1402835-20-4Relevant academic research and scientific papers
Ligand steric and fluoroalkyl substituent effects on enchainment cooperativity and stability in bimetallic nickel(II) polymerization catalysts
Weberski Jr., Michael P.,Chen, Changle,Delferro, Massimiliano,Marks, Tobin J.
, p. 10715 - 10732,18 (2012)
The synthesis and characterization of two neutrally charged bimetallic NiII ethylene polymerization catalysts, {2,7-di-[2,6-(3,5-di- methylphenylimino)methyl]1,8-naphthalenediolato}-bis-NiII(methyl) (trimethylphosphine) [(CH3)FI2-Ni2] and {2,7-di-[2,6-(3,5-di-trifluoromethyl-phenylimino)methyl]-1,8-naphthalenediolato} -bis-NiII(methyl)(trimethyl-phosphine) [(CF3)FI 2-Ni2)], are reported. The diffraction-derived molecular structure of (CF3)FI2-Ni2 reveals a Ni...Ni distance of 5.8024(5) A. In the presence of ethylene and Ni(COD)2 or B(C6F5)3 co-catalysts, these complexes along with their monometallic analogues [2-tert-butyl-6-((2,6- (3,5-dimethylphenyl)phenylimino)methyl)-phenolate]-NiII- methyl(trimethylphosphine) [(CH3)FI-Ni] and [2-tert-butyl-6-((2,6-(3, 5-ditrifluoromethyl-phenyl)phenylimino)methyl)phenolato]-NiII-methyl- (trimethylphosphine) [(CF3)FI-Ni], produce polyethylenes ranging from highly branched Mw=1400 oligomers (91 methyl branches per 1000 C) to low branch density Mw=92 000 polyethylenes (7 methyl branches per 1000 C). In the bimetallic catalysts, Ni...Ni cooperative effects are evidenced by increased product polyethylene branching in ethylene homopolymerizations (～3× for (CF3)FI2-Ni 2 vs. monometallic (CF3)FI-Ni), as well as by enhanced norbornene co-monomer incorporation selectivity, with bimetallic (CH 3)FI2-Ni2 and (CF3)FI 2-Ni2 enchaining approximately three- and six-times more norbornene, respectively, than monometallic (CH3)FI-Ni and (CF 3)FI-Ni. Additionally, (CH3)FI2-Ni2 and (CF3)FI2-Ni2 exhibit significantly enhanced thermal stability versus the less sterically encumbered dinickel catalyst {2,7-di-[(2,6-diisopropylphenyl)imino]-1,8-naphthalenediolato}-bis-Ni II(methyl)(trimethylphosphine). The pathway for bimetallic catalyst thermal deactivation is shown to involve an unexpected polymerization-active intermediate, {2,7-di-[2,6-(3,5-di-trifluoromethyl-phenylimino)methyl]-1- hydroxy,8-naphthalenediolato-NiII(methyl)-(trimethylphosphine). Ni-ce cats: Two neutrally charged bimetallic phenoxyiminato NiII ethylene polymerization catalysts are reported. Significant Ni...Ni cooperative effects are shown by increased product polyethylene branching in ethylene homopolymerizations and by enhanced norbornene co-monomer incorporation selectivity in ethylene-norbornene copolymerization compared with monometallic controls. Copyright
