Studies on the copolymerization of norbornene with CO catalyzed by a new catalytic system PdCl<Subscript>2</Subscript>/phen/M(CF<Subscript>3</Subscript>SO<Subscript>3</Subscript>)<Subscript>n</Subscript>

A new three-component catalytic system, PdCl₂/phen/M(CF₃SO₃)_n where M = La, Y, Yb, Zn, and Cu, was studied for the copolymerization of norbornene (NBE) with CO to prepare polyketone (PK). It was found that the CF₃SO₃H catalytic system gave a low catalytic activity for the copolymerization of norbornene with CO, but when M(CF₃SO₃)_n was introduced instead of CF₃SO₃H, the PdCl₂/phen/M(CF₃SO₃)_n catalytic system exhibited much higher activity. The effects of ligands, M(CF₃SO₃)_n, solvents, and temperatures on the copolymerization have been discussed in detail. The results showed that with 1,10-phenanthroline (phen) and Cu(CF₃SO₃)₂ used as cocatalysts, the corresponding reaction rate reached 82 000 g PK (mol Pd)⁻¹h⁻¹ when the reaction was carried out in methanol at 90°C and 3.0 MPa of CO, and the weight average molecular weight (M _w) of the resultant copolymer is 1090 g/mol. The copolymer was characterized with various techniques such as FT-IR, ¹HNMR, ¹³CNMR, TGA, and DSC. The infrared spectrum of the product includes two features at 1697 and 1732 cm⁻¹ for the NBE/CO copolymer in CH₃OH that are attributed to carbonyl groups in ketones (repeating unit) and esters (end group), respectively. Due to the tension of the ring of norbornene, the degree of copolymerization is not high. Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 1, pp. 51–58. This article was submitted by the authors in English.     

Synthesis of the first difunctional N-fluoro perfluoroalkylsulfonylimides, CF3SO2NFSO2(CF2)nSO2NFSO2CF3

Synthesis of difunctional N,N′-difluoro perfluoroalkylsulfonamides, CF₃SO₂NFSO₂(CF₂)_nSO₂NFSO₂CF₃, where n=4, 6 is reported. A related compound with an oxygen linkage CF₃SO₂NFSO₂(CF₂)₂O(CF₂)₂SO₂NFSO₂CF₃ has also been prepared. These reagents showed good activity for electrophilic fluorination.     

Synthesis,crystal structure and catalytic activity for H2O2 disproportionation of the manganese(II) coordination polymer {[Mn(O2C(CF2)8CO2)(phen)2]H2O}n (phen = 1,10-phenanthroline)

The title polymeric complex {[Mn(O₂C(CF₂)₈CO₂)(phen)₂]H₂O}_n was synthesized through the reaction of 1,10-phenanthroline, perfluorosebacic acid and MnCO₃ · H₂O. The molecular structure was characterized by X-ray diffraction, elemental analysis, thermal gravimetry, IR and UV–Vis spectroscopy and its catalytic activity has been studied. X-ray structure analysis shows that each Mn(II) ion is octahedrally coordinated by two bidentate phenanthroline ligands and the carboxylate oxygen atoms from two symmetry related perfluorosebacate ligands, which are coordinated in cisoid positions. The structure consists of polymeric chains, with the perfluorosebacato ligand bridging the Mn(II) ions in a monodentate fashion. Crystallographic characterization shows a supramolecular structure involving hydrogen bonds, π–π and π-ring interactions. The catalytic results indicated that the complex has reasonably good activity towards the disproportionation of hydrogen peroxide into water and dioxygen in methanol and it does not exhibit saturation kinetics with the substrate. The initial reaction rates and their temperature and base dependencies were investigated by monitoring the dioxygen evolution. Kinetic studies revealed a first-order dependence on the catalyst concentration. Activation parameters have been calculated at 301 K.     

Syntheses, crystal structures and optical spectroscopy of Ln2(SO4)3·8H2O (Ln=Ho, Tm) and Pr2(SO4)3·4H2O

The lanthanide sulphate octahydrates Ln₂(SO₄)₃·8H₂O (Ln=Ho, Tm) and the respective tetrahydrate Pr₂(SO₄)₃·4H₂O were obtained by evaporation of aqueous reaction mixtures of trivalent rare earth oxides and sulphuric acid at 300 K. Ln₂(SO₄)₃·8H₂O (Ln=Ho, Tm) crystallise in space group C2/c (Z=4, a_Ho=13.4421(4) Å, b_Ho=6.6745(2) Å, c_Ho=18.1642(5) Å, β_Ho=102.006(1) Å³ and a_Tm=13.4118(14) Å, b_Tm=6.6402(6) Å, c_Tm=18.1040(16) Å, β_Tm=101.980(8) Å³), Pr₂(SO₄)₃·4H₂O adopts space group P2₁/n (a=13.051(3) Å, b=7.2047(14) Å, c=13.316(3) Å, β=92.55(3) Å³). The vibrational and optical spectra of Ho₂(SO₄)₃·8H₂O and Pr₂(SO₄)₃·4H₂O are also reported.     

FT-IR and FT-Raman spectroscopy study of di-urethanesil hybrids doped with Mg(CF3SO3)2

In the present work di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrids (di-urethanesils) incorporating magnesium triflate (Mg(CF₃SO₃)₂) with 100 ≥ n ≥ 2 (where n, composition, is the molar ratio of oxyethylene repeat units per Mg²⁺ ion) have been characterized by Fourier transform infrared and Raman spectroscopy to elucidate the Mg²⁺/POE, Mg²⁺/urethane, Mg²⁺/CF₃SO₃⁻ and hydrogen bonding interactions. The Mg²⁺ ions bond to POE chains and to the carbonyl oxygen atoms of the urethane linkages over the whole range of salt content studied. A crystalline POE/Mg(CF₃SO₃)₂ complex of unknown stoichiometry is formed at n = 5. “Free” and weakly coordinated CF₃SO₃⁻ ions are present in all the materials examined. Contact ion pairs emerge at n ≤ 20 and higher ionic aggregates appear at n ≤ 5.     

Interaction of polyhedral boron hydride anions [B10H10] and [B12H12] with cyclic copper and silver 3,5-bis(trifluoromethyl)pyrazolate complexes

The interactions of cyclic trinuclear copper {[3,5-(CF₃)₂Pz]Cu}₃ and silver {[3,5-(CF₃)₂Pz]Ag}₃ complexes with polyhedral borate anions [B₁₀H₁₀]²⁻ and [B₁₂H₁₂]²⁻ in solvents of low-polarity were studied using IR spectroscopy (190-290 K). Two types of complexes were found in solution: {[((3,5-CF₃)₂PzM)₃][B_nH_n]}²⁻ and {[((3,5-CF₃)₂PzM)₃]₂[B_nH_n]}²⁻ (M = Ag, Cu; n = 10, 12). The stability constants of these complexes were determined from IR-spectra.     

Advantages of the Ns group in the reactions of N-SO2R inosines with benzylamine and with NH3

The reactivity of N¹-alkylsulfonyl- and N¹-arylsulfonyl-2′,3′,5′-tri-O-acetylinosine with benzylamine and with ¹⁵NH₃, regarding the attack on C2, has been shown to be in the order CF₃SO₂ (Tf) > 2,4-(NO₂)₂C₆H₃SO₂ (DNs) ? 4-NO₂C₆H₄SO₂ (pNs) ≈ C₆F₅SO₂ (PFBs) > 2-NO₂C₆H₄SO₂ (Ns) ? CH₃SO₂ (Ms) > 4-CH₃C₆H₄SO₂ (Ts) > 2,4,6-(CH₃)₃C₆H₂SO₂ (Mts). In spite of its intermediate reactivity, the Ns group is the most appropriate, since in this case the formation of by-products is minimised during the ring-opening and ring-closing steps of the process. Another advantage of the Ns group is thus disclosed.     

Phenoxide-assisted P-C bond cleavage in PdCl2(PPh3)2 under very mild conditions

PdCl₂(PPh₃)₂ reacted with NaOAr (Ar = Ph, p-tolyl) at 0 °C to afford PdCl(Ph)(PPh₃)₂, instead of PdCl(OAr)(PPh₃)₂, in 12-16% isolated yields based on Pd. The structure was confirmed by NMR and X-ray crystallography. GC-MS analysis of the reaction solution revealed that OPPh₂(OAr), OPPh(OAr)₂, and OP(OAr)₃ are formed, while NMR studies indicated that PdCl(Ph)(PPh₃)₂ is produced when PdCl(OAr)(PPh₃)₂ decomposes. The reaction of PdCl₂(PPh₃)₂ with Bu₃Sn(OC₆H₄-p-OMe) also gave PdCl(Ph)(PPh₃)₂ in 8% isolated yield. These results suggest that PdCl(OAr)(PPh₃)₂ is highly labile and the aryloxy ligand exchanges with the phenyl groups in triphenylphosphine even under very mild conditions.     

Syntheses, crystal structures, and characterization of As(III) and As(V) thioarsenates, [Mn2(phen)(As2S5)]n and [Mn3(phen)3(AsS4)2]n·nH2O

The hydrothermal reactions of As, Mn, S, phen (phen=1,10-phenanthroline), and en (en=ethylenediamine) yield two manganese As(III) and As(V) thioarsenates, [Mn₂(phen)(As^III₂S₅)]_n (1) and [Mn₃(phen)₃(As^VS₄)₂]_n·nH₂O (2), respectively. Single-crystal X-ray diffraction analyses reveal that compound 1 is a two-dimensional (2D) layer of (6,3) topology. The 18-membered rings within the 2D porous layers are formed by corner-, edge-, and face-sharing cubane-like [Mn₂As₂S₄] units along the [100] direction. Whereas compound 2 is a one-dimensional (1D) chain structure. They are both characterized by IR, elemental analysis, EDS, and X-ray powder diffraction. The thermogravimetric analysis of 1 and 2 are discussed. Both the compounds are semiconductors with the band gap of E_g (compound 1)=2.01 eV (617 nm) and E_g (compound 2)=1.97 eV (629 nm), respectively. In addition, the variable-temperature magnetic susceptibility data suggest weak antiferromagnetic interactions between the Mn²⁺ ions in these two compounds.     

An efficient and fast synthesis of 4-aryl-3,4-dihydrocoumarins by (CF3SO3)3Y catalysis under microwave irradiation

A new and efficient synthesis of eleven 4-aryl-3,4-dihydrocoumarins, in which six are new compounds, was performed using (CF₃SO₃)₃Y as catalyst under microwave irradiation. The target compounds were obtained in good yields (68-80%) and remarkable time (7-20 min) when compared to the literature reports (1-40 h).     

Modification effect of spherical zirconia with SiCl4 as a support of methylaluminoxane for heterogeneous single-site catalyst

Unmodified and SiCl₄-modified spherical zirconia-supported methylaluminoxane were used as cocatalyst for propylene polymerization as well as ethylene/1-hexene copolymerization in combined with Me₂Si(η³-C₁₃H₈)(η¹-N^tBu)TiMe₂ (1) at 0 °C. The modification with SiCl₄ improved the catalytic activity. The improvement was clearer in ethylene/1-hexene copolymerization than in propylene polymerization. The number average molecular weight (M_n) of polypropylenes increased linearly against the polymerization time regardless the cocatalyst used to give polymers with narrow molecular weight distribution (M_w/M_n < 1.32), indicating the living nature of the catalytic systems. Thus, propagation rate constant (k_p) and the number of active centers (C^*) were evaluated from M_n and the number of polymer-chains. When the zirconia was modified with SiCl₄, the k_p value decreased and the C^* increased. The latter effect was more significant to enhance the catalytic activity.     

Facile preparation and synthetic applications of LiCH2C(CF3)2OLi

Bromohydrin BrCH₂C(CF₃)₂OH readily reacts with two equivalents of n-BuLi at −78 °C to produce the corresponding dilithium derivative LiCH₂C(CF₃)₂OLi in high yield. This dilithiated derivative reacts selectively, acting as a C-nucleophile, with a variety of electrophiles such as R₂PCl, carbonyl compounds, and epoxides, to give electron-deficient phosphines R₂PCH₂C(CF₃)₂OH, 1,3- and 1,4-diols, correspondingly.     

Anodic oxidation of organometallic sandwich complexes using [Al(OC(CF3)3)4] or [AsF6] as the supporting electrolyte anion

Anodic voltammetry and electrolysis of the metallocenes ferrocene, ruthenocene, and nickelocene have been studied in dichloromethane containing two different fluorine-containing anions in the supporting electrolyte. The perfluoroalkoxyaluminate anion [Al(OC(CF₃)₃)₄]⁻ has very low nucleophilicity, as shown by its inertness towards the strong electrophile [RuCp₂]⁺ and by computation of its electrostatic potential in comparison to other frequently used electrolyte anions. The low ion-pairing ability of this anion was shown by the large spread in E_1/2 potentials (ΔE_1/2 = 769 mV) for the two one-electron oxidations of bis(fulvalene)dinickel. The hexafluoroarsenate anion [AsF₆]⁻, on the other hand, reacts rapidly with the ruthenocenium ion and is much more strongly ion-pairing towards oxidized bis(fulvalene)dinickel (ΔE_1/2 = 492 mV). In terms of applications of these two anions to the anodic oxidation of organometallic sandwich complexes, the behavior of [Al(OC(CF₃)₃)₄]⁻ is similar to that of other weakly-coordinating anions such as [B(C₆F₅)₄]⁻, whereas that of [AsF₆]⁻ is similar to the more traditional electrolyte anions such as [PF₆]⁻ and [BF₄]⁻. Additionally, the synthesis and crystal structure of [Cp₂Fe][Al(OC(CF₃)₃)₄] are reported.     

Direct dynamics studies for the reactions of CF3CHFCF3 and CF3CF2CHF2 with H atoms

The rate constants of the hydrogen abstraction reactions of CF₃CHFCF₃ + H (R1) and CF₃CF₂CHF₂ + H (R2) have been calculated by means of the dual-level direct dynamics method. Optimized geometries and frequencies of stationary points and extra points along the minimum-energy path (MEP) are obtained at the MPW1K/6-311+G(d,p) level, and the classical energetic information is further corrected with the interpolated single-point energy (ISPE) approach by the G3(MP2) level of theory. Using the canonical variational transition state theory (CVT) with small-curvature tunneling corrections (SCT), the rate constants are evaluated over a wide temperature range of 200-2000 K. The calculated CVT/SCT rate constants are in good agreement with available experimental values. It is found that the variational effect is very small and almost negligible over the whole temperature region. However, the small-curvature tunneling correction plays an important role in the lower temperature range. Furthermore, the heats of formation of species CF₃CF₂CHF₂ (SC₁ or SC₂) and CF₃CF₂CF₂ are studied using isodesmic reactions to further elucidate the thermodynamic properties.     

Polyvinylidenefluoride-hexafluoropropylene based nanocomposite polymer electrolytes (NCPE) complexed with LiPF3(CF3CF2)3

Merck KGaA, Germany recently tested a new electrolyte salt LiPF₃(CF₃CF₂)₃ (lithium fluoroalkyl phosphate (LiFAP)) for lithium ion power packs and suggested that it can be replaced with commercially used LiPF₆. LiFAP, for the first of its kind, was incorporated into polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP) matrix with ethylene carbonate and diethyl carbonate mixtures as plasticizing agents and SiO₂ nanoparticles as filler. Nanocomposite polymer electrolyte (NCPE) membranes were prepared by solvent casting technique. All NCPE membranes were subjected to a.c. impedance, fluorescence and morphological studies. NCPE membranes containing 2.5 wt% of SiO₂ exhibited enhanced conductivity of 1.13 mS cm⁻¹ at ambient temperature. Molecular motion in the polymeric media was supported by fluorescence studies. The percentage of crystallinity and activation energy has also been calculated.     

Solubility of trans-Co2(CO)6 [3,5-bis(CF3)C6H3P(i-C3H7)2] in dense carbon dioxide

The title compound (1) was prepared by the reaction of 3,5-bis(CF₃)C₆H₃P(i-C₃H₇)₂ (L1) and Co₂(CO)₈. Its solubility in supercritical carbon dioxide was measured at varying temperatures and pressures using a modified analytical extraction device. Solubility data were determined in the temperature and pressure ranges between 40 and 70 °C and between 100 and 300 bar, respectively. The solubility of 1 is lower compared to (p-CF₃C₆H₄)₃P, but much higher than for transition metal complexes bearing phosphines without fluorinated substituents.     

The metathesis reactions of [SNS][SbF6] and [SN][AsF6] with Li[Al(OC(CF3)3)4] in liquid SO2

The small di- and triatomic molecules [SN]⁺ and [SNS]⁺ have shown versatile chemistries and [SNS]⁺ is an important starting reagent for many sulfur-nitrogen radicals. However, their chemistry is limited to the more polar solvents (e.g. SO₂). In this work an attempt is made to increase their solubility in less polar solvents by exchange of the usual [MF₆]⁻ (M = As, Sb) anions by the large and weakly coordinating [Al(OC(CF₃)₃)₄]⁻. As expected the metathesis reactions of [SN][AsF₆] and [SNS][SbF₆] with Li[Al(OC(CF₃)₃)₄] in liquid sulfur dioxide resulted in the formation of the insoluble Li[SbF₆], which is the driving force for these metathesis reactions. The characterization of the compounds by IR and multinuclear NMR revealed that [SNS]⁺ formed a [Al(OC(CF₃)₃)₄]⁻ salt in a clean reaction. A preliminary crystal structure of [SNS][Al(OC(CF₃)₃)₄] is presented. The solubility of [SNS][Al(OC(CF₃)₃)₄] in CH₂Cl₂ is significantly increased with respect to the corresponding [MF₆]⁻ salts, and potentially opens up new areas of [SNS]⁺ chemistry. The reaction of the more reactive [SN]⁺ with Li[Al(OC(CF₃)₃)₄] was less clear. Multinuclear NMR and IR spectra were consistent with the formation of [SN][Al(OC(CF₃)₃)₄], which also showed significant decomposition.     

Hydridic reactivity of W(CO)(H)(NO)(PMe3)3 - Dihydrogen bonding and H2 formation with protic donors

The hydridic reactivity of the complex W(CO)(H)(NO)(PMe₃)₃ (1) was investigated applying a variety of protic donors. Formation of organyloxide complexes W(CO)(NO)(PMe₃)₃(OR) (R = C₆H₅ (2), 3,4,5-Me₃C₆H₂ (3), CF₃CH₂ (4), C₆H₅CH₂ (5), Me (6) and iPr (7)) and H₂ evolution was observed. The reactions of 1 accelerated with increasing acidity of the protic donor: Me₂CHOH (pK_a = 17) < MeOH (pK_a = 15.5) < C₆H₅CH₂OH (pK_a = 15) < CF₃CH₂OH (pK_a = 12.4) < C₆H₂Me₃OH (pK_a = 10.6) < C₆H₅OH (pK_a = 10).Regioselective hydrogen bonding of 1 was probed with two of the protic donors furnishing equilibrium formation of the dihydrogen bonded complexes ROH···HW(CO)(NO)(PMe₃)₃ (R = 3,4,5-Me₃C₆H_2,3a and iPr, 7a) and the O_NO hydrogen bonded species ROH···ONW(CO)(H)(PMe₃)₃ (R = C₆H₂Me_3,3b and iPr, 7b) which were studied in hexane and d₈-toluene solutions using variable temperature IR and NMR spectroscopy. Quantitative IR experiments at low temperatures using 3,4,5-trimethylphenol (TMP) confirmed the two types of competitive equilibria: dihydrogen bonding to give 3a (ΔH₁ = −5.8 ± 0.4 kcal/mol and ΔS₁ = −15.3 ± 1.4 e.u.) and hydrogen bonding to give 3b (ΔH₂ = −2.8 ± 0.1 kcal/mol and ΔS₂ = −5.8 ± 0.3 e.u.). Additional data for the hydrogen bonded complexes 3a,b and 7a,b were determined via NMR titrations in d₈-toluene from the equilibrium constants K_(Δδ) and K_(ΔR1) measuring either changes in the chemical shifts of H_W(_Δδ) or the excess relaxation rates of H_W (ΔR₁) (3a,b: ΔH_(Δδ) = −0.8 ± 0.1 kcal/mol; ΔS_(Δδ) = −1.4 ± 0.3 e.u. and ΔH_(ΔR1) = −5.8 ± 0.4 kcal/mol; ΔS_(ΔR1) = −22.9 ± 1.9 e.u) (7a,b: ΔH_(Δδ) = −2.3 ± 0.2 kcal/mol; ΔS_(Δδ) = −11.7 ± 0.9 e.u. and ΔH_(ΔR1) = −2.9 ± 0.2 kcal/mol; ΔS_(ΔR1) = −14.6 ± 1.0 e.u). Dihydrogen bonding distances of 1.9 Å and 2.1 Å were derived for 3a and 7a from the NMR excess relaxation rate measurements of H_W in d₈-toluene. An X-ray diffraction study was carried out on compound 2.     

Temperature behavior of the protonic conductor K4LiH3(SO4)4

The results of the X-ray structural study for the K₄LiH₃(SO₄)₄ single crystal are presented at a wide temperature range. The thermal expansion of the crystal using the X-ray dilatometry and the capacitance dilatometry from 8 to 500 K was carried out. The crystal structures data collection, solution and refinement at 125, 295, 443 and 480 K were performed. The K₄LiH₃(SO₄)₄ crystal has tetragonal symmetry with the P4₁ space group (Z=4) at room temperature as well as at the considered temperature range. The existence of a low-temperature, para-ferroelastic phase transition at about 120 K is excluded. The layered structure of the crystal reflects a cleavage plane parallel to (001) and an anisotropy of the protonic conductivity. The superionic high-temperature phase transition at T_S=425 K is isostructural. Nevertheless, taking into account an increase of the SO₄ tetrahedra libration above T_S, a mechanism of the Grotthus type could be applied for the proton transport explanation.     

Synthesis, crystal structures and photoluminescence properties of new oxyborates, Mg5NbO3(BO3)3 and Mg5TaO3(BO3)3, with novel warwickite-type superstructures

Single crystals of new oxyborates, Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃, were prepared at 1370 °C in air using B₂O₃ as a flux. They were colorless and transparent with block shapes. X-ray diffraction analysis of the single crystals revealed Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃ to be isostructural. The X-ray diffraction reflections were indexed to the orthorhombic Pnma (No. 62) system with a=9.3682(3) Å, b=9.4344(2) Å, c=9.3379(3) Å and Z=4 for Mg₅NbO₃(BO₃)₃ and a=9.3702(3) Å, b=9.4415(3) Å, c=9.3301(2) Å and Z=4 for Mg₅TaO₃(BO₃)₃. The crystal structures of Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃ are novel warwickite-type superstructures having ordered arrangements of Mg and Nb/Ta atoms. Polycrystals of Mg₅NbO₃(BO₃)₃ prepared by solid state reaction at 1200 °C in air showed broad blue-to-green emission with a peak wavelength of 470 nm under 270 nm ultraviolet excitation at room temperature.