Graduate Student Scott Shreiber

"New Advances in Ammonia Synthesis via Dinitrogen Cleavage by Transition Metals"

The need to develop chemical weapons such as nitroglycerine, ammonium nitrate, and TNT by Germany during World War I sparked the discovery of the Haber-Bosch Process for ammonia synthesis. The Haber-Bosch process provides a conservative estimate of over 100 million tons a year of ammonia, which is mainly used to create nitrogen rich fertilizers for crop growing. However, the process uses approximately 2 % of the worlds energy supply, and produces an excessive amount of greenhouse gases (CO2). Thus, new methods towards nitrogen fixation are desired, and transition metal catalyzed methods provide a potentially mild alternative. However, only in 2003 did Schrock report the first example of catalytic ammonia formation using a molybdenum catalyst, and the method was low yielding with less than 8 equivalents of ammonia formed based on catalyst.1 In the years to follow, a few other sporadic examples of catalytic ammonia formation have been reported, but none have led to promising results. Finally, in 2017, Yoshiaki Nishibayashi’s group reported the first example of catalytic ammonia synthesis involving a N2 cleavage mechanism with a molybdenum catalyst.2 Reported in this seminar will be the recent works of Nishibayashi’s group along with a collaborative work by the Miller group with a rhenium complex, all detailing N2 cleavage routes towards the synthesis of ammonia.2-4

References

1) Yandulov, D. V.; Schrock, R. R.; Science 2003, 301, 76.
2) Arashiba, K.; Eizawa, A.; Tanaka, H.; Nakajima, K.; Yoshizawa, K.; Nishibayashi, Y. Bull. Chem. Soc. Jpn. 2017, 90, 1111.
3) Ashida, Y.; Arashiba, K.; Nakajima, K.; Nishibayashi, Y. Nature, 2019, 568, 536.
4) Bruch, Q. J.; Connor, G. P.; Chen, C.; Holland, P. L.; Mayer, J. M.; Hasanayn, F.; Miller, A. J. M. J. Am. Chem. Soc. 2019, 141, 20198.