Kinetic Regularities of Catalytic Ethylene Polymerization on Single- and Multi-Site Cobalt and Vanadium Bis(imino)pyridine Complexes Full article
| Journal |
Kinetics and Catalysis
ISSN: 0023-1584 , E-ISSN: 1608-3210 |
||
|---|---|---|---|
| Output data | Year: 2013, Volume: 54, Number: 4, Pages: 475-480 Pages count : 6 DOI: 10.1134/S0023158413040022 | ||
| Tags | Molecular Weight Distribution; Imino; Ethylene Polymerization; Cobalt Complex; Aryl Ring | ||
| Authors |
|
||
| Affiliations |
|
Funding (1)
| 1 | Russian Foundation for Basic Research | 07-03-00311 |
Abstract:
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.
Cite:
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 ANCAN OpenAlex
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 ANCAN OpenAlex
Original:
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
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
Dates:
| Submitted: | Nov 14, 2012 |
| Published print: | Jul 1, 2013 |
| Published online: | Jul 24, 2013 |
Identifiers:
| Web of science: | WOS:000322183000013 |
| Scopus: | 2-s2.0-84887494462 |
| Elibrary: | 21464765 |
| Chemical Abstracts: | 2013:1156248 |
| Chemical Abstracts (print): | 159:455783 |
| OpenAlex: | W2136805196 |