Electron effect of p-substituent on iron(II) and cobalt(II) pyridinebisimine catalyst for ethylene polymerization

A series of 2,6-bis(imino)pyridyl iron and cobalt complexes bearing p-substituent [2,6-(ArN=CMe)(2)C5H3N]-MCl2 (Ar=2,6-Me2C6H3, 2,4,6-Me3C6H2, 2,6-Me-2-4-BrC6H2, 2,6-Me-2-4-ClC6H2, 2,4-Me-2-6-BrC6H2, 2,4-Me-(2)-6-ClC6H2, while M=Fe, Co) have been synthesized and investigated as catalysts for ethylene polymerization in the presence of modified methylaluminoxane as a cocatalyst. The electron effect and positions of the substitueni of pyridinebisimine ligands were observed to affect considerably catalyst activity and polymer property.

Ethylene polymerization with porous polystyrene spheres supported Cp2ZrCl2 catalyst

A catalyst with porous polystyrene beads supported Cp2ZrCl2 was prepared and tested for ethylene polymerization with methylaluminoxane as a cocatalyst. By comparison, the porous supported catalyst maintained higher activity and produced polyethylene with better morphology than its corresponding solid supported catalyst. The differences between activities of the catalysts and morphologies of the products were reasonably explained by the fragmentation processes of support as frequently observed with the inorganic supported Ziegler-Natta catalysts. Investigation into the distribution of polystyrene in the polyethylene revealed the fact that the porous polystyrene supported catalyst had undergone fragmentation during polymerization.

Novel, highly active binuclear 2,5-disubstituted Amino-p-benzoquinone-nickel(II) ethylene polymerization catalysts

Reaction of salts of the 2,5-disubstituted amino-p-benzoquinone bridging ligand (la-e) with trans-bis(triphenylphosphane)phenylnickel(II) chloride results in the binuclear complexes 2a-e, which show high activities for ethylene polymerization without any cocatalysts. High-molecular-weight, moderately branched polyethylene of broad molecular-weight distribution was obtained.

Ethylene polymerization by self-immobilized neutral nickel catalysts bearing allyl groups

[Ni(Ph)(PPh3)(N,O)] complexes containing phenyliminophenolato ligands (N,O) (1: N,O = A; 2: N,O = B; 3: N,O = Q 4: N,O = D; 5: N,O = E) have been synthesized and characterized. The molecular structure of 4 was determined by single-crystal X-ray analysis. Complexes 2-5 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization without the use of co-catalysts. The high ethylene polymerization activities of ca. 10(5) g.PE mol(-1) Ni.h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene could be accomplished by changing the ligand structures and reaction conditions. The self-immobilization of catalysts brings about a dramatic increase in the catalytic activities of ethylene polymerization.

Polymer immobilized silane bridged metallocene catalysts for ethylene polymerization

Ansa-zirconocene complex with an allyl substituted silane bridge [(CH2=CHCH2)CH3Si(C5H4)(2)]ZrCl2 (1a) has been synthesized and characterized. The molecular structure of la has been determined by X-ray crystallographic analysis. The polymer immobilized metallocene catalyst 1b is prepared by the co-polymerization of la with styrene in the presence of radical initiator. The result of ethylene polymerization showed that the polymer immobilized metallocene catalyst kept high activity for ethylene polymerization and was a potential supported catalyst for olefin polymerization.

Self-immobilized catalysts for ethylene polymerization: neutral, single-component salicylaldiminato phenyl nickel(II) complexes bearing allyl substituents

A new family of self-immobilized ethylene polymerization catalysts, derived from neutral, single-component salicylaldiminato phenyl nickel complexes, is described.

Synthesis of lanthanide-alkylaluminium bimetallic complexes and studies on their catalytic activities for polymerization of some polar monomers

Three new lanthanide (Ln)-alkylaluminium (Al) bimetallic complexes with the formula [(mu-CF3CO2)(2)Ln(mu-CF3CHO2)AIR(2) . 2THF](2) (Ln = Nd, Y, R=i-C4H9 (i-Bu); Ln=Eu, R=C2H5(Et); THF=tetrahydrofuran) were synthesized by the reaction of Ln(CF,CO,), (Ln=Nd, Y) with HAI (i-Bu)(2) and of Eu(CF3CO2)(3) with AlEt(3), respectively. Their crystal structures were determined by X-ray diffraction at 233 K. [(mu-CF3CO2)(2)Nd (mu-CF3CHO2)Al(i-Bu)(2) . 2THF](2) (Nd-Al) and [(mu-CF3CO2)(2)Y(mu-CF3CHO2)Al(i-Bu)(2) . 2THF](2) (Y-Al) are isomorphous and crystallize in space group with a=12.441(3) Angstrom [12.347(5) Angstrom for Y-Al], b=12.832(3) Angstrom [12.832(4) Angstrom], c=11.334(3) Angstrom [11.292(8) Angstrom], alpha=104.93 (2)degrees [104.45(4)degrees], beta=98.47(2)degrees [98.81(4)degrees], gamma=64.60(2)degrees [64.30(3)degrees], R=0.519 [0.113], R(w)=0.0532 [0.110], Z=1 and [(mu-CF3CO2)(2)Eu(CF3CHO2)AlEt(2) . 2THF](2)(Eu-Al) in space group P2(1)/n with a=11.913(6) Angstrom, b=14.051(9) Angstrom, c=17.920(9) Angstrom, alpha=101.88(11)degrees, beta=gamma=90 degrees, R=0.0509, R(w)=0.0471 and Z=2. The six CF3CO2- (including CF3CHO2-) of each complex, among which pairs are equivalent, coordinated to Ln and Al in three patterns: (A) the two oxygen atoms in one of the three CF3CO2- type coordinated to two different Ln; (B) the two oxygen atoms in the second of CF3CO2- type coordinated to Ln and Al, respectively; (C) one of the two oxygen atoms in the third CF3CO2- type bidentately coordinated to two Ln and another oxygen coordinated to Al and one of the two Ln, respectively. Unlike types A and B, in type C the carboxyl carbon with a hydrogen atom bonded to it was found to appear as an sp(3)-hybridized configuration rather than an sp(2)-one. 1D and 2D NMR results further confirmed the existence of such a disproportionated CF3CHO2- ligand. Methyl methacrylate (MMA) and epichlorohydrin (ECH) could be polymerized by Y-Al or Eu-Al as a single-component catalyst and highly syndiotactic poly(MMA) was obtained. THF could also be polymerized by Y-Al in the presence of a small amount of ECH.

Cortactin mediated morphogenic cell movements during zebrafish (Danio rerio) gastrulation

Cell migration is essential to direct embryonic cells to specific sites at which their developmental fates are ultimately determined. However, the mechanism by which cell motility is regulated in embryonic development is largely unknown. Cortactin, a filamentous actin binding protein, is an activator of Arp2/3 complex in the nucleation of actin cytoskeleton at the cell leading edge and acts directly on the machinery of cell motility. To determine whether cortactin and Arp2/3 mediated actin assembly plays a role in the morphogenic cell movements during the early development of zebrafish, we initiated a study of cortactin expression in zebrafish embryos at gastrulating stages when massive cell migrations occur. Western blot analysis using a cortactin specific monoclonal antibody demonstrated that cortactin protein is abundantly present in embryos at the most early developmental stages. Immunostaining of whole-mounted embryo showed that cortactin immunoreactivity was associated with the embryonic shield, predominantly at the dorsal side of the embryos during gastrulation. In addition, cortactin was detected in the convergent cells of the epiblast and hypoblast, and later in the central nervous system. Immunofluorescent staining with cortactin and Arp3 antibodies also revealed that cortactin and Arp2/3 complex colocalized at the periphery and many patches associated with the cell-to-cell junction in motile embryonic cells. Therefore, our data suggest that cortactin and Arp2/3 mediated actin polymerization is implicated in the cell movement during gastrulation and perhaps the development of the central neural system as well.

A new post-metallocene-ti catalyst with maltolate bidentade ligand: an investigation in heterogeneous polymerization reactions in different mesoporous supports

A new titanium catalyst easily synthesized from ethylmaltol bidentate chelator ligand was studied in homogeneous and heterogeneous ethylene polymerization. The dichlorobis(3-hydroxy-2-ethyl-4-pyrone)titanium(IV) complex was characterized by 1H and 13C NMR (nuclear magnetic resonance), UV-Vis and elemental analysis. Theoretical study by density functional theory (DFT) showed that the complex chlorines exhibit cis configuration, which is important for the activity in olefin polymerization. The complex was supported by two methods, direct impregnation or methylaluminoxane (MAO) pre-treatment, in five mesoporous supports: MCM-41 (micro and nano), SBA-15 and also the corresponding modified Al species. All the catalytic systems were active in ethylene polymerization and the catalytic activity was strongly influenced by the method of immobilization of the catalyst and the type of support.

Organotitanium and niobium chemistry. I. Structure and reactivity of a titanium ethylene complex. II. Reactivity of decamethyl niobocene derivatives

The synthesis and X-ray diffraction study of bis(pentamethylcyclopentadienyl) ethylene titanium (I) are reported. This complex represents the first example of an isolable ethylene adduct of a group IV metal, a key intermediate in Ziegler-Natta olefin polymerization schemes. While treatment of I with ethylene leads to only traces of polymer after months, I participates in a wide range of stoichiometric and catalytic reactions. These include the catalytic conversion of ethylene specifically to butadiene and ethane and the catalytic isomerization of alkenes. Detailed studies have been carried out on the stoichiometric reactions of I with nitriles and alkynes. At low temperatures, nitriles react to form metallacycloimine species which more slowly undergo a formal 1,3-hydrogen shift to generate metallacycloeneamines. The lowest energy pathway for this rearrangement is an intramolecular hydrogen shift which is sensitive to the steric bulk of the R substituent. The reactions of I with alkynes yield metallacyclopentene complexes with high regioisomer selectivity. Carbonylation of the metallacyclopentene (η-C₅Me₅5)₂TiC(CH₃)=C(CH₃)CH₂ under relatively mild conditions cleanly produces the corresponding cyclopentenone and [C₅(CH₃)₅]₂Ti(CO)₂. Compounds derived from CO₂ and acetaldehyde have also been isolated.

The synthesis and characterization of bis-(η-pentamethylcyclopentadienyl) niobium(III) tetrahydroborate (II) are described and a study of its temperature-dependent proton NMR spectroscopic behavior is reported. The complex is observed to undergo a rapid intramolecular averaging process at elevated temperatures. The free energy of activation, ΔG^≠ = 16.4 ± 0.4 kcal/mol, is calculated. The reinvestigation of a related compound, bis(η-cyclopentadienyl)niobium(III) tetrahydroborate, established ΔG^≠ = 14.6 ± 0.2 kcal/mol for the hydrogen exchange process. The tetrahydroborate complex, II reacts with pyridine and dihydrogen to yield (η-C₅Me₅5)₂NbH₃ (III). The reactivity of III with CO and ethylene is reported.

Investigations of the origin of stereocontrol in syndiospecific Ziegler-Natta polymerizations

In order to expand our understanding of the mechanism of stereocontrol in syndiospecific α-olefin polymerization, a family of Cs-symmetric, ansa-group 3 metallocenes was targeted as polymerization catalysts. The syntheses of new ansa-yttrocene and scandocene derivatives that employ the doubly [SiMe₂]- bridged ligand array (1,2-SiMe₂)₂{C₅H-3,5-(CHMe₂)₂} (where R = t- butyl, tBuThp; where R = i-propyl, iPrThp) are described. The structures of tBuThpY(µ-Cl)₂K(THF)₂, tBuThpSc(µ-Cl)₂K(Et₂O)₂, tBuThpYCH(SiMe₃)₂, Y₂{µ₂-(tBuThp)₂}(µ₂-H)₂, and tBuThpSc(µ-CH₃)₂ have been examined by single crystal X-ray diffraction methods. Ansa-yttrocenes and scandocenes that incorporate the singly [CPh₂]-bridged ligand array (CPh₂)(C₅H₄)(C₁₃H₈)(where C₅H₄ = Cp, cyclopentadienyl; where C₁₃H₈ = Flu, fluourenyl) have also been prepared. Select meallocene alkyl complexes are active single component catalysts for homopolymerization of propylene and 1-pentene. The scandocene tetramethylaluminate complexes generate polymers with the highes molecular weights of the series. Under all conditions examined atactic polymer microstructures are observed, suggesting a chain-end mechanism for stereocontrol.

A series of ansa-tantalocenes have been prepared as models for Ziegler-Natta polymerization catalysts. A singly bridged ansa-tantalocene trimethyl complex, Me₂Si(η⁵-C₅H₄)₂TaMe₃, has been prepared and used for the synthesis of a tantalocene ethylene-methyl complex. Addition of propylene to this ethylene-methyl adduct results in olefin exchange to give a mixture of endo and exo propylene isomers. Doubly-silylene bridged ansa-tantalocene complexes have been prepared with the tBuThp ligand; a tantalocene trimethyl complex and a tantalocene methylidene-methyl complex have been synthesized and characterized by X-ray diffraction. Thermolysis of the methylidene-methyl complex affords the corresponding ethylene-hydride complex. Addition of either propylene or styrene to this ethylene-hydride compound results in olefin exchange. In both cases, only one product isomer is observed. Studies of olefin exchange with ansa-tantalocene olefin-hydride and olefin-methyl complexes have provided information about the important steric influences for olefin coordination in Ziegler-Natta polymerization.

新型吡咯亚胺钒烯烃聚合催化剂的研究

本文的主要工作和研究结果如下： 1. 合成与表征了一系列吡咯亚胺钒(III)配合物。在Et2AlCl的活化下，它们能高效催化乙烯聚合，活性可高达48.6 kg PE/mmolVhbar，得到高分子量且分子量分布单分散的线性聚乙烯。吡咯亚胺钒催化体系具有较好的高温耐受性，即使在70 C下聚乙烯催化活性仅比50 C时下降30-40%，并且仍然比VCl3.(THF)3活性高,且分子量分布在70 C仍能保持2.5以下，说明催化剂是单活性基的。与单配的水杨醛亚胺钒催化剂相比，吡咯亚胺钒配合物具有更高的乙烯催化活性，得到具有更窄分子量分布的聚乙烯，说明具有五元环N,N螯合的吡咯亚胺配体能更好的稳定钒活性中心，增加催化剂的活性。 2. 通过采用烷基铝预先对功能性基团进行保护的方法，我们用吡咯亚胺钒/Et2AlCl催化体系实现了乙烯与一系列功能性单体如十一烯醇、十一烯酸甲酯、烯丁醇的共聚合。与其他共聚单体相比，十一烯醇的插入率更高。在温和条件下十一烯醇的插入率可以轻松达到15.8%，活性仍能保持1.4 kg/molVh。通过控制Al/V、共聚单体浓度、聚合温度等反应参数，共聚反应的活性、功能性单体插入率、以及共聚物的分子量可在很大范围内进行调控。 3．合成并表征了一系列双吡咯亚胺钒(Ⅲ)配合物，并初步研究了其乙烯聚合行为。在Et2AlCl和三氯乙酸乙酯的存在下，这些配合物具有优异的催化乙烯聚合的能力，其聚合活性可达28.8 kg PE/mmolVh。双吡咯亚胺钒(Ⅲ)配合物比单配的吡咯亚胺钒(Ⅲ)配合物具有更好的温度耐受性，随着温度的升高，乙烯聚合活性升高，70C时活性与50C时相当或者更高。 关键词：钒催化剂，乙烯聚合，乙烯与功能性单体共聚合

非茂过渡金属烯烃聚合催化剂的研究

本论文合成、表征了一系列以镍、钦为中心离子的非茂过渡金属配合物，研究了这些配合物催化烯烃聚合的反应行为。主要工作和结论如下：1．合成、表征了一系列水杨醛亚胺中性镍配合物。在改性甲基铝氧烷（MMAO）的活化下，这些中性镍配合物可高效催化降冰片烯伽BE）的加成聚合，在优化条件下，催化活性高达7.1×107 gPNBE／molNi.h，聚降冰片烯的分子量高达1.5×106g／mol。2．合成、表征了三种新型p一二酮单亚胺中性镍配合物。X-射线分析表明，这些中性镍配合物的空间构型为扭曲的平面四边形。在Ni（CO）2的活化下，这些中性镍配合物可催化乙烯聚合生成以甲基支化为主的支化聚乙烯。在MMAO的活化下，这些中性镍配合物是降冰片烯加成聚合的高效催化剂，在优化条件下，催化活性高达4.5×107gPNBE／molNi.h，聚降冰片烯的分子量高达1.1×106g／mol。另外，这些中性镍配合物在MMAO的活化下，可催化甲基丙烯酸甲酷（MMA）聚合，生成富间规的聚甲基丙烯酸甲酷（rr一70％）。令人惊讶的是，这些中性镍配合物／MMAO体系还能催化乙烯和MMA的共聚合反应，生成乙烯与MMA的无规共聚物，极性单体的插入率可达16.7 mol％。3．合成、表征了一系列新型β-二酮单亚胺钦配合物。X-射线分析表明，这些钦配合物的立体构型为含有一个CZ轴的变形八面体。常温下，这些钦配合物在MMAO的活化下，可以高效催化乙烯活性聚合，催化活性可达1.3×l06g PE/molTi-h，生成无支链的线性聚乙烯。常温下，这些钦配合物瓜IMAO体系还能高效催化乙烯和降冰片烯的活性共聚合反应，催化活性高达3.2×106gpolymer／molTi'h，所得聚合物为乙烯与降冰片烯的交替共聚物（COC）。利用该催化体系的活性聚合性质，制备了包含半晶和无定形两种结构片段的新型A-B二嵌段共聚物（PE-b1ock-COC）。4．合成、表征了一系列新型β-二亚胺钦配合物。在MMAO的活化下，这些钦配合物可以常温催化乙烯聚合，在优化条件下，催化活性可达4.6×105 gPe／molTi-h，生成双峰分布的聚乙烯，重均分子量高达6.6×105g／mol。

过渡金属烯烃聚合催化剂的研究

本论文合成、表征了一系列以铁、钻、镍、铬为中心离子的非茂过渡金属配合物，研究了这些配合物催化烯烃聚合的反应行为。主要工作和结论如下：1，合成、表征了一系列苯环邻、对位含取代基的毗咤双亚胺铁、钻乙烯聚合催化剂。在改性甲基铝氧烷（MMAO）的活化下，这些配合物可高效催化乙烯聚合。在优化条件下，研究了邻、对位取代基电子效应对催化活性的影响。对于铁催化剂来说，不仅邻位取代基体积的大小对乙烯的插入及所得聚合物的分子量有微调作用，对位取代基的电子效应也对催化活性和聚合物分子量影响也很大。2．我们在单核毗咤双亚胺铁催化剂的基础上，设计合成了环状三核铁催化剂。这种环状三核铁催化剂的活性中心位于环状结构的内部。在有机铝的活化下，可高效催化乙烯聚合。新的催化剂展示出更长的催化剂寿命，与单核铁催化剂相比，性能上得到非常大的改善，不但能防止催化剂分子间的失活，还可有效抑制链转移反应的发生。3．在MMAO的活化下，吡啶双亚胺铁可催化（甲基）丙烯酸酷的聚合。催化MMA的聚合时，得到低分子量、窄分布的间规PMMA；催化BMA的聚合时，活性很高，得到无规、低分子量的PBMA；催化丙烯酸酷聚合时，不仅活性高，而且易得到高分子量的聚合物。催化活性、聚合物产率、立构规整度、分子量及分子量分布都会受到反应参数、催化剂结构及助催化剂的性质的影响。4．合成、表征了一系列带有不同取代基的份二亚胺镍催化剂。在MMAO的活化下，这些镍配合物可以高效催化乙烯聚合。不仅邻位取代基体积的大小对乙烯的插入及所得聚合物的分子量有微调作用，对位取代基的电子效应也对催化活性、聚合物分子量及其支化度也有很大的影响。5．合成、表征了一系列新型二苯硫醚双亚胺铬催化剂。在MMAO的活化下，这些铬配合物可常温催化乙烯聚合，生成具有宽分布的聚乙烯。配体结构以及聚合条件对催化剂的活性及所得聚合物的性质有很大影响。

O-2 activation and hydrolysis of Salan rare-earth metal alkyl complexes

Salan ligated yttrium alkyl complex 1, (LY)-Y-1(CH2SiMe3)(THF) (Salan = L-1: [2-O-3,5-tBu(2)-C6H2CH2N(CH3) CH2](2)), was exposed to an oxygen/ nitrogen atmosphere to give a bimetallic alkoxide complex 4, [(LY)-Y-1(mu-OCH2SiMe3)](2). Whilst the lutetium counterparts 2 ((LLu)-Lu-1(CH2SiMe3)(THF)) and 3 ((LLu)-Lu-2(CH2SiMe3)(THF); L-2: [2-O-3-tBu-C6H2CH2N(CH3) CH2](2)) were hydrolysed with moist nitrogen to afford mixed hydroxy/silyloxy complexes 5 and 6 ([(LLu)-Lu-1,2(mu-OSiMe3)(mu-OH) LuL1,2]), respectively.