The role of H2O in the electron transfer-activation of substrates using SmI2: insights from DFT.

The first detailed theoretical study on the synthetically important electron transfer (ET) reductant SmI2-H2O has been conducted in the context of the activation of important alkyliodide, ketone, lactone and ester substrates, processes of importance in cross-coupling. Our studies give major insights into the nature of the reagent and suggest that; (i) H2O has a high affinity for Sm(ii) and displaces iodine from the metal center; (ii) SmI2-H2O has 6-7 molecules of H2O directly bound to the metal center; (iii) binding of H2O to Sm(II) promotes coordination of the substrate to Sm(II) and subsequent ET; (iv) resultant ketyl radicals are stabilized by hydrogen-bonding to H2O. The findings add greatly to the understanding of SmI2-H2O and the role of H2O in ET processes, and will facilitate the design of new processes initiated by reductive ET.