Formation and Evolution of Chain-Propagating Species Upon Ethylene Polymerization with Neutral Salicylaldiminato Nickel(II) Catalysts
Научная публикация
| Общее |
Язык:
Английский,
Жанр:
Статья (Full article),
Статус опубликования:
Опубликована,
Оригинальность:
Оригинальная
|
| Журнал |
Chemistry - A European Journal
ISSN: 0947-6539
, E-ISSN: 1521-3765
|
| Вых. Данные |
Год: 2013,
Том: 19,
Номер: 34,
Страницы: 11409-11417
Страниц
: 9
DOI:
10.1002/chem.201301037
|
| Ключевые слова |
nickel, NMR spectroscopy, polymerization, reaction mechanisms, reactive intermediates |
| Авторы |
Soshnikov Igor E.
1
,
Semikolenova Nina V.
1
,
Zakharov Vladimir A.
1
,
Moller Heiko M.
2
,
Olscher Franz
2
,
Osichow Anna
2
,
Gottker-Schnettmann Inigo
2
,
Mecking Stefan
2
,
Talsi Evgenii P.
1
,
Bryliakov Konstantin P.
1
|
| Организации |
| 1 |
Институт катализа им. Г.К. Борескова СО РАН
|
| 2 |
University of Konstanz
|
|
Информация о финансировании (3)
|
1
|
Российский фонд фундаментальных исследований
|
12-03-91159
|
|
2
|
Российский фонд фундаментальных исследований
|
10-03-91330
|
|
3
|
German Research Foundation
|
Me 1388/9-1
|
Formation of Ni–polymeryl propagating species upon the interaction of three salicylaldiminato nickel(II) complexes of the type [(N,O)Ni(CH3)(Py)] (where (N,O)=salicylaldimine ligands, Py=pyridine) with ethylene (C2H4/Ni=10:30) has been studied by 1H and 13C NMR spectroscopy. Typically, the ethylene/catalyst mixtures in [D8]toluene were stored for short periods of time at +60 °C to generate the [(N,O)Ni(polymeryl)] species, then quickly cooled, and the NMR measurements were conducted at −20 °C. At that temperature, the [(N,O)Ni(polymeryl)] species are stable for days; diffusion 1H NMR measurements provide an estimate of the average length of polymeryl chain (polymeryl=(C2H4)nH, n=6–18). At high ethylene consumptions, the [(N,O)Ni(polymeryl)] intermediates decline, releasing free polymer chains and yielding [(N,O)Ni(Et)(Py)] species, which also further decompose to form the ultimate catalyst degradation product, a paramagnetic [(N,O)2Ni(Py)] complex. In [(N,O)2Ni(Py)], the pyridine ligand is labile (with activation energy for its dissociation of (12.3±0.5) kcal mol−1, ΔH≠298=(11.7±0.5) kcal mol−1, ΔS≠298 =(−7±1) cal K−1 mol−1). Upon the addition of nonpolar solvent (pentane), the pyridine ligand is lost completely to yield the crystals of diamagnetic [(N,O)2Ni] complex. NMR spectroscopic analysis of the polyethylenes formed suggests that the evolution of chain-propagating species ends up with formation of polyethylene with predominately internal and terminal vinylene groups rather than vinyl groups.