"It is always important to strive to make industrial syntheses more green, and using iron catalysts is not only much less toxic, but it is also much more cost effective," said Jessica Sonnenberg, a PhD student and lead author of a paper published this week in the Journal of the American Chemical Society.
The research, which was directed by Robert Morris, chair of the Department of Chemistry, involved several steps. Suspecting the existence of nanoparticles, the team first set out to identify the iron catalysts. They then conducted investigations using an electron microscope to confirm that the iron nanoparticles were actually being formed during catalysis. The next step was to ensure that the iron nanoparticles were the active catalytic agents. This was done with polymer and poisoning experiments which showed that only the iron atoms on the surface of a nanoparticle were active.
But a further challenge remained. "Catalysts, even cheap iron ones developed for these types of reaction, still suffer one major downfall," explained Sonnenberg. "They require a one-to-one ratio of very expensive organic ligands -- the molecule that binds to the central metal atom of a chemical compound -- to yield catalytic activity. Our discovery of functional surface nanoparticles opens the door to using much smaller ratios of these expensive compounds relative to the metal centres. This drastically reduces the overall cost of the transformations."
The research team included Neil Coombs at U of T's Centre for Nanostructure Imaging and Imagetek Analytical Imaging Inc., and Paul Dube of the Brockhouse Institute for Materials Research at McMaster University in Hamilton, Ontario. Funding was provided by the Natural Sciences and Engineering Research Council of Canada as a Discovery grant to Morris and as an Alexander Graham Bell Canada Graduate Scholarship and Vanier Scholarship to Sonnenberg.
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Journal Reference:Jessica F. Sonnenberg, Neil Coombs, Paul A. Dube, Robert H. Morris. Iron Nanoparticles Catalyzing the Asymmetric Transfer Hydrogenation of Ketones. Journal of the American Chemical Society, 2012; 120326165122000 DOI: 10.1021/ja211658t