TY - JOUR
T1 - Synthesis and characterization of para-nitro substituted 2,6-bis(phenylimino)pyridyl Fe(II) and Co(II) complexes and their ethylene polymerization properties
AU - Long, Zerong
AU - Wu, Biao
AU - Yang, Peiju
AU - Li, Gang
AU - Liu, Yanyan
AU - Yang, Xiao Juan
PY - 2009/11/1
Y1 - 2009/11/1
N2 - Four iron(II) and cobalt(II) complexes ligated by 2,6-bis(4-nitro-2,6-R2-phenylimino)pyridines, LMCl2 (1: R = Me, M = Fe; 2: R = iPr, M = Fe; 3: R = Me, M = Co; 4: R = iPr, M = Co) have been synthesized and fully characterized, and their catalytic ethylene polymerization properties have been investigated. Among these complexes, the iron(II) pre-catalyst bearing the ortho-isopropyl groups (complex 2) exhibited higher activities and produced higher molecular weight polymers than the other complexes in the presence of methylaluminoxane (MAO). A comparison of 2 with the reference non-nitro-substituted catalyst (2,6-bis(2,6-diisopropylphenylimino)pyridyl)FeCl2 (FeCat 5) revealed a modest increase of the catalytic activity and longer lifetime upon substitution of the para-positions with nitro groups (activity up to 6.0 × 103 kg mol-1 h-1 bar-1 for 2 and 4.8 × 103 kg mol-1 h-1 bar-1 for 5), converting ethylene to highly linear polyethylenes with a unimodal molecular weight distribution around 456.4 kg mol-1. However, the iron(II) pre-catalyst 1 on changing from ortho-isopropyl to methyl groups displayed much lower activities (over an order of magnitude) than 2 under mild conditions. As expected, the cobalt analogues showed relatively low polymerization activities.
AB - Four iron(II) and cobalt(II) complexes ligated by 2,6-bis(4-nitro-2,6-R2-phenylimino)pyridines, LMCl2 (1: R = Me, M = Fe; 2: R = iPr, M = Fe; 3: R = Me, M = Co; 4: R = iPr, M = Co) have been synthesized and fully characterized, and their catalytic ethylene polymerization properties have been investigated. Among these complexes, the iron(II) pre-catalyst bearing the ortho-isopropyl groups (complex 2) exhibited higher activities and produced higher molecular weight polymers than the other complexes in the presence of methylaluminoxane (MAO). A comparison of 2 with the reference non-nitro-substituted catalyst (2,6-bis(2,6-diisopropylphenylimino)pyridyl)FeCl2 (FeCat 5) revealed a modest increase of the catalytic activity and longer lifetime upon substitution of the para-positions with nitro groups (activity up to 6.0 × 103 kg mol-1 h-1 bar-1 for 2 and 4.8 × 103 kg mol-1 h-1 bar-1 for 5), converting ethylene to highly linear polyethylenes with a unimodal molecular weight distribution around 456.4 kg mol-1. However, the iron(II) pre-catalyst 1 on changing from ortho-isopropyl to methyl groups displayed much lower activities (over an order of magnitude) than 2 under mild conditions. As expected, the cobalt analogues showed relatively low polymerization activities.
KW - 2,6-bis(4-nitro-2,6-R-phenylimino)pyridines
KW - Cobalt(II)
KW - Electronic effect
KW - Ethylene polymerization
KW - Iron(II)
UR - http://www.scopus.com/inward/record.url?scp=70349425753&partnerID=8YFLogxK
U2 - 10.1016/j.jorganchem.2009.07.027
DO - 10.1016/j.jorganchem.2009.07.027
M3 - Article
AN - SCOPUS:70349425753
SN - 0022-328X
VL - 694
SP - 3793
EP - 3799
JO - Journal of Organometallic Chemistry
JF - Journal of Organometallic Chemistry
IS - 23
ER -