Chromium complexes ligated by 2-carbethoxy-6-iminopyridines: Synthesis, characterization and their catalytic behavior toward ethylene polymerization
TL;DR: The titled chromium complexes (C1-C6) were prepared by the reaction of CrCl3(THF) with the corresponding 2-carbethoxy-6-iminopyridines (L1-L6) in dichloromethane.
Abstract: The titled chromium complexes (C1-C6) were prepared by the reaction of CrCl3(THF)(3) with the corresponding 2-carbethoxy-6-iminopyridines (L1-L6) in dichloromethane. All the complexes were characterized by IR spectroscopy and elemental analysis. The unambiguous solid-state structures of C1, C3 and C5 were determined by X-ray crystallography. The chromium core was found to be coordinated by a molecule of 2-carbethoxy-6-iminopyridine and three atoms of chlorine to form a distorted octahedral coordination geometry. Activated with ethylaluminum dichloride (EtAlCl2), these complexes showed notable catalytic activities for ethylene polymerization. The nature of the ligands and reaction parameters affected the properties of the resultant polyethylenes. (c) 2006 Elsevier B.V. All rights reserved.
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TL;DR: In this article, a review of the use of iron and cobalt complex pre-catalysts for ethylene reactivity is presented, with particular reference to the influence of the ligand frameworks and their substituents on the catalytic performance for oligomerization/polymerization catalysis.
Abstract: Recent progress on the use of iron and cobalt complex pre-catalysts for ethylene reactivity is reviewed. The review is organized in terms of the denticity of the chelate ligands employed, with particular reference to the influence of the ligand frameworks and their substituents on the catalytic performance for ethylene oligomerization/polymerization catalysis. The majority of the systems bear tri-dentate ligation at the iron/cobalt centre, though it is clear that bi-dentate iron/cobalt complex pre-catalysts have also attracted significant attention. Such systems produce in most cases highly linear products ranging from oligomeric α-olefins to high molecular weight polyethylene, and as such are promising candidates for both academic and industrial considerations.
107 citations
TL;DR: In this paper, a review of recent progress made using well-defined molecular chromium complexes that, upon suitable activation, can catalyze the tri-, tetra, oligo-and/or polymerization of ethylene.
92 citations
TL;DR: A series of bimetallic (ferrous and cobaltous) complexes ligated by 3,3-dihydro-2-methyl-2,4-bis(6-iminopyridin)-2-yl)-1H-1,5-benzodiazepines were synthesized and evaluated as catalysts for ethylene oligomerization and polymerization with high activity and α-olefin selectivity in the presence of modified methylaluminoxane (MMAO) as mentioned in this paper.
80 citations
TL;DR: In this article, the authors describe their experiences in innovating new models of iron and cobalt complexes as catalysts for ethylene oligomerization and polymerization, and present several alternative models with similar coordination sphere.
77 citations
TL;DR: A series of (arylimido)vanadium(V) dichloride complexes containing (2-anilidomethyl)pyridine ligands of the type V(NAr)Cl2[2-Ar′NCH2(C5H4N)] [Ar = 2,6-Me2C6H3; Ar′ = 2.6-me2C 6H3 (1a), 2, 6-IPr2C12H3(1b), 2. 6-F2C16H3, 2.
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TL;DR: Even late transition metal complexes function as active and selective catalysts for α-olefin polymerization, and an intense search has developed for new-generation catalysts, in both academic and industrial research laboratories.
Abstract: Even late transition metal complexes function as active and selective catalysts for α-olefin polymerization. The discovery of a highly active family of catalysts 1 based on iron, a metal that had no previous track record in this field, has highlighted the possibilities for further new catalyst discoveries. As a result, an intense search has developed for new-generation catalysts, in both academic and industrial research laboratories. R1=H, Me; R2=Me, iPr; R3=H, Me, iPr; R4=H, Me; X=halide.
1,737 citations
1,378 citations
TL;DR: A new family of olefin polymerization catalysts, derived from iron and cobalt complexes bearing 2,6-bis(imino)pyridyl ligands, was described in this paper.
1,045 citations
TL;DR: A family of catalysts has been developed whose members are tolerant of both heteroatoms and less pure starting materials, and which produce high-molecular-weight polyethylene, polymerize functionalized olefins, and require no cocatalyst.
Abstract: More than half of the 170 million metric tons of polymers produced each year are polyolefins. Current technology uses highly active cationic catalysts, which suffer from an inability to tolerate heteroatoms such as oxygen, nitrogen, and sulfur. These systems require scrupulously clean starting materials and activating cocatalysts. A family of catalysts has been developed whose members are tolerant of both heteroatoms and less pure starting materials. These heteroatom-tolerant neutral late transition metal complexes are in fact highly active systems that produce high-molecular-weight polyethylene, polymerize functionalized olefins, and require no cocatalyst.
999 citations
TL;DR: I. Supported Catalysts Activated by Alumoxanes 1349 A. Supporting Metal Complex−MAO Solutions 1352 D. Influence of Hydroxyl Groups 1352 E. SupportedCatalysts without Cocatalysts 1356 VII.
Abstract: IV. Supported Catalysts Activated by Alumoxanes 1349 A. Supported Alumoxanes 1350 B. Supported Metal Complexes 1350 C. Supporting Metal Complex−MAO Solutions 1352 D. Influence of Hydroxyl Groups 1352 E. Prepolymerization of Supported Catalysts 1353 V. Alumoxane-Free Supported Single-Site Catalysts 1354 VI. Supported Catalysts without Cocatalysts 1356 VII. Chemically Tethered Metal Complexes 1356 VIII. Chemically Tethered Activators 1361 A. Alumoxanes 1361 B. Boron Activators 1362 IX. Supported Group 3 and Lanthanide Single-Site Catalysts 1364
722 citations