On the basis of the strategy of promoting thermostability of α-diimine nickel catalyst by ligand backbone framework, a series of α-diimine nickel(II) complexes with bulky camphyl or diaryl-substituted backbones, [2,6-(R2)2C6H3−NC(R1)−C(R1)N−2,6-(R2)2C6H3]NiBr2 (1a, R1 = Ph, R2 = CH3; 2a, R1 = 4-methylphenyl, R2 = CH3; 3a, R1 = 4-fluorophenyl, R2 = CH3; 4a, R1 = camphyl, R2 = CH3; 4b, R1 = camphyl, R2 = i-Pr), were synthesized and used as catalyst precursors for ethylene polymerization. Crystallographic analysis revealed that the bulky camphyl backbone has a valid steric-effect on the nickel center by blocking the axial site for the metal center and suppressing the potential rotation of the CAr−N bond. Ethylene polymerizations catalyzed by these nickel α-diimine complexes activated by MAO were systematically investigated and the influences of the substituted backbones as well as reaction temperature on the catalytic activity, molecular weight and branching structure of the polymers were evaluated. It was found that the catalysts containing a camphyl backbone have excellent thermal stability and polymer structure control for ethylene polymerizations. Even at 80 °C, the 4b/MAO system still kept high activity and relatively stable kinetics and produced high molecular weight polyethylene. Moreover, the branching degrees and branched chain distribution of the polyethylenes obtained by the complex could also be controlled by tuning the reaction temperature.

An unconventional organic molecule (TBBU) showing obvious long‐lived room temperature phosphorescence (RTP) is reported. X‐ray single crystal analysis demonstrates that TBBU molecules are packed in a unique fashion with side‐by‐side arranged intermolecular aromatic rings, which is entirely different from the RTP molecules reported to date. Theoretical calculations verify that the extraordinary intermolecular interaction between neighboring molecules plays an important role in RTP of TBBU crystals. More importantly, the polymer film doped with TBBU inherits its distinctive RTP property, which is highly sensitive to oxygen. The color of the doped film changes and its RTP lifetime drops abruptly through a dynamic collisional quenching mechanism with increasing oxygen fraction, enabling visual and quantitative detection of oxygen. Through analyzing the grayscale of the phosphorescence images, a facile method is developed for rapid, visual, and quantitative detection of oxygen in the air.

A bulky amine-imine nickel complex containing two 2,6-diisopropyl substituents after activation with MMAO or Et(2)AlCl can polymerize ethylene in a living fashion over a period of 120 minutes at room temperature or above.

No abstract

A series of novel nickel complexes (1−4) bearing anilido−imine ligands, [(Ar1NCHC6H4NAr2)NiBr]2 (Ar1 = Ar2 = 2,6-dimethylphenyl, 1; Ar1 = 2,6-dimethylphenyl, Ar2 = 2,6-diisopropylphenyl, 2; Ar1 = Ar2 = 2,6-diisopropylphenyl, 3; Ar1 = 2,6-diisopropylphenyl, Ar2 = 2,6-dimethylphenyl, 4), have been synthesized and characterized. The solid-state structures of the complexes 1, 2, and 4 were confirmed by X-ray single-crystal analyses to be in the form of a dinuclear and bromine-bridged structure. However, there is an equilibrium that shifts between the monomer and dimer in solution, which has been monitored using 1H NMR and UV−vis spectrophotometry. The themodynamic parameters for the equilibriums were calculated to be ΔH = +13.68 kJ/mol and ΔS = 40.32 J/(mol K) for 1 and ΔH = +8.35 kJ/mol and ΔS = 15.21 J/(mol K) for 3. All nickel complexes show low activities for ethylene oligomerization with MAO as cocatalyst but high catalytic activities for norbornene polymerization in the presence of MAO.

Chiral (1S)- and (1R)-camphyl α-diimine nickel complexes were synthesized respectively with (1S)-(+) camphorquinone and (1R)-(−) camphorquinone as raw reagents and used as catalyst precursors for olefin polymerizations. It is found that the ligand chirality has no influence on catalytic activity and regioselectivity for olefin polymerizations. Ethylene, propylene, 1-hexene, and 4-methyl-1-pentene polymerizations with the camphyl α-diimine nickel activated by AlEt2Cl can exhibit some living characteristics under the optimized conditions. The resultant polypropylenes and poly(1-hexene)s have significantly narrow molecular weight distributions (PDI < 1.2) in a wide temperature range, even at an elevated temperature of 70 °C. Sustainable period of the linear relationship of M n vs polymerization time depends on temperature for propylene and 1-hexene polymerizations. Additionally, high 1,3-enchainment fraction of 45% is observed even at −60 °C for propylene polymerization using the camphyl α-diimine catalyst due to 2,1-insertion of propylene and chain walking.

A series of benzocyclobutene (BCB) polymers derived from a new readily available monomer, 4-(1 0 ,1 0 -dimethyl-1 0 -vinyl) silylbenzocyclobutene (4-DMVSBCB), were conveniently prepared by radical and anionic polymerization. The homo-and co-polymerization results show that the reactivity of 4-DMVSBCB in anionic polymerization is relatively higher compared with radical polymerization. The molecular weight of 4-DMVSBCB polymers and content of 4-DMVSBCB can be controlled by anionic copolymerization. The introduction of rigid and crosslinkable BCB building blocks in side chains and carbosilanes in molecule gives rise to insulating materials with good film-forming property, smooth and flat film surface, and low-dielectric constants of 2.41-2.45, as preserving good thermal stability. FIGURE 8 TGA spectrum of highly crosslinked poly(4-DMVSBCB) under nitrogen atmosphere.FIGURE 9 TGA spectrum of highly crosslinked poly(4-DMVSBCB) under oxygen atmosphere.FIGURE 7 AFM spectra of pre-crosslinked and highly crosslinked poly(4-DMVSBCB) film. ARTICLE NEW POLYMERS DERIVED FROM 4-DMVSBCB MONOMER, YANG ET AL. 389

Three new iron(II) 2,6-bis(imino)pyridyl complexes bearing bulky and unsymmetrical substituted aniline groups, [2-(CH(CH 3 )(C 6 H 5 ))-4