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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]

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]

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]

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]

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]