Experimental and Theoretical Studies on the Aqueous Solvation and Reactivity of SmCl₂ and Comparison with SmBr₂ and...

Water addition to Sm(II) has been shown to increase reactivity for both SmI₂ and SmBr₂. 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 (SmCl₂) and illustrates the importance of the Sm-X interaction and bond distance upon water addition critical for the reactivity of the reagent system. Born-Oppenheimer molecular dynamics simulations identify substantial variations among the reductants created in solution upon water addition to SmI₂, SmBr₂, and SmCl₂ with the latter showing the least halide dissociation. This results in a lower water coordination number for SmCl₂, creating a more powerful reducing system. As previously shown with the other SmX₂-water systems, coordination-induced bond-weakening of the O-H bond of water bound to Sm(II) results in significant bond weakening. In the case of SmCl₂, the bond weakening is estimated to be in the range of 83 to 88.5 kcal/mol.