Testing DFT ability to predict thestereoselectivity of group 4 metallocenes inpropylene polymerization
- سال انتشار: 1393
- محل انتشار: فصلنامه پلی اولفین ها، دوره: 1، شماره: 2
- کد COI اختصاصی: JR_POJ-1-2_006
- زبان مقاله: انگلیسی
- تعداد مشاهده: 472
نویسندگان
Department of Polymerization Engineering, Iran Polymer and Petrochemical Institute, P.O. Box۱۴۹۶۵/۱۱۵, Tehran, Iran.
Department of Chemistry and Biology, University of Salerno, Via Papa Giovanni Paolo II, FiscianoI-۸۴۰۸۴, Italy.
Department of Chemistry and Biology, University of Salerno, Via Papa Giovanni Paolo II, FiscianoI-۸۴۰۸۴, Italy
چکیده
In this study we have tested the ability of a standard DFT computational protocol to reproduce the experimentally obtained stereoselectivity of 26 different C2-symmetric zirconocene catalysts active in propylene polymerization. The catalysts werechosen for their relevance in metallocene catalyzed polymerization of propylene. To this end, primary insertion of both si- andre-propylene enantiofaces into the Zr-CH2-CH(CH3)2 bond was considered to simulate the growing chains step. The energydifference between these two transition states, ΔEre-si, was taken as a measure of the stereoselectivity (pentad: mmmm%) ofdifferent catalysts. The results clearly indicated that there was a good agreement between ΔEre-si and the mmmm% values, sothat greater ΔEre-si could correspond to higher mmmm%. A model was ftted to the experimentally obtained mmmm% againsttheoretical ΔEre-si. The coeffcient of determination (R2) of the resultant plot was 0.9793, which indicated a good accuracy of themodel. Finally, to quantify the steric role of the studied ligands in the observed stereoselectivity, the analysis of the buried volume(VBur) and of the steric maps was performed for two representative complexes. The images revealed that a greater asymmetriclocalization of the %VBur around the metal center led to a higher mmmm% in the resultant polymer. Polyolefns J (2014) 1:139-146کلیدواژه ها
Metallocene catalysts, DFT, Molecular simulation, Setereoselective polymerization, Isotactic polypropyleneاطلاعات بیشتر در مورد COI
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