Olefin Polymerization Catalysts Research Articles

Rational Design of Bian Based Anode Binder/Additive for High Performance Li Ion Secondary Batteries

Bisiminoacenaphthene (BIAN) has been an important ligand structure for a variety of metal complex and widely employed as a ligand for olefin polymerization catalysts. However, in spite of their unique electrochemistry, it has not been widely utilized for energy devices. In the present work, firstly BIAN based novel conjugated polymer was prepared by Sonogashira-coupling polymerization and the obtained polymer (P-BIAN) was employed as anode binder in Li/EC:DEC/C type anodic half cells. Second, novel additive material bearing BIAN structure (BIANODA) was synthesized, which was used as additive to improve the characteristics of MNC cathode material (LiMn1/3Ni1/3Co1/3O2). Electrochemistry of these materials along with characteristics of fabricated Li ion battery cells under these design protocol will be presented in detail. The BIAN based polymer, P-BIAN shows lower LUMO level in comparison with ethylene carbonate (EC). This means reductive doping of P-BIAN takes place prior to reductive decomposition of EC at anode surface, which will restrict thick SEI formation at anode. When cyclic voltammetry measurements were carried out for coin cell with P-BIAN, peak due to reductive decomposition of EC was not observed, unlike the case of PVDF. Further, after charge-discharge cycles, coin cell with P-BIAN exhibited much smaller internal resistance when compared with PVDF. This indicates that reductive doping of P-BIAN and restriction of SEI decomposition had synergistically decreased internal resistance of battery cells. As a result, coin cell with P-BIAN showed 1.5 times higher discharging capacity in comparison with coin cell with PVDF. On the other hand, BIANODA has higher HOMO level than that of EC, which enables oxidative polymerization of BIANODA prior to oxidative decomposition of EC. This will restrict thick SEI formation at MNC cathode surface. Use of Schiff base can trap HF generated during the cycling, and strong binding property of BIAN can stabilize MNC cathode for long term use. Consequently, BIANODA additive had enhanced the discharging performance of MNC/EC:DC/Li cathodic half cells. Both P-BIAN as anodic binder material and BIANODA as MNC cathode additive were found to be remarkably effective to improve the performance of Li ion battery cells.

Group 4 Post-Metallocenes Supported by [OCH2N,C(σ-aryl)] Auxiliaries Bearing a Seven-Membered Metallacycle: Synthesis, Characterization, and Catalysts for Olefin Polymerization

A series of pyridine-2-phenolate-6-(σ-aryl) [OCH2N,C] group 4 bis(benzyl) precatalysts, featuring a flexible O,N-donor chelate, have been prepared and characterized by multinuclear NMR spectroscopy...

Use of Synthetic and Natural Zeolites for Fabricating Immobilized Olefin Polymerization Catalysts and Polyolefin-Based Composite Materials

Synthetic zeolites differing in composition, framework parameters, and exchange cations that balance charges of aluminum–oxygen framework tetrahedra and natural finely divided clinoptilolite-containing tuffs have been used for heterogenization of metal complex catalysts. In the reaction of incomplete hydrolysis of alkylaluminum compounds with water contained on the surface and in the intracrystalline cavities of synthetic zeolites, bonded alkylalumoxanes have been synthesized and further used to create immobilized zirconocene olefin polymerization catalysts, close in activity to similar homogeneous Zr-cene systems, and heterogenized vanadium catalysts. Based on finely divided natural zeolites and ultrahigh-molecular-weight polyethylene, the following materials have been fabricated using the polymerization filling method: a composite that combines high wear-resistant properties with a low friction coefficient, has good strain–stress characteristics, and can be used for manufacturing friction units under load; an organomineral sorbent suitable for solving environmental problems associated with the treatment of natural water for the removal of cesium and strontium radionuclides, heavy metals, and ammonium.

A New Class of Pyridine-Amide Containing Ti and Zr Based Catalysts for Olefin Polymerization: Influence of Ligand Substituents

Two tridendate pyridine-amide ligands in di-deprotonated form have been used to synthesize new titanium and zirconium complexes. The molecular structure of pentafluoro containing Titanium and Zirconium complexes were determined by DFT calculations. These new metal complexes have been further evaluated for ethylene polymerization activity in the presence of co-catalyst methylaluminoxane (MAO) under atmospheric pressure, producing polyethylenes with moderate molecular weights and unimodal molecular weight distribution. Remarkably, zirconium complexes show higher activity than titanium complexes under the same polymerization condition. The catalytic activity of all the complexes were found to be temperature dependent and reach their highest efficiency at 70 °C. The influence of the nature of the ligands and reaction parameters upon the catalytic activities has been studied. Additionally, the pentafluoro containing Zirconium and Titanium complexes were further evaluated for the copolymerization of ethylene and propylene and exhibited good catalytic activity. A new class of titanium and zirconium based metal complexes were synthesised from pyridine-amide containing ligands. The synthesised complexes have been evaluated for ethylene polymerization in the presence of co-catalyst methylaluminoxane (MAO) under atmospheric pressure. Interestingly, zirconium complexes show high catalytic activities than titanium complexes under the same polymerization condition.

Reactivity of C1 -Symmetric Heteroarylamido Hafnium Complexes towards Unsaturated Electrophilic Molecules: Development of New Families of Olefin Polymerization Catalysts.

Heteroarylamido hafnium post-metallocenes with [C,N,N] ligands were functionalized by the insertion of small electrophilic unsaturated molecules into the CAr -Hf bond of the ligand, which gave rise to various 1,1- and 1,2-insertion complexes with the modified ligands of previously unknown [O,N,N], [N,N,N], [O,N,N,N], and [N,N,N,N] types. It was found that C1 symmetry of the starting complexes, in some cases, results in the formation of two diastereoisomers after 1,1- or 1,2-insertion. Most of the obtained novel complexes were shown to form active catalysts for olefin polymerization in the presence of MAO (methylaluminoxane). Thus, a new approach to the feasible and easy "late stage" modification of the precatalyst structure has been suggested; it can be performed immediately prior to the polymerization tests without isolation and even in a high-throughput manner.

Activity and Thermal Stability of Cobalt(II)-Based Olefin Polymerization Catalysts Adorned with Sterically Hindered Dibenzocycloheptyl Groups.

Five examples of unsymmetrical 2-(2,4-bis(dibenzocycloheptyl)-6-methylphenyl- imino)ethyl)-6-(1-(arylyimino)ethyl)pyridine derivatives (aryl = 2,6-Me2C6H3 in L1; 2,6-Et2C6H3 in L2; 2,6-i-Pr2C6H3 in L3; 2,4,6-Me3C6H2 in L4 and 2,6-Et2-4-MeC6H2 in L5) were prepared and characterized. Treatment with CoCl2 offered the corresponding cobalt precatalysts Co1–Co5, which were characterized by FT-IR and NMR spectroscopy as well as elemental analysis. The molecular structures of Co3 and Co4 determined by single crystal X-ray diffraction revealed distorted square pyramidal geometries with τ5 values of 0.052–0.215. Activated with either MAO or MMAO, the precatalysts displayed high activities in ethylene polymerization, where Co1 with the least bulky substituents exhibited a peak activity of 1.00 × 107 g PE mol−1 (Co) h−1 at 60 °C. With MAO as a cocatalyst, the activity was reduced only by one order of magnitude at 90 °C, which implies thermally stable active sites. The polymerization product was highly linear polyethylene with vinyl end groups. Co3 with the most sterically hindered active sites was capable of generating polyethylene of high molecular weight, reaching 6.46 × 105 g mol−1. Furthermore, high melting point and unimodal molecular weight distribution were observed in the resulting polyethylene. It must be stressed that the thermal stability of the catalyst and the molecular weight of the obtained polyethylene attain the highest values reported for the unsymmetrical 2,6-bis(imino)pyridylcobalt (II) chloride precatalysts.

Unexpected Precatalyst σ-Ligand Effects in Phenoxyimine Zr-Catalyzed Ethylene/1-Octene Copolymerizations.

Recent decades have witnessed intense research efforts aimed at developing new homogeneous olefin polymerization catalysts, with a primary focus on metal-Cl or metal-hydrocarbyl precursors. Curiously, metal-NR2 precursors have received far less attention. In this contribution, the Zr-amido complex FI2ZrX2 (FI = 2,4-di- tert-butyl-6-((isobutylimino)methyl)phenolate, X = NMe2) is found to exhibit high ethylene polymerization activity and relatively high 1-octene coenchainment selectivity (up to 7.2 mol%) after sequential activation with trimethylaluminum, then Ph3C+B(C6F5)4-. In sharp contrast, catalysts with traditional hydrocarbyl ligands such as benzyl and methyl give low 1-octene incorporation (0-1.0 mol%). This unexpected selectivity persists under scaled/industrial operating conditions and was previously inaccessible with traditional metal-Cl or -hydrocarbyl precursors. NMR, X-ray diffraction, and catalytic control experiments indicate that in this case an FI ligand is abstracted from FI2Zr(NMe2)2 by trimethylaluminum in the activation process to yield a catalytically active cationic mono-FIZr species. Heretofore this process was believed to serve only as a major catalyst deactivation pathway to be avoided. This work demonstrates the importance of investigating diverse precatalyst monodentate σ-ligands in developing new catalyst systems, especially for group 4 olefin polymerization catalysts.

Interaction of Neutral Donors with Methylaluminoxane

Methylaluminoxane (MAO) is a key activator for olefin polymerization catalysts, making its chemistry of ongoing interest. Strong and bidentate neutral donors such as 2,2′‐bipyridine are effective abstractors of the dimethylaluminum cation, [Me2Al]+, from methylaluminoxane (MAO), while monodentate, weaker donors such as THF appear most prone to adduct formation with both free and bound trimethylaluminum. The ionization process can be readily investigated using electrospray ionization mass spectrometry (ESI‐MS) in fluorobenzene (PhF) solution. Complementary studies employing 1D and 2D 1H NMR spectroscopic studies in [D5]bromobenzene solution provide details on the extent of ionization vs. donor‐acceptor complex formation for the different donors studied. DFT studies employing different neutral model precursors and mono‐ vs. didentate donors shed light on possible mechanisms for ion‐pair formation.

Synthesis and Application of Bis[1,2-(4-aryl-2-alkyl-1H- inden-1-yl)]Ethane as an Efficient`Ligand for Preparation of Olefin Polymerization Catalysts

In this study, a class of bis-1,2-(4-aryl-2-alkyl-1H- inden-1-yl) ethane was synthesized and characterized by spectroscopic methods such as 1HNMR, 13CNMR, melting point and FTIR. bis-1,2-(4-aryl-2-alkyl-1H- inden-1-yl) ethane was synthesized by the reaction of butyl­lithium, arylindenes and dibromoethane in a facile, one-pot strategy. It’s shown that these methods have a wide scope to afford libraries of aryl-substituted indenes. The prepared compounds was then applied as a ligand for the fabrication of a number of metal complexes which can be used as catalyst for the polymerization of the olefins.

Alkynyl Ether Labeling: A Selective and Efficient Approach to Count Active Sites of Olefin Polymerization Catalysts

Accurately measuring molecular kinetics of catalytic olefin polymerization has been a challenging objective. Many methods have been proposed in the literature, but all of them have drawback(s). In this paper, we introduce a labeling method to count active sites employing methyl propargyl ether (MPE) as the quench-labeling agent. It is commercially available, does not react with Al-alkyl species, and has a labeling efficiency close to 100%. The labeling reaction was evidenced by a mechanistic study on the reaction between the model system Cp2ZrMe2/MAO (Cp = cyclopentadienyl) and MPE that it may occur through a coordination–insertion mechanism without noticeable multiple insertions. The method was benchmarked by studying a MgCl2-supported Ziegler–Natta catalyst in 1-hexene polymerization. The fraction of the active transition metal χ* is found to be <1%. It rises in the very first few seconds and reaches a plateau within 10 s in the absence of precontact. With precontact, χ* remains constant over polymer yield from 0.3 up to 5.3 g(PH) g(cat)−1, demonstrating that χ* does not necessarily grow during polymerization. Longer precontact resulted in decreased χ* and decreased average rate constant of propagation <kp> which is in the order of 102 M–1 s–1.

Synthesis and characterisation of κ2-N,O-oxazoline-enolate complexes of nickel(ii): explorations in coordination chemistry and metal-mediated polymerisation.

The synthesis and characterisation (UV-Vis, IR, X-ray diffraction, etc.) of a series of Ni(ii) complexes derived from both known and novel 2-acylmethyl-2-oxazolines (2a–g: i.e., (Z)-1-R-2-(4,4′-dimethyl-2′-oxazolin-2′-yl)eth-1-en-1-ol; R = –Ph, –2-furanyl, –p-NO2-Ph, –t-Bu, –2-thiofuranyl, p-NC-Ph, –CF3) is reported. These Ni materials (3a–g) represent the first group 10 metal complexes of this ligand class. All derivatives reported are paramagnetic (S = 1) compounds of formulae Ni(κ2-N,O-L)2 where L represents an enolate of structure (Z)-1-R-2-(4′,4′-dimethyl-2′-oxazolin-2′-yl)eth-1-en-1-ate formed via proton loss from 2. The air- and moisture-stable metal complexes feature a less typical distorted seesaw-shaped disposition of binding atoms around the metal centre for six structurally characterised (X-ray) examples. Preliminary investigations indicate that 3a (R = –Ph) is a useful catalysts for olefin polymerisation in the presence of alkylaluminum reagents.

π-Bond Character in Metal-Alkyl Compounds for C-H Activation: How, When, and Why?

C-H bond activation via σ-bond metathesis is typically observed with transition-metal alkyl compounds in d0 or d0fn electron configurations, e.g., biscyclopentadienyl metal alkyls. Related C-H activation processes are also observed for transition-metal alkyls with higher d-electron counts, such as W(II), Fe(II), or Ir(III). A σ-bond metathesis mechanism has been proposed in all cases with a preference for an oxidative addition-reductive elimination pathway for Ir(III). Herein we show that, regardless of the exact mechanism, C-H activation with all of these compounds is associated with π-character of the M-C bond, according to a detailed analysis of the 13C NMR chemical shift tensor of the α-carbon. π-Character is also a requirement for olefin insertion, indicating its similarity to σ-bond metathesis. This observation explains the H2 response observed in d0 olefin polymerization catalysts and underlines that σ-bond metathesis, olefin insertion, and olefin metathesis are in fact isolobal reactions.

Correlation Between Catalyst Performance and Relaxation Time of Electron Donor in Olefin Polymerization Catalyst by Solid &lt;sup&gt;13&lt;/sup&gt;C NMR

Correlation Between Catalyst Performance and Relaxation Time of Electron Donor in Olefin Polymerization Catalyst by Solid &lt;sup&gt;13&lt;/sup&gt;C NMR

Multinuclear Palladium Olefin Polymerization Catalysts Based on Self-Assembled Zinc Phosphonate Cages

The phosphine–phosphonate–sulfonate proligand HP+(4-tBu-Ph)(2-PO3H2-5-Me-Ph)(2-SO3–-5-Me-Ph) (H3[OP-P-SO], 1-H3) was investigated as a building block for the self-assembly of multinuclear Pd compounds based on zinc phosphonate scaffolds. 1-H3 reacts with Zn(OAc)2·2H2O to afford {Zn[1-H]}4, which adopts a Zn4P4O8 ring structure in which the Zn centers are linked by μ2-κ1,κ1-bridging (aryl)PO3H– ligands. {Zn[1-H]}4 reacts with (TMEDA)PdMe2 and pyridine to generate {[(κ2-OP-P-SO)PdMe(py)][Zn(TMEDA)]}2 (2), in which two [(κ2-OP-P-SO)PdMe(py)]2– units are linked through a Zn2P2O4 ring. The sequential reaction of CH3OH-free {Zn[1-H]}4 with (COD)PdMe2 and 4-tBu-py generates {[κ2-(Zn-OP-P-SO)]PdMe(4-tBu-py)}4 (4-(4-tBu-py)), in which four [(κ2-OP-P-SO)PdMe(4-tBu-py)]2– units are arranged on the periphery of a double-four-ring (D4R) Zn4P4O12 cage. Analogous 4-L species were generated by the reaction of {Zn[1-H]}4, (COD)PdMe2, and other pyridine ligands. 4-py reacts with CH3OH to form a trimeric cluster 3-py, which...

Insights into the activation of silica-supported metallocene olefin polymerization catalysts by methylaluminoxane

Metallocene-based olefin polymerization catalysts often require large excesses of co-catalyst for optimal catalyst activation. In this work, mechanistic insights into the activation of supported metallocenes by methylaluminoxane as co-catalyst are acquired. UV–vis diffuse reflectance (DR) spectroscopy of five metallocene catalysts with varying co-catalyst loading reveals the presence of different metallocene species on the surface of the catalyst particles. Deconvolution of the obtained spectra, in combination with an extensive TD–DFT study of UV–vis DR spectra of metallocene structures results in a proposed activation mechanism. We find that with increasing MAO loading, more AlMe2+-bound metallocenes are observed with a shift towards the trimethylaluminum-stabilized cationic methylated metallocene compound. This shift can be directly correlated with a higher activity in the olefin polymerization reaction. Based on this finding, we propose a universal metallocene activation mechanism in which the cationic methylated metallocene is the active species. This species is formed through initial interaction with AlMe2+, followed by ligand exchange with MAO and stabilized in complex with trimethylaluminum as a dormant species.

Thermally Robust Heterobimetallic Palladium–Alkali Catalysts for Ethylene and Alkyl Acrylate Copolymerization

We report on the synthesis and characterization of a new family of palladium–alkali olefin polymerization catalysts using site-differentiated dinucleating platforms. Metal binding studies indicate that our palladium phosphine phosphonate polyethylene glycol (PEG) complexes form 1:1 adducts with alkali cations in solution, with relative affinities in the order Na+ ≈ K+ > Li+. We observed that these palladium–alkali complexes are more active for ethylene homopolymerization and ethylene/alkyl acrylate copolymerization in comparison to their monopalladium counterparts, although their effect on polymer branching and molecular weight is relatively modest. In some cases, the addition of external sodium salts to conventional palladium complexes (i.e., those that do not have pendant PEG chains) also led to remarkable catalyst enhancements, presumably also due to the formation of palladium–sodium species. The unique features of our heterobimetallic systems are that they display long catalyst lifetimes at 100 °C and...

Recent advances in thermally robust, late transition metal‐catalyzed olefin polymerization

AbstractOlefin polymerization catalysts employing late transition metals, such as Ni, Pd, Fe and Co, have been heavily investigated since their discovery in the mid‐1990s. Despite the advantages and appeal these catalysts have displayed in academic research, their implementation in industry has remained restricted due to a variety of limitations and drawbacks. One specific limitation is the relative thermal instability of most late transition metal olefin polymerization catalysts at the temperatures commonly utilized for industrial polymerizations. This review focuses on the development of Ni‐, Pd‐, Fe‐ and Co‐based olefin polymerization catalysts that display increased thermal stability at super‐ambient reaction temperatures. These advances in thermal stability have been realized using a variety of ligand modifications, and their polymerization activities and thermal stability are summarized herein. Lastly, a brief outlook on the future of thermally stable, late transition metal olefin polymerization catalysts is provided. © 2018 Society of Chemical Industry

Ethylene (co)Oligomerization by Phosphine‐Pyridine Based Palladium and Nickel Catalysts

AbstractPhosphine and pyridine groups have been widely employed in various olefin polymerization catalysts. In this contribution, these two moieties are connected using different bridges, and the properties of their corresponding palladium and nickel complexes are investigated. A series of CH2, NH and O bridged phosphine‐pyridine ligands (2‐(diarylphosphino)methyl‐pyridine, 2‐(diarylphosphino)amino‐pyridine, 2‐diarylphosphinito‐pyridine) are synthesized and characterized. For the CH2 bridged ligand, the introduction of a C6F5 substituent leads to the generation of a mixture of diastereomers, which can be separated by column chromatography. Starting with these five phosphine‐pyridine ligands, the corresponding palladium and nickel complexes are prepared and characterized. The bridging moiety (CH2, NH and O), the substituents on the bridge, and the ligand orientations significantly influence the properties of the metal complexes in ethylene oligomerization and cooligomerization reactions. For the palladium complexes, ethylene oligomerization and cooligomerization with some polar comonomers (methyl acrylate, butyl vinyl ether, vinyltrimethoxysilane, allyl acetate and allyl choride) can be realized. For the nickel complexes, ethylene oligomerization followed by Friedel‐Crafts addition of the resulting oligomers to toluene solvent leads to the formation of branched alkylated aromatic materials.

Research progress of pre-transition metal olefin polymerization catalyst for salicylaldehyde imine

Salicylaldehyde imine transition metal catalyst is a kind of olefin polymerization catalyst that is widely used in the coordination of salicylaldehyde imine ligand and pre-transition metal. Salicylaldehyde imine ligands have the characteristic of easily inserting different substituents via organic synthesis. Therefore, the regulation of the polymerization activity, polymerization product, and product distribution can be achieved by changing the steric hindrance effect, the electronic effect, and the number of metal active sites near the catalytic active center. The development status of the transition metal catalyst of salicylaldehyde imide was summarized in this paper. The influence of the ligand structure of the salicylaldehyde imide transition metal catalyst on the catalytic performance, which involved the high selectivity of ethylene trimerization, ethylene/α-olefin, polar monomer copolymerization, ethylene polymerization production, ultra-high molecular weight polyethylene, and many other areas of olefin polymerization, was elaborated, providing references for further study and industrial applications of this catalyst.

Genesis of MgCl2 -based Ziegler-Natta Catalysts as Probed with Operando Spectroscopy.

Ziegler-Natta catalysts for olefin polymerization are intrinsically complex multi-component systems. The genesis of the active sites involves several simultaneous and sequential steps, making the individual steps and interconnections difficult to be unraveled in an unambiguous manner. In this work, we combine X-ray diffraction and spectroscopy to probe each step of the birth and life of a MgCl2 -based Ziegler-Natta catalyst, namely the formation of high surface area MgCl2 by dealcoholation of an alcoholate precursor, the TiCl4 grafting, and the subsequent activation by triethylaluminum as co-catalyst. The so-prepared catalyst was tested towards ethylene polymerization, leading to the production of mainly crystalline high-density polyethylene. The use of operando characterization techniques allowed probing the transient details that are difficult to be dissected in the aftermath, but can radically affect the overall catalytic process.