The rates of ethylene polymerization catalyzed by Cp2ZrCl2-polymethylalumoxane and (Cp2ZrCl)2O-polymethylalumoxane are equal. According to NMR and ESR spectral data, the same precatalyst, presumably Cp2ZrMe2, is formed in both systems by the action of AlMe3. This accounts for the equal catalytic activity of the systems based on Cp2ZrCl2 and (Cp2ZrCl)2O. A scheme of reactions resulting in cleavage of the Zr-O-Zr bridge is proposed and confirmed by spectroscopic data.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2104–2107, December, 1993. 相似文献
Trimethylaluminum and the methylalumoxanes produced by its incomplete (controlled) hydrolysis in various organic solvents have been investigated by27Al and1H NMR spectroscopy. Differences in the properties and spectral characteristics of methylalumoxanes obtained in toluene and pentane have been found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1453–1457, August, 1993. 相似文献
Summary: The performances of ethylene polymerization catalysts based on III and commercial methylaluminoxane were investigated by reducing the content of free trimethylaluminum in methylaluminoxane by its reaction with 2,6‐di‐tert‐butylphenol. This allowed optimization of the formulation of the catalyst, affording a high‐molecular‐weight linear polyethylene (PE) with a productivity [(1 900 kg of PE/(mol of Ni × h)], ten‐fold higher than that previously achieved for the same system adopting commercial methylaluminoxane not pre‐treated with the above phenol derivative.
Photodissociation of trimethylaluminum [Al(CH3)3] adsorbed on a silica (SiO2) substrate at 110 K has been studied by multiphoton ionization time-of-flight mass spectrometry. Translational energy distributions of aluminum and AlCH3 fragments can be fitted with a composition of two Maxwell–Boltzmann distributions. The two components are attributed to different environments of photodissociating parent molecules in the multilayer. 相似文献
Highly purified trimethylaluminum [(CH3)3Al] was prepared by reducing the contamination of volatile impurities such as organic silicon and dimethyl-aluminum methoxide [(CH3)2AlOCH3]. The concentration of methoxy group in (CH3)3Al was found to decrease considerably when (CH3)2Al was distilled in the presence of aluminum trihalide. Among the halides, purification efficiency increased in the order I>Br>Cl. High-quality AlGaAs layer and AlGaAs/GaAs modulation doped structures were grown by organometallic vapor-phase epiloxy (OMVPE) using the purified (CH3)3Al. Their electrical properties were discussed in relation to the volatile impurity in the source gas. 相似文献
The title compounds were synthesized by the addition of AlMe3 to the corresponding azide suspended in an aromatic solvent. Both products were obtained as air-sensitive colorless crystals. Cs[Al2Me6N3]·2p-xylene crystallizes in the monoclinic space groupC2/m witha=19.143(6),b=16.227(6),c=10.392(5) Å, =114.06(2)o, and calc = 1.20 g cm–3 forZ=4. Refinement led to a conventionalR value of 0.037 for 2179 observed reflections. The cesium atom resides on a mirror plane, and the anion is disordered about a twofold axis. Thep-xylene molecules sandwich the cesium ion.[K·dibenzo-18-crown-6] [AlMe6N3]·1.5(1-methylnaphthalene) crystallizes in the monoclinic space groupP21/c witha=14.176(5),b=13.021(5),c=25.324(8) Å, =98.23(4)0, and calc = 1.08 g cm–3 forZ=4. The finalR value was 0.132 for 1402 observed reflections. One of the 1-methylnaphthalene molecules is disordered about a center of inversion and interacts with the potassium ion. The other solvent molecule is found roughly in layers in the lattice and also exhibits disorder of the methyl substituent. For both title compounds the AlMe3 groups of the anion exhibit a staggered (Cs) conformation.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82015 (32 pages). 相似文献
The crown ether 12-crown-4 reacts with trimethylaluminum in toluene to form the complex [AlMe3]2[12-crown-4]. Attempts to utilize the remaining two oxygen atoms for coordination to AlMe3 molecules were unsuccessful. The 21 complex crystallizes in the monoclinic space groupP21/n witha=11.342(7),b=12.941(4),c=6.973(6) Å, and =95.48(4)°. Refinement led to a finalR value of 0.047 for 925 observed reflections. The molecule resides on a crystallographic center of inversion, and as required by symmetry, the four oxygen atoms are planar. The Al–O bond is strong as revealed by the bond length of 1.977(3) Å.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82013 (9 pages). 相似文献