Constrained formation of 2-(1-(arylimino)ethyl)-7-arylimino-6,6-dimethylcyclopentapyridines and their cobalt(ii) chloride complexes: synthesis, characterization and ethylene polymerization

Abstract

The 2-(1-(arylimino)ethyl)-7-arylimino-6,6-dimethylcyclopentapyridylcobalt complexes were constrainedly prepared, performing polymerization with MAO but oligomerization with MMAO.

Fusing Carbocycles of Inequivalent Ring Size to a Bis(imino)pyridine-Iron Ethylene Polymerization Catalyst: Distinctive Effects on Activity, PE Molecular Weight, and Dispersity

“…As an alternative strategy in bis(imino)pyridine ligand design, our group has recently explored the fusion of carbocycles to the central pyridine unit in (Figure 1) as a means to form well-defined Fe-/Co-based complexes bearing singly [22][23][24][25][26][27][28][29][30] and doubly fused derivatives (e.g., B, C, D, and E in Figure 1) [31][32][33][34][35][36][37][38]. Indeed, the fused ring size has been shown to be pivotal to the catalytic activity and polymeric properties [6,[36][37][38].…”

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

“…Indeed cobalt catalysts based on a 2-(1-(arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinolyl ligand set (B, Scheme 1), incorporating a six-membered ring, exhibit much higher activities and better thermal stability than the prototypical 2,6-bis(imino)pyridyl cobalt complexes (A). 10 On the other hand, contraction of the ring to a five-membered cyclopentane ring (C, Scheme 1), leads to much lower activities in ethylene polymerization; 11 an observation that can be attributed to inefficient imine-N coordination to the cobalt. 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.…”

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

“…To explore the potential of precatalysts Co1 -Co5 to mediate the polymerization of ethylene, methylaluminoxane (MAO) and modified methylaluminoxane (MMAO) were chosen as co-catalysts; both aluminoxanes have a reputation for being among the most potent in cobalt polymerization catalysis. [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]43] The effect of the Al:Co molar ratio, reaction temperature, run time and ethylene pressure are all parameters to be investigated. The molecular weights (M w ) and molecular weight distributions (M w / M n ) of the resultant polyethylenes were determined by gel permeation chromatography (GPC), while their melt temperatures (T m ) were determined by differential scanning calorimetry (DSC).…”

“…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.…”

“…[25] 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 1). [26][27][28][29][30][31][32][33][34][35][36][37] 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.…”