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Our previous research showed that bis(benzocyclopentyl) α‐diimine Pd(II) complexes can facilitate chain transfer and polar monomer insertion in ethylene (co)polymerization. In this study, we synthesized two bis(benzocyclopentyl) α‐diimine Ni(II) complexes with different backbones. The Ni(II) complexes exhibited high activities (0.63–7.23 × 106 g·mol−1 h−1) and produced low molecular weight (2.7–7.8 kg mol−1) polyethylene waxes with high branching densities (43–86/1000 C) in ethylene polymerization. The use of a catalyst with a butyl backbone resulted in polyethylene waxes with significantly higher molecular weights. The axial substituent restriction strategy employed in the nickel catalyst allows for a sterically open structure, reducing the molecular weight of the resulting polyethylene by over two orders of magnitude, compared to ethyl catalysts without axial restrictions. This enables the production of polyethylene wax grade products with improved properties. The branched polyethylene wax chain ends were found to be aryl‐functionalized according to NMR characterization analysis, while the double bonds were absent. Also, the choice of solvent affects the branching, molecular weight, and chain end composition of the polyethylene wax. [ABSTRACT FROM AUTHOR]

Patients with substance use disorders (SUDs) often suffer from cognitive dysfunction (CD), affecting their quality of life and daily functioning. Current treatments, including pharmacotherapy and psychotherapy, have limited efficacy and notable side effects. Transcranial direct current stimulation (tDCS), a non-invasive technique that modulates cortical activity, shows promise in improving cognitive function with minimal side effects and low cost, and could potentially serve as a valuable adjunct to existing therapies. This systematic review aims to evaluate the literature on the effectiveness of tDCS for CD in SUD patients to inform clinical practice and future research. Following PRISMA guidelines, the review includes studies that used tDCS for SUD-related CD. The criteria for inclusion encompassed participants aged 18 and older with a diagnosis of SUD, the use of tDCS (either conventional or high-definition), control groups receiving sham stimulation or no intervention, and cognitive outcome measures for substance-related cognitive function using validated tools. Databases searched were Ovid MEDLINE, PubMed, Web of Science, Embase, Scopus, and PsycINFO, with specific keywords. Twenty-two studies met the criteria, suggesting tDCS can improve cognitive functions in SUD patients, though results varied. Effectiveness may depend on the brain area targeted, stimulation parameters, task requirements, and individual differences. tDCS shows potential in treating SUD-related CD, but further research is needed to optimize stimulation protocols and address study variability. Future studies should use functional magnetic resonance imaging to explore the brain mechanisms by which tDCS improves cognitive function in SUDs and focus on larger, long-term trials to confirm efficacy and refine tDCS treatment parameters. [ABSTRACT FROM AUTHOR]

Ligand steric hindrance and electronic effects play a crucial role in late-transition metal-catalyzed olefin polymerization. In this research, a series of o-aryl halogenated α-diimine ligands bearing bulky dibenzhydryl substituents, along with their corresponding nickel catalysts, have been synthesized and thoroughly characterized. The nickel catalysts demonstrated very high activity in ethylene polymerization, achieving a high rate of up to 107 g mol−1 h−1. The produced polyethylenes displayed a broad spectrum of molecular weights (12.2–871.7 kg mol−1) but maintained consistent branching densities (50–82/1000 C) when polymerized at a fixed temperature with different nickel catalysts. Notably, the polymerization temperature has a significant influence on both the molecular weight and branching density of the resulting polyethylene. Higher temperatures led to the formation of polyethylenes with lower molecular weights and increased branching densities. Interestingly, the o-aryl halogens significantly impact the molecular weight of the polyethylene. The size of the halogen substituents primarily determines the molecular weight of the polyethylene. However, in terms of branching density, the steric and electronic effects of these substituents appear to counteract each other. In addition, the branched high molecular weight polyethylenes from the bromine and chlorine substituted nickel catalysts are excellent polyethylene thermoplastic elastomers with high strain at break values (688–2478%) and high strain recovery values (42–62%). [ABSTRACT FROM AUTHOR]

Transition metal‐catalyzed copolymerization of ethylene with polar monomers is the most direct and efficient way to prepare polar functionalized polyethylene. Generally, the classical Brookhart type α‐diimine Pd(II) catalysts produced hyperbranched functionalized polyethylene with polar groups at the branch ends, which turns out to be amorphous polymer materials. In this contribution, we described the synthesis and characterization of three bulky diarylmethyl α‐diimine ligands and the corresponding Pd(II) complexes. Lightly branched (21–27/1000C) polyethylenes with high molecular weights (317.8–640.0 kg/mol) and high melting points (94–101°C) were prepared using these Pd(II) complexes at high activities (well above 105 g/mol.h). The resulting polyethylene materials exhibited high stress (23.8‐34.3 MPa) and high strain (559–839%) at break values with typical properties of thermoplastics. Polar functionalized semi‐crystalline polyethylenes with moderate incorporation ratios (0.35–2.99 mol%) and high melting points (84–109°C) were prepared using complexes Pd1‐3 in the copolymerization of ethylene with several polar comonomers (methyl acrylate and 10‐undecenoic acid and 10‐methyl undecanoate). The 1H and 13C NMR spectral analysis revealed that these polar functionalized polyethylenes have a low branching density (19–34/1000C) and are predominantly methyl‐branched, with polar groups located at the end of the branches. In addition, the 4‐methoxy group on the ligands in this work would facilitate the insertion of polar monomers in the copolymerization of ethylene with various polar monomers. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Usually, the aniline‐based late‐transition‐metal catalysts often require bulky steric substituents on both sides of the ortho‐aryl position to achieve efficient suppression of chain transfer in ethylene polymerization. In this contribution, we demonstrated that α‐diimine catalysts based on naphthylamine with only one bulky ortho‐aryl substituent also demonstrated excellent capabilities to suppress the chain transfer. Firstly, a class of α‐diimine nickel and palladium complexes with only one o‐aryl‐dibenzhydryl or o‐aryl‐dibenzosuberyl substituent were synthesized and characterized. Secondly, the as‐prepared naphthylamine‐based nickel catalysts demonstrated outstanding activities (up to 13.02 × 106 g·mol–1·h–1) and yielded lightly branched (16—40/1000C) polyethylenes with very high molecular weights (445.8—854.3 kg/mol) in ethylene polymerization. In comparison, the corresponding palladium catalysts showed moderate activities (level of 104—105 g·mol–1·h–1), generating moderately branched (47—78/1000C) polyethylenes with moderate molecular weights (21.6—82.0 kg/mol). Moreover, the palladium catalysts could also copolymerize ethylene and methyl acrylate (MA), albeit in low activities (level of 103 g·mol–1·h–1), providing E‐MA copolymers with low to moderate molecular weights (1.4—16.3 kg/mol) and a moderate level of incorporation ratio (2.4—7.4 mol%) and branching density (53—84/1000C). As compared with aniline‐based nickel and palladium catalysts, the naphthylamine‐based catalysts displayed a superior ability to suppress the chain transfer reactions and could give access to (co)polymers with orders of magnitude higher molecular weight in ethylene (co)polymerization. [ABSTRACT FROM AUTHOR]

Recently, polyolefin thermoplastic elastomers can be obtained directly using ethylene as a single feedstock via α-diimine nickel-catalyzed ethylene chain walking polymerization. Here, a new range of bulky acenaphthene-based α-diimine nickel complexes with hybrid o-phenyl and -diarylmethyl anilines were constructed and applied to ethylene polymerization. All the nickel complexes under the activation of excess Et2AlCl exhibited good activity (level of 106 g mol−1 h−1) and produced polyethylene with high molecular weight (75.6–352.4 kg/mol) as well as proper branching densities (55–77/1000C). All the branched polyethylenes obtained exhibited high strain (704–1097%) and moderate to high stress (7–25 MPa) at break values. Most interestingly, the polyethylene produced by the methoxy-substituted nickel complex exhibited significantly lower molecular weights and branching densities, as well as significantly poorer strain recovery values (48% vs. 78–80%) than those by the other two complexes under the same conditions. [ABSTRACT FROM AUTHOR]

Recently, the second coordination sphere effect has been successfully exploited to modulate the catalytic behavior of late-transition metal catalysts in olefin insertion polymerization. In this study, four bulky iminopyridyl Ni(II) and Pd(II) complexes that contain naphthalene or benzothiophene groups were firstly prepared and their applications in olefin oligomerization were also investigated. The as-prepared nickel and palladium complexes generally displayed good catalytic activity in ethylene oligomerization, providing hyperbranched oligomers with various microstructures. Notably, the molecular weights of the ethylene oligomers generated by the benzothiophene-based Ni(II)/Pd(II) complexes were significantly lower than those generated by the naphthalene-based complexes. In addition, these palladium complexes could catalyze the co-oligomerization of ethylene and MA, yielding hyperbranched co-oligomers with tunable incorporation ratios of MA. Moreover, for ethylene oligomerization catalyzed by nickel complexes, toluene-end-functionalized branched ethylene oligomers were formed via Friedel–Crafts addition of the resulting unsaturated ethylene oligomers to the toluene solvent. In this work, we found that the second coordination sphere effect of benzothiophene could facilitate chain transfer in iminopyridyl Ni(II)/Pd(II)-catalyzed ethylene (co)oligomerization, in contrast to the phenomenon observed in the corresponding α-diimine system. [ABSTRACT FROM AUTHOR]

In this study, a series of partially chain-straightened propylene oligomers and functional propylene–methyl acrylate (P-MA) co-oligomers were synthesized with 8-alkyl-iminopyridyl Pd(II) catalysts. The molecular weight and polar monomer incorporation ratio could be tuned by using Pd(II) catalysts with various 8-alkyl-naphthyl substituents (8-alkyl: H, Me, and n-Bu). In propylene oligomerization, all the 8-alkyl-iminopyridyl Pd(II) catalysts convert propylene to partially chain-straightened (119–136/1000 C) oligomers with low molecular weights (0.3–1.5 kg/mol). Among the catalysts, Pd1 with non-substituent (H) on the ligand showed the highest activity of 5.4 × 104 g/((mol of Pd) h), generating oligomers with the lowest molecular weight (Mn: 0.3 kg/mol). Moreover, polar-functionalized propylene-MA co-oligomers with very high incorporation ratios (22.8–36.5 mol %) could be obtained in the copolymerization using these 8-alkyl-iminopyridyl Pd(II) catalysts. Additionally, Pd1 exhibited the best performance in propylene-MA copolymerization as it displayed the highest MA incorporation ratio of up to 36.5 mol%. All the three catalysts are capable of generating partially chain-straightened P-MA co-oligomers and the activities decrease gradually while the molecular weight increases with the increasing steric hindrance of the alkyl substituent (H < Me < n-Bu). Compared to Pd4 with the rigid 8-aryl substituent, the flexible 8-alkyl-iminopyridyl Pd(II) catalysts (Pd1-3) not only showed much higher activities in the propylene oligomerization, but also yielded P-MA co-oligomers with significantly higher incorporation ratios in the propylene co-oligomerization. [ABSTRACT FROM AUTHOR]

Chain-end functionalized polymers play an important role in the field of building complex macromolecular structures. In this study, we have synthesized and characterized four dibenzhydryl iminopyridine Ni(II) complexes bearing remote flexible substituents (Et and n-Bu) to provide hyperbranched ethylene oligomers in ethylene oligomerization with moderate to good activities. Most notably, toluene-end-functionalized hyperbranched ethylene oligomers were obtained under elevated temperature conditions and validated by NMR. The tandem catalysis of ethylene oligomerization and the subsequent Friedel–Crafts addition of the resulting unsaturated products to toluene molecules was proposed as the cause of the observed phenomenon. [ABSTRACT FROM AUTHOR]

The synthesis of hyper‐branched ethene oligomers through catalytic insertion reactions with late transition metal catalysts is unique in its synthetic and practical scope. In this study, a series of iminopyridyl Ni(II) and Pd(II) complexes with electron‐rich distal aryl motifs were synthesized and characterized. These complexes were very efficient in ethene oligomerization and co‐oligomerization with methyl acrylate (MA). Hyperbranched ethene oligomers with different microstructures were generated using different metal species in ethene oligomerization. More importantly, hyperbranched ethene‐MA co‐oligomers with varying incorporation ratios were generated via ethene and MA co‐oligomerization using the Pd(II) complexes. Most notably, weak neighboring group interactions of distal aryl motifs in the nickel system are more effective in influencing the microstructure of ethene oligomers than the corresponding palladium system. [ABSTRACT FROM AUTHOR]