Ring-Opening Metathesis Polymerization and Related Olefin Metathesis Reactions in Benzotrifluoride as an Environmentally Advantageous Medium

A tremendous number of solvents, either as liquids or vapors, contaminate the environment on a daily basis worldwide. Olefin metathesis, which has been widely used as high-yielding protocols for ring-opening metathesis polymerization (ROMP), ring-closing metathesis (RCM), and isomerization reactions, is typically performed in toxic and volatile solvents such as dichloromethane. In this study, the results of our systematic experiments with the Grubbs G1, G2, and Hoveyda-Grubbs HG2 catalysts proved that benzotrifluoride (BTF) can replace dichloromethane (DCM) in these reactions, providing high yields and similar or even higher reaction rates in certain cases. The ROMP of norbornene resulted not only in high yields but also in polynorbornenes with a high molecular weight at low catalyst loadings. Ring-closing metathesis (RCM) experiments proved that, with the exception of the G1 catalyst, RCM occurs with similar high efficiencies in BTF as in DCM. It was found that isomerization of (Z)-but-2-ene-1,4-diyl diacetate with the G2 and HG2 catalysts proceeds at significantly higher initial rates in BTF than in DCM, leading to rapid isomerization with high yields in a short time. Overall, BTF is a suitable solvent for olefin metathesis, such as polymer syntheses by ROMP and the ring-closing and isomerization reactions.     

Tungsten and Molybdenum 2,4,6‐Trimethylbenzylidyne Complexes as Robust Pre‐Catalysts for Alkyne Metathesis

A series of 2,4,6‐trimethylbenzylidyne tungsten and molybdenum complexes was prepared from the tribromides mer‐[MesCMBr₃(dme)] ( 9a , M=W; 9b , M=Mo, dme=1,2‐dimethoxyethane). Successive reaction of complexes 9 with lithium or potassium hexafluoro‐tert‐butoxide and lithium 1,3‐di‐tert‐butylimidazolin‐2‐imide, (Im^t‐BuN)Li, afforded the imidazolin‐2‐iminato complexes [MesCM{OC(CF₃)₂Me}₂(Im^t‐BuN)] ( 10a , M=W; 10b , M=Mo), whereas the reactions of 9 with three equivalents of LiOSi(O‐t‐Bu)₃ or KOC(CF₃)₃ gave [MesCM{OSi(O‐t‐Bu)₃}₃] ( 11a , M=W; 11b , M=Mo) and [MesCM{OC(CF₃)₃}₃] ( 12a , M=W; 12b , M=Mo), respectively. For comparison, the benzylidyne complex [PhCMo{OSi(O‐t‐Bu)₃}₃] ( 7b ) was also prepared, and its molecular structure together with those of 10a , 10b , 11b , 12a and 12b were established by X‐ray diffraction analysis. Complexes 10 and 11 were employed as pre‐catalysts for the alkyne metathesis of the test substrate 3‐pentynyl benzyl ether ( 13 ) at low catalyst loadings (1 mol%) in the presence of molecular sieve (5 Å). Comparative studies of these 2,4,6‐trimethylbenzylidyne species (MesCM) with their benzylidyne analogues (PhCM) revealed that the increased steric bulk renders the former more stable and manageable in air in solid form for shorter periods of time, but at the expense of a slower initiation, which requires higher temperatures or longer reaction times.

     

Ring-Opening Olefin Metathesis Polymerisation (ROMP) as a Potential Cross-Linking Mechanism for Siloxane Polymers

Reported here are some results of rapid Ring Opening Metathesis Polymerization (ROMP) of norbornene-functional oligomeric siloxanes using a Ru-based catalytic system. The in situ formation of the active metal carbene catalyst by addition of a diazo compound to norbornene-functional siloxane containing the catalytic system, [(p-cymene)RuCl₂]₂/PCy₃ allowed fast but controlled polymerization of the norbornene functionalities. Thus, in a solventless system, polymerization of a norbornene-functional siloxane, e.g., 1,1,1,2,3,3,3-heptamethyl-2-norbornen-5-yltrisiloxane, at 60°C with low catalyst levels (2 to 200 ppm) led to a colourless monolithic gel in less than 30 seconds. Besides being an efficient cross-linking technology, ROMP of suitable precursors may also be a source of novel silicone-organic materials.     

烯烃复分解聚合用钌催化剂的合成和应用研究进展(续前)

<正>(续2010年第4期第23页)3配体的影响钌金属卡宾催化剂的通式为:配体X、L、L1和R都可以根据不同的需要进行改变,配体的改变可以形成不同的钌卡宾催化剂,且会对催化剂的各项性能产生影响。科学家们长期研究发现,配体的影响具有一定的规     

钼系催化剂催化异戊二烯聚合研究

以磷酸三丁酯取代的五氯化钼(简称Mo)及间甲酚取代的三异丁基铝(简称Al)为催化剂引发异戊二烯(Ip)聚合,考察了n(Mo):n(Ip)、n(Al):n(Mo)及聚合温度对单体转化率和催化剂效率的影响。采用FTIR和1H-NMR对聚合产物的微观结构进行测试表征,用DSC测定聚合产物的玻璃化转变温度(Tg);结果表明在反应温度为50℃、n(Mo):n(Ip)为4.0×10-4、n(Al):n(Mo)为30、聚合24h所得的聚异戊二烯(PIp)中1,4-结构摩尔分数为55.7%,3,4-结构的为22.5%和1,2-结构的为21.8%,该PIp的Tg为-35.1℃。     

Metathesis ring opening polymerization of 5,6-dimethylenebicyclo[2.2.1]hept-2-ene

5,6-Dimethylenebicyclo[2.2.1]hept-2-ene ( I ) polymerizes in the presence of the two-component ring opening metathesis polymerization (ROMP) initiators WCl₆/(CH₃)4Sn and MoCl₅/(CH₃)4Sn. The product polymers were insoluble in all of many solvents investigated and are presumably cross-linked. The product polymers were investigated by IR and solid state ¹³C NMR spectroscopy, which established that the material consisted predominantly of poly(1,4-(2,3-dimethylene-cyclopentylene)vinylene) ( II ). A possible alternative route to II via thermal dehydrochlorination of poly(1,4-(2,3-bis(chloromethyl)cyclopentylene) vinylene) ( IV ) was also examined.     

国产钨基催化剂在烯烃歧化制丙烯工业侧线装置上的性能研究

针对丁烯和乙烯歧化增产丙烯技术(OCT技术)所用进口BASF催化剂价格昂贵、运输条件苛刻等情况,自主研发了钨基歧化催化剂,并在实验室小试装置和OCT工业侧线固定床反应器上,考察了该催化剂在OCT技术制备丙烯过程中的催化性能。结果表明,1-丁烯的异构化率和丙烯的选择性均随反应温度的升高和乙烯、丁烯摩尔比的增加而逐渐增加,自主研发催化剂的催化活性和进口催化剂相当,且催化剂稳定性良好,可连续运行400 h以上。     

Polymerization of acrylamide and methacrylamide initiated by a potassium peroxydiphosphate/Mn(II) system

The kinetics of aqueous polymerization of acrylamide (AM) and methacrylamide (MAM) have been studied using a potassium peroxydiphosphate (PDP/Mn(II) system in an inert atmosphere at 40°C and at constant pH (1·30). The polymerization rate R_p has been found to be proportional to the half power of PDP and Mn(II) concentrations. The overall energy of activation (ΔE) was found to be 40·2±0·1kJmol^-1 and 45·0±0.1kJmol^-1 for AM and MAM, respectively. Intrinsic viscosity [η], viscometric average molecular weight (M_v) and number average degree of polymerization (P_n) at different concentrations of PDP, Mn(II) and monomer are reported. © 1998 SCI.     

Structural Diversity of Mercury(II) Halide Complexes Containing Bis-pyridyl-bis-amide with Bulky and Angular Backbones: Ligand Effect and Metal Sensing

Hg(II) halide complexes [HgCl₂] 2L¹ [L¹ = N,N’-bis(3-pyridyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide), 1, [HgBr₂(L¹)]_n, 2, [HgI₂(L¹)], 3, [Hg₂X₄(L²)₂] [X = Cl, 4, Br, 5, and I, 6; L² = N,N’-bis(4-pyridylmethyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide] and {[HgX₂(L³)]⋅H₂O}_n [X = Cl, 7, Br, 8 and I, 9; L³ = 4,4′-oxybis(N-(pyridine-3-yl)benzamide)] are reported and structurally characterized using single-crystal X-ray diffraction analyses. The linear HgCl₂ units of complex 1 are interlinked by the L¹ ligands through Hg---N and Hg---O interactions, resulting in 1D supramolecular chains. Complex 2 shows 1D zigzag chains interlinked through the Br---Br interactions to form 1D looped supramolecular chains, while the mononuclear [HgI₂L²] molecules of 3 are interlinked through Hg---O and I---I interactions, forming 2D supramolecular layers. Complexes 4–6 are isomorphous dinuclear metallocycles, and 7–9 form isomorphous 1D zigzag chains. The roles of the ligand type and the halide anion in determining the structural diversity of 1–9 is discussed and the luminescent properties of 7–9 evaluated. Complexes 7–9 manifest stability in aqueous environments. Moreover, complexes 7 and 8 show good sensing towards Fe³⁺ ions with low detection limits and good reusability up to five cycles, revealing that the Hg-X---Fe³⁺ (X = Cl and Br) interaction may have an important role in determining the quenching effect of 7 and 8.     

Preparation of Poly(acrylamide-maleic Acid) Resin by Template Polymerization and Its Use for Adsorption of Co(II) and Ni(II)

Poly(acrylamide-maleic acid) resin P(AAm-MA) was prepared by template polymerization. Polyacrylamide PAAm was used as a template for the polymerization of MA in an aqueous solution using gamma rays as the initiator. The effects on the capacity of P(AAm-MA), such as concentration of maleic acid and amount of template polymer, were investigated. P(AAm-MA) has been utilized as an adsorbent for the removal of Co(II) and Ni(II) ions from an aqueous solution. The effects of time of equilibrium, pH, temperatures, and dosage of the adsorbent on the removal of Co(II) and Ni(II) ions have been studied. The equilibrium data were analyzed using the Langmuir and Freundlich isotherm models. The equilibrium process was described well by the Langmuir isotherm model.     

Rubbery Thermosets by Ring‐Opening Metathesis Polymerization of a Functionalized Castor Oil and Cyclooctene

Rubbery thermosets prepared by ROMP of a modified castor oil containing norbornene moieties and cyclooctene have been synthesized and characterized. The thermosets range from 55 to 85 wt.‐% oil and are flexible, slightly transparent and have a sand‐like hue. Increasing concentration of the modified castor oil in the feed ratio results in an increase in the extracted (unreacted or oligomeric) components in the final thermoset. Thermogravimetric analysis reveals that all of the specimens have temperatures of maximum degradation around 500 °C. DMA and TGA analysis on solvent‐extracted specimens show that the presence of the soluble fractions helps to plasticize the materials and give added thermal stability.

     

Ring-opening metathesis polymerisable charged platinum(II) complexes: Towards enhanced phosphorescent quantum yields by aggregation in polymers

Phosphorescent copolymers bearing a covalently linked charged platinum(II) dye were prepared using ring-opening metathesis polymerisation (ROMP). Absorption, emission as well as dynamic light scattering measurements of these polyelectrolytes indicate the formation of red luminescent aggregates in solution with quantum yields up to 17% and luminescence decay times in the range of 250-300 ns. Neither the quantum yield nor lifetime of the luminescence is affected by the presence of oxygen. The resulting polymers are solution processible and exhibit good film-forming properties. In contrast, the mononuclear platinum species are poorly soluble and non-luminescent at room temperature in deaerated solution.     

Polymerization and characterization of various di(pyridine)bis(trihalophenolato)cobalt(II) complexes in solid and melt states

The syntheses of distorted tetrahedral bis(pyridine)bis(trihalophenolato)cobalt(II) complexes from an aqueus solution were achieved and their characterization by FT‐IR, X‐ray, DSC, UV‐visible and elemental analysis in solid state or in melt form is reported. Polymerizations of these complexes were accomplished either at constant temperature, employing different time intervals or constant decomposition times while varying the temperature range. The slow decomposition at constant temperature leads to long chain products, whereas long chains formed at higher temperatures were during a constant time. The resulting poly(dihalophenylene oxide)s were characterized by FT‐IR, ¹H NMR, ¹³C NMR spectral analysis, differential scanning calorimetry and molecular weight determinations by viscometric method. © 2001 Society of Chemical Industry     

Theoretical studies of the mechanism of ethylene polymerization reaction catalyzed by diimine-M(II) (M = Ni,Pd and Pt) and Ti- and Zr-chelating alkoxides

We have analyzed the computational results for several elementary reactions of the ethylene polymerization process catalyzed by an alternative (to the existing metallocene catalysts) “non-cyclopentadienyl” catalysts such as diimine-M(II) (where M = Ni and Pd) and chelating bridged Ti- and Zr-complexes. The obtained data have been compared with those for the existing zirconocene-based catalysts. In general, it was shown that: (i) the resting stage of the process is a metal-olefin-alkyl complex, the olefin coordination energy of which is a few kcal/mol larger for diimine-M(II) systems than zirconocene or dialkoxide systems; (ii) the rate-determining barrier is a migratory insertion barrier calculated from the metal-olefin-alkyl complex, which is found to be a few kcal/mol larger for the diimine-M(II) system compared to the Cp₂ZrCH ₃ ⁺ catalyst. The presence of certain flexible bridging ligands X in the Ti-alkoxide complex, [Y(Ph)X(Ph)Y]TiCH ₃ ⁺ , which are capable of donating electron density to the cationic metal center at various stages during the reaction makes this barrier a few kcal/mol smaller for the dialkoxide than the Cp₂ZrCH ₃ ⁺ catalyst. It was shown that an increase in the metal-bridge interaction decreases the migratory insertion barrier and, consequently, increases the catalytic activity of these complexes. Although the diimine-M(II) catalysts are less active than zirconocene-based ones, the microstructure of the polymers produced by the former catalyst, which is found to be a function of temperature, ethylene, steric bulkiness of the auxiliary ligands, and transition metal center, makes them attractive for practice. We also have studied the mechanisms of several chain termination/transfer reactions, as well as the role of steric effects in the studied elementary reactions. We have clearly demonstrated tremendous possibilities of the computational chemistry in solving complex problems of the homogenous catalyst, and its high capability of predicting new and more active catalysts for different commercially important processes including olefin polymerization reactions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis and characterization of tridentate phenoxy‐imine ligand [N,N,O] nickel(II) and palladium(II) complexes and their catalytic behaviors in vinyl polymerization of norbornene

In this study, new complexes LNiCl( 1 ), LNiBr( 2 ), LNiI( 3 ), and LPdCl( 4 ) (L = 4,6‐di‐tert‐butyl‐2‐(N‐(quinolin‐8‐yl)iminomethyl)phenolato) have been synthesized and characterized. X‐ray diffraction studies on Complexes 1 and 4 revealed that N, N, O, and halogen atoms coordinated to metal, with a nearly square planar geometries in all cases. All these complexes are robust and exhibit high activities for the addition polymerization of norbornene (NB) with methylaluminoxane as cocatalyst [up to 47.62 kg PNB(mmol of Ni)^?1h^?1] and also lead to various activities and molecular weights of polynorbornenes under different reaction conditions. It is noteworthy that Complexes 1 and 4 show better activity under higher reaction temperature of 80°C. However, Complex 2 showed lower activity, and Complex 3 was found nearly inert toward NB polymerization, probably, because of thermal instability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polymerization of styrene using pyrazolylimine nickel (II)/methylaluminoxane catalytic systems

The polymerization of styrene with two pyrazolylimine nickel (II) complexes of (2-(C₃HN₂Me₂-3, 5)(C(Ph) = N(4-R₂C₆H₂(R₁)₂-2, 6)NiBr₂ (Complex 1 , R₁ = ⁱPr, R₂ = H; Complex 2 , R₁ = H, R₂ = NO₂)) activated by methylaluminoxane was studied. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, and reaction time on catalytic activity and molecular weight of the polystyrene (PS) were investigated in detail. The electron-withdrawing of nitro group in Complex 2 could not enhance the catalytic activity for styrene polymerization; however, the molecular weights of polymers were increased. Both of the two catalytic systems exhibited high activity [up to 8.45 × 10⁵ gPS/(mol Ni h)] for styrene polymerization and provide PS with moderate to low-molecular weights (M_w = 2.21 × 10⁴∼ 5.71 × 10³ g/mol) and narrower molecular weight distributions about 2.0. The obtained PS were characterized by means of IR, ¹H NMR, and ¹³C NMR techniques. The results indicated that the PS was atactic polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Copolymerization of Norbornene and Styrene Catalyzed by a Series of Bis(β-ketoamine) Nickel(II) Complexes in the Presence of Methylaluminoxane

Summary Random copolymerization of norbornene with styrene was studied by using a series of late metal catalysts/MAO. The precatalysts used here are nickel complexes with b-ketoamine ligands based on pyrazolone derivatives. The copolymers obtained here suggest that only one type of active species is present. Copolymers were characterized by ¹³C NMR, Gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and FT-IR spectra. The analyses of the product by ¹H NMR and ¹³C NMR spectra gave the verification of “true” random vinyl addition copolymer. Varying the monomer feed ratio controlled the composition of the copolymers. A copolymerization reactivity ratio (r_NBE = 20.35 and r_Sty = 0.027) indicates a much higher reactivity of norbornene, which suggests a coordination polymerization mechanism. The solubility and processability of the copolymers are improved relative to polynorbornene and the thermostability of the copolymers is improved relative to polystyrene.     

Fabrication and Properties of Vegetable‐Oil‐Based Glass Fiber Composites by Ring‐Opening Metathesis Polymerization

Glass fiber biobased composites have been prepared by ROMP of a commercially available vegetable oil derivative possessing an unsaturated bicyclic moiety, and DCPD. The resins and the corresponding composites have been characterized thermophysically and mechanically. Higher DCPD content yields materials with higher glass transition temperatures. Glass fibers significantly improve the tensile modulus of the resin from 28.7 to 168 MPa. These biobased composites utilize only a limited amount of a petroleum‐based monomer, while employing substantial amounts of a renewable resource.

     

Polymerization of norbornene using bis(β‐ketoamino)nickel(II)/MAO catalytic systems

The polymerizations of norbornene were investigated using a series of bis(β‐ketoamino)nickel(II) complexes( 1–6 ) in combination with methylaluminoxane (MAO) in toluene solution. The effects of catalyst structure, Al/Ni molar ratio, reaction temperature, and reaction time on catalytic activity and molecular weight of the polynorbornene were examined in detail. The electronic effect of the substituent around the imino group in the ligand is stronger than the steric bulk one on the polymerization activities, and the activities are in the order of 1 > 2 > 4 > 5 > 6 > 3 . The obtained polynorbornenes were characterized by means of ¹H‐NMR, ¹³C‐NMR, FTIR, TG, and WAXD techniques. The analyses results of polymers' structures and properties indicate that the polymerization reaction of norbornene runs in vinyl‐addition polymerization mode. The obtained polynorbornene was confirmed to be vinyl‐type and atactic polymers and showed good thermostability (T_dec > 458°C) and were noncrystalline but had short‐range order. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4172–4180, 2006     

Bio‐Based Rubbers by Concurrent Cationic and Ring‐Opening Metathesis Polymerization of a Modified Linseed Oil

Bio‐based rubbers prepared by tandem cationic polymerization and ROMP using a norbornenyl‐modified linseed oil, Dilulin?, and a norbornene diester, NBDC, have been prepared and characterized. Increasing the concentration of the NBDC in the mixture results in a decrease in the glass transition temperature. The new bio‐based rubbers exhibit tensile test behavior ranging from relatively brittle (18% elongation) to moderately flexible (52% elongation) and with decreasing values of tensile stress with increasing NBDC content. Thermogravimetric analysis reveals that the bio‐based rubbers have maximum decomposition temperatures of over 450 °C with their thermal stability decreasing with increasing loadings of NBDC.