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As a powerful protocol for the preparation of common polymers, such as polyolefins, polyesters, and polycarbonates, late-transition-metal-catalyzed polymerization can be carried out by controlling the reaction conditions or developing dynamic catalytic systems that use external stimuli to influence the performance of the active sites, resulting in well-defined polymeric materials. In particularly, under the latter conditions, 'one catalyst' can provide more than one kind of polymer with a controlled sequence from the monomer mixture, making full use of the prepared catalyst. In this review, tunable modes, including reaction conditions, redox, light or electrochemical properties, Lewis acids, and alkali metal cations, of late-transition-metal-complex (especially iron, cobalt, and nickel)-catalyzed polymerization were collected and thoroughly discussed. [ABSTRACT FROM AUTHOR]

The copolymerization of carbon dioxide (CO2) with epoxides demonstrates promise as a new synthetic method for low-carbon polymer materials, such as aliphatic polycarbonate materials. In this study, a binary Schiff base cobalt system was successfully used to catalyze the copolymerization of 1,2-butylene oxide (BO) and CO2 and its terpolymerization with other epoxides such as propylene oxide (PO) and cyclohexene oxide (CHO). 1H nuclear magnetic resonance (1H NMR), diffusion-ordered spectroscopy (DOSY), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC) confirmed the successful synthesis of the alternating terpolymer. In addition, the effects of the polymerization reaction conditions and copolymerization monomer composition on the polymer structure and properties were examined systematically. By regulating the epoxide feed ratio, polycarbonates with an adjustable glass transition temperature (Tg) (11.2–67.8 °C) and hydrophilicity (water contact angle: 85.2–95.2°) were prepared. Thus, this ternary polymerization method provides an effective method of modulating the surface hydrophobicity of CO2-based polymers and their biodegradation properties. [ABSTRACT FROM AUTHOR]

Inspired by the cooperative multi-metallic activation in metalloenzyme catalysis, artificial enzymes as multi-metallic catalysts have been developed for improved kinetics and higher selectivity. Previous models about multi-metallic catalysts, such as cross-linked polymer-supported catalysts, failed to precisely control the number and location of their active sites, leading to low activity and selectivity. In recent years, metallopolymers with metals in the sidechain, also named as sidechain metallopolymers (SMPs), have attracted much attention because of their combination of the catalytic, magnetic, and electronic properties of metals with desirable mechanical and processing properties of polymeric backbones. Living and controlled polymerization techniques provide access to SMPs with precisely controlled structures, for example, controlled degree of polymerization (DP) and molecular weight dispersity (Đ), which may have excellent performance as multi-metallic catalysts in a variety of catalytic reactions. This review will cover the recent advances about SMPs, especially on their synthesis and application in catalysis. These tailor-made SMPs with metallic catalytic centers can precisely control the number and location of their active sites, exhibiting high catalytic efficiency. [ABSTRACT FROM AUTHOR]

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]

Six examples of α,α′-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridine-cobalt(II) chlorides, [2,3:5,6-{C 4 H 8 C(NAr)} 2 C 5 HN]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 ), containing N-aryl groups that differ in either the ring size of the ortho -cycloalkyl substituents or the para -R group (R = H, Me), have been synthesized using a one-pot template approach. The molecular structure of Co1 highlights the ring puckering of both the ortho -cyclopentyl substituents and the two pyridine-fused seven-membered rings; a square-based pyramidal geometry is conferred about the metal center. On activation with either methylaluminoxane (MAO) or modified MAO (MMAO), all six complexes afforded strictly linear polyethylene (all T m 's > 130 °C) with high molecular weight ( M w up to 64.3 kg mol −1 ). Furthermore, all precatalysts displayed high activities (up to 2 × 10 6  g PE mol -1 (Co) h −1 ) at temperatures between 20 and 60 °C with the catalytic activities correlating with the type of ortho -cycloalkyl substituent: cyclohexyl ( Co2 , Co5 ) > cyclopentyl ( Co1 , Co4 ) > cyclooctyl ( Co6 , Co3 ) for either R = H or Me. The narrow unimodal distributions of the resulting polymers are consistent with single-site active species for the catalysts. [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]

• Diversity of post-metallocene vanadium(III-V) complexes with various N-, O-, N,O- and even P-ligands. • Coordination polymerization of ethylene, propylene, higher linear α-olefins as well as cyclic olefins. • Activities controlled through finely tuning ligands and valence state of vanadium. • Achieving polyethylenes with high or even ultra-high molecular weights as well as narrow PDI. • Controlled incorporation of co-monomer in ethylene/other olefins copolymerizations. Polyolefins account for two thirds by weight of the global synthetic polymers. There are more than 300 grades of commercial polyolefins, whose properties depend on their microstructures being varied according to the type of catalyst used in the production process and ultimately on the final method of manufacture. Despite having catalytic activities not higher than those of common catalysts, vanadium-based catalysts display several advantages, such as ethylene polymerization for ultra-high molecular weight polyethylene, better copolymerization of alpha-olefins with ethylene which affords higher comonomer incorporation, producing good syndiotactic polypropylene, as well as producing synthetic rubbers by copolymerizing either ethylene-propylene or ethylene-propylene-diene. The latter materials, in particular, are known for their excellent applications with ozone, UV, heat and water-resistance, for the automotive industry and seal gaskets for shield tunnels and even in heat shielding materials for solid rocket motors. To tailor polyolefins in order to design their microstructures, there are more and more studies on post-metallocene vanadium(III-V) catalysts employing various N-, O-, N,O- and even P-ligands. Herein we summarize important developments of the vanadium complex catalysts within a decade. [ABSTRACT FROM AUTHOR]

A novel functional polycarbonate (PAGC), characterized by the presence of double bonds within its side chain, was successfully synthesized through a ternary copolymerization of propylene oxide (PO), allyl glycidyl ether (AGE), and carbon dioxide (CO2). Polyhedral oligomeric silsesquioxanes octamercaptopropyl (POSS-SH) was employed as a crosslinking agent, contributing to the formation of organic–inorganic hybrid materials. This incorporation was facilitated through thiol-ene click reactions, enabling effective interactions between the POSS molecules and the double bonds in the side chains of the polycarbonate. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) confirmed a homogeneous distribution of silicon (Si) and sulfur (S) in the polycarbonate matrix. The thiol-ene click reaction between POSS-SH and the polycarbonate led to a micro-crosslinked structure. This enhancement significantly increased the tensile strength of the polycarbonate to 42 MPa, a notable improvement over traditional poly (propylene carbonate) (PPC). Moreover, the cross-linked structure exhibited enhanced solvent resistance, expanding the potential applications of these polycarbonates in various plastic materials. [ABSTRACT FROM AUTHOR]

Based on iminopyridine ligands (L1–L3), Fe(II) (Fe1–Fe3) and Co(II) (Co1–Co3) complexes were synthesized and characterized well. According to single-crystal XRD studies, Co3 exhibits a dimeric structure with a four-coordinated metal center. Whereas, the iron complexes (Fe1 and Fe3) coordinate with two ligands to form a distorted-octahedral and distorted-trigonal bipyramidal geometry, respectively. All these catalysts were tested for the polymerization of isoprene. Using MAO as the co-catalyst, the Fe3 catalyst containing a bulky substituent can provide trans-1,4-unit (64%) polyisoprenes, while the Fe1 catalyst afforded trans-1,4-unit polyisoprenes (32%). Conversely, the combination of EASC as the co-catalyst with Fe1–Fe3 catalysts can give 1,4-unit polyisoprenes with high trans-1,4-unit selectivity (up to 88%). The central metal atom of the catalysts plays a crucial role in isoprene polymerization and significantly affects their activity. Fe(II) catalysts showed the highest activity (up to 99% yield), and afforded polyisoprenes with high molecular weights (191 kg mol−1). However, Co(II) systems exhibited lower activity (60% yield) and the obtained polyisoprenes were of lower molecular weights (2.15 kg mol−1) with broad molecular weight distribution. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Bis(imino)-2,3:5,6-bis(pentamethylene)pyridines and their cobalt complexes. • Highly active precatalysts for ethylene polymerization. • Linear polyethylenes with narrow dispersities and vinyl end-groups. • Modulation of molecular weight through ortho -benzhydryl substitution. Abstract The cycloheptyl-fused cobalt(II) chloride complexes, [2,3:5,6-{C 4 H 8 C(N(2-R1-4-R2-6-(CHPh 2)C 6 H 2))} 2 C 5 HN]CoCl 2 (R1 = R2 = Me Co1 , R1 = Me, R2 = CHPh 2 Co2 , R1 = Et, R2 = CHPh 2 Co3 , R1 = i -Pr, R2 = CHPh 2 Co4 , R1 = Cl, R2 = CHPh 2 Co5 , R1 = CHPh 2 , R2 = i -Pr Co6 , R1 = CHPh 2 , R2 = t -Bu Co7 , R1 = CHPh 2 , R2 = F Co8), have been prepared by a one-pot template approach. The molecular structures of Co1 , Co6 and Co8 highlight the varying degrees of steric protection of the metal center imposed by the ortho -benzhydryl/-R1 group pairing. On activation with either MAO or MMAO, Co1–Co5 collectively displayed high activity (up to 2.87 × 106 g (PE) mol−1 (Co) h−1 at 40 °C) affording highly linear low molecular weight polyethylene (M w range: 12.8–59.4 kg mol−1) with narrow polydispersities (M w / M n range: 1.4–2.7). End-group analysis of the polymers highlights the importance of both β-H elimination and chain transfer to aluminum as termination pathways. In relative terms, MMAO proved a marginally more effective activator than MAO with the catalytic activity, in either case, falling in the order: Co1 > Co5 > Co2 > Co3 > Co4. In marked contrast, the 2,6-(CHPh 2) 2 -substituted precatalysts, Co6 , Co7 and Co8 gave, in the presence of the same aluminoxane activators, only trace amounts of polyethylene. [ABSTRACT FROM AUTHOR]

A family of six unsymmetrical N,N′-diiminoacenaphthene-nickel(ii) bromide complexes, [1-{2,6-(Ph2CH)2-4-MeC6H2N}-2-(ArN)C2C10H6]NiBr2 (Ar = 2-(C6H11)-6-MeC6H2Ni1, 2-(C5H9)-6-MeC6H2Ni2, 2-(C8H15)-6-MeC6H2Ni3, 2-(C6H11)-4,6-Me2C6H2Ni4, 2-(C5H9)-4,6-Me2C6H2Ni5, 2-(C8H15)-4,6-Me2C6H2Ni6), each bearing one ring-size variable 4-R-2-methyl-6-cycloalkyl-substituted N-aryl group and one N′-4-methyl-2,6-dibenzhydrylphenyl group, have been prepared and fully characterized. The molecular structures of Ni1, Ni2, Ni3 and Ni5 reveal distorted tetrahedral geometries with different degrees of steric protection imparted by the two inequivalent N-aryl groups. On activation with either EASC or MMAO, all the precatalysts are highly active (up to 17.45 × 106 g PE mol−1 (Ni) h−1) for ethylene polymerization at 20–50 °C with their activities correlating with the type of cycloalkyl ortho-substituent: cyclooctyl (Ni6, Ni3) ＞ the cyclopentyl (Ni5, Ni2) ＞ cyclohexyl (Ni4, Ni1) for either R = H or Me. Moderately branched to hyperbranched polyethylenes (Tm's as low as 44.2 °C) can be obtained with molecular weights in the range 2.14–6.68 × 105 g mol−1 with the branching content enhanced by the temperature of the polymerization. Dynamic mechanical analysis (DMA) and monotonic tensile stress–strain tests have been employed on the polyethylene samples and reveal the more branched materials to show good elastic recovery properties (up to 75.5%). [ABSTRACT FROM AUTHOR]

Treatment of AlMe 3 with bidentate N, O-ligands, HOC(Me)(Ph)C 6 H 4 –NMe 2 -2 ( L 1 H) or HOC(CH 2 ) 5 C 6 H 4 –NMe 2 -2 ( L 2 H) in different molar ratios, four novel aluminum complexes ( 1 ), ( 2 ), ( 3 ) and ( 4 ) were obtained in good yield. Complexes 1 – 4 were characterized by 1 H and 13 C NMR spectroscopy, elemental analyses and single crystal X-ray diffraction techniques. Each of the complexes 1 , 2 , 3 and 4 was tested for the capable of catalyzed Meerwein–Ponndorf–Verley (MPV) reduction of ketones or aldehydes with low catalyst loadings under mild conditions and showed good to excellent catalytic activities. [ABSTRACT FROM AUTHOR]

The incorporation of diverse macromolecular blocks into CO 2 -based polycarbonates offers a promising approach for tailoring the properties of polycarbonates for special needs. In this work, we report for the first time the synthesis and characterization of an ABA triblock copolymer polycarbonate- b -polyalkenamer- b -polycarbonate in combination of ROCOP and ROMP via a one-pot route from CO 2 , epoxides and cycloalkenes. Cis -2-butene-1,4-diol as the bifunctional chain transfer agent was used as a "bridge" for the combination of different blocks as well as an effective regulator for the molecular weight of the polymers. In the one-pot reaction, the conversion of cycloalkenes reached 99.9% within 0.5 h, while the conversion of CHO was initially marginal at 0.5% but gradually increased to 99.7% after 24 h. The significant discrepancy in reaction rates between the two processes enables efficient synergistic reactions within the one-pot system. Specifically, hydroxyl-telechelic polyalkenamer is initially formed via ROMP and subsequently acts as an active species for ROCOP when coordinated with the porphyrin Al catalyst. This one-pot strategy provides a unique and simple method for controllably constructing functional polycarbonates with single-modal molecular weight distributions. By integrating the advantages of polyalkenamers and polycarbonates, this approach proves to be a viable solution for addressing the unsatisfactory thermal properties of aliphatic polycarbonates. [Display omitted] • CO 2 -based functional polycarbonate prepared via one pot reaction in combination of ROCOP and ROMP. • Bifunctional chain transfer agent as a bridge for polycarbonate and polyalkenamer to achieve block copolymer. • ABA block structure confirmed by 1H NMR, DOSY and MALDI-TOF analysis. [ABSTRACT FROM AUTHOR]

Five examples of hither-to-unknown ferrous chloride precatalysts have been prepared for ethylene polymerization. The impact of steric/electronic effect and polymerization reaction parameters on the catalytic performance, thermal stability with MAO or MMAO and the microstructure of the polyethylene are investigated in detail. [Display omitted] • Novel iron(II) complexes bearing sterically hindered dibenzocycloheptyl group were synthesized. • Higher activity towards ethylene polymerization. • Enhanced thermal stability. • Vinyl end polyethylene via modified bis(arylimino)pyridine-ferrous chloride precatalyst. Unsymmetrical Fe(II) complexes bearing tridentate NNN- bis(arylimino)pyridine ligand of the general formula [2-(2,4-bis(C 15 H 13) 2 -6-CH 3 C 6 H 2 N)-6-(ArN)C 9 H 9 N]FeCl 2 {Ar = 2,6-(CH 3) 2 C 6 H 3 (Fe1), 2,6-(C 2 H 5) 2 C 6 H 3 (Fe2), 2,6-(C 3 H 7) 2 C 6 H 3 (Fe3), 2,4,6-(CH 3) 3 C 6 H 2 (Fe4) and 2,6-(C 2 H 7) 2 -4-CH 3 C 6 H 2 (Fe5)} have been prepared in good yields. All the complexes were characterized by FT-IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction analysis for Fe2 and Fe3. Upon activation with MAO or modified-MAO, all the complexes displayed high activity at elevated temperature with peak performance up to 2.13 × 107 g PE (mol of Fe)−1 h-1 using Fe4 at 70 °C in combination with modified-MAO. The most sterically hindered precatalyst Fe3 produced high molecular-weight polyethylene up to 307.12 kg mol-1 at 70 °C with MAO as co-catalyst. Particularly, polyethylene of vinyl end functionality was obtained with MAO. Significantly, this developed catalytic system maintained the good catalytic performance of 9.67–7.59 × 106 g PE (mol of Fe)−1 h-1 and 1.51–1.09 × 107 g PE (mol of Fe)−1 h-1 using Fe1 with MAO or modified-MAO at 80 °C–90 °C, respectively. Notably, the activity of 3.12 or 2.76 × 106 g PE (mol of Fe)−1 h-1 was achieved even at 100 °C; indicating high thermal stability of the active species. Indeed, the thermal stability and molecular weight of the resultant polyethylene reached the highest values to be reported for this class of unsymmetrical 2,6-bis(arylimino)pyridine-ferrous precatalysts. [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]

The α,α′-bis(imino)-2,3:5,6-bis(pentamethylene)pyridyl-cobalt(II) chlorides, [2,3:5,6-{C4H8C(N(2-R1-4-R3-6-R2C6H2))}2C5HN] CoCl2 (R1 = Me, R2 = R3 = CH(p-FPh)2Co1; R1 = Et, R2 = R3 = CH(p-FPh)2Co2; R1 = i-Pr, R2 = R3 = CH(p-FPh)2Co3; R1 = Cl, R2 = R3 = CH(p-FPh)2Co4; R1 = F, R2 = R3 = CH(p-FPh)2Co5; R1 = F, R2 = R3 = CHPh2Co5′′, R1 = R2 = Me, R3 = CH(p-FPh)2Co6; R1 = R3 = Me, R2 = CH(p-FPh)2Co7), have been synthesized by a one-pot template reaction of α,α′-dioxo-2,3:5,6-bis(pentamethylene)pyridine, cobalt(II) chloride and the respective aniline in n-butanol. By contrast, the mixed cobalt(II) chloride/acetate complex, [2,3:5,6-{C4H8C(N(2-F-4,6-(CH(p-FPh)2)2C6H2))}2C5HN]CoCl(OAc) (Co5′), was isolated when the corresponding template reaction was carried out in acetic acid. Structural characterization of Co4, Co5 and Co5′′ revealed distorted square pyramidal geometries while six-coordinate Co5′, incorporating a chelating acetate ligand, exhibited a distorted octahedral geometry. On activation with either MAO or MMAO, 2-fluoride-4,6-bis{di(p-fluorophenyl)methyl}-substituted Co5 showed maximum catalytic activity for ethylene polymerization at a high operating temperature of 60 °C (up to 2.1 × 107 g (PE) mol−1 (Co) h−1), producing highly linear (Tms > 121 °C), low molecular weight polyethylene waxes (Mw range: 1.5–5.0 kg mol−1) with narrow dispersity (Mw/Mn range: 1.7–2.9). End-group analysis of the waxes reveals β-H elimination as the dominant chain transfer process. [ABSTRACT FROM AUTHOR]

A one-pot template strategy has been utilized to synthesize sterically enhanced bis(imino)cyclohepta[b]pyridine-cobalt(II) chlorides, [2-{(Ar)N＝CMe}-9-{N(Ar)}C10H10N]CoCl2 (Ar = 2-(C5H9)-4,6-(CHPh2)2C6H2Co1, 2-(C6H11)-4,6-(CHPh2)2C6H2Co2, 2-(C8H15)-4,6-(CHPh2)2C6H2Co3, 2-(C12H23)-4,6-(CHPh2)2C6H2Co4, 2,6-(C5H9)2-4-(CHPh2)C6H2Co5). All five complexes have been characterized by a combination of FT-IR spectroscopy, elemental analysis and single crystal X-ray diffraction. The molecular structures of Co1, Co3 and Co5 highlight the substantial steric hindrance imparted by the 2-cycloalkyl-6-benzhydryl or 2,6-dicyclopentyl ortho-substitution pattern; distorted square pyramidal geometries are exhibited in each case. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the complexes (apart from Co4/MAO) were active ethylene polymerization catalysts (up to 3.70 × 106 g PE per mol (Co) per h for Co5/MMAO), operating effectively at temperatures between 50 °C and 60 °C, producing polyethylenes with high molecular weights (up to 589.5 kg mol−1 for Co3/MAO). Furthermore, all polymers were highly linear (Tm > 130 °C) with narrow dispersities (Mw/Mn range: 2.0–3.0). The coexistence of two chain termination pathways, β-H elimination and transfer to aluminum, has been demonstrated using 13C/1H NMR spectroscopy. [ABSTRACT FROM AUTHOR]

CO 2 -based polycarbonates are among the most promising eco-friendly polymers with excellent biodegradability and biocompatibility. However, the poor performance of conventional CO 2 -based polycarbonates such as poly(propylene carbonate) (PPC) and poly(cyclohexene oxide) (PCHC) limits their application. Herein, a series of siloxane functionalized CO 2 -based polycarbonates were obtained via terpolymerization of carbon dioxide (CO 2), propylene oxide (PO), and [2-(3, 4-epoxycyclohexyl)-ethyl] trimethoxysilane (TMSO) using a SalenCoCl/PPNCl catalyst system. A systematic study of these polycarbonate's thermal, mechanical, and surface properties was conducted by tuning the ratio between TMSO and PO. The siloxane units offered polycarbonate with a higher surface energy, resulting in a water contact angle of 110° and a significant improvement in glass transition temperature (T g) and decomposition temperature (T d). Additionally, the micro-crosslinked structure formed by the hydrolysis and condensation of methoxysilane groups provided to the polycarbonate's remarkable mechanical strength, with a high tensile strength of 46 MPa. As a result, a novel CO 2 -based polycarbonate derived from cost-efficient silane coupling agents and CO 2 has shown promising results as an alternative to rigid plastics used in industry. [Display omitted] • Siloxane functionalized polycarbonates were prepared from carbon dioxide and epoxides. • Micro-crosslinked structure of polycarbonate endows its excellent mechanical properties. • Methoxysilane groups increase surface energy and permit post-modification. [ABSTRACT FROM AUTHOR]

Five examples of bis(arylimino)tetrahydrocyclohepta[b]pyridine dichloroiron(II) complex, [2-{(Ar)N=CMe}-9-{N(Ar)}C10H10N]FeCl2 (Ar = 2-(C5H9)-4,6-(CHPh2)2C6H2Fe1, 2-(C6H11)-4,6-(CHPh2)2C6H2Fe2, 2-(C8H15)-4,6-(CHPh2)2C6H2Fe3, 2-(C12H23)-4,6-(CHPh2)2C6H2Fe4, and 2,6-(C5H9)2-4-(CHPh2)C6H2Fe5), incorporating ortho-pairings based on either benzhydryl/cycloalkyl (ring sizes ranging from 5 to 12) or cyclopentyl/cyclopentyl groups, have been prepared in reasonable yield by employing a simple one-pot template strategy. Each complex was characterized by FT-IR spectroscopy, elemental analysis, and for Fe3 and Fe5 by single crystal X-ray diffraction; pseudo-square pyramidal geometries are a feature of their coordination spheres. On treatment of Fe1–Fe5 with modified methylaluminoxane (MMAO) or methylaluminoxane (MAO), a range in catalytic activities for ethylene polymerization were observed with benzhydryl/cyclopentyl-containing Fe1/MMAO achieving the maximum level of 15.3 × 106 g PE mol−1 (Fe) h−1 at an operating temperature of 70 °C. As a key trend, the activity was found to drop as the ortho-cycloalkyl ring size increased: Fe1C5H9/CHPh2~Fe5C5H9/C5H9 > Fe2C6H11/CHPh2 > Fe3C8H15/CHPh2 > Fe4C12H23/CHPh2. Furthermore, strictly linear polyethylenes (Tm > 126 °C) were formed with molecular weights again dependent on the ortho-cycloalkyl ring size (up to 55.6 kg mol−1 for Fe1/MAO); narrow dispersities were a characteristic of all the polymers (Mw/Mn range: 2.3–4.7), highlighting the well-controlled nature of these polymerizations. [ABSTRACT FROM AUTHOR]