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Six examples of newly synthesized α,α'‐bis (aryl)‐2,3:5,6‐bis (pentame thylene)pyridyliron complexes [2,3:5,6‐{C4H8C(NAr)}2C5HN]FeCl2 (Ar = 2‐(c‐C5H9)‐6‐MeC6H3Fe1, 2‐(c‐C6H11)‐6‐MeC6H3Fe2, 2‐(c‐C8H15)‐6‐MeC6H3Fe3, 2‐(c‐C5H9)‐4,6‐Me2C6H2Fe4, 2‐(c‐C6H11)‐4,6‐Me2C6H2Fe5, 2‐(c‐C8H15)‐4,6‐Me2C6H2Fe6; c refers as cyclic), on activation with methylalumoxane (MAO) or modified MAO (MMAO), exhibit high activities towards ethylene polymerization, producing strictly linear polyethylenes with terminal vinyl groups. The catalytic performances are systematically investigated along with various polymerization parameters as well as the microstructures of resultant polyethylenes. The steric hindrances of ortho‐cycloalkyl substituents of Nimino‐aryl groups significantly affect the activities of the corresponding iron precatalysts as well as the microstructures of resultant polyethylenes: higher steric hindrance the ortho‐cycloalkyl substituents, higher activity the iron precatalyst, lower molecular weight the resultant polyethylenes. Experimental observations are additionally supported by the computational study. The resultant polyethylenes exhibited excellent hydrophobicity. [ABSTRACT FROM AUTHOR]

Six examples of dinuclear bis(imino)pyridine-cobalt(ii) complexes, [1,5-{2-(CMe=N)-6-(CMe=N(2,6-R12-4-R2-C6H2))C5H3N}2(C10H6)]Co2Cl4 (R1 = Me, R2 = H Co1; R1 = Et, R2 = H Co2; R1 = iPr, R2 = H Co3; R1 = Me, R2 = Me Co4; R1 = Et, R2 = Me Co5; R1 = CHPh2, R2 = Me Co6), have been prepared from the corresponding bis(tridentate) compartmental ligands (L1–L6) in reasonable yields. The molecular structures of Co3 and Co5 revealed two N,N,N-cobalt dichloride units to adopt anti-positions about the 1,5-naphthyl linking unit, with each cobalt center exhibiting a distorted trigonal bipyramidal geometry. On activation with either MAO or MMAO, Co1–Co6 were shown to promote both polymerization and oligomerization of ethylene with high overall activities (up to 1.03 × 107 gPE per·mol(Co) per·h for Co1/MAO at 70 °C). Curiously, on increasing the reaction temperature a larger proportion of polymer was noted, while at lower temperature an enhanced selectivity for oligomer was seen. In general, the oligomeric products displayed Schulz–Flory distributions with high selectivities for α-olefins (＞99%). On the other hand, the highly linear polymers displayed narrow dispersities and comprised both fully saturated and unsaturated chain ends with the vinyl content (–CH=CH2) found to rise with the reaction temperature. By modulating the steric hindrance exerted by the ortho-R1 substituents in the precatalyst, polyethylenes displaying a remarkably broad range of molecular weights could be obtained [from 4.52 kg mol−1 (R1 = Me) to 246.7 kg mol−1 (R1 = CHPh2)]. [ABSTRACT FROM AUTHOR]

Recent progress concerning the application of compartmentalized bimetallic complexes as homogeneous catalysts in ethylene polymerization is reviewed with particular regard to metal-metal combinations based on either early- (Ti, Zr, Hf and V) or late-transition metals (Fe, Co and Ni). The effect of positioning two polymerization-active metal centers in close proximity on catalytic activity, molecular weight, molecular weight distribution and levels of branching are thoroughly documented. Compartmental ligands comprising binding domains consisting of phenoxyimines, ansa -bridged cyclopentadienyl-amides, α-diimines and iminopyridines are described as is their capacity to serve as compatible binucleating supports for homobimetallic and also for the less investigated heterobimetallic counterparts. By comparison with their mononuclear analogues, any synergic properties exhibited by these binuclear catalysts represents an underlying theme to be developed where possible throughout this review. [ABSTRACT FROM AUTHOR]

2-Chloro/phenyl-7-arylimino-6,6-dimethylcyclopenta [b] pyridylnickel chlorides ( Ni1 – Ni8 ) were synthesized from the respective ligands L1 – L8 and characterized. Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (EASC), they show high catalytic activity of up to 10.84 × 10 6 g(oligomer) mol − 1 (Ni) h − 1 in ethylene oligomerization. The products range from butenes to dodecenes for Ni1 – Ni4 , but are limited to butenes and hexenes in the case of Ni5 – Ni8 . DFT calculations indicate that the Ni C bond length in the model alkyl complexes depends both on the nature of the substituents at the heterocycles and the kind of the alkyl group, shedding some light on the preferences of the precatalysts toward oligomers or polyethylene. [ABSTRACT FROM AUTHOR]

ABSTRACT A series of 2-(arylimino)benzylidene-9-arylimino-5,6,7,8-tetrahydrocyclohepta [b]pyridyliron(II) chlorides was synthesized and characterized using FT-IR and elemental analysis, and the molecular structures of complexes Fe3 and Fe4 have been confirmed by the single-crystal X-ray diffraction as a pseudo-square-pyramidal or distorted trigonal-bipyramidal geometry around the iron core. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all iron precatalysts exhibited high activities toward ethylene polymerization with a marvelous thermo-stability and long lifetime. The Fe4/MAO system showed highest activity of 1.56 × 107 gPE·mol−1(Fe)·h−1 at 70 °C, which is one of the highest activities toward ethylene polymerization by iron precatalysts. Even up to 80 °C, Fe3/MAO system still persist high activity as 6.87 × 106 g(PE)·mol−1(Fe)·h−1, demonstrating remarkable thermal stability for industrial polymerizations (80-100 °C). This was mainly attributing to the phenyl modification of the framework of the iron precatalysts. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 830-842 [ABSTRACT FROM AUTHOR]

Six structurally related bis(arylimino)trihydroquinolyl-cobalt (II) chloride complexes [2-(ArN CCH 3)-8-(ArN)-5,6,7-C 9 H 8 N]CoCl 2 (Ar = 2-(C 5 H 9)-6-MeC 6 H 3 Co1 , 2-(C 6 H 11)-6-MeC 6 H 3 Co2 , 2-(C 8 H 15)-6-MeC 6 H 3 Co3 , 2-(C 5 H 9)-4,6-Me 2 C 6 H 2 Co4 , 2-(C 6 H 11)-4,6-Me 2 C 6 H 2 Co5 , 2-(C 8 H 15)-4,6-Me 2 C 6 H 2 Co6), distinguishable by the ring size of the ortho -cycloalkyl substituent and type of para -R group, have been synthesized and characterized. A distorted square pyramidal geometry is a feature of the molecular structure of Co4 with the two ortho -cyclopentyl groups located on neighboring N -aryl groups trans -configured. Compounds Co1 – Co6 , on activation with methylaluminoxane (MAO) or modified MAO (MMAO), proved highly productive catalysts for ethylene polymerization at 60 °C [up to 17.1 × 106 g (PE) mol−1(Co) h−1 for cyclopentyl-containing Co4 /MAO]; even at 90 °C significant activity was attainable (up to 6.75 × 106 g (PE) mol−1(Co) h−1). Strictly linear polyethylene waxes of low molecular weight (ca. 1.50 kg mol−1), narrow dispersity (M w / M n range: 1.1–2.4) and incorporating high levels of vinyl end-groups were generated. Post-functionalization of these PE waxes by epoxidation, thiol-ene addition and cross-olefin metathesis to form e-PE, PE-S-CH 2 CH 2 NH 2 ·HCl and PE-MMA, respectively, has been demonstrated. For comparative purposes, [2-(ArN CCH 3)-8-ArN-5,6,7-C 9 H 8 N]CoCl 2 (Ar = 2,4,6-Me 3 C 6 H 2 Co o -Me , 2-(Ph 2 CH)-4,6-Me 2 C 6 H 2 Co o -CHPh2) have also been prepared and evaluated as polymerization catalysts. Image 1 • Cobalt ethylene polymerization catalysts capable of running at temperatures up to 90 °C. • ortho -Cycloalkyl ring-size variation allows fine control of catalytic performance. • PE waxes with narrow dispersities and high levels of vinyl end-groups are produced. • Amenability of the PE waxes to post-functionalization by epoxidation, thiol-ene addition and cross-olefin metathesis has been demonstrated. • Ready synthesis of catalysts and characteristic vinyl-polyethylenes offer industrial potential. [ABSTRACT FROM AUTHOR]

The unsymmetrical bis (arylimino)pyridines, 2‐[CMeN{2,6‐{(4‐FC6H4)2CH}2–4‐t‐BuC6H2}]‐6‐(CMeNAr)C5H3N (Ar = 2,6‐Me2C6H3L1, 2,6‐Et2C6H3L2, 2,6‐i‐Pr2C6H3L3, 2,4,6‐Me3C6H2L4, 2,6‐Et2–4‐MeC6H2L5), each containing one N‐aryl group bedecked with ortho‐substituted fluorobenzhydryl groups, have been employed in the preparation of the corresponding five‐coordinate cobalt (II) chelates, LCoCl2 (Co1 – Co5); the symmetrical comparator [2,6‐{CMeN(2,6‐(4‐FC6H4)2CH)2–4‐t‐BuC6H2}2C5H3N]CoCl2 (Co6) is also reported. All cobaltous complexes are paramagnetic and have been characterized by 1H/19F NMR spectroscopy, FT‐IR spectroscopy and elemental analysis. The molecular structures of Co3 and Co6 highlight the different degrees of steric protection given to the metal center by the particular N‐aryl group combination. Depending on the aluminoxane co‐catalyst employed to activate the cobalt precatalyst, distinct variations in thermal stability and activity of the catalyst towards ethylene polymerization were exhibited. In particular with MAO, the resultant catalysts reached their optimal performance at 70 °C delivering high activities of up to 10.1 × 106 g PE (mol of Co)−1 h−1 with Co1 > Co4 > Co2 > Co5 > Co3 >> Co6. On the other hand, using MMAO, the catalysts operate most effectively at 30 °C but are by comparison less productive. In general, the polyethylenes were highly linear, narrowly disperse and displayed a wide range of molecular weights [Mw range: 18.5–58.7 kg mol−1 (MAO); 206.1–352.5 kg mol−1 (MMAO)]. [ABSTRACT FROM AUTHOR]