An exploration of the effect on organic radical reactivity catalysed by SmI2 of changing the Sm ligand environment

Abstract

This thesis investigates the effects of varying ligand environments on SmI2-catalysed radical relay reactions using density functional theory (DFT). Two reaction systems are explored: cyclopropyl ketones with alkynes and bicyclo[1.1.0]butyl ketones with alkenes. In this study we found that substituting THF with HMPA ligands in these SmI2-mediated reactions significantly lowers their energy profiles. Mixed ligand SmI2 complexes were also examined to identify the most efficient ligand combination. As these reactions are typically in THF solution with HMPA as an additive, we calculated the ligand exchange reaction energies of stepwise replacement of THF for HMPA, which showed to improve reaction energetics at each step. Additionally, the energetic span model was utilised for determining the turnover frequency of the reactions, as well as the energetic span, and the rate-determining states (the highest energy transition state and the most abundant reaction intermediate). The electron-donating abilities of the ligands were assessed using the Tolman electronic parameter, with comparisons to other ligands (P(t-Bu)3 and PF3). Several methods were utilised for determining the causes of HMPA's influence, including Mulliken spin density analysis on relevant sites in the organic substrate, dihedral angles between the samarium, an iodide ligand, and the substrate, as well as bond distances between samarium and the organic ligands (THF and HMPA). Key findings suggest that HMPA's influence arises from its strong electron-donating abilities. This work provides computational insight into the acceleration observed when HMPA is added to SmI2-catalysed reactions in THF.

Date of Award	1 Aug 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Procter (Supervisor) & Nikolas Kaltsoyannis (Supervisor)