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普遍认为,以d-轨道过渡金属化合物为催化剂的双烯定向聚合中,活性链端具η~3-烯丙基结构,而聚合物中顺-1,4及反-1,4链节的相对含量,则取决于烯丙基络合物的对式(anti)和同式(syn)异构体的含量及其异构化作用。本文作者之一曾提出,在以稀土化合物为催化剂的己二烯-2,4的定向聚合中,活性链端也应具有η~3-烯丙基结构,否则无法解释生成反-1,4-苏式-双全同立构(trans-1,4-threo-dilsolactic)聚合物。诚然,如果稀土催化双烯聚合过程也与d-轨道过渡金属的情况类似,那么,从上述概念出发,丁二烯在稀土催化剂作用下生成顺-1,4聚合物的过程,可图示如下:
It is generally accepted that the d-orbital transition metal compound catalyzed diene directional polymerization, the active end of the chain with η 3-allyl structure, and the polymer cis-1,4 and trans-1,4 chain of The relative content depends on the content of the anti and syn isomers of the allyl complex and its isomerization. One of the authors of this paper has suggested that in the targeted polymerization of hexadiene-2,4 with a rare earth compound as a catalyst, the active end should have an n-3-allyl structure, otherwise it can not be explained that trans-1,4 - Trans-1,4-threo-dilsolactic polymers. Admittedly, if the rare earth catalyzed polymerization of diene is also similar to the case of the d-orbital transition metal, the process of producing cis-1,4 polymer with butadiene over a rare earth catalyst from the above concept can be illustrated as follows :