TY - JOUR

T1 - Origin of "multisite-like" ethylene polymerization behavior of the single-site nonsymmetrical bis(imino)pyridine iron(II) complex in the presence of modified methylaluminoxane

AU - Semikolenova, Nina V.

AU - Sun, Wen Hua

AU - Soshnikov, Igor E.

AU - Matsko, Mikhail A.

AU - Kolesova, Olga V.

AU - Zakharov, Vladimir A.

AU - Bryliakov, Konstantin P.

PY - 2017/4/7

Y1 - 2017/4/7

N2 - A detailed study of the effect of reaction temperature, time, and cocatalyst composition on the ethylene polymerization performance of 2-[1-(2,6-dibenzhydryl-4-chlorophenylimino)ethyl]-6-(1-mesityliminoethyl)pyridyliron dichloride (1) is reported. In the presence of modified methylaluminoxane (MMAO), 1 behaves like a highly active, "multisite-like" ethylene polymerization catalyst, with the resulting polyethylenes having time-dependent bimodal-like molecular-weight distributions and featuring saturated (n-propyl- and i-butyl-terminated) chain ends. To readily distinguish between bimodal and bimodal-like molecular-weight distributions, we have proposed the use of the dNf/(d log M) - log M representation further to the mainstream dWf/(d log M) - log M one. The consensus mechanism of chain transfer and chain-end formation in the presence of MMAO has been proposed, which explains the composition and amount of terminal alkyl groups in the polymer, and the apparent "multisite-like" nature of the iron catalyst. A comparison between the catalytic behaviors of the "multisite-like" 1/MMAO catalyst system and the truly multisite catalyst system based on Brookhart's symmetrical bis(imino)pyridine iron catalyst 2 is given. (Graph Presented).

AB - A detailed study of the effect of reaction temperature, time, and cocatalyst composition on the ethylene polymerization performance of 2-[1-(2,6-dibenzhydryl-4-chlorophenylimino)ethyl]-6-(1-mesityliminoethyl)pyridyliron dichloride (1) is reported. In the presence of modified methylaluminoxane (MMAO), 1 behaves like a highly active, "multisite-like" ethylene polymerization catalyst, with the resulting polyethylenes having time-dependent bimodal-like molecular-weight distributions and featuring saturated (n-propyl- and i-butyl-terminated) chain ends. To readily distinguish between bimodal and bimodal-like molecular-weight distributions, we have proposed the use of the dNf/(d log M) - log M representation further to the mainstream dWf/(d log M) - log M one. The consensus mechanism of chain transfer and chain-end formation in the presence of MMAO has been proposed, which explains the composition and amount of terminal alkyl groups in the polymer, and the apparent "multisite-like" nature of the iron catalyst. A comparison between the catalytic behaviors of the "multisite-like" 1/MMAO catalyst system and the truly multisite catalyst system based on Brookhart's symmetrical bis(imino)pyridine iron catalyst 2 is given. (Graph Presented).

KW - Bis(imino)pyridine

KW - Chain transfer

KW - Ethylene polymerization

KW - MMAO

KW - Molecular-weight distribution

KW - Multisite catalysts

KW - bis(imino)pyridine

KW - molecular-weight distribution

KW - ACTIVATION

KW - PRECATALYSTS

KW - 2,6-BIS(IMINO)PYRIDYL COMPLEXES

KW - ethylene polymerization

KW - POLYETHYLENE

KW - FE(II)

KW - multisite catalysts

KW - chain transfer

KW - NEW-GENERATION

KW - CATALYSTS

KW - COBALT

UR - http://www.scopus.com/inward/record.url?scp=85019085389&partnerID=8YFLogxK

U2 - 10.1021/acscatal.7b00486

DO - 10.1021/acscatal.7b00486

M3 - Article

AN - SCOPUS:85019085389

VL - 7

SP - 2868

EP - 2877

JO - Topics in Catalysis

JF - Topics in Catalysis

SN - 1022-5528

IS - 4

ER -