Graduate Student Nick Boekell

"Studies of Coordination-Induced Bond Weakening in Divalent Samarium Complexes"

Samarium diiodide (SmI2) is a powerful single electron reductant used in organic synthesis for reactions such as cross-couplings and radical cyclization reactions.1 Previous work in the Flowers lab has demonstrated that SmI2 can be utilized in conjunction with small protic ligands such as water and alcohols to promote proton-coupled electron transfer (PCET).2,3 Moreover, a reduction in homolytic bond strength of the proton donor ligand upon coordination to Sm(II) leads to PCET from the Sm(II)-proton donor complex to substrates.4–6 The coupling of ligand bond homolysis to a favorable oxidation state change at the metal center is referred to as coordination-induced bond weakening. This phenomenon is a promising strategy to promote homolytic X-H bond cleavage from small feedstock molecules including water, ammonia, and alcohols.7–9 The ease of preparation of SmI2 and its interactions with a diverse range of small protic ligands make Sm(II) systems well suited to the study of the basis and scope of coordination-induced bond weakening chemistry. This seminar will discuss several recent studies elucidating the nature of coordination-induced bond weakening in Sm(II) reagents and utilizing powerful Sm(II) coordination-induced bond weakening systems to achieve challenging reductions under mild conditions.10

(1) Flowers, II, R. A.; Bartulovich, C. O.; Chciuk, T. V. Samarium-Mediated Reductions. In Free Radicals: Fundamentals and Applications in Organic Synthesis; Georg Thieme Verlag KG, 2021
(2) Chciuk, T. V.; Flowers, R. A. J. Am. Chem. Soc. 2015, 137 (35), 11526–11531.
(3) Ramírez-Solís, A.; Bartulovich, C. O.; León-Pimentel, C. I.; Saint-Martin, H.; Boekell, N. G.; Flowers, R. A. Dalt. Trans. 2020, 49 (23), 7897–7902.
(4) Chciuk, T. V.; Anderson, W. R.; Flowers, R. A. J. Am. Chem. Soc. 2018, 140 (45), 15342–15352.
(5) Chciuk, T. V; Anderson, W. R.; Flowers, R. A. J. Am. Chem. Soc. 2016, 138, 8738−8741.
(6) Bartulovich, C. O.; Flowers, R. A. Dalt. Trans. 2019, 48 (43), 16129–16462.
(7) Bezdek, M. J.; Guo, S.; Chirik, P. J. Science 2016, 354 (6313), 730–733.
(8) Brines, L. M.; Coggins, M. K.; Chaau, P.; Poon, Y.; Toledo, S.; Kaminsky, W.; Kirk, M. L.; Kovacs, J. A. J. Am. Chem. Soc. 2015, 137, 2253−2264.
(9) Hoover, J. M.; Ryland, B. L.; Stahl, S. S. J. Am. Chem. Soc. 2013, 135, 2357–2367.
(10) Ramírez-Solís, A.; Boekell, N. G.; León-Pimentel, I.; Saint-Martin, H.; Bartulovich, C. O.; Flowers, R. A. J. Org. Chem 2022, 87 (3), 1689–1697.