Abstract
The synthesis and characterization of two neutrally charged Ni(II) ethylene polymerization catalysts, [2-tert-butyl-6-((2,6-(3,5-dimethylphenyl) phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CH 3)FI-Ni) and [2-tert-butyl-6-((2,6-(3,5-bis(trifluoromethyl)phenyl) phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CF 3)FI-Ni) are reported. In the presence of a Ni(COD) 2 cocatalyst, these catalysts produce markedly different polyethylenes: densely branched oligomers with M w = 1.4 × 10 3 g mol -1 for (CH 3)FI-Ni vs lightly branched polyethylenes with M w = 92 × 10 3 g mol -1 for (CF 3)FI-Ni and with ∼6.5× the polymerization activity and with much greater performance thermal stability. HOESY 2D 19F, 1H NMR spectra of a model Ni-ethyl compound, [2-tert-butyl-6-((2,6- (3,5-bis(trifluoromethyl)phenyl)phenylimino)methyl)phenolato]nickel(II) ethyl 2,4-lutidine ((CF 3)FI-Ni-Et), indicate non-negligible C β-H β•••F 3C through-space dipolar interactions, and molecular modeling reveals that C β-H β•••F(C) distances can be as small as ∼2.61 Å during the polymerization process. Furthermore, there is no structural or spectroscopic evidence for fluorocarbon inductive effects on the structure, bonding, and reactivity of these complexes, and a catalyst with CF 3 introduced β to the imino N produces only low-M w oligomers with low activity. These results argue that weak (ligand)C-F•••H-C(polymer) interactions can significantly influence the chain transfer characteristics of these catalysts.
| Original language | English |
|---|---|
| Pages (from-to) | 3773-3789 |
| Number of pages | 17 |
| Journal | Organometallics |
| Volume | 31 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - May 14 2012 |
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ASJC Scopus subject areas
- Organic Chemistry
- Physical and Theoretical Chemistry
- Inorganic Chemistry
Cite this
Suppression of β-hydride chain transfer in nickel(II)-catalyzed ethylene polymerization via weak fluorocarbon ligand-product interactions. / Weberski, Michael P.; Chen, Changle; Delferro, Massimiliano; Zuccaccia, Cristiano; MacChioni, Alceo; Marks, Tobin J.
In: Organometallics, Vol. 31, No. 9, 14.05.2012, p. 3773-3789.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Suppression of β-hydride chain transfer in nickel(II)-catalyzed ethylene polymerization via weak fluorocarbon ligand-product interactions
AU - Weberski, Michael P.
AU - Chen, Changle
AU - Delferro, Massimiliano
AU - Zuccaccia, Cristiano
AU - MacChioni, Alceo
AU - Marks, Tobin J
PY - 2012/5/14
Y1 - 2012/5/14
N2 - The synthesis and characterization of two neutrally charged Ni(II) ethylene polymerization catalysts, [2-tert-butyl-6-((2,6-(3,5-dimethylphenyl) phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CH 3)FI-Ni) and [2-tert-butyl-6-((2,6-(3,5-bis(trifluoromethyl)phenyl) phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CF 3)FI-Ni) are reported. In the presence of a Ni(COD) 2 cocatalyst, these catalysts produce markedly different polyethylenes: densely branched oligomers with M w = 1.4 × 10 3 g mol -1 for (CH 3)FI-Ni vs lightly branched polyethylenes with M w = 92 × 10 3 g mol -1 for (CF 3)FI-Ni and with ∼6.5× the polymerization activity and with much greater performance thermal stability. HOESY 2D 19F, 1H NMR spectra of a model Ni-ethyl compound, [2-tert-butyl-6-((2,6- (3,5-bis(trifluoromethyl)phenyl)phenylimino)methyl)phenolato]nickel(II) ethyl 2,4-lutidine ((CF 3)FI-Ni-Et), indicate non-negligible C β-H β•••F 3C through-space dipolar interactions, and molecular modeling reveals that C β-H β•••F(C) distances can be as small as ∼2.61 Å during the polymerization process. Furthermore, there is no structural or spectroscopic evidence for fluorocarbon inductive effects on the structure, bonding, and reactivity of these complexes, and a catalyst with CF 3 introduced β to the imino N produces only low-M w oligomers with low activity. These results argue that weak (ligand)C-F•••H-C(polymer) interactions can significantly influence the chain transfer characteristics of these catalysts.
AB - The synthesis and characterization of two neutrally charged Ni(II) ethylene polymerization catalysts, [2-tert-butyl-6-((2,6-(3,5-dimethylphenyl) phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CH 3)FI-Ni) and [2-tert-butyl-6-((2,6-(3,5-bis(trifluoromethyl)phenyl) phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CF 3)FI-Ni) are reported. In the presence of a Ni(COD) 2 cocatalyst, these catalysts produce markedly different polyethylenes: densely branched oligomers with M w = 1.4 × 10 3 g mol -1 for (CH 3)FI-Ni vs lightly branched polyethylenes with M w = 92 × 10 3 g mol -1 for (CF 3)FI-Ni and with ∼6.5× the polymerization activity and with much greater performance thermal stability. HOESY 2D 19F, 1H NMR spectra of a model Ni-ethyl compound, [2-tert-butyl-6-((2,6- (3,5-bis(trifluoromethyl)phenyl)phenylimino)methyl)phenolato]nickel(II) ethyl 2,4-lutidine ((CF 3)FI-Ni-Et), indicate non-negligible C β-H β•••F 3C through-space dipolar interactions, and molecular modeling reveals that C β-H β•••F(C) distances can be as small as ∼2.61 Å during the polymerization process. Furthermore, there is no structural or spectroscopic evidence for fluorocarbon inductive effects on the structure, bonding, and reactivity of these complexes, and a catalyst with CF 3 introduced β to the imino N produces only low-M w oligomers with low activity. These results argue that weak (ligand)C-F•••H-C(polymer) interactions can significantly influence the chain transfer characteristics of these catalysts.
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U2 - 10.1021/om3002735
DO - 10.1021/om3002735
M3 - Article
AN - SCOPUS:84861155763
VL - 31
SP - 3773
EP - 3789
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 9
ER -