO)₆-(OPh)₃]-CH₃CN, 2 , are reported and compared with the structures of tetranuclear tungsten derivatives previously described. The dimer 1 crystalizes in the triclinic space group P 1 with unit cell parameters a = 13.460(11) Å, b = 12.318(5) Å, c = 13.842(10) Å, α = 82.73(5)°, β = 59.11(5)°, γ= 80.09(5)°, V = 1938(2) ų, and Z = 1. The complex 2 crystalizes in the monoclinic space group P2₁/n with unit cell parameters a = 11.954(2) Å, b = 19.359(4) Å, c = 26.462(5) Å, β = 102.50(16)°, V = 5979(2) ų, Z = 4. Molecular modeling software was utilized to construct a tetranuclear derivative from 1 similar to the structurally characterized [W(CO)₃OH]₄₋⁴ tetramer. The two tetramers were found to possess similar molecular parameters. This supports the contention that dimers of type 1 are the precursors of the tetramers. Comparisons of the tungsten alkoxides and aryloxides with the behavior of W(CO)₆ on γ-alumina are provided.     

Ethylene polymerization catalyzed by diamide complexes of Ti(IV) and Zr(IV)

In this research, we describe the application of the complexes o‐C₆H₄(NSiMe₃)₂ZrCl₂ ( 1 ), o‐C₆H₄(NSiMe₃)₂TiBr₂ ( 2 ), o‐C₆H₄(NSiMe₃)₂TiCl₂ ( 3 ), C₂H₄(NSiMe₃)₂ZrCl₂ ( 4 ), in the ethylene polymerization with different Al/M ratios and temperatures. These complexes presented significant catalytic activities in the presence of methyaluminoxane (MAO) as cocatalyst and toluene as solvent, producing high molecular weight linear polyethylenes. Zirconium complexes were more active at 60°C and titanium complexes at 40°C. Zirconium complex ( 1 ) showed the best values of activity (347 kg PE/mol Zr h atm) for Al/Zr ratio of 340 and 60°C of temperature. In ethylene‐1‐hexene copolymerization, the best result was also reached with catalyst 1 , at the same conditions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008