Triazolecarboxamidate Donors as Supporting Ligands for Nickel Olefin Polymerization Catalysts

To increase the structural diversity of dinucleating platforms that are used in the construction of olefin polymerization catalysts, we are exploring new ligand designs that feature non-alkoxide/phenoxide bridging groups. In the current study, we demonstrate that 1,2,3-triazole-4-carboxamidate donors are excellent <i>N</i>,<i>N</i>-chelators for nickel and can readily bind secondary metal ions. We found that sterically bulky nickel triazolecarboxamidate complexes are active as ethylene homopolymerization catalysts and can afford low molecular weight polyethylene with about 80–130 branches per 1000 carbon atoms. The addition of zinc salts to our nickel complexes led to catalyst inhibition in some cases, which we have attributed to the formation of catalytically inactive mixed-metal species. To circumvent this problem, we anticipate that further elaboration of the triazolecarboxamidate ligand could provide discrete heterobimetallic complexes that will be useful as single-site catalysts with unique reactivity patterns

Fine-Tuning Nickel Phenoxyimine Olefin Polymerization Catalysts: Performance Boosting by Alkali Cations

To gain a better understanding of the influence of cationic additives on coordination–insertion polymerization and to leverage this knowledge in the construction of enhanced olefin polymerization catalysts, we have synthesized a new family of nickel phenoxyimine–polyethylene glycol complexes (<b>NiL0</b>, <b>NiL2</b>–<b>NiL4</b>) that form discrete molecular species with alkali metal ions (M⁺ = Li⁺, Na⁺, K⁺). Metal binding titration studies and structural characterization by X-ray crystallography provide evidence for the self-assembly of both 1:1 and 2:1 <b>NiL</b>:M⁺ species in solution, except for <b>NiL4</b>/Na⁺ which form only the 1:1 complex. It was found that upon treatment with a phosphine scavenger, these <b>NiL</b> complexes are active catalysts for ethylene polymerization. We demonstrate that the addition of M⁺ to <b>NiL</b> can result in up to a 20-fold increase in catalytic efficiency as well as enhancement in polymer molecular weight and branching frequency compared to the use of <b>NiL</b> without coadditives. To the best of our knowledge, this work provides the first systematic study of the effect of secondary metal ions on metal-catalyzed polymerization processes and offers a new general design strategy for developing the next generation of high performance olefin polymerization catalysts

ESCC patient clusters and survival analysis.

<p>(<b>A</b>) The cluster of miR-31 and miR-338-3p in 89 ESCC patients. The prefix 0 represents deceased ESCC patients, while the prefix 1 represents living ESCC patients. (<b>B</b>) Survival of grouped ESCC patients is analyzed by Kaplan-Meier analysis and the log-rank test.</p

Power law of node degree distribution for the miRNA-subpathway networks.

<p>(<b>A</b>) Degree distribution of the downregulated miRNA-subpathway network. (<b>B</b>) Degree distribution of the upregulated miRNA-subpathway network. (<b>C</b>) Degree distribution of the total miRNA-subpathway network.</p

Graphic representation of three miRNA-subpathway networks.

<p>(<b>A</b>) Downregulated miRNA-subpathway network. (<b>B</b>) Upregulated miRNA-subpathway network. (<b>C</b>) Total miRNA-subpathway network. Nodes colored in green are downregulated miRNA, and red nodes are upregulated miRNAs. Blue nodes represent the subpathways. The size of the miRNA nodes correspond to the node degree (the number of subpathways that miRNA connected). <i>P</i>-value strength is represented by edge line width, with wider edges representing more significant interactions. Hsa-miR-320b and hsa-miR-1248 had the biggest degree are shaded in yellow.</p

The k = 12 clique from the downregulated miRNA-miRNA network and its co-regulated subpathways.

<p>Green nodes represent downregulated miRNAs, while upregulated miRNA is colored red. The size of the miRNA nodes corresponds to the node degree. <i>P</i>-value strength is represented by edge line width, with darker edges representing more significant interactions.</p

Network parameters of miRNA-subpathway and subpathway-subpathway networks.

<p>Network parameters of miRNA-subpathway and subpathway-subpathway networks.</p

The k = 6 clique from total miRNA-miRNA and its co-regulated subpathways.

<p>Red nodes represent upregulated miRNAs, while blue nodes are downregulated miRNAs. The size of the miRNA nodes corresponds to the node degree. <i>P</i>-value strength is represented by edge line width, with wider edges representing more significant interactions.</p

Summary of differentially-expressed ESCC miRNAs applied in this study.

<p>Summary of differentially-expressed ESCC miRNAs applied in this study.</p