Lawrence Sita

Redesigning Synthetic Nitrogen Fixation

 The development of new energy-efficient and atom-economical chemical technologies that can be used for the production of high-value industrial chemicals through the ‘chemical fixation’ of inexpensive and abundant small molecule feedstocks (e.g., N₂, CO₂, CO, and S₈) must be made in the near term in order to meet the demands of a global population that is expected to increase by an additional 3 to 4 billion people within only the next 50 years.  In this regard, the century-old Haber-Bosch process, which converts N₂ and H₂ under high temperature and pressure into NH₃ on a staggering volume of 140 million metric tons per year, currently consumes up to 5% of the world’s energy and it generates an equal quantity of CO₂ to provide the required amount of H₂. 

This talk will present recent results obtained in our quest to establish new paradigms and chemical processes that can be used for the transition-metal-mediated conversion of N₂ into higher-value nitrogen-containing products under near ambient conditions.  Specific examples include complete chemical cycles for the conversion of N₂, CO₂ and R₃SiCl into trialkylsilyl isocyanates (R₃SiNCO)^,1,2 and more recently, the chemoselective conversion of N₂, R₃SiCl and “H₂O” into bis(trialkylsilyl)amines, (R₃Si)₂NH.  Future directions for our research with these alternative synthetic nitrogen fixation schemes will also be discussed.

References:

Keane, A. J.; Farrell, W. S.; Yonke, B. L.; Zavalij, P. Y.; Sita, L. R. Angew. Chem. Int. Ed. 2015, 54, 4269.
Duman, L. M.; Farrell, W. S.; Zavalij, P. Y.; Sita, L. R. J. Am. Chem. Soc. 2016, 138, 14856.