Stereo- and enantioselective polymerization of hexa-1,5-diene on heterogeneous Ziegler-Natta catalysts obtained with the use of optically active internal donors
作者:A. L. Lyubimtsev、I. E. Nifant’ev
DOI:10.1007/s11172-009-0231-z
日期:2009.8
Pure racemates and individual enantiomers of diethyl 2,3-diisopropylsuccinate ((+,−)-DIPS and (−)-DIPS) and 2,3-diisopropyl-1,4-dimethoxybutane ((+,−)-DPDMB and (+)-DPDMB) were prepared. The synthesized compounds and diethyl phthalate were used as internal donors for the preparation of heterogeneous Ziegler-Natta catalysts. Polymerization of hexa-1,5-diene was carried out on these catalysts. The obtained samples of poly(methylene-1,3-cyclopentane) were studied by 13C NMR spectroscopy and polarimetry. The induction of optical activity to polymer is observed with (−)-DIPS as the internal donor. The induction value makes up 15–20% from the value recorded in the case of optically active metallocene catalysts. The emergence of induction may be associated with the presence of close contact between the titanium atom and the donor molecule within the active site of catalyst, as well as with the fact that the donor molecule either deactivates a part of the stereospecific titanium centers or influences the structure of the titanium centers during their formation and development.
2,3-二异丙基琥珀酸二乙酯((+,−)-DIPS 和 (−)-DIPS)和 2,3-二异丙基-1,4-二甲氧基丁烷((+,−)-DPDMB 和 (+) 的纯外消旋体和单个对映体)-DPDMB)被制备。合成的化合物和邻苯二甲酸二乙酯作为内给体用于制备非均相齐格勒-纳塔催化剂。在这些催化剂上进行了六-1,5-二烯的聚合。通过 13C NMR 光谱和旋光分析对所得聚(亚甲基-1,3-环戊烷)样品进行了研究。使用 (-)-DIPS 作为内给体观察到聚合物的光学活性诱导。诱导值占光学活性茂金属催化剂记录值的 15-20%。诱导的出现可能与催化剂活性位点内钛原子和供体分子之间存在紧密接触有关,也与供体分子使部分立体定向钛中心失活或影响钛原子中心的事实有关。钛中心在其形成和发展过程中的结构。