Proton donor effects on the reactivity of SmI 2 . Experimental and theoretical studies on methanol solvation vs . aqueous solvation

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 49; no. 23; pp. 7897 - 7902
• Main Authors: Ramírez-Solís, Alejandro, Bartulovich, Caroline O., León-Pimentel, César Iván, Saint-Martin, Humberto, Boekell, Nicholas G., Flowers, Robert A.
• Format: Journal Article
• Language: English
• Published: 16.06.2020
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/D0DT01221A

Proton donors are important components of many reactions mediated by samarium diiodide (SmI 2 ). The addition of water to SmI 2 creates a reagent system that enables the reduction of challenging substrates through proton-coupled electron-transfer (PCET). Simple alcohols such as methanol are often used successfully in reductions with SmI 2 but often have reduced reactivity. The basis for the change in reactivity of SmI 2 –H 2 O and SmI 2 –MeOH is not apparent given the modest differences between water and methanol. A combination of Born–Oppenheimer molecular dynamics simulations and mechanistic experiments were performed to examine the differences between the reductants formed in situ for the SmI 2 –H 2 O and SmI 2 –MeOH systems. This work demonstrates that reduced coordination of MeOH to Sm( ii ) results in a complex that reduces arenes through a sequential electron proton transfer at low concentrations and that this process is significantly slower than reduction by SmI 2 –H 2 O.