- Indenyl-titaniumchlorides: Ethene-polymerization and structure-reactivity studies
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The halfsandwich complexes [(η5-C9H 7)TiCl3] (3a), [(η5-Me3Si-1- C9H6)TiCl3] (3b), [(η-Me-1-C 9H6)TiCl3] (3c), [(η-Me2-4,7- C9H5)TiCl3] (3d), [(η5-Me 3Si-2-C9H6)TiCl3] (3e), [(η5-Me2-1,3-C9H5)TiCl 3] (3f), [(η5-(CH2)3-5,6-C 9H5)TiCl3] (4), and [(η5- (CH2)3-1,7-C9H5)TiCl3] (5) are accessible by reacting the in position 1 or 3 Me3Si- functionalized appropriate indenes with TiCl4. CG-TiCl2 compounds (CG = Constraint Geometry) can be synthesized by the subsequent reaction of Br-2-C9H7 (6a), Br-2-Me2-1,3-C 9H5 (6b) and Br-2-(CH2)3-5,6-C 9H5 (6c), respectively, with magnesium in presence of Me2SiCl2 to give the respective Me2SiCl- functionalized indenes which further react with an excess of H2N tBu to afford tBuHN-SiMe2-C9H 7 (8a), tBuHN-2-Me2-1,3-C9H 5 (8b) and tBuHN-2-(CH2)3-5,6-C 9H5 (8c). The latter species produce on their consecutive reaction with nBuLi, [TiCl3·3Thf] and PbCl 2 the titanium CG-complexes [(η5-SiMe 2NtBu-2-C9H6)TiCl2] (9a), [(η5-Me2-1,3-SiMe2NtBu-2-C 9H4)TiCl2] (9b), and [(η5- Me2SiNtBu-2-(CH2)3-5,6-C 9H4)TiCl2] (10). The same synthesis protocol allows the preparation of [(η5-Me2SiN tBu-1-Me3Si-2-C9H5)TiCl 2] (12) a CG complex in which the Me2SiNtBu unit is located in position 1. The polymerization of ethene by using 3-5 and 9-12 and MAO (MAO = methylaluminoxane) as cocatalyst is described to show if a strong activity correlation between 3-5 and 9-12 exists. In order to optimize the catalytic activity of 3-5 the electronic (cyclic voltammetry, UV-Vis spectroscopy) and steric properties (Multiple Overlap Solid Angle) of these species were analyzed. Based on the obtained data, semi-empirical structure-activity models for 3-5 are proposed to obtain an optimized substituent pattern for the indenyl moiety. Substituents in position 1 or 4 of the appropriate indenyl π-perimeters show a strong bathochromic (+M) and electro-neutral to electro-negativ effect (0/-I).
- Weiss,Voelkening,Rueffer,Meichel,Sachse,Rheinwald,Lang
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- Steric and electronic effects of the R in IndTiCl2(OR) catalysts on the syndiospecific polymerization of styrene
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Four alkoxyl ligand substituted indenyl titanium dichloride complexes, IndTiCl2(OR) (R = Me (2), Et (3), iPr (4), cyclohexyl (5)) were prepared, and evaluated as catalysts for the syndiospecific polymerization of styrene when activated with methylaluminoxane (MAO). Alkoxyl ligand substituted complexes showed higher catalytic activities than IndTiCl3 (1) except for complex 5. When R = Et, the catalyst 3 showed the highest activity. A study of the steric and electronic effects of alkoxyl ligand revealed that the more electron-donating and less steric bulky R group was more suitable for the improvement of the catalytic activity. When the polymerization was carried in solution at high molar ratio of Al/Ti = 4000, the s-PS% of obtained polymer were in the range of 99.0-99.6%. The highest melting point of 276.9°C was obtained by using 2 as catalyst. The influence of polymerization temperature was also investigated. The maximum polymerization activities were found at 50°C for all of the above complexes, but the percentages of s-PS were insensitive to the polymerization temperature.
- Ma, Haiyan,Chen, Bin,Huang, Jiling,Qian, Yanlong
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- Synthesis and characterization of cyclopentadienyl titanium trichloride and indenyltitanium trichloride; monocyclictitanium trihalide complexes
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CpTiCl3 and IndTiCl3 are homogeneous metallocene catalysts that are produced under highly controlled conditions. Syndiotactic polymerization of styrene is carried out using these catalysts while methylaluminoxane (MAO) is used as a cocatalyst. In the present paper synthesis of CpTiCl3 was examined at first by reacting TiCl4 with CpNa, this reaction just led to formation of Cp2TiCl2 so CpNa was not a suitable Cp donor compound, therefore CpSiMe3 was used instead of CpNa. Reaction of CpSiMe3 with TiCl4, produced CpTiCl3 immediately. IndTiCl3 was synthesized by reacting IndSiMe3 and TiCl4 as well. At the end two synthetic catalysts were characterized by FTIR and 1H-NMR spectrometers. Copyright
- Masnadi, Mitra,Jamjah, Roghieh,Ahmadjo, Saeed,Nekoomanesh, Mehdi
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p. 543 - 547
(2008/10/09)
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- Alkyl-substituted indenyl titanium precursors for syndiospecific ziegler-natta polymerization of styrene
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A variety of 1- and 3-substituted alkylindenes (R = H, Me, Et, tert-butyl, Me3Si) as well as 2-methylindene and 3-(methylthio)indene have been prepared in good yields. The substituted indenes were converted into trimethylsilyl derivatives via reactions of intermediate organolithium complexes with chlorotrimethylsilane. The corresponding titanium complexes, (R-Ind)TiCl3, were synthesized in excellent yield from reactions of the trimethylsilyl derivatives with TiCl4. The titanium complexes were evaluated as styrene polymerization catalysts in toluene solution when activated by methylaluminoxane. Activities increased in the order: Cp 4 Ind 3Si, corresponding to an increase in the steric bulk of the substituent in the catalyst precursor. 1-(MeS)IndTiCl3 was found to be ineffective as a styrene polymerization catalyst. Syndiospecificities of the titanium complexes were generally very good (65-98%).
- Ready, Thomas E.,Chien, James C.W.,Rausch, Marvin D.
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- Synthesis and characterisation of (η5-cyclopentadienyl)(η5-ring)titanium alkyl (ring = indenyl or C5H4But) complexes. Crystal and molecular structure of racemic [Ti(η5-C5H5)(η5-C 9H7)(CH2SiMe3)CI]
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New, selective and high-yielding preparations of the mixed-ring complexes [Ti(η5-C5H5)(η5-C 9H7)Cl2] and [Ti(η5-C5H5)(η5-C 5H4But)Cl2] are reported. These have been used to prepare a range of mono- and di-substituted titanium(IV) alkyl and benzenethiolate complexes of the form [Ti(η5-C5H5)(η 5-ring)(CH2SiMe3)Cl] and [Ti(η5-C5H5)(η5-ring)R 2] (ring = indenyl or C5H4But; R = Me, CH2Ph, CH2SiMe3 or SPh). While the indenyl ligand in the racemic, chiral-at-metal complex [Ti(η5-C5H5)(η5-C 9H7)(CH2SiMe3)Cl] is bound in an η5 fashion, X-ray structural data clearly indicate that there is some 'η3 ring-slip' character to the bonding. The NMR and nuclear Overhauser effect experiments conducted on [Ti(η5-C5H5)(η5-C 5H4But)(CH2SiMe3)Cl] demonstrate hindered rotation around the Ti-C5H4But bond and show the geometry to be fixed such that the But and SiMe3 groups are remote.
- Hart, Suzanne L.,Duncalf, David J.,Hastings, Jeremy J.,McCamley, Andrew,Taylor, Paul C.
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p. 2843 - 2849
(2007/10/03)
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