Unifying Molecular Weights of Highly Linear Polyethylene Waxes through Unsymmetrical 2,4-Bis(imino)pyridylchromium Chlorides

By dealing CrCl₃∙3THF with the corresponding ligands (L1–L5), an array of fluoro-substituted chromium (III) chlorides (Cr1–Cr5) bearing 2-[1-(2,4-dibenzhydryl-6-fluoro- phenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine (aryl = 2,6-Me₂Ph Cr1, 2,6-Et₂Ph Cr2, 2,6-iPr₂Ph Cr3, 2,4,6-Me₃Ph Cr4, 2,6-Et₂-4-MePh Cr5) was synthesized in good yield and validated via Fourier Transform Infrared (FT-IR) spectroscopy and elemental analysis. Besides the routine characterizations, the single-crystal X-ray diffraction study revealed the solid-state structures of complexes Cr2 and Cr4 as the distorted-octahedral geometry around the chromium center. Activated by either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the chromium catalysts exhibited high activities toward ethylene polymerization with the MMAO-promoted polymerizations far more productive than with MAO (20.14 × 10⁶ g (PE) mol⁻¹ (Cr) h⁻¹ vs. 10.03 × 10⁶ g (PE) mol⁻¹ (Cr) h⁻¹). In both cases, the resultant polyethylenes were found as highly linear polyethylene waxes with low molecular weights around 1–2 kg mol⁻¹ and narrow molecular weight distribution (MWD range: 1.68–2.25). In general, both the catalytic performance of the ortho-fluorinated chromium complexes and polymer properties have been the subject of a detailed investigation and proved to be highly dependent on the polymerization reaction parameters (including cocatalyst type and amount, reaction temperature, ethylene pressure and run time).     

Transition metal complexes bearing 2,6-bis(imino)pyridyl:Synthesis, structure, ethylene polymerization/oligomerization studies

A series of new complexes {2,6-bis[1-((2-methyl-4-methoxyphenyl)imino)ethyl]pyri-dine}MCI2 [M=Fe(Ⅱ) (2), Co(Ⅱ) (3), Ni(Ⅱ) (4), Cu(Ⅱ) (5), Zn(Ⅱ) (6)] have been synthesized. At 25℃, using 500 equiv of methylaluminoxane (MAO), the activities of Fe(Ⅱ), Co(Ⅱ) catalysts can reach 4.02×106 g/mol-Fehatm for ethylene polymerization and 3.98×105 g/mol-Cohatm for ethylene oligomerization. The effects of polymerization conditions such as reaction temperature, Al/M molar ratio and time on the activity of catalyst have been explored.     

Synthesis of tridentate 2,6-bis(imino)pyridyl aminechlorohydro ruthenium(II) complexes: The convenient use of amine hydrochlorides to generate metal-hydride

The reaction of low-valent ruthenium complexes with 2,6-bis(imino)pyridine ligand, [η²-N₃]Ru(η⁶-Ar) (1) or {[N₃]Ru}₂(μ-N₂) (2) with amine hydrochlorides generates six-coordinate chlorohydro ruthenium (II) complexes with amine ligands, [N₃]Ru(H)(Cl)(amine) (4). Either complex 1 or 2 activates amine hydrochlorides 3, and the amines coordinate to the ruthenium center to give complex 4. This is a convenient and useful synthetic approach to form ruthenium complexes with amine and hydride ligands using amine hydrochloride.     

Unique catalytic behavior of chromium complexes having halogenated bis(imino)pyridine ligands for ethylene polymerization

Reactions of CrCl₃(thf)₃ with bis(imino)pyridines gave a series of {bis(imino)pyridine}chromium(III) trichloride complexes, {2,6‐(RN?CMe)₂C₅H₃N}CrCl₃ [R = C₆HPr₂‐2,6 ( 1 ), C₆H₃Et₂‐2,6 ( 2 ), C₆H₃Me₂‐2,6 ( 3 ), C₆H₂Me₃‐2,4,6 ( 4 ), C₆H₃Me₂‐3,5 ( 5 ), C₆H₅ ( 6 ), cyclohexyl ( 7 ), 2‐methyl‐1‐naphthyl ( 8 ), C₆H₃F₂‐2,6 ( 9 ), C₆H₃Br₂‐2,6 ( 10 ), C₆F₅ ( 11 )]. Pseudo‐octahedral geometries of 6 , 10 , and 11 were revealed by X‐ray crystallography. The complexes having bulky substituents such as 1 – 4 showed high activity for ethylene polymerization in combination with modified methylaluminoxane (MMAO) to give linear polyethylenes. In sharp contrast, the pentafluorophenyl complex 11 /modified methylaluminoxane system was found to be moderately active for ethylene homopolymerization to give moderately branched polyethylene with only ethyl branches. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3368–3375, 2005     

Syntheses,structures, and luminescent properties of Zn(II) and Cd(II) complexes: 3-D supramolecules based on 2,6-bis(imino)pyridine ligands constructed by hydrogen bonding interactions

Six 5-coordinate 2,6-bis(imino)pyridine metal complexes, [2,6-(ArN=CMe)₂C₅H₃NMCl₂ · nCH₃CN] (Ar = 4-MeC₆H₄, M = Zn, n = 0.5, Zn1, M = Cd, n = 1, Cd1; Ar = 2,6-Et₂C₆H₃, M = Zn, n = 0.5, Zn2, M = Cd, n = 0.5, Cd2; Ar = 2,4,6-Me₃C₆H₂, M = Zn, n = 1, Zn3, M = Cd, n = 1, Cd3), were synthesized in acetonitrile by the reactions of the corresponding bis(imino)pyridines with ZnCl₂ or CdCl₂ · 2.5H₂O, respectively. The structures of Zn1–Zn3 and Cd1–Cd3 were determined by the single-crystal X-ray diffraction. In all complexes, the ligand is tridentate with further coordination by two chlorides, resulting in a distorted trigonal bipyramid. All complexes self-assemble through hydrogen bonding interactions to form a 3-D supramolecular structure. At 298 K in dichloromethane, all complexes have blue luminescent emissions at 405–465 nm, which can be attributed to ligand-centered π* → π transitions. The zinc and cadmium centers play a key role in enhancing fluorescent emission of the ligands.     

Iron(II)–ethylene polymerization catalysts bearing 2,6-bis(imino)pyrazine ligands: Part I. Synthesis and characterization

The synthesis of a new series of 2,6-bis(imino)pyrazinyl ligands, [ArNCPyzCNAr] where the aryl groups Ar = naphtyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-trimethylphenyl, and their iron(II) complexes is described starting from monoacetylpyrazine.     

Bis(pyrazolyl)pyridine vanadium(III) complexes as highly active ethylene polymerization catalysts

The synthesis, characterization and catalytic activity in ethylene polymerization of novel mononuclear vanadium complexes bearing N^∧N^∧N-tridentate (pyrazolyl-pyridine) ligands are described. With AlEtCl₂ as co-catalyst, complexes 1 and 2 produce single-site catalysts that polymerized ethylene affording high density polyethylene with fairly narrow molecular weight distribution.     

Iron(II)–ethylene polymerization catalysts bearing 2,6-bis(imino)pyrazine ligands: Part II. Catalytic behaviour, homogeneous and heterogeneous insights

A series of new iron(II) complexes bearing tridentate pyrazine-bis(2,6-arylimino) ligands where the aryl groups are 1-naphthyl, 2,6-dimethylphenyl, and 2,6-diisopropylphenyl have been used as ethylene polymerization catalysts after activation with alkylaluminiums. The new complexes display a lesser catalytic activity than those bearing the corresponding pyridine-bis(2,6-arylimino) ligands. Varying the steric bulkiness of the aromatic groups in the tridentate ligands and the polymerization conditions affects the catalytic productivity.     

Bis(imino)pyridine palladium(II) complexes: Synthesis, structure and catalytic activity

Bis(imino)pyridine palladium(II) complexes 3-6 were synthesized by two different methods. The structure of complexes 3 and 4 has been confirmed by X-ray structure analysis. The catalytic studies show that bis(imino)pyridine palladium(II) complexes are highly efficient catalysts in the Suzuki-Miyaura reaction and the complex 4 was used to catalyze the synthesis of fluorinated liquid crystalline compounds via Suzuki coupling reaction.     

Co‐catalyst effects on the thermal stability/activity of N,N,N‐Co ethylene polymerization Catalysts Bearing Fluoro‐Substituted N‐2,6‐dibenzhydrylphenyl groups

The unsymmetrical bis (arylimino)pyridines, 2‐[CMeN{2,6‐{(4‐FC₆H₄)₂CH}₂–4‐t‐BuC₆H₂}]‐6‐(CMeNAr)C₅H₃N (Ar = 2,6‐Me₂C₆H₃ L1 , 2,6‐Et₂C₆H₃ L2 , 2,6‐i‐Pr₂C₆H₃ L3 , 2,4,6‐Me₃C₆H₂ L4 , 2,6‐Et₂–4‐MeC₆H₂ L5 ), each containing one N‐aryl group bedecked with ortho‐substituted fluorobenzhydryl groups, have been employed in the preparation of the corresponding five‐coordinate cobalt (II) chelates, LCoCl₂ ( Co1 – Co5 ); the symmetrical comparator [2,6‐{CMeN(2,6‐(4‐FC₆H₄)₂CH)₂–4‐t‐BuC₆H₂}₂C₅H₃N]CoCl₂ (Co6) is also reported. All cobaltous complexes are paramagnetic and have been characterized by ¹H/¹⁹F NMR spectroscopy, FT‐IR spectroscopy and elemental analysis. The molecular structures of Co3 and Co6 highlight the different degrees of steric protection given to the metal center by the particular N‐aryl group combination. Depending on the aluminoxane co‐catalyst employed to activate the cobalt precatalyst, distinct variations in thermal stability and activity of the catalyst towards ethylene polymerization were exhibited. In particular with MAO, the resultant catalysts reached their optimal performance at 70 °C delivering high activities of up to 10.1 × 10⁶ g PE (mol of Co)^?1 h^?1 with Co1  >  Co4  >  Co2  >  Co5  >  Co3 >>  Co6 . On the other hand, using MMAO, the catalysts operate most effectively at 30 °C but are by comparison less productive. In general, the polyethylenes were highly linear, narrowly disperse and displayed a wide range of molecular weights [M_w range: 18.5–58.7 kg mol^?1 (MAO); 206.1–352.5 kg mol^?1 (MMAO)].     

Substantially enhancing the catalytic performance of bis(imino)pyridylcobaltous chloride pre‐catalysts adorned with benzhydryl and nitro groups for ethylene polymerization

Variations in the ligand structure of homogeneous late transition metal catalysts through judicious choice and location of substituent is the foremost strategy in improving their catalytic performance for ethylene polymerization. In this contribution, symmetrical and unsymmetrical bis(imino)pyridylcobaltous chloride complexes adorned with nitro and benzhydryl groups {2‐[1‐(2,6‐dibenzhydryl‐4‐nitrophenylimino)ethyl]‐6‐[1‐(alkylphenylimino)ethyl]pyridylcobaltous chloride (alkyl: R¹ = Me and R² = H, Co1 ; R¹ = Et and R² = H, Co2 ; R¹ = ⁱPr and R² = H, Co3 ; R¹ and R² = Me, Co4 ; R¹ = Et and R² = Me, Co5 ; R¹ = benzhydryl and R² = NO₂, Co6 )} have been prepared and applied as catalysts for ethylene polymerization. The molecular structure of Co1 and Co2 revealed the unequal steric protection of the cobalt center induced by bis(imino)pyridine chelate. In the presence of methylaluminoxane (MAO) or modified methylaluminoxane (MMAO) activators at different ethylene feeding rates (1 and 10 atm), catalysts Co1 – Co5 displayed high activities at 10 atm ethylene and produced strictly linear polyethylene (PE) with high molecular weight, Co2 /MMAO being the most highly active catalytic system showing the highest activity of 9.41 × 10⁶ g of PE (mol of Co)^?1 h^?1 which is three times higher than that of prototypal cobalt catalyst ( Co0 ) under identical conditions. Moreover, high melt temperature and unimodal molecular weight distribution are the characteristics of the resulting polyethylene.     

Thermo‐stable 2‐(arylimino)benzylidene‐9‐arylimino‐5,6,7,8‐tetrahydro cyclohepta[b]pyridyliron(II) precatalysts toward ethylene polymerization and highly linear polyethylenes

A series of 2‐(arylimino)benzylidene‐9‐arylimino‐5,6,7,8‐tetrahydrocyclohepta[b] pyridyliron(II) chlorides was synthesized and characterized using FT‐IR and elemental analysis, and the molecular structures of complexes Fe3 and Fe4 have been confirmed by the single‐crystal X‐ray diffraction as a pseudo‐square‐pyramidal or distorted trigonal‐bipyramidal geometry around the iron core. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all iron precatalysts exhibited high activities toward ethylene polymerization with a marvelous thermo‐stability and long lifetime. The Fe4 /MAO system showed highest activity of 1.56 × 10⁷ gPE·mol^?1(Fe)·h^?1 at 70 °C, which is one of the highest activities toward ethylene polymerization by iron precatalysts. Even up to 80 °C, Fe3 /MAO system still persist high activity as 6.87 × 10⁶ g(PE)·mol^?1(Fe)·h^?1, demonstrating remarkable thermal stability for industrial polymerizations (80–100 °C). This was mainly attributing to the phenyl modification of the framework of the iron precatalysts. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 830–842     

吡啶二亚胺Ni(Ⅱ)配合物的合成、晶体结构及其催化乙烯聚合的研究

由三齿配体2,6-二[1-(2-甲基苯基亚胺)乙基]吡啶(L₁)和2,6-二[(1-苯基亚胺)乙基]吡啶(L₂)分别与NiCl₂.6H₂O在乙腈中反应,合成了两个吡啶二亚胺基氯化镍配合物L₁Ni(Ⅱ)Cl₂.CH₃CN(1)和L₂Ni(Ⅱ)Cl₂(2).通过元素分析、IR和¹HNMR对配体和配合物进行了结构表征,并测定了配合物1和2的晶体结构.X射线衍射分析结果表明,两个配合物均为五配位扭曲三角双锥构型,属单斜晶系,C_c空间群.配合物1的晶胞参数a=2.5783(5)nm,b=1.4843(3)nm,c=1.5866(3)nm;β=122.82(3),°V=5.1024(18)nm³,Z=4,R₁=0.0708,配合物2的晶胞参数a=1.5772(1)nm,b=0.8594(1)nm,c=1.5459(1)nm;β=103.27(1),°V=2.039(2)nm³,Z=4,R₁=0.0375.配合物1和2经MAO活化后对乙烯聚合表现出较低的催化活性.     

一种嵌有双亚胺基吡啶配体的全共轭有机聚合物材料及其在C-C偶联反应中的应用

报道了一种嵌有双亚胺基吡啶配体的全共轭有机聚合物材料. 该材料所具有的双亚胺基吡啶配体起到链接聚合物单元和络合金属中心的双重作用. 采用紫外可见光谱、红外光谱以及基质辅助激光解吸电离飞行时间质谱等对其结构进行了详细表征和确认. 由于具有全共轭结构,该材料的热稳定性达到440 ℃,并且在常规溶剂中较难溶解. 作为多相催化剂载体,可以络合Pd离子形成新的多相配位催化剂,在经典的Suzuki-Miyaura C-C偶联反应中转化率和选择性均达到99%.     

Preparation and catalytic properties of bis(imino)pyridine palladium(II) complexes as efficient catalysts for Suzuki cross‐coupling reaction in water

Air‐stable bis(imino)pyridine palladium(II) complexes were synthesized and complex 12 proved to be a highly efficient catalyst for the Suzuki cross‐coupling reaction between aryl bromides and arylboronic acids in air using water as solvent. The coupling reaction proceeded smoothly under mild conditions to provide biaryls in excellent yields and Pd black was not observed. The recycling of the catalysts was also investigated, for up to three cycles, and complex 12 still exhibited good activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of temperature on the number of active sites and propagation rate constant at ethylene polymerization over supported bis(imino)pyridine iron catalysts

The inhibition of ethylene polymerization with radioactive carbon monoxide (¹⁴CO) was used to obtain data on the number of active sites (C_P) and propagation rate constant (k_P) at ethylene polymerization in the temperature range of 35–70 °C over supported catalysts LFeCl₂/Al₂O₃, LFeCl₂/SiO₂, and LFeCl₂/MgCl₂ (L: 2,6‐(2,6‐(Me)₂C₆H₃N = CMe)₂C₅H₃N) with activator Al(i‐Bu)₃. The values of effective activation energy (E_eff), activation energy of propagation reaction (E_P), and temperature coefficients of variation of the number of active sites (E_Cp = E_eff ? E_P) were determined. The activation energies of propagation reaction for catalysts LFeCl₂/Al₂O₃, LFeCl₂/SiO₂, and LFeCl₂/MgCl₂ were found to be quite similar (5.2–5.7 kcal/mol). The number of active sites diminished considerably as the polymerization temperature decreased, the E_Cp value being 5.2–6.2 kcal/mol for these catalysts at polymerization in the presence of hydrogen. The reactions of reversible transformations of active centers to the surface hydride species at polymerization in the presence and absence of hydrogen are proposed as the derivation of E_Cp. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6621–6629, 2008     

吡啶二亚胺过渡金属配合物的二阶非线性光学性质

采用密度泛函理论(DFT) B3LYP方法,对8个吡啶二亚胺配合物的几何结构、电子光谱和二阶非线性光学(NLO)性质进行了计算和分析.结果表明,配合物的极化率受副配体和中心金属离子的影响不大,副配体对配合物二阶NLO系数的影响也不明显.随金属离子d电子数的增加,配合物二阶NLO系数(β)有所减小,同一族金属离子随半径增大,其配合物相应的βtot值增加.配合物中的金属离子起到供电子作用时,配合物最大振子强度下的跃迁能较小,其相应的βtot值较大.     

Producing highly linear polyethylenes by using t‐butyl‐functionalized 2,6‐bis(imino)pyridylchromium(III) chlorides

A new family of t‐butyl substituted chromium(III) chloride complexes ( Cr1 – Cr6 ), bearing 2‐(1‐(2,6‐dibenzhydryl‐4‐t‐butylphenylimino)ethyl)‐6‐(1‐(arylimino)ethyl)pyridine (aryl = 2,6‐Me₂C₆H₃ Cr1 , 2,6‐Et₂C₆H₃ Cr2 , 2,6‐i‐Pr₂C₆H₃ Cr3 , 2,4,6‐Me₃C₆H₂ Cr4 and 2,6‐Et₂‐4‐MeC₆H₂ Cr5 ) or 2,6‐bis(1‐(2,6‐dibenzhydryl‐4‐t‐butylphenylimino)ethyl)pyridine ( Cr6 ), has been synthesized by the reaction of CrCl₃·6H₂O in good yield with the corresponding ligands ( L1 – L6 ), respectively. The molecular structures of Cr2 and Cr6 were characterized by X‐ray diffraction highlighted a distorted octahedral geometry with the coordinated N,N,N ligand and three bonded chlorides around the metal center. On activation with modified methylaluminoxane or triisobutyl aluminum, most of the chromium precatalysts exhibit good activities toward ethylene polymerization and produce linear polyethylenes with high‐molecular weight. In addition, an in‐depth catalytic evaluation of Cr2 was conducted to investigate how cocatalyst type and amount, reaction temperature, and run time affect the catalytic activities and polymer properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1049–1058     

Syntheses, Characterization and Crystal Structures of New Nickel Complexes with 2,6-Bis(imino)pyridyl Ligands

Introduction In the past decade, the imino-complexes based on late transition metal have received significantly increasing attention for their excellent performance in the olefin polymerization area since Brookhart et al.[1-8]