10049-06-6Relevant articles and documents
Direct epimetallation of π-bonded organic substrates with titanium(II) isopropoxide: Intermediacy of biradical, oligomeric titanium(II) reagents
Eisch, John J.,Gitua, John N.,Doetschman, David C.
, p. 1968 - 1975 (2006)
Extensive EPR experiments show that a titanium-containing molecular triplet state is formed in solution by the reaction of two equivalents of butyllithium with one equivalent of titanium(IV) isopropoxide. At higher concentrations this product, titanium(II) isopropoxide, admixed with two equivalents of lithium isopropoxide, is accompanied by the formation of a variety of nontitanium-containing side products. The powder EPR spectrum of the molecular triplet state in frozen solution is consistent with an asymmetric molecular chain of three Ti centers on which the unpaired electron centers are three metal atoms apart. Dilution experiments show that at lower concentrations, where the nontitanium-containing side products have dissipated, the intensity of the molecular triplet spectrum varies approximately linearly with concentration. Thus there is no evidence that the observed triplet molecule is one component in a series of concentration-dependent oligomerization steps. The bulky isopropoxy substituents and the coordination of the isopropoxide anions from the LiOiPr present appear to prevent closure of the Ti3 centers into an equilateral triangular diamagnetic structure. This steric hindrance, operative at the terminal diisopropoxytitanium centers and preventing closure to a ring, seems not to be observed with TiCl2·2THF, which is diamagnetic and may thus be expected to exist as an equilateral triangular cluster of three units of TiCl2·2THF, a structural model currently under further investigation. The smaller steric demand of the chloro and THF units would seem to permit octahedral coordination about each Ti center in such an equilateral trigonal array of Ti3 atoms. Chemical reactions carried out individually with diphenylacetylene, cis-stilbene or cis-stilbene oxide and titanium(II) diisopropoxide provide stoichiometric and stereochemical evidence that the attacking titanium(II) reagent is in fact the trimeric biradical. The role of the lithium isopropoxide byproduct in fostering the course of the previously reported SET reactions of titanium(II) isopropoxide and in determining the detailed structure of the open-chain Ti trimer biradical has been explicated. Wiley-VCH Verlag-GmbH & Co. KGaA, 2006.
Combined far infrared RAIRS and XPS studies of TiCl4 adsorption and reaction on Mg films
Pilling,Fonseca, A. Amieiro,Cousins,Waugh,Surman,Gardner
, p. 78 - 87 (2005)
In recent years there has been an increase in interest in the study of model Ziegler-Natta catalysts used for the polymerisation of ethene and propene. Particular attention has focused on catalysts consisting of TiCl4 on activated MgCl2 accompanied by a co-catalyst, usually triethylaluminium (AlEt3). As part of a wider project on the characterisation of model Ziegler-Natta catalysts we have investigated the interaction of TiCl4 with metallic Mg films grown on a Au surface using X-ray photoelectron spectroscopy (XPS) and far infrared reflection absorption infrared spectroscopy. Somewhat surprisingly, the infrared spectra show little variation as a function of exposure to TiCl4. A very broad asymmetric vibrational band grows in with maximum intensity at 382 cm -1. Three prominent low frequency shoulders are observed at approximately 360, 320, and 260 cm-1. For monolayer coverages of Mg the main band at 382 cm-1 is narrower, less asymmetric and accompanied by a prominent shoulder at 398 cm-1, which increases with increasing exposure to TiCl4. TiCl4 exposure in the presence of 5 × 10-8 Torr of ethyl benzoate results in a change in line shape with low frequency broadening and a small shift in the frequency of the band. These spectra are discussed in the light of the possible constituent species making up the surface layer.
The heat capacity of titanium di-and tetrachloride over the temperature range 7-314 K
Berezovskii,Snigireva
, p. 1656 - 1660 (2006)
The temperature dependences of the heat capacities of titanium di-and tetrachloride were studied by vacuum adiabatic calorimetry. The parameters of fusion (T tr, Δtr H, and Δtr S) were determined for TiCl4. The
High temperature interactions of metal oxides with NaCl
Mobin, M.,Malik, A. U.,Ahmad, Sultan
, p. 1 - 14 (1990)
The interaction of different metal oxides with NaCl in the temperature range 800-1200 K in flowing oxygen has been studied. These oxides are present on the scales formed on Na2SO4 or NaCl during the initiation stage of hot corrosion
Gaseous Species in the Ti-Al-Cl System and Reaction with H2O
Hildenbrand, D. L.,Lau, K. H.
, p. 3435 - 3437 (1991)
Chemical species in the Ti-Al-Cl system at elevated temperatures were studied by effusion-beam mass spectrometry up to 1400 K.Gaseous TiAlCl5 and TiAlCl6 were identified as products of the reaction of TiCl4(g) and a Ti-Al mixture above about 900 K, for which AlCl3, TiCl2, and TiCl3 were also present.No evidence was found for TiAlCl7.When gaseous TiCl4, AlCl3, and H2O and admitted simultaneously, TiOCl2, Al(OH)Cl2, and TiAl(OH)Cl5 were observed.All ion species showed the correct isotopic distribution.The results confirm earlier indications that AlCl3 forms gaseous complexes with divalent and trivalent Ti, but not with tetravalent Ti.
Titanium-catalyzed cyclotrimerization of butadiene. Part II. The (C6H6)TiII(AlCl4)2-EtxAlCl3-x (x=1-3) systems
Polacek, J.,Antropiusova, H.,Petrusova, L.,Mach, K.
, p. 53 - 74 (1990)
This paper describes the kinetics of butadiene cyclotrimerization catalyzed by the Ia-EtAlCl2, Et2AlCl or Et3Al systems and the results of investigations of these systems by electronic absorption spectroscopy. The study was carried out to improve understanding of the effects of organo-aluminum compounds on the catalytic properties of Ia and to find the optimum conditions for (Z,E,E)-CDT production. In view of our long-term efforts to identify the catalytic species in the butadiene cyclotrimerization in systems based on different titanium precursors, this is the initial step in a comparative study of the (arene)titanium (II) systems and the Ti(IV)-based systems.
Fundamental study on synthesis and enrichment of titanium subchloride
Takeda, Osamu,Okabe, Toru H.
, p. 376 - 383 (2008)
In order to establish a new high-speed/(semi-)continuous titanium production process based on the magnesiothermic reduction of titanium subchlorides (subhalide reduction process), a novel synthetic process for obtaining titanium subchlorides (TiClx, x = 2, 3) by the reaction of titanium tetrachloride (TiCl4) with titanium metal at 1273 K was investigated. It was demonstrated that the efficiency of the TiClx formation improved drastically when molten salts were used as the reaction medium as compared with that of the synthesis by employing the direct reaction of TiCl4 gas with solid titanium. The feasibility of the enrichment process of TiClx in molten salt was also demonstrated. The method for producing the titanium subchlorides investigated in this study can be applied to the new high-speed production process of titanium.
New syntheses of ansa-metallocenes or unbridged substituted metallocenes by the respective reductive dimerization of fulvenes with Group 4 metal divalent halides or with Group 4 metal dichloride dihydrides
Eisch, John J.,Owuor, Fredrick A.,Shi, Xian
, p. 1325 - 1339 (2008/10/09)
Two unprecedented syntheses of Group 4 metallocenes from 6-substituted fulvenes have been discovered and developed into high-yielding processes. In the first route the di-n-butylmetal dichlorides of Ti, Zr and Hf are generated in toluene suspensions of LiCl at -78°C from the metal tetrachlorides and 2 equiv. of n-butyllithium. Bringing the Bun2MCl2 to 25°C and then heating at reflux for several hours gave complete conversion to slurries of MCl2 (M = Ti, Zr, Hf). Heating such slurries of MCl2 with 2 equiv. of 6-substituted or 6,6-disubstituted fulvenes gave high yields of ansa-metallocenes or substituted ethylene-bis(cyclopentadienyl)metallocene dichlorides (fulvenes: 6,6-dimethyl-, 6-phenyl-, 6-(1-naphthyl)-, 6-(9-anthryl)-). For 6-substituted fulvenes, both racemic- and meso-1,2-disubstituted ethylene-ansa-metallocene dichlorides are expected to form, but with M = Zr (or Ti), the actual racemic- to meso-ansa-metallocene dichloride ratios observed were: phenyl, 50:50; 1-naphthyl, 83:17; 9-anthryl, 100:0. Apparently for steric reasons 6,6-diphenylfulvene underwent no ansa-metallocene dichloride formation with ZrCl2 but rather produced bis(diphenylmethyl(cyclopentadienyl))zirconium dichloride. The second route to novel metallocenes involves generating Bun2MCl2 at -78°C in toluene slurry, as in the foregoing method, but then adding 2 equiv. of the 6-substituted or 6,6-disubstituted fulvene immediately thereafter at -78°C. Except with Bun2TiCl2, warming the reaction mixture to 25°C and then further heating at 65°C cause a smooth bis-hydrometallation by transfer to occur, giving good to very good yields of bis(substituted cyclopentadienyl)metal dichlorides (M = Zn, Hf). The instability of Bun2TiCl2, even at -78°C, rapidly led to a mixture of TiCl2 and Bun2TiCl2and hence to a mixture of ansa-titanocene dichlorides and unbridged, bis(substituted cyclopentadienyl) titanocene dichlorides. With a detailed study of the attainment and the stereochemistry of the formation of ansa-bridged complexes or metallocenes with acetophenone, benzylideneaniline and 6-arylfulvenes, a mechanistic model is developed involving either a three-membered metallocycle formed from MCl 2 or an open-face sandwich complex of the fulvene and MCl2. Such intermediates offer a rational steric explanation for the observed stereochemistry of ansa-bridge C-C bond formation. Finally, in comparative polymerizations of ethylene by such metallocenes, cocatalyzed by MAO, the superior catalytic activity of ansa-metallocenes in the order, Ti > Zr > Hf and of ansa-metallocenes over unbridged substituted metallocenes is attributed to the hyperconjugative stabilization afforded by the ansa σ C-C bond to the metallocenium cation at the active olefin-polymerization site.
METAL COMPLEXES CONTAINING BRIDGING HETEROATOM FOR OLEFIN-POLYMERIZATION-PROCESS
-
, (2008/06/13)
Metal complexes comprising an oxygen, sulfur, or nitrogen containing bridging group which are useful as catalyst components for the polymerization of olefins.
Method for purifying transition metal compound and method for producing the same
-
, (2008/06/13)
A method for purifying a transition metal compound, which comprises conducting crystallization of a transition metal compound from a solution containing the transition metal compound while stirring. According to the present invention, it is possible to purify and produce efficiently a transition metal compound at high purity under industrially and economically advantageous conditions.
