Reversible Bimetallic Inhibition to Modulate Selectivity During Catalysis

• Published in: Journal of the American Chemical Society 2024-12
• Main Authors: Serrano-Díez, Emmanuel, Pita-Milleiro, Alejandra, Rangel-García, Jesús, Moreno, Juan J, Roselló-Merino, Marta, Campos, Jesús
• Format: Article
• Language: English
• ISSN: 1520-5126; 1520-5126
• DOI: 10.1021/jacs.4c15359

Bimetallic complexes have demonstrated a great ability to enhance the activity of monometallic systems for bond activation and catalysis. In this work, we explore the opposite approach: using a second metal to passivate the activity of another by reversible bimetallic inhibition. To do so we have synthesized a family of nine electrophilic gold complexes of formula Au(PR )(NTf ) ([NTf ] = [N(SO CF ) ] ) that can act as inhibitors in the semihydrogenation of terminal and internal alkynes catalyzed by the iconic iridium Vaska complex IrCl(CO)(PPh ) . This behavior parallels the well-known passivation effect of lead over palladium in the heterogeneous Lindlard catalyst. Most gold fragments, except for the most hindered, form metal-only Lewis pairs upon combination with iridium, which have been fully characterized and exhibit distinct dative Ir → Au bonds. When applied to alkyne hydrogenation, these bimetallic structures have a clear tendency toward olefin formation, while the monometallic catalyst unselectively leads to overreduction products. Our computational studies not only provide a feasible mechanism for the Ir-only system, but also evince the active role of gold in passivating iridium by reversibly forming heterobimetallic structures that lead to enhanced selectivity.