Iron Catalyzed Ring-Opening Metathesis Polymerization (ROMP)

The Need

Mo- and Ru-carbene catalysts are the most common choice for the olefin metathesis reaction but they have
economical and toxicological drawbacks. Although it has been anticipated that an iron-based catalyst would be an
economical and biocompatible substitute of the Ru-catalysts, there is no report of a well-defined iron-based olefin
metathesis catalyst. Being the most abundant and biocompatible transition metal, a catalyst based on iron would
be ideal for the olefin metathesis reaction. However, this is challenging2, due to the tendency of iron alkylidene
complexes, which are envisioned as intermediates in this reaction, to catalyze alkene cyclopropanation.

The Solution

Prof. David Milstein and his team developed a novel iron-catalyzed ROMP of olefins which leads to several new
catalytic reactions.

Technology Essence

The team synthesized new iron complexes and their derivatives using new bulky pyridine-phosphine (PN) ligands.
The catalytic activity of the paramagnetic complexes was examined, including ROMP of norbornene and its
derivatives. The initiation mechanism of the different catalysts and the effect of the PN ligand structure were
studied, including screening of several FeCl2(PN) complexes, discovering that fine tuning of steric and electronic
factors of the ligand is essential for the catalytic activity.

Applications

New polymeric materials.

New engineering materials.

A polynorbornene product using iron-based catalyst.

Advantages

Non-toxic metal solution.
Economical and biocompatible substitute of the Ru-catalysts.
Forms high stereoregular and molecular weight (>107 g/mol) polynorbornene.

Development Status

Prof. Milstein and his team discovered iron-catalyzed ROMP of norbornene and its derivatives utilizing
dearomatization of pyridine-based ligands. They showed, for the first time, that by proper ligand design, ironcomplexes can be efficient, economical and biocompatible catalysts for olefin metathesis reactions. Moreover, the
iron-catalyst enables production of isotactic trans-polynorbornene that has not been accessible using other
catalysts. In addition, a record high molecular weight polymer was obtained. The team went on to propose a
mechanism for the ROMP on norbornene catalyzed based on the experimental observations.

Market Opportunity

ROMP is one of the largest scale applications of the olefin metathesis reaction in the chemical industry. The
development of the iron catalyzed ROMP will accelerate further development of iron metathesis catalysts. ROMP
with well-defined organometallic catalysts is a versatile method for the preparation of well-defined polyolefines.
Therefore, it could be implemented in a range of industrial processes for the synthesis of polymers, and bulk and
fine chemicals3.

References

Suriboot J, Bazzi HS, Bergbreiter DE. Supported Catalysts Useful in Ring-Closing Metathesis, Cross
Metathesis, and Ring-Opening Metathesis Polymerization. Polymers. 2016; 8(4):140. [1]
Bielawski, C. W., Grubbs, R. H. Living ring-opening metathesis polymerization. Progress in Polymer
Science. (2007); 32(1), 1-29. [2]‏
Grubbs R.G, Wenzel A.G, O’Leary D.J, Khosravi E., Eds. 2015, Handbook of Metathesis
(Wiley-VCH, Weinheim, Germany, ed. 2). [3]