Synthesis, Characterization, and Ethylene Oligomerization and Polymerization of Ferrous and Cobaltous 2-(Ethylcarboxylato)-6-iminopyridyl Complexes

Abstract

A series of ferrous complexes (L)FeCl2 (3a−f) and cobaltous complexes (L)CoCl2 (4a−f) were prepared by the reaction of 2-(carboxylato)-6-iminopyridines 2a−f (2-COOEt-6-(2,6-R2C6H3NCCH3)C5H3N: 2a, R = CH3; 2b, R = Et; 2c, R = i-Pr; 2d, R = F; 2e, R = Cl; 2f, R = Br) with FeCl2 or CoCl2. The obtained complexes were characterized by elemental analysis and IR spectroscopy, and the solid-state structures of 2b,c, 3b,c,e,f, and 4c,f were determined by X-ray diffraction analysis. X-ray crystallographic analyses of complexes 3c,e,f and 4c,f reveal a four-coordinated distorted-tetrahedral geometry, except for complex 3b, in which the tridentate ligand is coordinated through a weak bonding between iron and the carbonyl oxygen of the ester group. The complexes were studied for ethylene oligomerization and polymerization in the presence of methylaluminoxane (MAO) under various reaction conditions. It was found that the ferrous complexes exhibit higher activities for ethylene polymerization than for oligomerization, while the cobaltous complexes show higher activities for ethylene oligomerization. In addition, the ferrous catalytic systems predominantly produce linear oligomers and polyethylene with unsaturated end groups.

Crystal structure of 1-(6-(1-(perfluorophenylimino)ethyl)pyridin-2-yl)ethanone, C15H9F5N2O

“…Recently, aserieso fi minopyridyl-based ferrous and cobaltous complexes have obtained greatinterest due to their high activities for ethylene oligomerization and polymerization [1][2][3][4]. The catalytic performances have been greatly improved by introducing halogen atoms into ligands [5,6], and anew method for synthesis of halogen substituted bis(imino)pyridines hasbeen reported [7].…”

Syntheses and characterisation of tris(3-(pyridin-2-yl)-1H-pyrazol-1-yl)methane and its bis(µ-hydroxo) dicobalt(II) complex

“…The geometric centre of the cation lies on a crystallographic inversion centre. Figure 1 shows the molecular structure of [Co 2 (µ-OH) 2 …”

“…as catalysts for industrially useful oxidation processes like the oxidation of alkenes 1 and for various polymerisation processes. The application in polymerisation processes ranges from ethene oligomerisation with iminopyridine cobalt complexes 2 and propyleneoxide polymerisation with phenoxide Schiff base cobalt complexes 3 to the living radical polymerisation of acrylates with tetramesitylporphyrin cobalt systems, which generate stable radicals. 4 Furthermore, stoichiometric applications like the transformation of nitriles to aldehydes or cyanides have been subject of considerable interest.…”

“…In this ligand the CH head-group is replaced by a CPh group. 12 In the field of bis(pyrazolyl)methanes, the analogous bis(pyrazolyl)methane (H 2 C(3-Pypz) 2 ) with a pyridinyl function in the 3-position was synthesised by Ward et al as well.…”

“…Herein we report on the synthesis and characterisation of the new ligand and a structural characterisation of its cobalt(II) bis(µ-hydroxo) dicobalt(II) complex [Co 2 (µ-OH) 2 …”