caa a22 4500 475760638 CHVBK 20180406123550.0 cr unu---uuuuu 170329e20001001xx s 000 0 eng 10.1007/BF02496344 doi (NATIONALLICENCE)springer-10.1007/BF02496344 Density functional study of ethylene polymerization on zirconocene catalysts [Elektronische Daten] 2. Substituted zirconocene catalysts [I. Nifant'ev, L. Ustynyuk, D. Laikov] Polymerization of ethylene on zirconocene catalysts was studied with the density functional theory. The approach proposed previously for the model system Cp2ZrEt++C2H4 was extended to substituted zirconocene catalysts (RCp)2ZrEt+, which allowed us to compare the results of calculations with the experimentally found rate constants of chain propagation. The ethyl fragment was demonstrated to be an adequate model for a growing polymer chain. The order of decrease in the activation energy of chain propagation calculated for compounds with R=H, Me, Prn, and Bun is in qualitative agreement with the experimental data. However, the quantitative description gave underestimated theoretical rate constants of chain propagation compared to the experimental values. In the case of polyalkyl-substituted zirconocenes (R=1.2-Me2 or Me4), no correlation between the calculated and experimental characteristics was observed. The results were explained using the simplest model reaction of the replacement of the MeMAO− counterion by an ethylene molecule accompanied by displacement of the former to the outer coordination sphere of the Zr atom. This step was demonstrated to control the kinetics of the process. It was concluded that the isolated-cation model used in early investigations is not adequate and calls for modification with regard to the effect of the counterion. Kluwer Academic/Plenum Publishers, 2000 polyolefins nationallicence substituted zirconocenes nationallicence quantum-chemical calculations nationallicence density functional theory nationallicence Nifant'ev I. Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory, 119899, Moscow, Russian Federation aut Ustynyuk L. Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory, 119899, Moscow, Russian Federation aut Laikov D. Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory, 119899, Moscow, Russian Federation aut Russian Chemical Bulletin Kluwer Academic Publishers-Plenum Publishers 49/10(2000-10-01), 1735-1741 1066-5285 49:10<1735 2000 49 11172 https://doi.org/10.1007/BF02496344 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02496344 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Nifant'ev I. Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory, 119899, Moscow, Russian Federation aut NATIONALLICENCE 700 1- Ustynyuk L. Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory, 119899, Moscow, Russian Federation aut NATIONALLICENCE 700 1- Laikov D. Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory, 119899, Moscow, Russian Federation aut NATIONALLICENCE 773 0- Russian Chemical Bulletin Kluwer Academic Publishers-Plenum Publishers 49/10(2000-10-01), 1735-1741 1066-5285 49:10<1735 2000 49 11172 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer