199190-77-7Relevant articles and documents
Synthesis and characterization of 'calixsalens': A new class of macrocyclic chiral ligands
Li, Zengmin,Jablonski, Chet
, p. 1531 - 1532 (1999)
Template directed reaction of dialdehydes and (R,R)- or (S,S)-1,2-diaminocyclohexane affords a practical route to chiral, metal-free macrocyclic salen dimers which have a novel calixarene-like structure and show catalytic activity for enantioselective epo
Asymmetric bis-salicylaldiminato binuclear titanium complexes for ethylene polymerization and copolymerization
Qin, Yawen,Li, Tingcheng,Chen, Xiong,Li, Jian,Meng, Xiang,You, Qingliang,Xie, Guangyong
, p. 11390 - 11398 (2021/07/06)
Polyolefins with high molecular weight and broad molecular weight distribution have attracted great attention due to their ease of processing and wide applications. In this paper, methylene-bridged asymmetric disalicylaldimine ligands bearing phenylthio and alkylthio sidearms (4a-4c) were synthesized from methylene-bridged disalicylaldehyde that reacted successively with 2-phenylthio and 2-alkylthio anilines, which then directly coordinated with TiCl4to afford asymmetric bis-salicylaldiminato binuclear titanium complexes5a-5cin one step. The asymmetric complexes were detailedly characterized by FTIR,1H NMR,13C NMR, and elemental analysis. Under the activation of modified methylaluminoxane (MMAO), these asymmetric complexes displayed high activity over 106g mol(Ti)?1h?1atm?1for ethylene polymerization and copolymerization with 1-hexene or norbornene. Compared with the corresponding mononuclear complexes, the asymmetric binuclear catalysts showed higher catalytic activity (up to 2.29 × 106g mol(Ti)?1h?1atm?1) for ethylene polymerization to produce higher molecular weight polyethylenes with much wider molecular weight distribution due to the presence of two different active centers. For ethylene polymerization and copolymerization with 1-hexene, the catalytic activity of binuclear5awhich carries phenylthio and methylthio sidearms and the properties of the obtained polyolefins were more similar to those of mononuclear6bwhich bears a phenylthio sidearm, indicating that the phenylthio group exerted major influences. However, for ethylene/norbornene copolymerization,5ashowed an activity significantly higher than that of6b, yet similar to that of mononuclear6awhich bears a methylthio sidearm, indicating that the methylthio sidearm in5aplayed a major role in this case. A smaller sidearm in the ligand was more conducive to the polymerization reaction when large comonomers were involved, and a balance of the steric hindrance between the ligand and the comonomer might be needed for achieving high catalytic performance.
A dimeric form of Jacobsen's catalyst for improved retention in a polydimethylsiloxane membrane
Janssen, Kristien B. M.,Laquiere, Isabelle,Dehaen, Wim,Parton, Rudy F.,Vankelecom, Ivo F. J.,Jacobs, Pierre A.
, p. 3481 - 3487 (2007/10/03)
A dimeric form 1 of Jacobsen's catalyst was synthesized for better steric occlusion in a polydimethylsiloxane membrane. In homogeneous conditions, the dimer is about as active and enantioselective as Jacobsen's catalyst itself. The relationship between leaching of the complex out of the membrane on one hand and the solubility of the complex and the swelling of the membrane in the solvent used on the other, showed that leaching could be avoided only if low solubility was combined with low swelling or in the case of complete insolubility. As the dimer is less soluble and larger than the monomeric form, this form leaches less. The yields and enantioselectivities of the heterogenised system are comparable to those of the homogeneous monomer.