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Diimine Catalysts (diimine + catalyst)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Copolymerization of Ethylene with 2,7-Octadienyl Methyl Ether in the Presence of Metallocene and Nickel Diimine Catalysts

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2009
Mércia Fernandes
Abstract In this work, copolymers of ethylene with 2,7-octadienyl methyl ether have been synthesized in the presence of three single-site catalysts. The obtained copolymers not only have a polar ether function but also a double bond in the side chains that is useful for secondary reactions. The polymers were characterized by GPC, EA, DSC, NMR, and FT-IR. The catalytic activity depends on the kind of catalysts, the concentration of the polar monomer, and the concentration of the protecting agent. Up to 7.3 wt.-% of MODE could be incorporated by the metallocene catalyst. These are in average 120 functional side groups in a polymer molecule with a molecular mass of 230,000. [source]

The Effect of Counterion/Ligand Interplay on the Activity and Stereoselectivity of Palladium(II),Diimine Catalysts for CO/p -Methylstyrene Copolymerization

CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2007
Barbara Binotti Dr.
Abstract The catalytic activity and stereoselectivity of complexes [Pd(,1,,2 -C8H12OMe)(ArNC(R,)C(R,)NAr)]X in the copolymerization of CO and p -methylstyrene have been correlated with their interionic structure in solution and in the solid state, as determined by 19F,1H-HOESY NMR spectroscopy and X-ray diffraction studies, respectively. The highest productivity is obtained with unhindered diimine ligands bearing electron-donating substituents and with the least coordinating counterion. Copolymers with a microstructure ranging from atactic to predominantly isotactic are obtained. The degree of isotacticity increases as the steric hindrance in the apical positions and the coordinating ability of the counterion increase. The counterion is located close to the diimine in both solution and the solid state but it moves toward the palladium as the steric hindrance in the apical positions decreases. When the latter is small the counterion competes with the substrate for apical coordination, and consequently it affects the productivity. In the case of ortho -dimethyl-substituted ligands the counterion is confined in the back, above the NC(R,)C(R,)N moiety, and does not affect the productivity. However, it contributes to increasing the stereoregularity of the copolymer by making the aryl moieties more rigid. With R,=Me and Ar=o -Me2C6H3 an ll of 81,% and 72,% was obtained with X,=CF3SO3, or BArF,, respectively. The isotacticity of the copolymers produced by ortho -monosubstituted catalysts depends greatly on the counterion and ranges from 30,% to 59,% with X,=BArF, and X,=CF3SO3,, respectively, with Ar=o -EtC6H4 and R,=Me. Based on the interionic structural results, this effect can be explained by a greater reduction of the copolymerization rate of Cs -symmetric isomers with respect to their C2 -symmetric counterparts. [source]

Micron-granula polyolefin with self-immobilized nickel and iron diimine catalysts bearing one or two allyl groups

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004
Guoxin Jin
Abstract Self-immobilized nickel and iron diimine catalysts bearing one or two allyl groups of [ArNC]2(C10H6)NiBr2 [Ar = 4-allyl-2,6-(i -Pr)2C6H2] (1), [ArNC(Me)][Ar,N C(Me)]C5H3NFeCl2 [Ar = Ar, = 4-allyl-2,6-(i -Pr)2C6H3, Ar = 2,6-(i -Pr)2C6H3, and Ar, = 4-allyl-2,6-(i -Pr)2C6H3] were synthesized and characterized. All three catalysts were investigated for olefin polymerization. As a result, these catalysts not only showed high activities as the catalyst free from the allyl group, such as [ArNC]2C10H6NiBr2 (Ar = 2,6-(i-Pr)2C6H2)], but also greatly improved the morphology of polymer particles to afford micron-granula polyolefin. The self-immobilization of catalysts, the formation mechanism of microspherical polymer, and the influence on the size of the particles are discussed. The molecular structure of self-immobilized nickel catalyst 1 was also characterized by crystallographic analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1018,1024, 2004 [source]