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Light-Emitting Polymers
Published in Zhigang Rick Li, Organic Light-Emitting Materials and Devices, 2017
Shidi Xun, Dmitrii F. Perepichka, Igor F. Perepichka, Hong Meng, Fred Wudl
Into a Schlenk tube was placed bis(1,5-cyclooctadiene)-nickel(0) (2.6 mmol), 2,2′-bipyridyl (2.6 mmol), 1,5-cyclooctadiene (0.2 ml), DMF (4 ml), and toluene (8 ml). The reaction mixture was heated to 80°C for 0.5 h under argon. The dibromide comonomers 665 and 676 dissolved in degassed toluene (8 ml; molar ratio of dibromides to nickel complex: 0.65) were added under argon to the DMF–toluene solution, and the polymerization was maintained at 80°C for 3 days in the dark. 2-Bromofluorene (molar ratio of dibromides to monobromide: 0.1) dissolved in degassed toluene (1 ml) was added, and the reaction continued for 12 h. The polymers were precipitated by addition of the hot solution dropwise to an equivolume mixture of concentrated HCl, methanol, and acetone. The isolated polymers were then dissolved in toluene or dichloromethane and reprecipitated with methanol/acetone (1:1). The copolymers were dried at 80°C in vacuo. The isolated yields of copolymers 253a–c were 79%–85%.
The Nature of Sulfur Vulcanization
Published in Nicholas P. Cheremisinoff, Elastomer Technology Handbook, 2020
Michael R. Krejsa, Jack L. Koenig
Model compound work on polybutadiene models led to higher levels of vicinal crosslinks and saturation then did natural rubber models.28,55,58 Gregg and Lattimer indicated that this may be due to the reactive behavior of the polybutadiene models.54 Their work found that cyclohexene and 1,5-cyclooctadiene did not react fully. Their work also found that a 16- membered ring with four double bonds was a better model for polybutadiene and resulted in products similar to those from natural rubber model compounds.
Copolymerization of Nonconjugated Dienes with Conventional Vinyl Monomers
Published in George B. Butler, Cyclopolymerization and Cyclocopolymerization, 2020
Poly(1,5-cyclooctadiene sulfone) was obtained by a radical-initiated transannular copolymerization of 1,5-cyclooctadiene and sulfur dioxide.122 The copolymer was more stable thermally than single stranded alkene-sulfur dioxide copolymers.
Cytotoxic potential of silver, palladium, rhodium, ruthenium, and iridium complexes of a cycloheptyl-substituted lipophilic N-heterocyclic carbene ligand
Published in Journal of Coordination Chemistry, 2023
Mert Olgun Karataş, Güldeniz Şekerci, Suat Tekin, Süleyman Sandal, Hasan Küçükbay
Synthesis and structures of benzimidazolium chloride and the complexes are outlined in Scheme 1. Cycloheptyl-substituted benzimidazolium chloride (1) [45], Ag–NHC (2) [45], and Pd–NHC (3) [46] were reported in our previous studies and we re-synthesized these compounds according to described procedures. Rh–NHC (4), Ru–NHC (5), and Ir–NHC (6) complexes were synthesized by transmetalation between Ag–NHC and [RhCl(cod)]2 (cod = 1,5-cyclooctadiene), [RuCl2(p-cymene)]2 or [IrCl(cod)]2, respectively. The reactions were carried out in dichloromethane in the absence of light. After 48 h of reaction time at room temperature, the target complexes were obtained in 53, 45, and 38% yields, respectively. At the end of reaction period, the solutions were separated from silver chloride precipitate by filtration, and Rh– and Ru–NHC complexes were obtained as pure solids after evaporation of dichloromethane and washing with n-hexane. However, Ir–NHC is soluble in n-hexane and it was purified by extraction with n-hexane. All complexes were stable under air both in solid state and in solution, therefore, we did not use argon or nitrogen gases for inert atmosphere during the reaction period or storage.
Synthesis and characterization of Ni(0) complexes supported by an unsymmetric C,N ligand
Published in Journal of Coordination Chemistry, 2022
Sarah M. Craig, Kaycie R. Malyk, Elliot S. Silk, Daniel T. Nakamura, William W. Brennessel, C. Rose Kennedy
In light of the structural similarities of the two complexes, we sought to determine whether their interconversion was reversible. As expected, treating [Ni(cod)(hIMesPy)] with ≥1.0 equiv additional hIMesPy in either C6D6 or toluene resulted in clean formation of [Ni(hIMesPy)2] in yields comparable to the direct method (Figure 4). More surprisingly, treating [Ni(cod)(hIMesPy)] with ≥1.0 equiv [Ni(cod)2] resulted in reversion to [Ni(cod)(hIMesPy)] as monitored by 1H NMR spectroscopy (Figure 5). Addition of excess, free 1,5-cyclooctadiene (35 equiv, instead of [Ni(cod)2]) was less efficient and afforded a mixture of 3 and 4 even after 24 h. Although attempts to quantify the ligand exchange rate by 2 D exchange spectroscopy (EXSY) were unsuccessful, these results highlight a dynamic equilibrium of ligand exchange between 3 and 4, presumably via a dissociative mechanism. This finding suggests that both 3 and 4 may be used as suitable single-component precatalysts for future studies [45].
Ketone transfer hydrogenation reactions catalyzed by catalysts based on a phosphinite ligand
Published in Journal of Coordination Chemistry, 2022
Duygu Elma Karakaş, Khadichakhan Rafikova, Akin Baysal, Nermin Meriç, Alexey Zazybin, Cezmi Kayan, Uğur Işik, Islam Sholpan Saparbaykyzy, Feyyaz Durap, Murat Aydemir
Since generally high catalytic performances were achieved in these preliminary studies, transfer hydrogenation of a variety of simple ketones were explored. Results of these experiments indicated that 2-5 efficiently catalyzed reduction of these ketones and provided almost quantitative transformation in short times. [Dichloro(η5-pentamethylcyclopentadienyl)(1-furan-2-ylethyl diphenylphosphinite)iridium(III)] (5) is more active than [chloro(η4-1,5-cyclooctadiene)(1-furan-2-ylethyl diphenylphosphinite)rhodium(I)] (4) (Table 3). For instance, hydrogenations of cyclohexanone and cyclopentanone could be achieved in 4 h and 2 h by 4 and 5, respectively. Methyl isobutyl ketone reduced in 12 h and 7 h by 4 and 5, respectively, while diethyl ketone was hydrogenated in 18 h and 12 h by 4 and 5, respectively. The catalytic activity of 5 was generally higher than that of 4. Because of the high catalytic activities obtained by 5, further experiments were conducted to invetigate how the bulkiness of alkyl groups affects the catalytic activity (Table 4, entries 1–4). The catalytic activity of the subsrates was very dependent on the steric hindrance of the alkyl moiety. As anticipitated, the reactivity gradually decreased by increasing the bulkiness of the alkyl groups [59–62].