- Di- and trinuclear iron/titanium and iron/zirconium complexes with heterocyclic ligands as catalysts for ethylene polymerization
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The properties of polyolefin resins depend very much on their molecular weights, the amount of side chain branchings and molecular weight distributions. One way to obtain such tailored products in only one reaction step consists in the application of dissymmetric multi nuclear catalysts with different active sites. Since every active site is producing its own polymer, a “molecular blending” is the result. In order to reach this goal, a variety of mono, di- and trinuclear complexes of iron, titanium and zirconium, containing 2,6-bis(aryliminoethyl)pyridine and phenoxyimine building blocks have been synthesized and characterized. The reaction of iodo functionalized 2,6-bis(arylimino-ethyl)pyridine derivatives with alkyne functionalized phenoxyimine compounds via Sonogashira cross-coupling reactions results in ligand precursors that can provide coordination sites for two different metals. Trinuclear complexes with the combinations Ti/Fe and Zr/Fe, each molecule containing two iron atoms in two 2,6-bis(aryliminoethyl)pyridine units, gave the best ethylene polymerization results. Due to fast ligand exchange reactions, dinuclear iron/titanium complexes could not be isolated from reactions of mono(phenoxyimine) titanium complexes and the coupled bis(chelate) ligand precursor. Since the metal centers show their best performances at different polymerization temperatures, the compositions (and, therefore, the molecular weight distributions) of the desired polyethylenes may be adjusted by a simple change of the reaction temperature.
- G?rl, Christian,Betthausen, Eva,Alt, Helmut G.
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- Bis(arylimino)pyridine derivatives of Group 4 metals: Preparation, characterization and activity in ethylene polymerization
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Titanium tetrachloride reacts with 2,6-bis[(1-phenylimino)ethyl]pyridine, 1, and 2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine, 2, giving the adducts of general formulae [Ti(1)Cl3]Cl, 3, and [Ti(2)Cl 3]Cl, 6, the latter through the intermediacy of the covalently bonded [Ti(2)Cl4], 4. Heating 6 leads to reduction to the titanium(III) derivative [Ti(2)Cl3], 12, the latter characterized by X-ray diffraction methods. The reaction of [Ti(1)Cl3]Cl with a toluene solution of MAO proceeds with methylation at the ortho-position of the pyridine ring to give the titanium(IV) derivative [Ti(C22H21N 3)Cl3], 8. The reaction of [Ti(2)Cl3]Cl with MAO gives a mixture of products containing [Ti(2)Cl2(OAlCl 3)], 9. Compound 9, which has been prepared independently by reacting 6 with AlOCl, is a rare case of a compound containing the -OAlCl3 moiety, as shown by a single-crystal X-ray diffraction study. From the tetrachlorides of zirconium and hafnium with 1 or 2, the corresponding adducts [M(L)Cl4] have been obtained in high yields. These derivatives of Group 4 metals act as ethylene polymerization catalytic precursors: the substitution of the phenyl ring of the imino fragment strongly influences the catalytic activity which is 5,544 kgPE molTi-1 h-1 in the case of 3 and 267 kgPE molTi -1 h-1 with 6. Catalytic activity has been observed for zirconium and hafnium too, the activity decreasing from zirconium to hafnium, under comparable conditions. The Royal Society of Chemistry 2005.
- Calderazzo, Fausto,Englert, Ulli,Pampaloni, Guido,Santi, Roberto,Sommazzi, Anna,Zinna, Marianna
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p. 914 - 922
(2007/10/03)
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- The synthesis, structure and catalytic activity of mono(salicylaldiminato) titanium complexes
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The synthesis of mono(salicylaldiminato) complexes of titanium was reported. The catalytic activity of the compounds to the polymerization of ethene was studied. The complexes were shown to give good productivities for ethene polymerization when activated by methylaluminoxane. The results were found to comparable with those obtained for cyclopentadienyl salicylaldiminato titanium complexes.
- Pennington, Dale A.,Hughes, David L.,Bochmann, Manfred,Lancaster, Simon J.
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p. 3480 - 3482
(2007/10/03)
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- Synthesis and characterization of titanium(IV) complexes containing the diphenylphosphino- and diphenylthiophosphoryl-functionalized cyclopentadienyl ligand. Crystal and molecular structure of Ti(η5-C5H4PPh2)Cl3
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The trimethylsilyl cyclopentadiene derivative C5H4(SiMe3)PPh2 (1) was treated with TiCl4 to give the air- and moisture-sensitive mono(cyclopentadienyl) compound Ti(η5-C5H4PPh2)Cl3 (4). Reaction of 4 with Mg(CH2C6H5)2(THF)2 gave Ti(η5-C5H4PPh2)(CH2C6H5)3 (5). Reactions of the lithium and thallium derivatives M{C5H4P(S)Ph2} (M=Li (2), Tl (3)) with one equiv. of TiCl4 afforded the mono(cyclopentadienyl) complex Ti{η5-C5H4P(S)Ph2}Cl3 (6), whereas reaction with 0.5 equiv. of TiCl4 gave the bis(cyclopentadienyl) complex Ti{η5-C5H4P(S)Ph2}2Cl2 (8). Compound 6 was also isolated as a minor product from the reaction of Ti{η5-C5H4P(S)Ph2}2Cl2 (8) with one equiv. of TiCl4. The major product was identified as an inseparable mixture of two compounds [Ti{η5-C5H4P(S)Ph2}2Cl2·TiCl4]n (7a and 7b). Reaction of Ti(η5-C5H5)Cl3 with 3 afforded the `mixed-ring' bis(cyclopentadienyl) complex Ti{η5-C5H4P(S)Ph2}(η5-C5H5)Cl2 (9). Compounds 6-9 are very moisture-sensitive and easily decompose to form the cyclopentadiene C5H5P(S)Ph2. Structural data of these complexes indicate η5-coordination of the substituted cyclopentadienyl ligands and this coordination mode was confirmed by X-ray crystal structure analysis of compound 4.
- Flores, Juan C.,Hernández, Rocío,Royo, Pascual,Butt, Angelika,Spaniol, Thomas P.,Okuda, Jun
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p. 202 - 210
(2007/10/03)
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- Electronic structure of titanium tetrachloride complexes
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Chlorine Kα-line and 35Cl NQR frequency shifts were measured for a series of titanium tetrachloride complexes. Ab initio calculations of the electronic structure of the corresponding free ligands were performed at the MP2/6-31G* level. The dependences of the obtained results on the experimental and calculated parameters characterizing the donating abilities of the ligands were analyzed. The electron density on the chlorine atoms of the acceptor is mainly determined by the polarization effects, while the electric field gradient at the Cl nuclei is mainly due to the multiplicity of the metal-chlorine bonds.
- Dolenko,Poleshchuk,Gostevskii,Latoshinska,Ostafin
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p. 744 - 747
(2008/10/09)
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- New 2-tetrahydrofurfuryloxotitanium(IV) intermediates for the synthesis of olefin polymerization catalysts
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The complexes [TiCl3(tmen){η1-OCH2CH(CH2) 3O}] 1, [Ti2(μ-Cl)2Cl4{η2-OCH 2CH(CH2)3O}2] 2 and [TiCl4(tmen)] 3 (tmen = Me2NCH2CH2NMe2) have been synthesized and structurally characterized by X-ray diffraction. The crystals of 1 consist of monomeric [TiCl3(tmen){η1-OCH2CH(CH2) 3O}] molecules. Three chloride, one oxygen and two nitrogen atoms form a distorted octahedron around the titanium atom. Compound 2 has a dimeric structure. Each titanium atom is surrounded by two bridging chloride atoms, two terminal chloride atoms and two oxygen atoms of the 2-tetrahydrofurfuryloxide ligand. The crystals of compound 3 consist of monomeric molecules in which four terminal chloride atoms and two nitrogen atoms from the chelate tmen ligand form a distorted octahedron around Ti. High catalytic activity was found for 1 and 2.
- Sobota, Piotr,Utko, Jozef,Szafert, Slawomir,Szczegot, Krzysztof
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p. 679 - 683
(2007/10/03)
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- Complexation and Exchange Reactions of some Dimethylamino-substituted Group 4 Compounds
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Reactions of CH2(NMe2)2, (1), SiMe2(NMe2)2, (2), (cp=η-cyclopentadienyl), (3), and , (4), with covalent metal halides MCl4 (M=Ti,Zr,Si,Ge,or Sn) and MCl3 (M=Ti,V,or Cr) fall into two categories: (a) N-donor chelation leading to complex formation and (b) halide-NMe2 exchange.Compound (1) gives 1:1 complexes with MCl4 (M=Ti or Sn) and 2:1 complex with VCl3.Compound (2) provides 1:1 complexes with MCl4 (M=Ti,Zr,Hf, or Sn).The decomposition of TiCl4*SiMe2(NMe2)2 --> invariably occurs in both the solid state and solution.There is no reaction of (2) with metal(III) chlorides.With MCl4 (M=Si or Ge 'scrambling' reactions involving halide-NMe2 exchange occur and these have been monitored by 1H n.m.r. spectroscopy.Reactions of (3) and (4) with MCl4 (M=Si,Ge,Sn,Ti,Zr,or Hf) consistently feature halide-NMe2 exchange rather than adduct formation.All complexes have been characterised by analytical and spectroscopic (1H n.m.r. and i.r.) investigations.
- Wade, Steven R.,Willey, Gerald R.
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p. 1264 - 1267
(2007/10/02)
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