Faculty Advisor: Vlad Iluc, Department of Chemistry and Biochemistry

Replacing Ruthenium With Iron for Sustainable Olefin Metathesis (Summer 2024)

Catalysts play a vital role in industrial and biological processes in relation to organic synthesis. As of 2012, an estimated 90% of commercial chemicals are produced via catalytic reactions. Transition metal carbene complexes are especially useful as some have the ability to catalyze olefin metathesis, a broad term that encompasses ring-opening reactions, ring-closing reactions, cross metathesis, enyne metathesis, and polymerization reactions. This process is widely used industrially and academically to create specialty chemicals and create polymers. Two notable classes of transition metal carbene complexes used for this purpose are Grubbs and Schrock catalysts, which contain ruthenium and molybdenum respectively. Although these complexes work well in catalyzing these types of reactions, they require a vast amount of energy to produce and are not environmentally benign. Mining ruthenium and molybdenum takes a tremendous amount of energy. Ruthenium is a byproduct of extracting platinum, making up only 0.3-0.7 grams per ton of ore mined, while based on estimates for Rhodium, a PGM which has a very similar abundance to Ruthenium, mining one ton of Rhodium requires 235,447 mmBtu in the form of electricity, diesel, coal, and natural gas. Molybdenum mining is less energy demanding but still costly, requiring between 29.1 and 188.6 GJ (29.1-178.8 mmBtu) per ton.

The Iluc lab focuses on synthesizing metal catalysts with earth-abundant elements for sustainable synthesis. The project that I am working on specifically focuses on the synthesis of iron carbenes. Being ruthenium’s group 8 congener, iron has somewhat similar properties to ruthenium while holding the immediate benefits of being much easier to mine, cheaper, and less toxic. From an energy standpoint, to produce a ton of iron, only 94,400 Btu (0.0944mmBtu) is required; this is 2,494,142 times more efficient than mining ruthenium and 1,894 times more efficient than mining molybdenum. An iron carbene has  previously been synthesized in the Iluc lab using phosphine ligand PCP, but being a pincer complex, the carbene will only be able to perform the [2+2] cycloaddition step of the metathesis mechanism and  furthermore, after the cycloaddition, generate a new carbene. The PCP iron carbene was used as a model and proved that iron can be a suitable catalyst for olefin metathesis. My research is centered on  creating non-pincer iron carbenes with chelated phosphine ligands present in other known carbenes. The ideal outcome of this research is a metathesis active iron carbene; however, any progress in this  direction is significant.