Iron III Half Salen Catalysts for Atom Transfer Radical and Ring-Opening Polymerizations

Eszter Fazekas, Gary S. Nichol, Jennifer A. Garden, Michael P. Shaver

Research output: Contribution to journalArticlepeer-review

Abstract

A series of monometallic pentacoordinate FeIII chloride complexes has been prepared and characterized by high resolution mass spectrometry and elemental analysis. X-ray diffraction analysis showed that the pentacoordinate FeIII complexes bear distorted trigonal bipyramidal geometries. The air- and moisture-stable FeIII complexes were screened as mediators in the reverse atom transfer radical polymerization of styrene and methyl methacrylate. Moderate to excellent control was achieved with dispersities as low as 1.1 for both poly(methyl methacrylate) and polystyrene. Kinetic studies showed living characteristics and end group analysis revealed the presence of olefin terminated polymer chains suggesting catalytic chain transfer as a competing polymerization mechanism. While the catalysts are not the fastest Fe ATRP mediators, they are robust and flexible. Using propylene oxide as an initiator, the complexes were active catalysts for the ring opening polymerization of rac-lactide with moderate control. While the addition of propylene oxide has been reported as an efficient method of converting a metal-halide bond to a metal-alkoxide bond in situ, we show herein that this initiation mechanism can limit polymerization reproducibility and introduce an induction period.
Original languageEnglish
Pages (from-to)16945-16953
JournalACS Omega
Volume3
Issue number12
Early online date10 Dec 2018
DOIs
Publication statusE-pub ahead of print - 10 Dec 2018

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