α,α′‐Bis(arylimino)‐2,3:5,6‐bis(pentamethylene)pyridylcobalt Chlorides: Synthesis, Characterization, and Ethylene Polymerization Behavior

Abstract

A series of α,α′-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridylcobalt chlorides was synthesized by the one-pot template reaction of α,α′-dioxo-2,3:5,6-bis(pentamethylene)pyridine, anilines, and cobalt chloride in refluxing acetic acid. The molecular structure of complex Co1 was determined by singlecrystal X-ray crystallography, which revealed a distorted squarepyramidal geometry around the cobalt center. On activation with methylaluminoxane or modified methylaluminoxane, all of [a]

Thermally stable and highly active cobalt precatalysts for vinyl-polyethylenes with narrow polydispersities: integrating fused-ring and imino-carbon protection into ligand design

“…8a In addition, the difference of Co-N imino bond lengths between D and Co3 (vide supra) might also affect the catalytic performances of these pre-catalysts. In all cases, the molecular weight distributions of the polyethylenes generally remained narrow and unimodal (PDIs = 1.9  2.4), and similar to those of their analogs E. 13 The melting points of all the polymers were in the range 126.8 -133.7 °C, consistent with highly linear materials. To understand the microstructure of the polyethylenes obtained, a representative sample prepared using Co4/MAO at 60 °C was examined using 1 H NMR spectroscopy at 100 °C in deuterated 1,1,2,2-tetrachloroethane (C 2 D 2 Cl 4 ).…”

“…Please do not adjust margins pyridylcobalt chlorides (E) 13 . Once again this can be attributed to the presence of the imino C-phenyl group that prevents deprotonation at higher temperature.…”

“…Significantly however, the sevenmembered ring system (D, Scheme 1) exhibits the highest activity among these cobalt systems, the longest catalyst lifetime and displays reasonable thermal stability. 12 Subsequent work has seen the development of alternative ligand sets incorporating two fused rings namely α,α'-dibenzylidene-2,3:5,6-bis(pentamethylene)pyridine 13 (E, Scheme 1), their cobalt derivatives display high activity in ethylene polymerization. 13 Herein, we are concerned with the synthesis of a new family of cobalt(II) chloride precatalysts bearing the unsymmetrical tridentate ligands of 2-(1-aryliminobenzylidene)-9-arylimino-5,6,7,8-tetrahydrocyclo hepta [b]pyridines (F, Scheme 1), in which a single fused seven-membered ring and an imino C-phenyl group are incorporated into the ligand design.…”

“…Synthesis and characterization of the cobalt complexes. As in previous work, 13 we attempted to prepare the free bisimino 2-(1-aryliminobenzylidene)-9-arylimino-5,6,7,8-tetra hydrocyclohepta [b]pyridine compounds, by condensation of diketone 5 with the corresponding aniline. However, these compounds were not stable and the yields were poor.…”

Exceptionally high molecular weight linear polyethylene by using N,N,N′‐Co catalysts appended with a N′‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group

“…Of particular note have been the raft of steric and electronic variations made to the ortho ‐ and para ‐positions of the N ‐aryl groups of the tridentate ligand . Elsewhere, ligand development has seen the emergence of bis(imino)pyridines fused with carbocycles that can be varied in terms of their ring size ( B , n = 0–3, Scheme ) . Collectively, these structural changes to the chelating ligand have seen important correlations with the activity and temperature stability of the active catalyst as well as the molecular weight of the polyethylene.…”