TY - JOUR
T1 - Solvent and co-catalyst dependent pyrazolylpyridinamine and pyrazolylpyrroleamine nickel(II) catalyzed oligomerization and polymerization of ethylene
AU - Obuah, Collins
AU - Omondi, Bernard
AU - Nozaki, Kyoko
AU - Darkwa, James
PY - 2014
Y1 - 2014
N2 - The pyrazolylamine ligands, 2-(3,5-dimethyl-1H-pyrazol-1-yl)-N-(pyridin-2- ylmethyl)ethan-amine (L1a), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)-N-(pyridin-2- ylmethyl)ethan-amine (L2a), 2-(3,5-dimethyl-pyrazol-1-yl)-ethyl-(1H-pyrrol-2- ylmethyl)-amine (L3a), 2-(3,5-di-tert-butyl-pyrazol-1-yl)-ethyl-(1H-pyrrol-2- ylmethyl)-amine (L4a), were prepared by reducing the corresponding imine compounds L1-L4. L1a-L4a were then reacted with [NiBr2(DME)] to form the nickel complexes, [NiBr2(L1a)] (1), [NiBr2(L2a)] (2), [NiBr2(L3a)] (3) and [NiBr2(L4a)] (4) in high yields. When activated with aluminum co-catalysts, all four nickel complexes were able to catalyze the oligomerization or polymerization of ethylene; but the products of these reactions were co-catalyst and solvent dependent. With EtAlCl2 as co-catalyst and in toluene, butene and hexene were formed, which subsequently alkylated the solvent selectively to butyl-, dibutyl- and tri-butyltoluene. The same catalysts in chlorobenzene produced butene, hexene and highly branched polyethylene. Changing the co-catalysts to MAO and with toluene as solvent, complexes 2 and 3 catalyzed the polymerization of ethylene to high molecular weight (447,300 Da) linear high density polyethylene (ca Tm = 135.5 C); with polydispersity indices ranging from 1.63 to 2.51.
AB - The pyrazolylamine ligands, 2-(3,5-dimethyl-1H-pyrazol-1-yl)-N-(pyridin-2- ylmethyl)ethan-amine (L1a), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)-N-(pyridin-2- ylmethyl)ethan-amine (L2a), 2-(3,5-dimethyl-pyrazol-1-yl)-ethyl-(1H-pyrrol-2- ylmethyl)-amine (L3a), 2-(3,5-di-tert-butyl-pyrazol-1-yl)-ethyl-(1H-pyrrol-2- ylmethyl)-amine (L4a), were prepared by reducing the corresponding imine compounds L1-L4. L1a-L4a were then reacted with [NiBr2(DME)] to form the nickel complexes, [NiBr2(L1a)] (1), [NiBr2(L2a)] (2), [NiBr2(L3a)] (3) and [NiBr2(L4a)] (4) in high yields. When activated with aluminum co-catalysts, all four nickel complexes were able to catalyze the oligomerization or polymerization of ethylene; but the products of these reactions were co-catalyst and solvent dependent. With EtAlCl2 as co-catalyst and in toluene, butene and hexene were formed, which subsequently alkylated the solvent selectively to butyl-, dibutyl- and tri-butyltoluene. The same catalysts in chlorobenzene produced butene, hexene and highly branched polyethylene. Changing the co-catalysts to MAO and with toluene as solvent, complexes 2 and 3 catalyzed the polymerization of ethylene to high molecular weight (447,300 Da) linear high density polyethylene (ca Tm = 135.5 C); with polydispersity indices ranging from 1.63 to 2.51.
KW - Al co-catalyst
KW - Ethylene
KW - Friedel-Crafts
KW - Oligomerization
KW - Polymerization
UR - http://www.scopus.com/inward/record.url?scp=84888082156&partnerID=8YFLogxK
U2 - 10.1016/j.molcata.2013.10.024
DO - 10.1016/j.molcata.2013.10.024
M3 - Article
AN - SCOPUS:84888082156
SN - 1381-1169
VL - 382
SP - 31
EP - 40
JO - Journal of Molecular Catalysis A: Chemical
JF - Journal of Molecular Catalysis A: Chemical
ER -