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1.
This summary explores three main topics: (1) zwitterionic alternatives to cationic metallocene alkyl complexes as olefin polymerization
catalysts, based on borato (–BR
3
-
) and boryl (–BR2) substituted cyclopentadienyl ligands (R = C6F5); including zwitterionic zirconium allyl complexes of the type CpZr(η3-allyl){η3-allyl–CH2B(C6F5)3}; (2) reactions which contribute to catalyst deactivation, notably aluminum alkyl mediated C6F5 transfer reactions as well as C–H activation reactions including an unusual case of catalyst self-reactivation; (3) the role
of highly electrophilic metallocene complexes of aluminum, zirconium and yttrium in combination with weakly coordinating anions
as initiators for the carbocationic polymerization of isobutene and isobutene–isoprene copolymerizations is discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
《Journal of Adhesion Science and Technology》2013,27(11):1561-1572
Photocuring of epoxides proceeds by a cationic mechanism. The required photoinitiators are iodonium or sulfonium salts with non-nucleophilic anions. The influence of different photoinitiators on the adhesion properties of both a rigid and a soft epoxide is examined. Depending on the substrates to be joined, different decomposition products of the initiators are concentrated in the interphase. This accumulation of decomposition products in the interphase leads to a decreased adhesion. On gold surfaces the sulfur of sulfonium salts is concentrated as expected. But surprisingly the iodine of the iodonium salts is also concentrated on gold. It could be shown by immobilization experiments that organic iodine compounds with the iodine in any oxidation state reacted with gold surfaces. Due to this reaction iodide anions are formed. On silicon surfaces the fluorine of the anions PF6 - and SbF6 - is concentrated due to the high affinity of silicon for fluorine. The iodonium salt with [B(C6F5)4]anion contains no fluorine able to react with the silicon. Therefore, the fluorine cannot be concentrated in the interphase and the joints prepared with the soft epoxide containing this initiator have a higher shear strength compared to adhesives with conventional anions. 相似文献
3.
Bimetallic salicylaldimine-nickel complexes, 2,4,6-Me3-1,3-{[NCH–(3′-R-5′-Y-2′-O–C6H3)-κ2-N,O]Ni(Ph) (PPh3)}2 [R = tert-Bu, Y = Me, 1b; R = Ph, Y = H, 2b] were prepared and their catalytic behaviors of ethylene polymerization were investigated. The bimetallic complex 2b shows higher activities (2.9 × 105 g PE mol−1 Ni h−1) for ethylene polymerization and affords polymer with high molecular weight (Mw = 1.41 × 105) and broad molecular weight distribution (Mw/Mn = 6.1) than its mononuclear matrix, {[(2,6-Me2C6H3)–NCH–(3′-Ph-2′-O–C6H3)-κ2-N,O]Ni(Ph)(PPh3)} (3) (Activity = 5.5 × 104 g PE mol−1 Ni h−1; Mw = 1.86 × 104; Mw/Mn = 2.8). 相似文献
4.
Syndiospecific styrene polymerization by (tert-BuC5H4)TiCl2(O-2,6-iPr2C6H3) – borate catalyst system
《Catalysis communications》2003,4(6):269-274
(tBuC5H4)TiCl2(O-2,6-iPr2C6H3) (2) exhibited relatively high catalytic activity for syndiospecific polymerization of styrene at 25 °C if both [PhMe2NH]B(C6F5)4 and a mixture of AliBu3/Al(n-C8H17)3 were used as the cocatalyst. Effects of both organoaluminum and organoboron compounds were explored, and the effect of cocatalyst was different from that observed in 1-hexene polymerization catalyzed by Cp*TiCl2(O-2,6-iPr2C6H3) (1). Resultant syndiotactic polystyrene possessed narrow molecular weight distribution under the optimized conditions, and the Mw values were unchanged during the time course. 相似文献
5.
Bertuleit Axel Könemann Martin Duda Lothar Erker Gerhard Fröhlich Roland 《Topics in Catalysis》1999,7(1-4):37-44
6-dimethylamino-6-methylfulvene (7) was converted to the [(C5H4)–CMe2–NMe2]− ligand system (8) by treatment with methyllithium. Its reaction with MCl4 (M = Zr, Ti) followed by treatment with CH3Li gave the respective [(C5H4)–CMe2–NMe2]2M(CH3)2 complexes (12). Their reaction with B(C6F5)3 led to reactive metallocene cation complexes that instantaneously underwent CH activation at a N–CH3 group to yield the metallacyclic cation complexes 15. (tert-butylaminomethyl)fluorene was prepared by the addition of tert-butylisocyanate
to fluorenyllithium followed by hydride reduction. Deprotonation by a variety of bases gave rise to a series of competing
and consecutive reactions to yield several unusually structured products, among them a fluorenyl-anellated η5-1-azapentadienyl anion equivalent (25) and [(flu)-CH2–NCMe3]Li2 (23). An improved way of generating synthetically useful C1-linked [Cp–C1(R)
n
–NR1]2- dianion equivalents was developed starting from 6-amino-6-methylfulvene (26). N-silylation followed by double deprotonation
with, e.g., lithium diisopropylamide cleanly furnished the respective [(C5H4)–C(=CH2)–NSiMe3]2- dianion 33 (isolated as the dilithio derivative). Its reaction with Cl2Zr(NEt2)2 in THF gave [η5:κ-N-(C5H4)–C(=CH2)–NSiMe3]Zr(NEt2)2 36. Activation of 36 with methylalumoxane in toluene led to the formation of a C1-linked “constrained geometry” Ziegler catalyst that polymerized ethylene similarly as the [(C5Me4)SiMe2NCMe3]ZrCl2 derived literature system.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
Daniel Carmona M. Pilar Lamata Fernando Viguri Ricardo Rodríguez Thomas Fischer FernandoJ. Lahoz IsabelT. Dobrinovitch LuisA. Oro 《Advanced Synthesis \u0026amp; Catalysis》2007,349(10):1751-1758
Reaction of the complexes (SM,RC)‐[(η5‐C5Me5)M{(R)‐Prophos}(H2O)](SbF6)2 (M=Rh, Ir) with α,β‐unsaturated aldehydes diastereoselectively gave complexes (SM,RC)‐[(η5‐C5Me5)M{(R)‐Prophos}(enal)](SbF6)2 which have been fully characterized, including an X‐ray molecular structure determination of the complex (SRh,RC)‐[(η5‐C5Me5)Rh{(R)‐Prophos}(trans‐2‐methyl‐2‐pentenal)](SbF6)2. These enal complexes efficiently catalyze the enantioselective 1,3‐dipolar cycloaddition of the nitrones N‐benzylideneaniline N‐oxide and 3,4‐dihydroisoquinoline N‐oxide to the corresponding enals. Reactions occur with excellent regioselectivity, perfect endo selectivity and with enantiomeric excesses up to 94 %. The absolute configuration of the adduct 5‐methyl‐2,3‐diphenylisoxazolidine‐4‐carboxaldehyde was determined through its (R)‐(−)‐α‐methylbenzylamine derivative. 相似文献
7.
The fluorescence of 5-(2′-ethyl-hexyloxy)-p-phenylene vinylene (MEH-PPV) quenched in solution in 1,2-dichlorobenzene by a soluble derivative of C60 [1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C61; [6,6]PCBM] is studied by changing the concentration of the quencher and by varying the temperature. For MEH-PPV and PCBM dissolved in 1,2-dichlorobenzene, the Stern–Volmer constant (KSV) is 2 × 103M−1. At high temperature, KSV is enhanced because thermal energy facilitates the diffusion of PCBM. The results show that dynamic quenching (rather than static quenching) is the basic mechanism. Comparison with data obtained from quenching studies of trans-stilbene indicates that a single acceptor in contact with an MEH-PPV macromolecule quenches the luminescence from hundreds of repeat units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2553–2557, 2001 相似文献
8.
Directly starting from lactic acid (LA) and trimesic acid (TMA), novel biodegradable material poly(lactic acid-trimesic acid)
(PLT), a modified polylactic acid (PLA) with terminal carboxyl, was synthesized via melt copolycondensation. The optimal synthetic
conditions, including catalyst kinds and dosage, prepolymerization time, copolymerization temperature and time, were discussed.
When L-lactic acid (L-LA) and TMA as molar feed ratio n(L-LA)/n(TMA) 120/1 was prepolymerized for 8 h at 140 °C, the copolycondensation catalyzed by 0.9 wt % SnCl2 at 190 °C for 8 h gave PLT with the biggest intrinsic viscosity ([η]) 1.91 dL∙g−1, and the corresponding weight-average molecular weight (Mw) was 14,100 Da. Serial L-PLTs at different molar feed ratios were synthesized and characterized with FTIR, 1H NMR, GPC, DSC, and XRD. Increasing n(L-LA), Mw increased first, and the biggest Mw was 17500 Da at n(L-LA)/ n(TMA) 240/1, then decreased. Using D,L-lactic acid (D,L-LA) instead of L-LA, the influences of LA stereochemical configuration were investigated. The peak phenomenon of Mw was similar, but the biggest Mw was 23,100 Da at n(D,L-LA)/n(TMA) 320/1. The serial L-PLTs had a certain crystallinity (10.2%∼23.0%), while all D,L-PLTs were amorphous. These differences may be in touch with the reaction mechanism of direct melt copolycondensation. The
method was simple and practical for the synthesis of PLA biomedical materials applied in drug delivery carrier, and vessel
substitution material. 相似文献
9.
Joep vandenBroeke Elwin deWolf Berth‐Jan Deelman Gerard vanKoten 《Advanced Synthesis \u0026amp; Catalysis》2003,345(5):625-634
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. 相似文献
10.
J. C. Phillips 《应用聚合物科学杂志》1998,70(4):731-746
Enthalpies of vaporization for esters covering a molecular weight range of about 74–939 g/mol · [monocarboxylics; linear esters of sebacic series; branched esters of triglyceride series; and, oligomer esters of poly(hexamethylene sebacate)] and a temperature range of about 273.15–523.15 K have been empirically fitted to within about 5% to an equation of the following form: ΔHv(T,M) = S(T)f(M) + I0(T), where S(T) = C Ln(T) + K0, I0(T) = aT + b0, and f(M) = M/(1 + a0M), M is the molecular weight (molar mass); T is in degrees Kelvin; and, C, K0, a, b0, and a0 are constants. These results were used to determine the heat capacity difference, ΔCp = Cp(l) − Cp(g), and compared to calculated values from functional relationships of Cp(l) and Cp(g), l is liquid g is gas. The heat capacity difference results in conjunction with Cp(l) were used to empirically calculate the heat capacity of the gas, Cp(g), over the molecular weight and temperature ranges investigated and compared to a group contribution method. The functional forms for ΔHv(T,M), ΔCp(T,M), Cp(l), and Cp(g) were also found to be applicable for n-alkanes. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 731–746, 1998 相似文献
11.
Janos H. Endler 《Israel journal of chemistry》1985,25(1):3-10
Irradiation of surfactant vesicles prepared from (C18H37)2 N+(CH3)C6H4-CHCH2p,CT−, 1, [C15H31CO2(CH2)2]2N+(CH3)CH2C6H4CHCH2,CL− 2, and (C18-H37)2N+(CH3)CH2CH2OCOC6H4CHCH2p,Br−, 3, by ultraviolet light or by bursts of 266 nm laser pulses have resulted in the loss of styrene absorbances. This process has been accounted for in terms of a model which considers intravesicular surface reactions to give polymers with average chainlength of 22. Degreees of photopolymerization have been determined in vesicles prepared from 3 subsequent to separating the polystryrene, formed in the photolysis, from the surfactants. Vesicle surface photopolymerizations result in aqueous cleft formation and in enhanced stabilities. Polymerized vesicles provide media for in situ generation of colloidal catalysts and semiconductors. 相似文献
12.
In the present work, a two-step method was adopted to synthesize a series of novel Gemini surfactants using N,N-dimethylalkyl amines (alkyl length = C12, C16 and C18), epichlorohydrin, and n-phenyllenediamine as starting materials. The products were characterized using mass spectroscopy (MS) and nuclear magnetic resonance spectroscopy (1H NMR). Systematic experiments were conducted to evaluate their surface activity, foaming properties, and antibacterial performance. Results showed the critical micelle concentrations (CMC) of the C12-based, C16-based, and C18-based phenylenediamine surfactants were 3.295 × 10−3, 2.532 × 10−4, and 3.140 × 10−4 mol L−1 at 298 K, respectively, with corresponding surface tension (γcmc) values of 28.24, 31.95, and 35.06 mN m−1 under the same conditions. The Gemini surfactants showed not only good surface activity and foaming properties, but also demonstrated good antimicrobial performance against Gram-positive and Gram-negative bacteria and fungi. 相似文献
13.
We present a generalized view of d0and d0f
n
metal complexes as olefin polymerization catalysts from computational studies of the {L}M–C2H5
(0,+,2+)-fragments (M = Sc(III), Y(III), La(III), Lu(III), Ti(IV), Zr(IV), Hf(IV), Ce(IV), Th(IV) and V(V); L = NH–(CH)2–NH2- {1}, N(BH2)–(CH)2–(BH2)N2- {2}, O–(CH)3–O- {3}, Cp2
2- {4}, NH–Si(H2)–C5H4
2- {5}, {(oxo)(O–(CH)3–O)}3- {6}, (NH2)2
2- {7}, (OH)2
2- {8}, (CH3)2
2- {9}, NH–(CH2)3–NH2- {10} and O–(CH2)3–O2- {11}).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
The development of multicompartment rotating cylinder electrode reactors for the removal of metal from aqueous solutions is described. Such reactors approximate to a cascade of continuously stirred tank reactors and the results illustrate that, for electrodeposition of copper powder from acid sulphate solutions, high overall conversions (about 98%) may be realised, with low exit metal concentrations (about 1 mg dm–3) and reasonable current efficiencies (65–87%).Nomenclature
A
electroactive surface area (cm2)
-
C
in
inlet concentration of metal (mg dm–3)
-
C
out
outlet concentration of metal (mg dm–3)
-
C
reactor
reactor concentration of metal (mg dm–3)
-
f
R
fractional conversion
- (f
R)n
overall fractional conversion
-
F
Faraday=96 500 (C mol–1)
-
I
L
limiting current (A)
-
k
l
mass transfer coefficient (cms–1)
-
m
weight of metal (g)
-
M
molecular weight of metal
-
n
number of reactor elements in the cascade
-
N
volumetric flow rate (cm3 s–1)
-
z
electron change
- dm/dt
rate of removal of metal (gs–1)
This paper was presented, in part, at the Electrochemical Reaction Engineering Symposium, Southampton University, April (1979). 相似文献
15.
Rui-Feng Song Ying-Ying Sun Jun Yang 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(1):143-149
Two structurally related heterocyclic monothioether ligands containing long S-alkyl(hexadecyl) chain, 2-methyl-5-(1-n-hexadecylsulfanyl)-1,3,4-thiadiazole (L
1
) and 2-(1-n-hexadecylsulfanyl) pyridine (L
2
), have been designed, and two CuI complexes with these ligands, [Cu4I4(L1)2]
n
(1) and [Cu4I4(L2)2]
n
(2), have been synthesized and characterized by IR, elemental analysis, UV–vis spectra, thermal analysis and X-ray diffraction
analysis. Single-crystal X-ray analyses show that two complexes are all 1-D coordination polymer with a double-stranded stair
CuI-chain. Optical diffuse-reflection spectra results complex 1 and 2 have the properties of the semiconductor. 相似文献
16.
Photoinitiated cationic polymerization of crystalline monomers based on urethane vinyl ether has been investigated by means of differential photocalorimetry (DPC). The crystalline monomers in the melt state polymerized rapidly by exposure to UV light in the presence of a cationic photoinitiator such as an iodonium salt, sulfonium salt or iron arene salt. The kinetics of the cationic photopolymerization process were studied by following kp[M+] as a function of conversion. High conversions, of around 90 %, were obtained for most of the systems investigated. The efficiency of the cationic photoinitiators in initiating the polymerization of the vinyl ether monomers was in the order: iodonium salt > iron arene salt > sulfonium salt. Monomers modified with different saturated alcohols had different activities in photopolymerization, although they all carry the same functional group, i.e. vinyl ether. Copyright © 2005 Society of Chemical Industry 相似文献
17.
《Ceramics International》2017,43(3):3339-3345
In this study, we propose an effective approach to gain prominent electrostrictive behavior by taking advantage of texture construction in lead-free (Bi0.5Na0.5)TiO3(BNT)-based piezoceramics for actuator applications. The electrostrictive effect was explored systematically in <00 l> textured 0.90(0.83Bi0.5Na0.5TiO3-0.17Bi0.5K0.5TiO3)-0.10NaNbO3(BNT-BKT-NN) ceramics with respect to grain orientation, temperature and electric fields. It was found that the electrostrctive coefficient Q33 and recoverable strain increase monotonously with the grain orientation increasing. At the optimized microstructure (F00 l=92%), a giant Q33 with nearly purely electrostrictive characteristics was detected to be around ~0.0354 m4C−2, which was far larger than the reported values of Pb(Mg1/3Nb2/3)O3 (PMN) and the existing BNT-based electrostrictive materials. Meanwhile, the acquired Q33 was found to exhibit excellent stability for the highly textured sample under different temperature or electric field conditions. Our achievement demonstrates that the giant electrostrictive properties with superior temperature and electric field stability for <00 l> textured BNT-BKT-NN ceramic are of great significance in replacing traditional PMN ceramics for actuator applications. 相似文献
18.
Rukiye Oztekin Delia Teresa Sponza 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(2):212-225
BACKGROUND: In this study, the effects of additives (manganese (III) oxide (Mn3O4), Cu+2, Fe0 and potassium iodate (KIO3)) and radical scavengers (sodium carbonate (Na2CO3), perfluorohexane (C6F14) and t‐buthyl alcohol (C4H10O)) on the dephenolization, decolorization, dearomatization and detoxification of olive mill wastewater (OMW) by sonication were investigated because wastewaters from this industry are not removed effectively. RESULTS: The maximum COD, color, total phenol and total aromatic amines (TAAs) removal efficiencies were 63, 82, 78 and 71%, respectively, at 60 °C with sonication only. The TAAs and phenol yields were increased to 96 and 97% with 6 mg L?1 KIO3 and 3 mg L?1 Fe0 while color removal reached 97% with 6 mg L?1 C6F14. The total annual cost with sonication only was 665 € m?3 year?1 while the cost slightly increased (666€ m3 year?1) with C6F14. The maximum acute toxicity removals were 97‐98% in Daphnia magna and Vibrio fischeri The Microtox acute toxicity test was more sensitive than the Daphnia magna to the OMW samples. CONCLUSION: COD, color, total phenol, TAAs and toxicity in an OMW were removed efficiently and cost‐effectively by sonication. © 2012 Society of Chemical Industry 相似文献
19.
The overall mass transfer coefficient kLa,F
in the flow characteristics was determined by the measurement of the diffusivity of ozone, density of aqueous solution, and
viscosity. However, the measured values kLa,F
in the range of 0.0096–0.0622 min-1 show large changes in hydraulic retention time, and the dissolved ozone concentration CL,F
presented under 0.1 mg/l is lower than the dissolved ozone observed. The overall mass transfer coefficient kLa,M in the ozone decomposition was determined by measurement of the equilibrium dissolved ozone, overall decomposition rate constant,
and overall Henry’s law constant. The measured values kLa,M
are in the range of 0.0441–0.0749 min-1, and they present small changes depending on the hydraulic retention time. Furthermore, the measured dissolved ozone concentration
CL,M presents a larger value than the CL,F. Then, the kLa,M is selected as an input overall mass transfer coefficient to predict the dissolved ozone requirement in the ozone contactor. 相似文献
20.
Mingxing Zhou Ruihong Liang Zhiyong Zhou Xianlin Dong 《Journal of the American Ceramic Society》2020,103(1):193-201
In this study, (1 − x)NaNbO3–xBa0.6(Bi0.5K0.5)0.4TiO3 (abbreviated as NN-xBBKT, x = 0.05, 0.10, 0.15, and 0.20) lead-free pyroelectric ceramics were synthesized by conventional solid-state reaction method. Moreover, their microstructure, phase structure, dielectric, ferroelectric, piezoelectric, and pyroelectric characteristics were studied systematically. The X-ray diffraction result showed that the phase structure of NN-xBBKT ceramics changed from orthorhombic to tetragonal and finally became pseudocubic symmetry. The ferroelectric-paraelectric phase transition temperature and depolarization temperature shifted to lower temperature with the increase in BBKT content. Furthermore, with increasing BBKT content, piezoelectric coefficient, figures of merit, and pyroelectric coefficient first increased and then decreased. The optimum pyroelectric properties (eg Fd = 0.81 × 10−5 Pa−1/2, Fv = 1.02 × 10−2 m2 C−1, Fi = 1.04 × 10−10 m V−1, and p = 3.11 × 10−8 C cm−2 K−1) were observed in sample composition with x = 0.15. More importantly, the pyroelectric coefficient of ceramic with x = 0.15 also displayed relatively high thermal stability because of high depolarization temperature (~110°C). These parameters demonstrate that the novel Pb-free NaNbO3-based ceramics form an important class of pyroelectric material with broad range of application prospect. 相似文献