ATRP/OMRP/CCT Interplay in Styrene Polymerization Mediated by Iron(II) Complexes: A DFT Study of the α-Diimine System

Rinaldo Poli, Michael P. Shaver

Research output: Contribution to journalArticlepeer-review

Abstract

A DFT study of various model systems has addressed the interference of catalytic chain transfer (CCT) as a function of the R2 substituent in the atom-transfer radical polymerization (ATRP) of styrene catalyzed by [FeCl2(R1N[DOUBLE BOND]C(R2)—C(R2)[DOUBLE BOND]NR1)] complexes. All model systems used R1=CH3 in place of the experimental Cy and tBu substituents and 1-phenylethyl in place of the polystyrene (PS) chain. A mechanistic investigation of 1) ATRP activation, 2) radical trapping in organometallic-mediated radical polymerization (OMRP), and 3) pathways to the hydride CCT intermediate was conducted with a simplified system with R2=H. This study suggests that CCT could occur by direct hydrogen-atom transfer without any activation barrier. Further analysis of more realistic models with R2=p-C6H4F or p-C6H4NMe2 suggests that the electronic effect of the aryl para substituents significantly alters the ATRP activation barrier. Conversely, the hydrogen-atom-transfer barrier is essentially unaffected. Thus, the greater ATRP catalytic activity of the p-NMe2 system makes the background CCT process less significant. The DFT study also compares the [FeCl2(R1N[DOUBLE BOND]C(R2)[BOND]C(R2)[DOUBLE BOND]NR1)] systems with a diaminobis(phenolato) derivative for which the CCT process shows even greater accessibility but has less incidence because of faster ATRP chain growth and interplay with a more efficient OMRP trapping. The difference between the two systems is attributed to destabilization of the FeII catalyst by the geometric constraints of the tetradentate diaminobis(phenolato) ligand.
Original languageEnglish
Pages (from-to)17530-17540
JournalChemistry - A European Journal
Volume20
Issue number52
Early online date17 Nov 2014
DOIs
Publication statusPublished - 22 Dec 2014

Keywords

  • chain transfer
  • density functional calculations
  • iron
  • radical polymerization
  • styrene

Fingerprint

Dive into the research topics of 'ATRP/OMRP/CCT Interplay in Styrene Polymerization Mediated by Iron(II) Complexes: A DFT Study of the α-Diimine System'. Together they form a unique fingerprint.

Cite this