China
Africa
Explore chapters and articles related to this topic
Organic Polymers, Oligomers, and Catalysis
Published in Qingmin Ji, Harald Fuchs, Soft Matters for Catalysts, 2019
Cu(II)-loaded dendrimers were obtained by peripheral grafting of bis(oxazoline) [61] or bipyridine [62] moieties on poly(benzylether) and subsequent incubation with Cu(II) triflate complexes. These dendrimer-supported organometallic catalysts exhibited Lewis acid character that allowed catalyzing aldol and Diels-Alder reactions. For instance, cyclopentadiene, 1,3-cyclohexadiene, and dimethylbutadiene could all react with activated dienophiles in dichloromethane with yields higher than 85% [62]. Recycling the catalyst was possible by changing the solvent to hexane, and catalytic performances were preserved after five cycles. Recently the need of Cu(I) ions-based catalysts has emerged due to the rise of the Cu(I) catalyzed alkyne-azide “click” reaction (CuAAC). PAMAM dendrimers offer ideal platforms for designing this type of catalyst, without any functionalization step, due to their ability to complex Cu(II) ions which can subsequently be converted into Cu(I) [63]. The resulting catalyst was reusable by ultrafiltration and allowed performing faster click couplings between azido-propanol and propargyl-alcohol in water. When the click catalyst was designed as a Cu(I) core surrounded by dendritic branches, catalysis performances increased significantly [64].
Clay Mineral Catalysis of Redox, Asymmetric, and Enantioselective Reactions
Published in Benny K.G. Theng, Clay Mineral Catalysis of Organic Reactions, 2018
For both Cu-5 and Cu-6 complexes (with Laponite), the yield of products (3R, 3S, 4R, 4S) and their respective trans/cis ratios are influenced by the type of solvent used. Since the Cu-bis(oxazoline) complex is apparently immobilized as an almost square-planar structure, a reduction in solvent polarity would make it easier for the complex to approach the clay surface and establish close surface-complex interactions (Alonso et al. 2000; Fernandez et al. 2001). Interestingly, Bigi et al. (2001) also noted that the regioselective conversion of 2,4-di-tert-butylphenol and phenol to 4-tert-butylphenol over KSF montmorillonite was solvent-dependent. Furthermore, the trans/cis diastereoselectivity of the reaction between styrene and ethyl diazoacetate (Scheme 7.1), catalyzed by the Laponite-supported Cu complex with pyridine-oxazoline (6), is the reverse of that observed with the bis(oxazoline) complex (5) as ligand (Table 7.5). Using Cu2+-exchanged K10 montmorillonite as a catalyst, Fraile et al. (1996)also found that the normal trans/cis selectivity in solution was reversed, giving the cis-cyclopropane as the major product. The immobilization of enantioselective (chiral) catalysts on solid supports, including clay minerals, has been reviewed by Fraile et al. (2009b).
Antioxidants
Published in Leslie R. Rudnick, Lubricant Additives, 2017
Robert G. Rowland, Jun Dong, Cyril A. Migdal
More complex compounds obtained from further reactions of copper salts have also been reported to be effective antioxidants in a variety of lubrication applications. For example, copper carboxylate or copper thiocyanate was reacted with a mono-oxazoline, bis-oxazoline, or lactone oxazoline dispersant to form coordination complexes wherein the nitrogen contained in the oxazoline moiety is the ligand that complexes with copper. The resulting products exhibit improved varnish control and oxidation inhibition capabilities [158]. Reaction products of a copper salt (acetate, carbonate, or hydroxide) with a substituted succinic anhydride derivative containing at least one free carboxylic acid group are effective high-temperature antioxidants and friction modifiers. When incorporated in an engine oil formulation, the oil passed rust, oxidation, and bearing corrosion engine tests [159]. In another patent [160], a hindered phenolic carboxylic acid was used as the coupling reagent. The resulting copper compounds are reported to be effective in the control of high-temperature sludge formation and oil viscosity increase when used alone or in synergistic mixtures with a conventional aminic or phenolic antioxidant.
Carbazolyl-bis(triazole) and Carbazolyl-bis(tetrazole) Complexes of Palladium(II) and Platinum(II)
Published in Journal of Coordination Chemistry, 2021
Samya Samanta, Cameron Zheng, Leah Gajecki, David J. Berg, Allen G. Oliver, Tristan Crosby, Logan Godin, Jaylene Sandhu
Anionic pincer complexes of Pd based on diphenylamido-bis(oxazoline) ligands have been shown to be good polymerization catalysts for chloroalkynes and norbornadiene [19, 20]. Phosphorescent Pt(II) complexes of metallated aryl-bis(heterocycles) (N^C^N: heterocycles = py, 1,2,3-triazole) and py-bis(1,2,3-triazoles) have also been reported recently [17]. With these interesting observations in mind, we herein report the synthesis of several new ligands, including the new carbazole-bis(1,2,4-triazole) series, and their square planar, divalent Pd and Pt complexes. Several ligands and metal complexes are characterized crystallographically and the electronic properties of select metal complexes are investigated by cyclic voltammetry (CV) and DFT calculations.
Molecular design of supramolecular polymers with chelated units and their application as functional materials
Published in Journal of Coordination Chemistry, 2018
Igor E. Uflyand, Gulzhian I. Dzhardimalieva
An interesting class of soluble Eu(III)-based MSPs [73] was developed on the basis of the tridentate ditopic ligand pyridine-bis(oxazoline) (pybox), which shows high quantum yields of metal emission up to 73%, and also unique dynamic behavior in solution (Figure 8).