Browsing by Author "Peoples, Brian C."

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    Mono and bimetallic nickel bromide complexes bearing azolate-imine ligands: Synthesis, structural characterization and ethylene polymerization studies
    (ELSEVIER SCIENCE SA, 2009) Caris, Rodrigo; Peoples, Brian C.; Valderrama, Mauricio; Wu, Guang; Rojas, Rene
    The synthesis of N-(1-(3,5-dimethylpyrazol-1-yl)ethylidene)-2,6-diisopropylaniline (1) and N-(1-(indazol-2-yl)ethylidene)-2,6-diisopropylaniline (2) allowed access to new transition metal complexes. When reacted with dibromo(2,2'-dimethoxyethylether) nickel(II) the complexes [NiBr2{N-(1-(3,5-dimethylpyrazol-1-yl) ethylidene)-2,6-diisopropylaniline}] (3) and [Ni2Br2(mu-Br)2{N-(1-(indazol-1-yl)ethylidene)-2,6-diisopropylaniline} 2] (4) are yielded, respectively. The addition of MAO generates catalytically active species for the homopolymerization of ethylene. The polymer products were low molecular weight (3-6 K) and a monomodal molecular weight distribution, consistent with the presence of a single active site. In addition, the catalyst was found to efficiently oligomerize higher olefins to high molecular weights with narrow PDIs. (C) 2009 Elsevier B.V. All rights reserved.
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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.