Ithaca College

Professor Robert Flowers will present 
Unraveling the Mechanism of Electron Transfer from Samarium(II)-Water Complexes

Tuesday, September 24th 12:10 pm in CNS 333
Pizza and Beverages Provided

Students are also invited to meet informally with the speaker at 4pm in the CNS 3rd floor Atrium.

Rare Earth elements are ubiquitous in the lithosphere and have become important components in a range of applications including electronics, alternative energy, defense systems, and organic synthesis.  Rare earth elements are most stable in the +3 oxidation state. Among the rare earth elements used in synthesis, samarium is important because it has an accessible +2 oxidation state making it a strong reductant.  The most common form of Sm(II) used in synthesis is samarium diiodide (SmI2). The addition of water to samarium diiodide (SmI2) has been demonstrated to enable the reduction of organic substrates traditionally thought to be outside of the reducing power of divalent samarium.1 We recently reported experimental evidence consistent with proton coupled electron transfer (PCET) from SmI2-water in the reduction of arenes and carbonyls.2-5  The key feature of the system is strong coordination of water to SmI2 that induces an O-H bond weakening in the bound proton donor (alcohol or water) enabling formal hydrogen atom transfer to substrate through PCET.  In this seminar, studies designed to examine several questions will be introduced including:  1) What is the role of halides6 and other ligands on substrate reduction by Sm(II)-proton donor complexes?  2) What is the relationship between the competing affinity of solvent and proton donors for Sm(II) and can this be used to design stable and selective reductants?  3) What is the limit of substrates that can be reduced by Sm(II)-proton donor complexes?  These studies demonstrate an unusual, but predictable reactivity for Sm(II)-proton donor complexes with a wide range of substrates and provide insight into the development of new reactions.   

Individuals with disabilities requiring accommodations should contact Paula Larsen at plarsen@ithaca.edu or (607) 274-3238. We ask that requests for accommodations be made as soon as possible.