后过渡金属烯烃聚合催化剂研究进展

烯烃在催化剂的作用下形成聚合物 .改变催化剂的结构 ,可以得到特定分子结构和特定性能的聚烯烃产物 ,因而催化剂的研究开发是聚烯烃升级换代的核心 .烯烃聚合催化剂的发展大致经历了 3个阶段 :Ziegler- Natta催化剂 -茂金属催化剂 -后过渡金属催化剂 .Ziegler[1]和 Natta[2 ]发现了用于各种 α-烯烃聚合的催化剂 ,并已作为主导技术应用于工业化大生产 . 2 0世纪 80年代初 ,Kaminsky等 [3～ 5] 发现 ,二氯二茂锆与烷基铝氧烷组成的体系(茂金属催化剂 )是一种高催化活性、高立体选择性、长寿命的催化剂 .茂金属催化剂的设计、合成和应用 ,…     

后过渡金属烯烃聚合催化剂的研究进展

综述了近两年来后过渡金属(VIII族)催化剂在乙烯、丙烯和α-烯烃聚合,α-烯烃和极性单体共聚,α-烯烃活性聚合,以及乙烯齐聚等方面的最新进展.     

多氮螯合配位后过渡金属络合物烯烃聚合催化剂

A2二亚胺镍、钯络合物和吡啶二亚胺铁、钴络合物是近几年来发现的新一代烯烃均相聚合后过渡金属催化剂。这类催化剂具有活性高、选择性易调变、聚合物性质可控制的特点, 尤其是对官能团中的杂原子的稳定性方面优于前过渡金属催化剂。本文将近年来的有关报道归纳为4 个方面进行评述: 络合物的合成和结构; 配体结构因素对络合物催化性能的影响; 催化烯烃高聚、齐聚和共聚以及催化反应机理。     

新型后过渡金属烯烃聚合催化剂－－镍系烯烃聚合催化剂*

镍系烯烃聚合催化剂是近年来受到广泛关注的一类新型催化剂,是配位催化研究的热点之一。这类催化剂具有高催化活性、单活性中心和良好的分子剪栽性,可以在分子层次上实现烯烃聚合的分子设计与组装。本文介绍了镍系烯烃聚合催化剂的发展和研究概况,并评述了聚合特性及最新研究进展。     

后过渡金属催化烯烃可控/活性聚合的研究进展

烯烃活性聚合由于可以制备出预定分子量的窄分布聚合物,以及各种嵌段共聚物、末端功能化聚合物等而受到广泛关注.过渡金属催化的烯烃配位聚合反应活性高,催化剂性能可通过配体结构的修饰进行调节,聚合物微观结构易于调控,其活性聚合进一步拓展了对烯烃聚合物分子设计的手段,具有重要的意义.除了以钛、锆、钒等为金属中心的前过渡系催化剂之...     

烯烃聚合钯催化剂研究进展

综述了烯烃聚合钯催化剂的研究进展,烯烃聚合钯催化剂的配体类型有膦配体、氮配体、碳配体、氧配体、氮-氧配体、膦-氧配体、氮-膦配体等。与齐格勒-纳塔催化剂和茂金属催化剂相比,烯烃聚合钯催化剂具有高催化活性、单活性中心和良好的分子剪裁性等优点,可在分子层次上实现烯烃聚合的分子设计与组装;与铁、钴、镍等后过渡金属催化剂相比,烯烃聚合钯催化剂具有反应条件较温和、催化活性和立体选择性较高的优势。     

新型后过滤金属烯烃聚合催化剂——镍系烯烃聚合催化剂

镍系烯烃聚合催化剂是近年来受到广泛关注的一类新型催化剂，是配位催化研究的热点之一。这类催化剂具有高催化活性、单活性中心和良好的分子剪栽性，可以在分子层次上实现烯烃聚合的分子设计与组装。本文介绍了镍系烯烃聚合催化剂的发展和研究概况，并评述了聚合特性及最新研究进展。     

新型Ni(Ⅱ)、Pd(Ⅱ)基后过渡金属络合物催化烯烃聚合的研究进展

综述了以α-二亚胺为配体的新型Ni(Ⅱ )、Pd(Ⅱ )后过渡金属催化剂 ,包括催化剂的组成、活化及其对烯烃均聚、共聚和与极性单体共聚的性能、聚合机理。     

有机金属烯烃配位聚合催化剂

有机金属烯烃配位聚合催化剂具有高催化活性和良好的分子剪裁性,通过调节催化剂的微结构,如配体的取代基?配位原子以及配位中心的电子与立体环境等,可以在分子层次上实现烯烃聚合物的分子设计与组装;实现聚合物物理性质的调控,从而得到各种具有新型功能和立体异构的聚合物。本文综述了金属烯烃聚合催化剂研究进展,并展望该领域的发展趋势。     

新一代单活性中心聚烯烃催化剂--水杨醛亚胺基过渡金属化合物

对新型的单活性中心聚烯烃催化剂——以水杨醛亚胺基配体稳定的后过渡金属络合物和前过渡金属络合物催化的结构性能特点、设计合成方法等做了较说尽的评述。     

Advances in late transition metal catalysts for olefin polymerization/oligomerizarion

In this review article, we have consolidated our recent studies on late transition metal catalysts (mainly Fe, Co) for olefin polymerization/oligomerization. A series of bisiminopyridyl Co(II) and Fe(II) complexes were synthesized. These catalysts when activated with MAO in aromatic or aliphatic hydrocarbon solvents, oligomerize or polymerize ethylene to α-olefins or high molecular weight polymers with exceptionally high activities and selectivities. The electronic and steric effects of allyloxy and benzyloxy substituted bisiminopyridyl Fe(II) and Co(II) complexes were also investigated. The influence of catalyst structure and temperature on the polymerization activity, thermal properties and molecular weight were discussed. The effects of heterogenization of these catalysts on silica and modified SBA-15 were analyzed. The polymerization of polar monomers such as vinyl ethers and methyl methacrylate was tested and no specific trends in activity and polymer molecular weight with changes in steric bulkiness around the metal center were observed with the same catalyst system.     

FI catalysts: new olefin polymerization catalysts for the creation of value-added polymers

This contribution reports the discovery and application of phenoxy-imine-based catalysts for olefin polymerization. Ligand-oriented catalyst design research has led to the discovery of remarkably active ethylene polymerization catalysts (FI Catalysts), which are based on electronically flexible phenoxy-imine chelate ligands combined with early transition metals. Upon activation with appropriate cocatalysts, FI Catalysts can exhibit unique polymerization catalysis (e.g., precise control of product molecular weights, highly isospecific and syndiospecific propylene polymerization, regio-irregular polymerization of higher alpha-olefins, highly controlled living polymerization of both ethylene and propylene at elevated temperatures, and precise control over polymer morphology) and thus provide extraordinary opportunities for the syntheses of value-added polymers with distinctive architectural characteristics. Many of the polymers that are available via the use of FI Catalysts were previously inaccessible through other means of polymerization. For example, FI Catalysts can form vinyl-terminated low molecular weight polyethylenes, ultra-high molecular weight amorphous ethylene-propylene copolymers and atactic polypropylenes, highly isotactic and syndiotactic polypropylenes with exceptionally high peak melting temperatures, well-defined and controlled multimodal polyethylenes, and high molecular weight regio-irregular poly(higher alpha-olefin)s. In addition, FI Catalysts combined with MgCl(2)-based compounds can produce polymers that exhibit desirable morphological features (e.g., very high bulk density polyethylenes and highly controlled particle-size polyethylenes) that are difficult to obtain with conventionally supported catalysts. In addition, FI Catalysts are capable of creating a large variety of living-polymerization-based polymers, including terminally functionalized polymers and block copolymers from ethylene, propylene, and higher alpha-olefins. Furthermore, some of the FI Catalysts can furnish living-polymerization-based polymers catalytically by combination with appropriate chain transfer agents. Therefore, the development of FI Catalysts has enabled some crucial advances in the fields of polymerization catalysis and polymer syntheses.     

Electron transfer mechanism in olefin polymerization

Polymerization of olefins mediated by transition metal derivatives (Ziegler–Natta polymerization) is one of the most scientifically and industrially important processes of molecular conversion. Electron transfer mechanism could play a significant role in both heterogeneous and homogeneous catalysts. The catalytic activity strongly depends on the presence of two metallocene ligands attached to the transition metal (more commonly zirconium) which grants the valence form of zirconium in complexes of the type Cp₂ZrX₂(X=Cl or CH₃) followed by the formation of the (Cp₂ZrX)⁺ cation under the effect of a Lewis acid. On the other hand, Ti complexes with only one metallocene ligand give the syndiospecific polymerization of styrene, where the phenyl group appears to act as electron donor for the transition metal. The remarkable electronic effect of the metallocene groups in determining catalytic activity is demonstrated by the study of substituted metallocene ligands as well as other ligands around the metal. These effects cannot be, however, completely separated from steric effects which seem to be responsible for the impressive and versatile stereochemical control determined by symmetry properties of the transition metal complex.     

Novel cationic rare earth metal alkyl catalysts for precise olefin polymerization

This mini‐review provides recent progress in the synthesis of rare earth metal dialkyl complexes and their application as highly efficient and regio‐/stereoselective catalysts in the coordination‐insertion (co)polymerization of olefins such as styrene, isoprene, 1,3‐cyclohexadiene, and ocimene. Through modifying the coordination atom, the ligand skeleton, and the substitutent on the skeleton of the chelating ligand, tuning the electron density and the steric environment around the rare earth metal center, the precise control of the activity and regio‐/stereoselectivity of the (co)polymerization as well as the comonomer incorporation and sequence distribution of the resulting copolymers are achieved. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2271–2280     

Late transition metal-based catalysts for olefin cyclopropanation or olefin metathesis. Importance of catalyst unsaturation

Ruthenium- and rhodium-based catalysts can be designed and finely tuned to some extent so as to mediate either carbene transfer to olefins (e.g., olefin cyclopropanation) or olefin metathesis. The different outcome of the reactions can be quite simply predicted based on either the ability or the absence of ability of the metal center to coordinate both the carbene and the olefin. Several available coordination sites at the metal center are favorable for metathesis to the prejudice of olefin cyclopropanation. Based on the report presented at the conference “Organometallic Chemistry on the Eve of the 21st Century,” May 19–23, 1998, Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1219–1224, July, 1999.     

Heterogenization of metalorganic catalysts of olefin polymerization and evaluation of active site non-uniformity

Heterogenized activators - “support-H₂O/AlR₃” (where R=Me, iBu, support=montmorillonite, zeolite), synthesized directly on the support, form with metallocenes metal alkyl complexes highly active in olefin polymerization without the use of commercial methylaluminoxane (MAO). It was shown by the method of temperature programmed desorption with the application of mass-spectrometry (TPD-MS) that the aluminumorganic compound in support-H₂O/AlR₃ is in general similar to the structure of commercial MAO. The heterogenization of Zr-cenes on support-H₂O/AlR₃ is accompanied by the appearance of the energy non-uniformity of active sites. The activation energy of thermal destruction of active Zr-C bonds in the active sites of prepared catalysts changes in the range from 25 to 32 kcal/mol.     

Reaction of vinyl chloride with late transition metal olefin polymerization catalysts

The reactions of vinyl chloride (VC) with representative late metal, single-site olefin dimerization and polymerization catalysts have been investigated. VC coordinates more weakly than ethylene or propylene to the simple catalyst (Me(2)bipy)PdMe(+) (Me(2)bipy = 4,4'-Me(2)-2,2'-bipyridine). Insertion rates of (Me(2)bipy)Pd(Me)(olefin)(+) species vary in the order VC > ethylene > propylene. The VC complexes (Me(2)bipy)Pd(Me)(VC)(+) and (alpha-diimine)Pd(Me)(VC)(+) (alpha-diimine = (2,6-(i)Pr(2)[bond]C(6)H(3))N[double bond]CMeCMe[double bond]N(2,6-(i)Pr(2)[bond]C(6)H(3))) undergo net 1,2 VC insertion and beta-Cl elimination to yield Pd[bond]Cl species and propylene. Analogous chemistry occurs for (pyridine-bisimine)MCl(2)/MAO catalysts (M = Fe, Co; pyridine-bisimine = 2,6-[(2,6-(i)Pr(2)[bond]C(6)H(3))N[double bond]CMe](2)-pyridine) and for neutral (sal)Ni(Ph)PPh(3) and (P[bond]O)Ni(Ph)PPh(3) catalysts (sal = 2-[C(H)[double bond]N(2,6-(i)Pr(2)-C(6)H(3))]-6-Ph-phenoxide; P[bond]O = [Ph(2)PC(SO(3)Na)[double bond]C(p-tol)O]), although the initial metal alkyl VC adducts were not detected in these cases. These results show that the L(n)MCH(2)CHClR species formed by VC insertion into the active species of late metal olefin polymerization catalysts undergo rapid beta-Cl elimination which precludes VC polymerization. Termination of chain growth by beta-Cl elimination is the most significant obstacle to metal-catalyzed insertion polymerization of VC.