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1.
Two benzene centered tri- and tetracyclopentadienyl ligands C6H3(CH2C5H5)3-1,3,5 (1) and C6H2(CH2C5H5)4-1,2,4,5 (2) and their titanium complexes C6H3[CH2C5H4Ti(C5H5)Cl2]3-1,3,5 (3), C6H3[CH2C5H4Ti(C5H4CH3)Cl2]3-1,3,5 (4), as well as C6H2[CH2C5H4Ti(C5H5)Cl2]4-1,2,4,5 (5) were synthesized and characterized by mass and 1H NMR spectra. In the presence of methylaluminoxane (MAO), 3, 4 and 5 are efficient catalysts for ethylene polymerization in toluene. The influence of the polymerization conditions such as catalyst concentration, MAO/Ti molar ratio, polymerization time and temperature were investigated in detail. 3, 4 and 5 produce linear polyethylene (PE) with broad molecular weight distributions (MWD) and a little lower molecular weight.  相似文献   

2.
Reaction of (omp) disodium(phenylenedimethylene)dicyclopentadienide C6H4(CH2C5H4Na)2 with 2 equiv of (MeCp)TiCl3 yields the phenylenedimethylene bridged binuclear titanocenes complexes [(MeC5H4)TiCl2](C5H4CH2C6H4CH2C5H4)[(MeC5H4)TiCl2] (345) in high yield, which were characterized by 1H NMR and elemental analysis. They were used successfully as efficient catalysts for ethylene polymerization in the presence of methylaluminoxane (MAO). The catalytic activities of 4 and 5 are somewhat higher than that of 3 and the molecular weight distributions (MWD = 4.8-6.2) of the polymers generated from the bimetallic catalytic systems are obviously higher than that obtained by conventional Cp2TiCl2.  相似文献   

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Summary Complexes of pentachlorotantalum with the Schiff bases: bis(vanillin)benzidine, bis(vanillin)-o-dianisidine, bis(acetylacetone)benzidine, bis(p-dimethylaminobenzaldehyde)-o-dianisidine, bis(anisaldehyde)-1, 3-propanediamine and bis(p-dimethylaminobenzaldehyde)-o-phenylenediamine have been prepared and characterized by molar conductance, decomposition temperature, elemental and t.g. analyses and i.r. spectral measurements. The conductances reveal that pentachlorotantalum (1 mole) interacts with all the ligands (1 mole), all five chloride ions thus forming simple adducts. A comparative study of the i.r. spectra of the parent ligands and their complexes allows the coordination sites to be ascertained. The studies show that tantalum(V) chloride prefers to form complexes of high coordination number.  相似文献   

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Summary Niobium(V) and tantalum(V) pentaethoxides react with monofunctional benzoyl hydrazones (BHy) in refluxing benzene to give products of the type, M(OEt)5–n(BHy)n (where M=Nb or Ta and n=1, 2 or 3). The complexes have been characterised on the basis of elemental analysis, spectral (i.r. and n.m.r.) and molecular weight data.  相似文献   

8.
4,4′-Bis(methylene)biphenylene bridged homodinuclear titanocene (3) and zirconocene (4) have been synthesized by treatment of CpTiCl3 and CpZrCl3 · DME with Na2[C5H4CH2C6H4-p-C6H4CH2C5H4], respectively, in THF and characterized by 1H NMR and element analysis. After activation with methyl aluminoxane (MAO), these catalysts were used for the homogeneous polymerization of ethylene. The influences of reaction conditions, such as temperature, time, catalyst concentration and molar ratio of MAO/Cat. on ethylene polymerization were investigated in detail. The catalytic activities of 3 and 4 are more than three times higher than that of the phenyldimethylene bridged homodinuclear metallocene of titanocene (5) and zirconocene (6), respectively, and also twice higher than that of Cp2TiCl2/MAO and Cp2ZrCl2/MAO, respectively. However, the catalytic activity of 3 is nearly half as high as that of 4, which reached 1.31 × 106 g PE/mol cat h. The molecular weight of polyethylene increases simultaneously with prolongation of polymerization time. GPC spectra show that 3 and 4 produce polyethylene with broad molecular weight distribution (4.28 and 3.18). The high melting points of the products (131-134 °C) indicate that the polyethylene formed is highly linear and highly crystalline.  相似文献   

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The reactions of [MCl4(eta-C5H5)](M = Nb, Ta) with Ph3Sn{HB(mt)3} (mt = methimazolyl) provide structurally characterised complexes of the new chlorobis(methimazolyl)borate ligand, [MCl3(eta-C5H5){kappa2-S,S'-HClB(mt)2}].  相似文献   

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A hexafluorotantalate(V)-selective coated-graphite electrode was prepared by coating a graphite rod with brilliant green-hexafluorotantalate(V) extract in 1-chloronaphthalene in a PVC matrix. Potential measurements were made against an HF-resistant plastic sleeve (Ag/AgCl) external reference electrode. The concentrations of sulfuric and hydrofluoric acids, for the optimum response of the electrode to hexafluorotantalate(V), were found to be 1M each in the test solutions. The electrode responded to hexafluorotantalate(V) in the linear range 5.0 × 10–6-5.0 × 10–3 M, with a slope of -58 mV per decade and detection limit of 8.0 × 10–7 M within 5–15s. The relative standard deviation for six determinations of 1.0 × 10–4 M tantalum(V) was 2%. The life-time of the electrode was 60 days. The effects of forty diverse ions on the electrode response to the hexafluorotantalate(V) were studied and the electrode was found to be highly selective to hexafluorotantalate(V). Niobium, the element that commonly occurs with tantalum ores, showed a very low level of interference. The newly developed coated-graphite electrode has been applied to the determination of tantalum in tantalite-columbite ores and several synthetic matrices by direct, sample addition, standard addition, and Gran's plot potentiometric techniques with reasonable precision (2–4%) and accuracy.  相似文献   

13.
Two hetero-atom containing bridged dinuclear metallocene complexes, (CpMCl2)2(C5H4CH2CH2OCH2CH2C5H4) [M = Ti (1), Zr (2)], have been synthesized by treating the disodium salt of the corresponding ligand (C5H5CH2CH2)2O with two equivalents of CpTiCl3 and CpZrCl3 · DME, respectively, in THF at 0 °C and characterized by 1H- and 13C-NMR, MS and IR spectroscopy. Homogenous ethylene polymerization by those complexes has been conducted systematically in the presence of methylaluminoxane (MAO). The influences of reaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature and time, have been studied in detail. The catalytic activities of the dinuclear complexes 1 and 2 were higher than those of (MeCpTiCl2)2(C5H4CH2C6H4CH2C5H4) (3), (CpZrCl2)2(C5H4CH2C6H4CH2C5H4) (4) and the mononuclear metallocenes Cp2TiCl2 and Cp2ZrCl2, respectively. Complex 2 showed high catalytic activity at high temperature (50-100 °C) and high pressure (6 bar). The molecular weight distributions of polyethylene produced by 1 and 2 (MWD = 2.49 and 5.90) were broader than those using the corresponding mononuclear metallocenes (MWD = 2.05 and 2.15). The melting points of the polyethylene produced ranged from 129 to 133 °C, indicating a high linearity and a high crystallinity.  相似文献   

14.
Ta2Cl6(SMe2)3 reacts with one equivalent of C4H9CO2Li to give a complex with a bridging carboxylate ligand, Ta2Cl5(O2CC4H9)(SMe2)(THF)2. The product was isolated in two crystalline forms, 1 and 2, from a THF/hexane and benzene/hexane solvent mixture, respectively. The following are the unit cell parameters, for 1: monoclinic (P21/n), a = 10.537(5) Å, b = 22.015(4) Å, c = 11.663(4) Å, β = 107.80(3)°, V = 2576(3) Å3, and Z = 4; for 2: monoclinic (P21/c), a = 15.584(4) Å, b = 15.647(4) Å, c = 11.275(3) Å, β = 106.04(5)°, V = 2642(3) Å3 and Z = 4. The complex is a dimer with a distorted octahedra-sharing-an-edge geometry. The TaTa distances in 1 and 2 were 2.766(1) Å and 2.779(1) Å, respectively, which is somewhat longer than in previously reported Nb(III) and Ta(III) dinuclear compounds. Diamagnetism of the complex is shown by NMR. Fenske—Hall calculations, which correctly predict an electronic transition at about 16,000 cm?1, indicate a double TaTa bond. The observed elongation of the metalmetal bond is attributed mainly to steric crowding. The complex is the first proven low-valent Ta species with a coordinated carboxylate ion.  相似文献   

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The synthesis and characterization of (η5-C5Me5)TaCl4, (η5-C5Me5)TaCl4L (L  PMe3, P(OMe)3, Ph2PCH2CH2PPh2), (η5-C5Me5)TaMe4, and (η5-C5Me5)Ta(CH2Ph)2(CHPh) is described. NMR studies of the bis(1,2-diphenylphosphino)ethane (dppe) adduct show exchange of free and ligated dppe, possibly via dissociation of the ligand from a monodentate compound.  相似文献   

17.
Summary Compounds of composition MCl5–n(OPh)n · L (M = Nb or Ta; n = 1 or 2 and L = monodentate ligand) have been prepared by reacting phosphoryl and amine oxide ligands with phenoxy-niobium(V) and -tantalum(V) chlorides and characterized by their analytical data, molecular weights, molar conductance and i.r. spectra.  相似文献   

18.
Two rigid benzene centered dinuclear metallocene complexes C6H2[(CH2C5H4)2MCl2]2, M = Ti (1), Zr (2) have been prepared by treating two equivalents of TiCl4 and ZrCl4 with the tetralithium salt of the ligand C6H2(CH2C5H5)4-1,2,4,5 in toluene and characterized by 1H NMR and elemental analysis. Both complexes are effective catalysts for ethylene polymerization in the presence of methylaluminoxane (MAO). The influence of [MAO]/[Cat] molar ratio, catalyst concentration, polymerization temperature and time has been tested in detail. The catalytic activity of complex 2 is more than two times higher than that of complex 1, which is still more active than that of the tetranuclear titanocene C6H2[CH2C5H4Ti(C5H5)Cl2]4-1,2,4,5 (5). On the other hand, the catalytic activities of 1 and 2 is slightly lower than that of the dinuclear metallocene complexes C6H4[CH2C5H4Ti(C5H4CH3)Cl2]2-1,3 (3) and C6H4[CH2C5H4Zr(C5H5)Cl2]2-1,3 (4), respectively, which is related to the limited intermolecular rotation of the metallocene units in 1 and 2. The melting points above 130 °C indicate a polyethylene formed by complexes 1 and 2 with highly linear and highly crystalline. GPC spectra show that polyethylene produced by complexes 1 and 2 has a broad and even bimodal molecular weight distribution (MWD).  相似文献   

19.
Anions of the type MFnX-6-n (M = NbV, TaV; X = Cl-, Br-), including geometric isomers, have been characterised in solution by 19F NMR spectroscopy. Thirty eight fluorine-containing complexes of tantalum of the type TaFxClyBr-z have been found from the 46 theoretically possible. The relative stability of mixed tantalum fluorochloro and fluorobromo anions of the type TaFnX-6-n has been studied.  相似文献   

20.
Proton and subsequent hydride abstraction from the bis(phenoxide) ligand of the trimethyltantalum(V) complex affords a cationic tantalum(V) carbene complex, in which two phenoxide groups are linked to the carbene center. The electrophilic nature of the carbene functionality is demonstrated by the reaction with PPh3.  相似文献   

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