Molecule of the Week (11): Organometallic carbon-oxygen bond cleavage
This article focuses on the synthesis of iron catalysts which are less toxic than those used in industry (Ryan J. Trovitch, Emil Lobkovsky, Marco W. Bouwkamp, Paul J. Chirik. Organometallics 2008 27, 6264-6278). Oxidative addition is a common process involved in organometallic chemistry. This process typically constitutes a two electron redox reaction and is more common when late transition metal complexes are involved. This molecule is part of continuing research as chemists strive to replace toxic and expensive precious metal catalysts with more cost effective and benign iron compounds. However, such research also requires a deeper understanding of the elementary steps involved in oxidative addition catalysis.
The Chirik laboratory at Cornell University has reported the synthesis of aryl-substituted bis(imino)pyridine iron dinitrogen compounds that have the capacity of functioning as efficient catalysts for hydrogenation and hydrosilylation of olefins and alkynes. Even more interesting is that some of these iron containing catalysts were able to promote catalytic cycloisomerizations. Fortunately, researchers have found a convenient way to synthesize four coordinate bis(imino)pyridine iron aklyls. One possible focus of future research may include extending this approach to sp2 hybridized alkenyl to allow the synthesis of the desired vinyl compound. One ongoing problem these researchers face is that many of the iron containing catalysts they attempt to synthesize are too unstable to perform organometallic bond cleavage. Overall, this research could provide advantages over those currently used in industry, especially when considering toxicity. I am hopeful that we will eventually reach a point where more reactions can be carried out with non-toxic catalysts.