端基功能化聚烯烃的合成与应用

端基功能化聚烯烃（Cef-PO）在聚烯烃改性和构筑复杂结构聚合物方面有着重要应用。可通过控制烯烃配位聚合过程中的自发链转移反应,得到端基不饱和聚烯烃;或通过引入硼烷、磷烷、苯乙烯及其衍生物/氢气等链转移剂得到不同反应性基团封端的聚烯烃;再经进一步基团转化反应,得到多种不同性能的Cef-PO。另外,活性配位聚合过程中,通过对活性增长聚烯烃链选择性封端处理,或使用功能化的催化剂,也可以用来制备Cef-PO。通过配位链转移聚合,即聚烯烃链在催化剂金属中心和烷基金属链转移剂之间快速可逆链转移的聚合过程,可以直接得到具有高度反应活性的碳-金属键封端的聚烯烃,经化学转化得到Cef-PO。此外,叶立德活性聚合、共轭二烯烃的阴离子活性聚合和环烯烃的开环易位聚合也可以用来制备Cef-PO。向其他聚合方式（活性自由基聚合、活性阴离子聚合等）的转换及与点击化学的结合是Cef-PO应用的明显特点。Cef-PO的应用包括作为聚合物的改性剂以及用于合成具有复杂结构的聚合物。     

由金属粉末直接合成铁、钴、镍、铜N-杂环卡宾配合物的新方法

VIII族贵金属N-杂环卡宾(NHC)化合物已在许多有机合成反应如烯烃歧化、碳—碳/氮偶联反应中得到广泛应用. 第一过渡系金属价格低廉且毒性小, 发展铁、 钴、镍、铜等的非膦系催化剂具有重要应用价值. 合成第一过渡系金属的NHC化合物需要使用自由卡宾或者由M(NR2)2与咪唑盐反应制备, 这类制备方法通常需要特殊试剂, 反应条件苛刻. 浙江大学化学系刘斌和陈万芝等利用金属单质粉末 (M＝Fe, Co, Ni和Cu)与Ag-NHC配合物的金属置换反应直接合成了相应的M-NHC化合物. 在氧化银存在下, 金属粉末与咪唑盐反应也可以获得相同金属卡宾化合物. 另外, M-NHC化合物也可由咪唑盐在氧气存在下与金属单质直接反应得到. 这些新合成方法收率高, 不需要特殊或贵重试剂, 产物分离简单, 适宜于规模化制备铁、钴、镍、铜的卡宾催化剂, 为非贵金属卡宾催化剂的工业应用奠定了基础.     

以NaBrO_3/H_2SO_4氧化体系合成己二酰-1,′6′一双(4-卤偶氮苯)

取代酰肼化合物是制备偶氮化合物的原料,是一种非常重要的有机化合物,具有广泛的应用价值。它可以和金属形成稳定络合物,对聚烯烃等高分子材料的“铜害”有良好的防护,因而在电线、电缆、钢丝、轮胎等与铜及其它重金属相接触的高分子工业制品中得到广泛应用,被称为金属减活剂[2     

不同配体的稀土金属配合物在烯烃聚合领域的研究进展

催化剂在推动聚烯烃工业发展中有着举足轻重的作用,其中金属催化剂的设计与合成更是金属有机催化化学的关键.稀土金属具有独特的轨道结构、反应活性和配位准则,因此稀土金属配合物通过在金属中心周围引入空间位阻,在聚烯烃材料制备中表现出独特优势.其中配体是决定稀土金属配合物的结构、化学活性及稳定性等方面的关键因素.本综述介绍了茂基配体(烷基取代、芳基取代、茚和芴配体)和非茂基配体(大环四齿配体、三齿配体、双齿配体和单齿配体)的稀土金属配合物的发展及其在聚烯烃制备中的应用.这项工作旨在促进稀土金属催化剂在聚烯烃催化和金属有机催化领域的研究,为高端化、差异化聚烯烃聚合催化剂的制备提供新的设计思路和研究方法.     

钯催化重氮化合物反应的研究进展

重氮化合物在过渡金属催化剂作用下的分解以及后续反应在有机合成上得到了非常广泛的应用. 综述了近年来钯催化重氮化合物反应的研究进展, 主要包括环丙烷化反应、聚合反应、插入反应、交叉偶联反应及其机理的探讨.     

可循环金属铋配合物催化对亚甲基苯醌化合物的1,6-共轭加成反应研究（英文）

设计并合成了一种可催化对亚甲基苯醌化合物的1,6-加成反应的金属铋络合物,并得到二芳基及其取代化合物.该反应的显著特征是使用了廉价、未开发、未引起重视和可重复利用的金属铋络合物,使反应更具有可持续性.另外二芳基甲基取代化合物产率高、底物范围广、官能团耐受性好,反应操作简便、条件温和,是一种可行性高且有吸引力的方案.     

含半夹心铱/铑/钌结构基元的离散型金属环状化合物的研究进展

由于离散型金属环状化合物在主客体化学、气体吸附、分子识别及催化等领域被广泛应用,因此,构筑新型金属环状化合物并研究它们的物理化学性质及应用成为无机化学、有机化学和超分子化学中热门研究方向之一.具有半夹心结构的钌、铱和铑有机金属单元在形成金属环状化合物时具有以下的优势:增强了化合物的溶解性,屏蔽住金属的一半以减少反应的复杂性,易于修饰得到不同结构的产物.综述了近年来以半夹心结构的钌、铱和铑结构基元的离散型金属框架化合物的组装合成和应用.     

钴催化异腈参与的偶联反应研究进展

异腈是一种含有稳定二价碳原子的重要活性反应物,在含氮化合物的构建、新药物的研发以及天然产物的合成中得到了广泛的应用.在过去的十年中,以Passerini和Ugi反应为基础,化学家们致力于研究异腈参与的多组分反应.最近,过渡金属催化异腈参与的氧化偶联反应得到广泛的发展,而使用的催化剂主要集中在一些贵重的过渡金属（Pd、Rh、Ag等）化合物,如何利用廉价过渡金属Co来催化异腈参与的偶联反应具有非常重要的意义.在这里我们概述了近年来Co催化异腈参与的偶联反应的最新研究进展.     

氨水介质中金属锌促进醛的呐偶联反应

传统的呐偶合反应必须在无水有机溶剂条件下, 由金属或金属化合物促进羰基化合物进行呐偶合反应. 曾经报道过金属锌在强碱介质或弱酸介质中, 促进羰基化合物进行水相呐偶合反应. 本文报道一种简便、有效的水相呐偶合反应, 它是在含有少量冠醚的稀氨水溶液中, 使用锌粉促进醛基化合物进行水相呐偶合反应, 其中加入少量的冠醚有助于提高反应的产率, 呐醇产率由63%提高到84%. 然而, 呐偶合反应的产率受到羰基周围环境的立体位阻影响较大, 在此条件下, 锌粉能有效地促进芳香族醛类化合物进行水相呐偶合反应, 得到的呐醇产率高, 但非对映异构体选择性差, 而脂肪族醛类化合物得到的呐醇产率较低, 在同样的条件下, 酮类化合物不能顺利进行呐偶合反应.     

过渡金属杂小环的扩环反应研究进展

过渡金属杂环化合物特别是过渡金属杂小环化合物(成环原子数小于6)在金属有机化学和配位化学领域中具有重要的地位,它们是许多过渡金属催化反应包括烯烃复分解反应、炔烃聚合反应的中间体.通常过渡金属杂小环化合物具有较大的环张力,因此极易与不饱和化合物反应生成环张力较小的扩环产物.针对过渡金属杂小环化学研究现状,综述了几类典型的过渡金属杂三、四、五元环的扩环反应.     

IVB金属配合物催化烯烃聚合的研究进展

IVB金属配合物催化烯烃聚合的研究,不仅为工业界提供大量新型高效的催化剂模型,同时也为探索烯烃配位聚合机理提供了可能.更为重要的是,这些新型的配合物催化剂,可以制备具有优异性能的新型聚烯烃树脂.研究的核心仍然是新型聚烯烃催化剂,基于配合物中配位原子种类的不同,将催化剂的种类分为氮配位和氧配位催化剂.文中综述了近年来IVB金属配合物作为烯烃聚合催化剂的研究进展,集中讨论催化剂结构的变化对催化性能的影响.     

Early Transition Metal Catalysis for Olefin–Polar Monomer Copolymerization

Introducing polar functional groups into widely used polyolefins can enhance polymer surface, rheological, mixing, and other properties, potentially upgrading polyolefins for advanced, value-added applications. The metal catalyst-mediated copolymerization of non-polar olefins with polar comonomers represents the seemingly most straightforward, atom- and energy-efficient approach for synthesizing polar functionalized polyolefins. However, electrophilic early transition metal (groups 3 and 4)-catalyzed processes which have achieved remarkable success in conventional olefin polymerizations, encounter severe limitations here, largely associated with the Lewis basicity of the polar co-monomers. In recent years, however, new catalytic systems have been developed and successful strategies have emerged. In this Minireview, we summarize the recent progress in early transition metal polymerization catalyst development, categorized by the catalytic metal complex and polar comonomer identity. Furthermore, we discuss advances in the mechanistic understanding of these polymerizations, focusing on critical challenges and strategies that mitigate them.     

双烯烃橡胶复分解-加氢制备端羧基聚烯烃

采用烯烃复分解法,以双烯烃橡胶为原料,在Grubbs II代催化剂和链转移剂(马来酸)的作用下制得相应的端羧基聚二烯烃,通过对甲苯磺酰肼/三正丙胺试剂对其进一步加氢得到端羧基聚烯烃.主要研究了反应时间、反应温度、橡胶中双键/催化剂摩尔比、橡胶中双键/链转移剂摩尔比等因素对产物分子量及分子量分布的影响.通过核磁共振氢谱(1H-NMR)和碳谱(13C-NMR)、红外光谱(FTIR)、凝胶渗透色谱仪(GPC)、热重分析(TGA)和示差扫描量热分析(DSC)对产物的结构和性能进行了测试表征.结果表明,通过调整橡胶中双键/催化剂的摩尔比或橡胶中双键/链转移剂的摩尔比可以调控产物的分子量.另外,采用该方法制得的端羧基聚丁二烯具有较高的反式1,4-结构含量,与原料相比其顺式1,4-结构含量大幅下降,从而对产物的性能产生一定影响;而以异戊橡胶为原料时并没有观察到该现象.端羧基聚二烯烃经加氢反应后转变成端羧基聚烯烃,具有更好的热稳定性.该方法合成步骤简单,产物分子量可控,为功能材料的制备提供了新的可能.     

Early Transition Metal Catalysis for Olefin–Polar Monomer Copolymerization

Introducing polar functional groups into widely used polyolefins can enhance polymer surface, rheological, mixing, and other properties, potentially upgrading polyolefins for advanced, value‐added applications. The metal catalyst‐mediated copolymerization of non‐polar olefins with polar comonomers represents the seemingly most straightforward, atom‐ and energy‐efficient approach for synthesizing polar functionalized polyolefins. However, electrophilic early transition metal (groups 3 and 4)‐catalyzed processes which have achieved remarkable success in conventional olefin polymerizations, encounter severe limitations here, largely associated with the Lewis basicity of the polar co‐monomers. In recent years, however, new catalytic systems have been developed and successful strategies have emerged. In this Minireview, we summarize the recent progress in early transition metal polymerization catalyst development, categorized by the catalytic metal complex and polar comonomer identity. Furthermore, we discuss advances in the mechanistic understanding of these polymerizations, focusing on critical challenges and strategies that mitigate them.     

Simulation of Crystallization Analysis Fractionation (Crystaf) of Linear Olefin Block Copolymers

Summary: Linear olefin block copolymers (OBCs) have microstructures that are unique among polyolefins and exhibit properties that are different from those of other polyolefin elastomers. Characterizing their chain microstructures is a challenging task, as conventional characterization techniques cannot probe directly block length distribution or composition. In this work, we used a Monte Carlo model to predict the microstructure details of OBCs and a modified version of the Crystaf model previously developed in our groups to describe theoretical Crystaf profiles for model OBCs. This model can be used as a tool to interpret Crystaf results of these interesting new polyolefins and to relate them to OBC microstructures. Effects of polymerization parameters on OBC microstructure and Crystaf profiles were also discussed.     

Upcycling of Polybutadiene Facilitated by Selenium-Mediated Allylic Amination

Accumulation of end-of-life plastics presents ongoing environmental concerns. One strategy to solve this grand challenge is to invent new techniques that modify post-consumer waste and impart new functionality. While promising approaches for the chemical upcycling of commodity polyolefins and polyaromatics exist, analogous approaches to repurpose unsaturated polymers (e.g., polybutadiene) are scarce. In this work, we propose a method to upcycle polybutadiene, one of the most widely used commercial rubbers, via a mild, metal-free allylic amination reaction. The resulting materials have tunable thermal and surface wetting properties as a function of both sulfonamide identity and grafting density. Importantly, this approach maintains the parent alkene microstructure without evidence of olefin reduction, olefin transposition, and/or chain scission. Based on these findings, we anticipate future applications in the remediation of complex elastomers and vulcanized rubbers.     

Regioselective C−H Xanthylation as a Platform for Polyolefin Functionalization

Polyolefins that contain polar functional groups are important materials for next‐generation lightweight engineering thermoplastics. Post‐polymerization modification is an ideal method for the incorporation of polar groups into branched polyolefins; however, it typically results in chain scission events, which have deleterious effects on polymer properties. Herein, we report a metal‐free method for radical‐mediated C?H xanthylation that results in the regioselective functionalization of branched polyolefins without coincident polymer‐chain scission. This method enables a tunable degree of polymer functionalization and capitalizes on the versatility of the xanthate functional group to unlock a wide variety of C?H transformations previously inaccessible on branched polyolefins.     

Advanced Characterization of Propylene-Based Copolymers and Olefin Block Copolymers

Summary: The newly developed interactive separation of polyolefins by high temperature liquid chromatography (HTLC) provides new information about the chemical composition distribution of polyolefin elastomers. The technique has the advantage of being quantitative in its separation, and has high resolution for the separation of polyolefins by their chemical composition without influence by cocrystallization. Chemical composition distributions can be determined for individual polymers and blends which contain the full range of comonomer typically present in polyethylene and poylypropylene homopolymers, semi-crystalline copolymers, and amorphous copolymers. HTLC analysis in combination with the other fractionation techniques, such as DSC, TREF, NMR, and xylene fractionation, can be used to estimate the amount of olefin block copolymer present in a block composite produced by chain shuttling catalysis.     

The hydrogenation of olefins using a polymer supported ruthenium complex

RuCl₂(PPH₃)3 has been attached to a phosphinated polymer support (phosphinated polystyrene crosslinked with 2% divinylbenzene) and the reagent converted to the polymer supported analogue of RuClH(PPH₃)₃ in the presence of base. The polymer supported catalyst efficiently hydrogenates terminal olefins under ambient conditions. Hydrogenation of 1-hexene has revealed that the reaction rate is proportional to [Ru], [H₂] and [olefin]/(1 + [olefin]). The polymer support environment allows for selectivity in olefin hydrogenation and under suitable reaction conditions short chain terminal olefins are hydrogenated more rapidly than long chain terminal olefins. The extent of metal loading on the polymer and the reaction solvent composition also influence the reaction selectivity and these effects are discussed.     

Design and synthesis of structurally well-defined functional polypropylenes via transition metal-mediated olefin polymerization chemistry

Functionalization of polyolefins is an industrially important yet scientifically challenging research subject. This paper summarizes our recent effort to access structurally well-defined functional polypropylenes via transition metal-mediated olefin polymerization. In one approach, polypropylenes containing side chain functional groups of controlled concentrations were obtained by Ziegler-Natta-catalyzed copolymerization of propylene in combination with either living anionic or controlled radical polymerization of polar monomers. The copolymerization of propylene with 1,4-divinylbenzene using an isospecific MgCl₂-supported TiCl₄ catalyst yielded polypropylenes containing pendant styrene moieties. Both metalation reaction with n-butyllithium and hydrochlorination reaction with dry hydrogen chloride selectively and quantitatively occurred at the pendant reactive sites, generating polymeric benzyllithium and 1-chloroethylbenzene species. These species initiated living anionic polymerization of styrene (S) and atom transfer radical polymerization (in the presence of CuCl and pentamethyldiethylenetriamine) of methyl methacrylate (MMA), respectively, resulting in functional polypropylene graft copolymers (PP-g-PS and PP-g-PMMA) with controllable graft lengths. In another approach, chain end-functionalized polypropylenes containing a terminal OH-group with controlled molecular weights were directly prepared by propylene polymerization with a metallocene catalyst through a selective aluminum chain transfer reaction. Both approaches proved to be desirable polyolefin functionalization routes in terms of efficiency and polymer structure controllability.