Ammonia Solvation vs Aqueous Solvation of Samarium Diiodide. A Theoretical and Experimental Approach to Understanding Bond Activation Upon Coordination to Sm(II).

Coordination-induced desolvation or ligand displacement by cosolvents and additives is a key feature responsible for the reactivity of Sm(II)-based reagent systems. High-affinity proton donor cosolvents such as water and glycols also demonstrate coordination-induced bond weakening of the O-H bond, facilitating reduction of a broad range of substrates. In the present work, the coordination of ammonia to SmI was examined using Born-Oppenheimer molecular dynamics simulations and mechanistic studies, and the SmI-ammonia system is compared to the SmI-water system.

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

Proton donors are important components of many reactions mediated by samarium diiodide (SmI). The addition of water to SmI 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 but often have reduced reactivity.

Experimental and Theoretical Studies on the Aqueous Solvation and Reactivity of SmCl and Comparison with SmBr and SmI.

Water addition to Sm(II) has been shown to increase reactivity for both SmI and SmBr. Previous work in our groups has demonstrated that this increase in reactivity can be attributed to coordination induced bond weakening enabling substrate reduction through proton-coupled electron transfer. The present work examines the interaction of water with samarium dichloride (SmCl) and illustrates the importance of the Sm-X interaction and bond distance upon water addition critical for the reactivity of the reagent system.