RSI Research Seminar

Join us every other Monday at noon for lunch and a 30-minute research talk, presented by Resnick Sustainability Institute Graduate Fellows and Caltech researchers funded by the Resnick Sustainability Institute. To see the full schedule of speakers, visit the RSI Research Seminar web page. Seminars are currently in-person only. For more information, please reach out to ramonae@caltech.edu

Development of Fe-Based N₂ Fixation Catalysts for Selective Hydrazine Formation: A Combined Computational and Experimental Approach

Catalytic nitrogen reduction reaction (N₂RR) is an important chemical transformation in both biology and industry, enabling the conversion of inert atmospheric N₂ into valuable nitrogen-containing compounds such as ammonia (NH₃) and hydrazine (N₂H₄). In the Peters group, we have shown that iron complexes supported by tris(phosphino)borane ligands can serve as well-defined platforms for catalytic N₂ fixation, with product selectivity governed by the choice of proton (H⁺) and electron (e⁻) sources.

In this talk, I will present a molecular catalyst design strategy that enables selective reduction of N₂ to hydrazine under protic conditions. Incorporation of proton-responsive dimethylamino (NMe₂) or cationic trimethylammonium (NMe₃⁺) groups into the tris(phosphino)borane ligand framework yields Fe-precatalysts that operate efficiently in methanol. Newly prepared iron catalysts achieved N₂ fixation yields of up to 73%, with hydrazine selectivity over ammonia (>20:1). Computational analyses reveal that these electrostatic ligand modifications significantly lower the reduction potential of Fe–hydrazido intermediates, which is proposed as the key selectivity determining step. This work demonstrates how mechanistically guided ligand design can control product distribution in N₂RR, offering insights into catalyst development for sustainable nitrogen conversion under mild, protic conditions.