Year: 2024
Type: article
Abstract: 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 3 )(NTf 2 ) ([NTf 2 ] − = [N(SO 2 CF 3 ) 2 ] − ) that can act as inhibitors in the semihydrogenation of terminal and internal alkynes catalyzed by the iconic iridium Vaska complex IrCl(CO)(PPh 3 ) 2 . 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.
DOI: 10.1021/jacs.4c15359
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4405727473