Titanium(IV) complexes with monocyclopentadienyl and phenoxy-alkoxo ligands: Synthesis,structures and catalytic properties for ethylene polymerization

Three monochlorotitanium complexes Cp′Ti(2,4-^tBu₂-6-(CPh₂O)C₆H₂O)Cl [Cp′ = η⁵-C₅H₅ (2), η⁵-C₅(CH₃)₅ (3), η⁵-C₅H₂Ph₂CH₃ (4)] have been synthesized in high yields (>90%) by the reaction of corresponding Cp′TiCl₃ with the dilithium salt of ligand 2,4-^tBu₂-6-(CPh₂OH)C₆H₂OH (1). When activated by [Ph₃C]⁺[B(C₆F₅)₄]⁻ and AlⁱBu₃, complexes 2–4 exhibit reasonable catalytic activity for ethylene polymerization, producing polyethylenes with moderate molecular weights and melting points. Addition of excess water to complex 2 gave the oxo-bridged complex [Ti(η⁵-C₅H₅)(2,4-^tBu₂-6-(CPh₂O)C₆H₂O)]₂O (5). Complexes 4 and 5 were characterized by single crystal X-ray diffraction.     

Synthesis,structure and catalytic properties of new half-titanocene complexes bearing substituted cyclopentadienyl and aryloxide ligands

New cyclopentadienyltitanium aryloxide complexes, 1-phenyl-2,3,4,5-Me4CpTi(O-2,6-ⁱPr₂-4-ⁿBu-C₆H₂)Cl₂ (1) and [4,4′-biphenyl-(2,3,4,5-Me₄Cp)₂][Ti(O-2,6-ⁱPr₂-4-ⁿBu-C₆H₂)Cl₂]₂ (2), have been prepared by treatment of cyclopentadienyltitanium trichloride complexes [PhMe₄CpTiCl₃ and 4,4′-biphenyl-(Me₄CpTiCl₃)₂] with 1 or 2 equiv of lithium salt of 2,6-di-isopropyl-4-butylphenol. Complexes 1 and 2 have been characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy. The molecular structure of 1 has been determined by single-crystal X-ray diffraction. Upon activation with ⁱBu₃Al and Ph₃CB(C₆F₅)₄, 1 and 2 both exhibit good catalytic activity for ethylene polymerization, producing polyethylene with moderate molecular weight and melting point.     

Synthesis of anilinonaphthoquinone-based nickel complexes and their application for olefin polymerization

A series of anilinonaphthoquinone-based nickel complexes, Ni(C₁₀H₅O₂NAr)(Ph)(PPh₃) (Ar = C₆H₃-2,6-Me (1c); Ar = C₆H₂-2,4,6-Me (2c); Ar = C₆H₃-2,6-Et (3c)), were synthesized and the structures of 1c-3c were confirmed by single crystal X-ray analyses. The anilinonaphthoquinone-ligated nickel complexes activated with B(C₆F₅)₃ showed high activities for ethylene polymerization at 40 °C under atmospheric pressure of ethylene and gave polyethylene with long chain branches and short chain branches. The activity of these systems was decreased by lowering polymerization temperature accompanied by increase in molecular weight. The number of the chain branches was also decreased with lowering polymerization temperature and increasing the bulkiness of the ligand.     

Highly fluorous zirconocene(IV) complexes and their catalytic applications in the polymerization of ethylene

The catalytic activities of the highly fluorous systems formed by the zirconocene(IV) complexes [Zr{η⁵-C₅H₄SiMe₂C₂H₄R_F}₂Cl₂] (R_F = C₆F₁₃ (4a), C₁₀F₂₁ (4b)) or [Zr-{η⁵-C₅H₃(SiMe₂C₂H₄C₆F₁₃)₂}₂Cl₂] (5a) and MMAO in toluene have been studied and compared with analogous nonfluorous systems generated from [Zr{η⁵-C₅H₄SiMe₃}₂Cl₂] and [Zr{η⁵-C₅H₅}₂Cl₂]. Although less active than the reference systems, the fluorous catalysts are stable over prolonged polymerization times, giving rise to polymers with similar molecular weights to those obtained with [Zr{η⁵-C₅H₄SiMe₃}₂Cl₂].     

New binuclear half-titanocene derivatives with aryl-substituted cyclopentadienyl ligands: synthesis,structures, and catalytic properties

Two binuclear oxo-bridged half-titanocene complexes, µ-oxo-bis[(1-aryl-2,3,4,5-tetramethylcyclopentadienyl)dichlorotitanium] [(ArMe₄CpTiCl₂)₂O, Ar?=?4- ⁱ PrC₆H₄ (3), 4- ^t BuC₆H₄ (4)], have been prepared by the treatment of 1-aryl-2,3,4,5-tetramethylcyclopentadienyltitanium trichloride [ArMe₄CpTiCl₃, Ar?=?4- ⁱ PrC₆H₄ (1), 4- ^t BuC₆H₄ (2)] with 0.5?equiv of H₂O. Complexes 3 and 4 have been characterized by elemental analysis and ¹H- and ¹³C-NMR (nuclear magnetic resonance; NMR) spectroscopies, and their molecular structures have been determined by X-ray crystallography. When activated with ⁱ Bu₃Al and Ph₃CB(C₆F₅)₄, complexes 3 and 4 both exhibit reasonable catalytic activity for ethylene polymerization (90?×?10³ to 280?×?10³?kg PE (mol?Ti)^?1?bar^?1?h^?1), producing polyethylenes with moderate molecular weight.     

New o-methoxyphenylcyclopentadienylchromium (III) complexes: Synthesis, structures and catalytic properties for ethylene polymerization

Two new ligands 1-(2-methoxyphenyl)-3,4-diphenylcyclopentadiene (1) and 1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadiene (2), as well as their corresponding cyclopentadienylchromium complexes η⁵-1-(2-methoxyphenyl)-3,4-diphenylcyclopentadienyl chromium dichloride (3) and η⁵-1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadienyl chromium dichloride (4) were synthesized and characterized. Molecular structures of 3 and 4 were determined by single-crystal X-ray diffraction. Complexes 3 and 4 were tested as catalyst precursors for ethylene polymerization. When activated with Al(ⁱBu)₃ and , complex 3 shows reasonable catalytic activity while 4 exhibits high catalytic activity for ethylene polymerization. The effects of temperature and Al/Cr ratio on the catalytic activity were studied. The molecular weight and melting temperature of the produced polyethylenes were determined.     

Synthesis,structure and olefin polymerization catalysis of nickel(II) complexes bearing N,O-chelate ligands

Four β-ketoimine ligands (two series) were prepared through traditional condensation reactions of β-diketones with 2,6-substituted anilines. Reaction took place only at the cyclohexanone carbonyl rather than at the acetyl or benzoyl carbonyl, even if more than two equivalents of the amines were added. Consequently, four new moisture- and air-stable bis(β-ketoamino)nickel(II) complexes, Ni[2–CH₃C(O)C₆H₈(=NAr)]₂ (Ar?=?2, 6-iPr₂C₆H₃, (1); Ar?=?2, 6-Me₂C₆H₃, (2) and Ni[2–PhC(O)C₆H₈(=NAr)]₂ (Ar?=?2, 6-iPr₂C₆H₃, (3); Ar?=?2, 6-Me₂C₆H₃, (4) were obtained and characterized. The solid-state structures of complex 1, 2 and 3 have been determined by single-crystal X-ray diffraction. Additionally, these complexes can be applied as highly active catalyst precursors for vinyl polymerization of norbornene (NBE) after activation with methylaluminoxane (MAO).     

New Half-sandwich Zirconium（IV） Complexes Containing Salicylaldimine Ligands： Synthesis,Characterizations and Catalytic Properties

Two new half-sandwich zirconium（IV） complexes bearing salicylaldimine ligands of the type Cp＊Zr[2-tBu-4-R-6-（CH=NiPr）C6H2O]C12[R=H（1）, tBu（2）] were prepared by the reaction of Cp＊ZrC13 with the corresponding lithium of salicylaldimine ligands 2-tBu-4-R-6-（CH=NiPr）C6H2OLi[R=H（LiLa）, tBu（LiLb）]. Com- plexes 1 and 2 were characterized by 1H NMR, BC NMR spectroscopy and elemental analysis. When activated with AliBu3 and Ph3CB（C6F5）4, both complexes 1 and 2 exhibited reasonable catalytic activities for ethylene polymeriza- tion, producing polyethylenes with moderate molecular weight. Complexes 1 and 2 also exhibited reasonable catalyt- ic activities for ethylene copolymerization with 1-hexene, producing poly（ethylene-co-l-hexene）s with moderate molecular weight and reasonable 1-hexene content.     

Syntheses and structures of non-symmetric guanidinato zirconium and hafnium complexes and their catalytic behavior for ethylene polymerization

Equivalent addition reactions of PhN(Li)SiMe₃ to nitriles, RCN (R = dimethylamido, 1-piperidino), generated non-symmetric guanidinato lithium [(Et₂O)LiN(SiMe₃)C(NMe₂)N(Ph)]₂ (1) or [(THF)LiN(SiMe₃)C(NMe₂)N(Ph)]₂ (2) and [(Et₂O)LiN(SiMe₃)C(N(CH₂)₅)N(Ph)]₂ (5) which further reacted with zirconium or hafnium tetrachloride to form Zr and Hf guanidinato complexes with the general formula [PhNC(R)NSiMe₃]₃MCl (R = dimethylamido, M = Zr (3), Hf (4); R = 1-piperidino, M = Zr (6), Hf (7)). Complexes 1-4, 6 and 7 were well characterized by ¹H, ¹³C NMR and microanalysis, the single crystal X-ray diffraction analysis data for complexes 1, 3, 4 and 7 were also provided. Furthermore, complexes 3, 4, 6 and 7 were found to be active for ethylene polymerization. The influences of cocatalyst, pressure, reaction temperature and Al/M ratio on activity were investigated.     

Titanium complexes bearing bidentate benzimidazole-containing ligands and their behavior in ethylene polymerization

A series of potentially bidentate benzimidazolyl ligands of the type (Bim)CH₂D (where Bim = benzimidazolyl and D = NMe₂L1, NEt₂L2, NPrⁱ₂L3, OMe L4 and SMe L5) has been reacted with Ti(NMe₂)₄ to give five- and six-coordinate Ti(IV) complexes of the type [(Bim)CH₂D]Ti(NMe₂)₃ and [(Bim)CH₂D]₂Ti(NMe₂)₂, respectively. The X-ray structures of [(Bim)CH₂OMe]Ti(NMe₂)₃, [(Bim)CH₂NMe₂]₂Ti(NMe₂)₂ and [(Bim)CH₂OMe)]₂Ti(NMe₂)₂ are reported along with an evaluation of their behavior in ethylene polymerization.     

Bis(pyrrolide-imine) Ti complexes with MAO: A new family of high performance catalysts for olefin polymerization

This contribution reports on the syntheses, structures and olefin polymerization behavior of Ti complexes having a pair of chelating pyrrolide-imine [N⁻,N] ligands. X-ray analyses as well as ¹H NMR studies demonstrate that bis(pyrrolide-imine) Ti complexes (named PI Catalysts) contain approximately octahedrally coordinated metal centers with mutually trans-pyrrolide-Ns, cis-imine-Ns and cis-Cls. DFT studies suggest that PI Catalysts, when activated, provide a metal alkyl in the cis position to a vacant coordination site for monomer binding. These theoretical studies also show that the active species derived from PI Catalysts normally possess higher electrophilicity and a sterically more open nature compared with those produced using bis(phenoxy-imine) Ti complexes (Ti-FI Catalysts) which are known as high performance olefin polymerization catalysts. These structural as well as electronic features suggest that PI Catalysts have high potential for the polymerization of olefinic monomers.Unlike high performance Ti-FI Catalysts, PI Catalysts do not require the presence of steric bulk in close proximity to the anionic donor. PI Catalysts combined with MAO display high ethylene polymerization activities (max. 33,200 kg-polymer/mol-cat/h, 25 °C, atmospheric pressure) comparable to those obtained with early group 4 metallocene catalysts (e.g., Cp₂TiCl₂ 16,700 kg-polymer/mol-cat/h) under identical conditions. As expected, PI Catalysts exhibit higher incorporation capability for propylene and 1-hexene relative to FI Catalysts though the incorporation levels are lower than those for Cp₂TiCl₂. To our surprise, PI Catalysts/MAO show remarkably high norbornene (NB) incorporation, superior to that seen with the [Me₂Si(Me₄Cp)N-tBu]TiCl₂ (CGC) catalyst system, and they readily form ethylene-NB copolymers with high NB contents. The highly electrophilic and sterically open nature is probably responsible for the high NB affinity. Additionally, PI Catalysts/MAO possess characteristics of living ethylene polymerization (though under limited conditions) and afford high molecular weight PEs with very narrow molecular weight distributions (M_n 225,000, M_w/M_n 1.15, 10-s polymerization, 25 °C). Moreover, these catalysts can copolymerize ethylene and NB in a highly controlled living manner to afford monodisperse alternating copolymers with very high molecular weights (M_n > 500,000, M_w/M_n < 1.2) at room temperature. This unique living nature allows the preparation of a number of ethylene- and NB-based block copolymers, including PE-b-poly(ethylene-co-NB) and poly(ethylene-co-NB)_a-b-poly(ethylene-co-NB)_b, in which each segment contains a different NB content. These are probably the first examples of the syntheses of block copolymers from ethylene and NB. Consequently, the discovery and application of PI Catalysts has exercised a significant influence on olefin polymerization catalysis and polymer synthesis.     

Non-Cp type homogeneous catalytic systems for olefin polymerization

Development of homogeneous metallocene catalysts for olefin polymerization has been briefly overviewed prior to detailed examination of the chemistry of non-Cp type homogeneous catalytic systems. In order to emphasize the structural characteristics of non-Cp catalysts, they were initially classified according to the coordination numbers of 4-7 and then further subclassified according to the ligand types. Over 100 line drawings and 200 references are utilized.     

Synthesis, structure and ethylene polymerization behavior of titanium phosphinoamide complexes

(Phosphinoamide)(cyclopentadienyl)titanium(IV) complexes of the type Cp*TiCl₂(η²-Ph₂PNR) [Cp*=C₅Me₅; R = t-Bu (2a), R = n-Bu (2b), R = Ph (2c)] have been prepared by the reaction of Cp*TiCl₃ with the corresponding lithium phosphinoamides. The structure of Cp*TiCl₂(η²-Ph₂PN^tBu) (2a) and Cp*TiCl₂(η²-Ph₂PNPh) (2c) have been determined by X-ray crystallography. These complexes exhibited moderate catalytic activities for ethylene polymerization in the presence of modified methylaluminoxane (MMAO). Catalytic activity of up to 2.5 × 10⁶ g/(mol Ti h) was observed when activated by i-Bu₃Al/Ph₃CB(C₆F₅)₄.     

Titanium complexes with novel triaryl-substituted phosphinimide ligands: Synthesis, structure and ethylene polymerization behavior

A series of titanium phosphinimide complexes [Ph₂P(2-RO-C₆H₄)]₂TiCl₂ (7, R = CH₃; 8, R = CHMe₂) and [PhP(2-Me₂CHO-C₆H₄)][THF]TiCl₃ (9) have been prepared by reaction of TiCl₄ with the corresponding phosphinimines under dehalosilylation. The structure of complex 9 has been determined by X-ray crystallography, and a solvent molecule THF was found to be coordinated with the central metal and the Ti-O bond was consistent with the normal Ti-O (donor) bond length. The complexes 7 and 8 displayed inactive to ethylene polymerization, and the complex 9 displayed moderate activity in the presence of modified methylaluminoxane (MMAO) or i-Bu₃Al/Ph₃CB(C₆F₅)₄, and this should be partly attributed to coordination of THF with titanium and the steric effect of two iso-propoxyl. And catalytic activity up to 32.2 kg-PE/(mol-Ti h bar) was observed.     

二甲基二茂锆化合物(1,2-Ph2-4-MeCp)2 ZrMe2的合成及催化乙烯聚合反应研究

在惰性气氛下, 用2 mol甲基锂处理二(1,2-二苯基-4-甲基环戊二烯基)二氯化锆, 合成了大立体位阻的二甲基二茂锆化合物[(1,2-Ph2-4-MeCp)2ZrMe2]. 经元素分析、 核磁共振氢谱、 碳谱和X射线晶体衍射分析, 确定了该化合物的结构. 经Al( i Bu)3/Ph3C+B(C6F5)-4活化, 该化合物催化乙烯聚合反应显示出较高的催化活性, 生成高分子量及高熔点聚乙烯. 该体系的特点是在较低的n(Al)/n(Zr)比下即可有效地催化乙烯聚合.     

Cationic rare earth metal alkyls as novel catalysts for olefin polymerization and copolymerization

Cationic rare earth metal alkyl species, generated by the treatment of mono(cyclopentadienyl) bis(alkyl) rare earth metal complexes with 1 equiv. of a borate compound such as [Ph₃C][B(C₆F₅)₄], act as an excellent catalyst for the polymerization and copolymerization of various olefins such as ethylene, 1-hexene, styrene, norbornene, dicyclopentadiene, and isoprene. These catalysts show unprecedented activity and regio- and stereo-selectivity and afford a series of new polymers which are difficult to be prepared previously.     

Zirconocene complexes with a biphenyl substituted cyclopentadienyl ligand: synthesis, characterization, and olefin polymerization behavior

Novel zirconocene complexes (1-Biph-3,4-Me₂Cp)₂ZrCl₂ (3), (C₅Me₅)(1-Biph-3,4-Me₂Cp)ZrCl₂ (4), and (C₅H₅)(1-Biph-3,4-Me₂Cp)ZrCl₂ (5) containing a 1-biphenyl-3,4-dimethylcyclopentadienyl ligand (2) have been prepared and their solid state structures were characterized by X-ray diffraction method. The crystal structure of 3 revealed a racemic, C₂-symmetric nature in the solid state. In ethylene polymerization, they all afforded high-density polyethylene with very high activity. Especially, the catalytic properties of 3 were most marked in terms of both polymerization activity and molecular weight of polyethylene among them. They also showed good activity on the polymerization of propylene, but afforded nearly atactic, amorphous polypropylenes with a little higher [mmmm] methyl pentad values by 3 and 4 than that by the most active 5 under the given reaction conditions.     

四甲基环戊二烯基苯氧基二氯化钛衍生物的合成及催化烯烃聚合研究

4-R1-6-R-2-Me4CpH—PhOH[R1=^tBu,R=^tBu(1);R1=H,R=^tBu(2),Ph(3),Me(4)]经双三甲基硅基化后与TiCl4反应,合成了4种限制几何构型茂金属催化剂4-R1-6-R-2-Me4CpH-PhOTiCl2[R1=^tBu,R=^tBu(5);R1=H,R=^tBu(6),Ph(7),Me(8)]。合成产率有较大提高．这些茂金属化合物经过^tBu3Al和Ph3C^ B(C6F5)4^-活化后对乙烯聚合有很好的催化活性,并生成乙基支化聚乙烯．考察了催化剂结构与活性的关系以及聚合反应条件对催化剂性能的影响。并对聚乙烯样品进行了表征．