Реферат: The number of active centers C p in the homogeneous complexes LCoCl2 and LVCl3 (L = 2,6-(2,6-R2C6H3N=CMe)2C5H3N; R = Me, Et, t Bu) and the propagation rate constants k p have been determined by the radioactive 14CO quenching of ethylene polymerization on these complexes in the presence of the methylaluminoxane (MAO) activator. For the systems studied, a significant portion of the initial complex (up to 70%) transforms into polymerization-active centers. The catalysts based on the cobalt complexes are single-site, and the constant k p in these systems is independent of the volume of substituent R in the ligand, being (2.4−3.5) × 103 L mol−1 s−1 at 35°C. The much larger molecular weight of the polymer formed on the complex with the tert-butyl substituent in the aryl rings of the ligand compared to the product formed on the complex with the methyl substituent is due to the substantial (∼11-fold) decrease in the rate constant of chain transfer to the monomer. At the early stages of the reaction (before 5 min), the vanadium complexes contain active centers of one type only, for which k p = 2.6 × 103 L mol−1 s−1 at 35°C. An increase in the polymerization time to 20 min results in the appearance, in the vanadium systems, of new, substantially less reactive centers on which high-molecular-weight polyethylene forms. The number of active centers C p in the 2,5-tBu2LCoCl2 and 2,6-Et2LVCl3 systems with the MAO activator increases as the polymerization temperature is raised from 25 to 60°C. The activation energies of the chain propagation reaction (E p) have been calculated. The value of E p for complex 2,5-tBu2LCoCl2 is 4.5 kcal/mol. It is assumed that the so-called “dormant” centers form in ethylene polymerization on the 2,6-Et2LVCl3 complex, and their proportion increases with a decrease in the polymerization temperature. Probably, the anomalously high value E p = 14.2 kcal/mol for the vanadium system is explained by the formation of these “dormant” centers.

Библиографическая ссылка: Barabanov A.A. , Semikolenova N.V. , Matsko M.A. , Zakharov V.A.
Kinetic Regularities of Catalytic Ethylene Polymerization on Single- and Multi-Site Cobalt and Vanadium Bis(imino)pyridine Complexes
Kinetics and Catalysis. 2013. V.54. N4. P.475-480. DOI: 10.1134/S0023158413040022 WOS Scopus РИНЦ CAPlusCA OpenAlex

Оригинальная: Барабанов А.А. , Семиколенова Н.В. , Мацько М.А. , Захаров В.А.
Кинетические особенности каталитической полимеризации этилена на моноцентровых и полицентровых бис(имино)пиридиновых комплексах кобальта и ванадия
Кинетика и катализ. 2013. Т.54. №4. С.500-506. DOI: 10.7868/S0453881113040023 РИНЦ OpenAlex

Даты:

Поступила в редакцию:	14 нояб. 2012 г.
Опубликована в печати:	1 июл. 2013 г.
Опубликована online:	24 июл. 2013 г.

Идентификаторы БД:

Web of science:	WOS:000322183000013
Scopus:	2-s2.0-84887494462
РИНЦ:	21464765
Chemical Abstracts:	2013:1156248
Chemical Abstracts (print):	159:455783
OpenAlex:	W2136805196

Цитирование в БД:

БД	Цитирований
Web of science	3
Scopus	3
РИНЦ	3
OpenAlex	3

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