Iron and Cobalt Complexes of Tridentate N‐Donor Ligands in Ethylene Polymerization: Efficient Shielding of the Active Sites by Simple Phenyl Groups

Abstract

Tridentate 2,6-bis[3(5)-pyrazolyl]pyridines and 2,6-bis(4-pyrimidinyl)pyridine were synthesized and characterized spectroscopically and by single-crystal X-ray structure analysis. The derived complexes with FeCl 2 and CoCl 2 were investigated for their activity in the ethylene polymerization in the presence of methylalumoxane (MAO). Iron and cobalt catalysts bearing the ligand 2,6-bis[5-butyl-1-(4-nitrophenyl)pyrazol-3-yl]pyridine showed moderate catalytic activity and

Bis(Pyrazolyl)Pyridine Late Transition Metal Complexes as Single-Site Catalysts for Ethylene Polymerization to Highly Linear Polyethylene

“…The nature of metal centre has a significant effect on catalyst activity, which may be attributed to the differences of the electronic environments [10,11,13]. The Co precatalyst 1 is more active than the corresponding Ni and Fe precatalysts, which is in agreement with the reported results [37].…”

“…From Table 1, 1-3/MAO catalytic systems show moderate activities at 10 bar ethylene pressure, which is in agreement to the observation that higher pressure is necessary for other Co and Fe catalysts related systems [37].…”

“…The molecular weights of polymer produced were high (0.7-1.4) 9 10 6 g mol -1 in all runs performed, which is similar or higher than those reported for related systems [36,37].…”

“…The results obtained with 1-3/MAO catalytic systems show higher or comparable activity than those reported analogues under the conditions reported here [36,37].…”

Synthesis, characterization, and MMA polymerization activity of tetrahedral Co (II) complex bearing N, N-bis(1-pyrazolyl)methyl ligand based on aniline moiety

“…These include β-diimines and analogs the Ni(II) and Pd(II) complexes of which usually exhibit lower catalytic activities than the α-diimine complexes [6]. Specifically, the highly active 2,6-bis (imino)pyridines initially discovered independently by the groups of Brookhart and Gibson [7][8][9][10][11] are well known cobalt and iron systems [12][13][14][15][16]. A further modification involves appending a donor side arm to construct tridentate chelating ligands, such as [N,O], [N,N,N], and [N,N,O] ligands [17,18].…”