A Catalyst for the Simultaneous Ring-Opening Metathesis Polymerization/Vinyl Insertion Polymerization
A Catalyst for the Simultaneous Ring-Opening Metathesis Polymerization/Vinyl Insertion Polymerization
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DOI：
10.1002/anie.201004125
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发表时间：
2011-01-01
影响因子：
16.6
通讯作者：
Reinhardt, Ingrid
中科院分区：
文献类型：
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作者：
Buchmeiser, Michael R.;Camadanli, Sebnem;Reinhardt, Ingrid
烯烃的乙烯基插入聚合（VIP）[1-7]和环烯烃的开环复分解聚合（ROMP）[8,9]都是基于在过渡金属（离子）和生长的聚合物链之间插入单体的成熟聚合技术。事实上，它们是相互关联的，因为阳离子的vip活性催化剂可以通过简单的α-消除过程转化为romp活性催化剂。相反，相反的过程，即α加成一个质子到金属烷基烯上形成一个阳离子的vip活性物质，要以可控的方式完成要困难得多。聚（NBE）（NBE= norborn-2-ene）中VIP-(Scheme1a)和romp衍生（Scheme1b）结构的出现在聚烯烃化学的早期就已经被观察到，这为识别和理解基于元合成的过程铺平了道路。[10,11]然而，当时并没有明确的证据表明这两种结构，即romp和vip衍生的重复单元都存在于一条聚合物链中。[10-14]事实上，由于这些聚合物的高结晶度，有人认为两种不同的聚合物同时形成，即一种是vip衍生的，一种是romp衍生的。Farina etal首次报道了romp和vip衍生结构在单个聚合物链中存在的明确证据。使用mo和re基引发剂；[15,16]他们明确地为VIP/ romp衍生聚（NBE）中的季碳和亚甲基分配了特征信号（方案1c）。事实上，这种特殊聚合物的结构只能用可逆的α-消除/α-加成过程来解释，该过程允许VIP和ROMP在同一聚合物链中发生。由于VIP和ROMP之间的关系，即使VIP和ROMP之间的一个开关，也会导致AB二嵌段共聚物的合成，这引起了人们的关注。因此，Grubbs等人报道了一种在NBE的ROMP中具有活性的钛环丁烷化合物；在乙烯(E)的VIP中产生了一种具有活性的阳离子物质，从而合成了聚（NBE） ROMP-bpoly (E)Kaminsky等人报道了在制备聚（NBE） VIP-bpoly (NBE) ROMP、聚（NBE） VIP-b-poly (CPE) ROMP和聚-(NBE) VIP-b-poly (COE) ROMP（CPE=环戊烯，COE=顺式环烯）过程中从VIP到ROMP的受控切换。(18、19)
Both the vinyl insertion polymerization (VIP) of olefins [1–7] and the ring-opening metathesis polymerization (ROMP)[8, 9] of cyclic olefins are well-established polymerization techniques based on the insertion of a monomer between a transition metal (ion) and a growing polymer chain. In fact, they are related to each other, since a cationic, VIP-active catalyst may be converted into a ROMP-active catalyst by a simple α-elimination process. In contrast, the reverse process, that is, the α addition of a proton to a metal alkylidene to form a cationic VIP-active species, is much more difficult to accomplish in a controlled way. The occurrence of both VIP-(Scheme1a) and ROMP-derived (Scheme1b) structures in poly (NBE)(NBE= norborn-2-ene) was observed already in the early days of polyolefin chemistry and paved the way for identifying and understanding metathesis-based processes.[10, 11] Nevertheless, at that time there was no clear evidence for the presence of both structures, that is, both ROMP-and VIP-derived repeat units, within one single polymer chain.[10–14] In fact, because of the high crystallinity of these polymers, it was argued that two different polymers, that is, one VIP-and one ROMP-derived, had formed concomitantly. The first unequivocal evidence for the presence of both ROMP-and VIP-derived structures within one single polymer chain was reported by Farina etal. using Mo-and Re-based initiators;[15, 16] they unambiguously assigned characteristic signals for the quaternary carbon and for the methylene group in VIP/ROMP-derived poly (NBE)(Scheme 1c). In fact, the structure of this particular polymer can be explained only by a reversible α-elimination/α-addition process, which permits VIP and ROMP to take place within the same polymer chain. Owing to the relationship between VIP and ROMP, even one single switch between VIP and ROMP, resulting in the synthesis of AB diblock copolymers, has attracted attention. Thus, Grubbs et al. reported on a titanacyclobutane compound active in the ROMP of NBE; upon addition of an alcohol and activation with Et2AlCl, a cationic species was created that is active in the VIP of ethylene (E), resulting in the synthesis of poly (NBE) ROMP-bpoly (E).[17] Kaminsky et al. reported on a controlled switch from VIP to ROMP in the preparation of poly (NBE) VIP-bpoly (NBE) ROMP, poly (NBE) VIP-b-poly (CPE) ROMP, and poly-(NBE) VIP-b-poly (COE) ROMP(CPE= cyclopentene, COE= cis-cyclooctene).[18, 19]