Neodymium alkoxides: synthesis, characterization and their combinations with dialkylmagnesiums as unique systems for polymerization and block copolymerization of ethylene and methyl methacrylate.
Neodymium alkoxides: synthesis, characterization and their combinations with dialkylmagnesiums as unique systems for polymerization and block copolymerization of ethylene and methyl methacrylate.
复制标题
DOI：
10.1002/1521-3765(20020816)8:16
复制
发表时间：
2002-08
期刊：
影响因子：
--
通讯作者：
Jérôme Gromada;A. Mortreux;T. Chenal;J. Ziller;Frédéric Leising;J. Carpentier
中科院分区：
文献类型：
--
作者：
Jérôme Gromada;A. Mortreux;T. Chenal;J. Ziller;Frédéric Leising;J. Carpentier
研究了由简单和官能化的叔一醇制得的各种钕醇类化合物的合成和表征，以及它们作为无机前驱体与二烷基镁试剂在乙烯和甲基丙烯酸甲酯(MMA)(Co)聚合中的应用。NdCl3与醇钠在四氢呋喃中的盐异构化反应生成R=tBu(1)、(2)的三核配合物[Nd(3)(mu(3)-OR)(2)(mu(2)-OR)(3)(OR)(4)(thf)(2)]，而在Et(2)O中合成得到聚集体结构[Nd(12)(OtAm)(26)(HOtAm)(2)Cl(11)Na].(OEt(2))(2)(3)。[Nd(3)(mu(3)-OtBu)(2)(mu(2)-OtBu)(3)(OtBu)(4)(HOtBu)(2)](4)在正己烷中氨解制得，在甲苯中缓慢分解为氧配合物[Nd(5)(mu(5)-O)(mu(3)-OtBu)(4)(mu(2)-OtBu)(4)(OtBu)(5)](5)。最后，以相应的伽马给体功能化乙醇为原料，通过氨解反应合成了二聚体[ND(2)(Mu(2)，ETA(2)-OR)(2)(ETA(2)-OR)(2)(ETA(1)-OR)(2)](OR=OCME(2)CH(2)CH(2)OMe)(6)。这些化合物中的一些，特别是同质络合物1，当与一个当量的二烷基镁在原位结合时，允许形成乙烯聚合的活性催化剂。在温和的条件下(0℃，1bar)，后者的催化体系表现出中等的活性(5-10 kg mol(-1)h(-1)bar(-1))。在H(2)或PhSiH(3)存在下观察到有效的转移反应，额外添加二烷基镁可更新/提高活性。该催化体系最显著的特点是在乙烯聚合过程中以固体S的形式析出了活性的“ND-聚乙烯基”物种。这种非均质性得到了很好的利用，实现了非均相固-气乙烯聚合，并制备了具有高嵌段效率和高相对分子质量(M(N)>；200000)的两嵌段PE-PMMA共聚物。提出了这一独特体系的催化循环，其基础是从二烷基镁化合物中分离出过渡金属产物(7)，并对后者进行了核磁共振研究。
The synthesis and characterization (NMR and X-ray) of a variety of neodymium alkoxides derived from simple and functionalized tertiary monoalcohols, and their application as inorganic precursors in combination with dialkylmagnesium reagents for ethylene and methyl methacrylate (MMA) (co)polymerization have been investigated. Salt metathesis reactions between NdCl(3) and sodium alkoxides in THF led to the formation of trinuclear complexes [Nd(3)(mu(3)-OR)(2)(mu(2)-OR)(3)(OR)(4)(thf)(2)] with R=tBu (1), tAm (2), while aggregate structure [Nd(12)(OtAm)(26)(HOtAm)(2)Cl(11)Na].(OEt(2))(2) (3) was obtained when the synthesis was performed in Et(2)O. [Nd(3)(mu(3)-OtBu)(2)(mu(2)-OtBu)(3)(OtBu)(4)(HOtBu)(2)] (4), prepared by aminolysis of Nd[N(SiMe(3))(2)](3) in hexane, slowly decomposed in toluene into oxo complex [Nd(5)(mu(5)-O)(mu(3)-OtBu)(4)(mu(2)-OtBu)(4)(OtBu)(5)] (5). Finally, the dimer [Nd(2)(mu(2),eta(2)-OR)(2)(eta(2)-OR)(2)(eta(1)-OR)(2)] (OR=OCMe(2)CH(2)CH(2)OMe) (6) was synthesised by aminolysis reaction from the corresponding gamma-donor-functionalized alcohol. Some of these neodymium alkoxides, in particular homoleptic complex 1, when associated in situ to one equivalent of a dialkylmagnesium, allow the formation of an active catalyst for ethylene polymerization. Under mild conditions (0 degrees C, 1 bar), the latter catalyst system exhibited a moderate activity (5-10 kg mol(-1) h(-1) bar(-1)). Effective transfer reactions were observed in the presence of H(2) or PhSiH(3) and renewal/improvement of activity occurred upon extra addition of dialkylmagnesium. The most outstanding feature of this catalytic system lies in the precipitation of the active "Nd-polyethylenyl" species during the ethylene polymerization course as solid S which could be isolated. This heterogeneity was turned to good account, enabling to achieve heterogeneous solid-gas ethylene polymerization and to prepare diblock PE-PMMA copolymers with high diblock efficiency and high molecular weights (M(n) > 200 000). A catalytic cycle for this unique system is proposed based on the isolation of a transmetallation product (7) from a neodymium alkoxide/dialkylmagnesium combination and NMR studies of the latter.