Browsing by Author "Quijada, Raul"

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    Acetamidine complexes as catalysts for ethylene polymerization
    (2009) Valdebenito, Carolina; Garland, Maria Teresa; Quijada, Raul; Rojas Guerrero, René
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    Ethylene polymerization using dealuminated ZSM-2 zeolite nanocrystals as an active metallocene catalyst support
    (2008) Covarrubias, Cristian; Quijada, Raul; Rojas Guerrero, René
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    Nickel pre-catalysts bearing [(N)-imidoylamidine] ligands; influence of the presence of pyridine and pentafluorophenyl groups in ligand backbone on the reactivity in ethylene polymerizations
    (2012) Peoples, Brian C.; De la Vega, Gala; Valdebenito, Carolina; Quijada, Raul; Ibanez, Andres; Valderrama, Mauricio; Rojas, Rene
    In this contribution the synthesis and polymerization activity of the nickel complexes [NiBr2{N'-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)ethyl]-N-(2,3,4,5,6-pentafluorophenyl)acetamidine}] (2), [NiBr2{N'-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)ethyl]-N-(2,3,4,5,6-pentafluorophenylimine) ethylacetamidine}] (2a) and [NiBr2 {N-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)]-N-(pyridin-4-yl)acetamidine}] (3)are reported. The variation of the phenyl substituents on the beta amine was found to influence the polymerization activity of the complexes. The electron withdrawing/donating capacity of the substituted ring was found to be correlated with the polymerization activity, with the pentafluoro substituted ring increasing the polymerization activity and the pyridine ring decreasing the activity. The ligands and complexes were characterized using standard techniques and the polymer properties analyzed. (C) 2011 Elsevier B. V. All rights reserved.
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    Tris(pyrazolyl)methane-chromium(III) complexes as highly active catalysts for ethylene polymerization
    (ELSEVIER SCIENCE BV, 2006) Garcia Rozco, Ivan; Quijada, Raul; Vera, Karen; Valderrama, Mauricio
    Reaction of complex CrCl3 (THF)(3) with the tris(pyrazolyl)methane ligands, HC(Pz)(3), HC(3,5-Me(2)Pz)(3) and their substituted derivatives RC(Pz)(3) (R = Me, CH2OH, CH2OSO2Me) in THF lead to the formation of neutral complexes of the types [RC(PZ)(3)CrCl3] and [RC(3,5-Me(2)PZ)(3)CrCl3]. After reaction with methylalumoxane (MAO) these complexes are active in the polymerization of ethylene. The substituent on the methane central carbon atom of the ligand has some influence in polymerization behavior. This compounds present higher activities than similar chromium complexes, in the ethylene polymerization reaction. (c) 2006 Elsevier B.V. All rights reserved.