Chemistry Final Defense – Vinny Groner

About the event

Speaker: Vincent (Vinny) Groner

Group: Dr. Jim Boncella

Title: The Stabilization of Low-Valent Uranium Complexes Featuring Bulky Terphenyl Amido Ligands

Abstract:

The trialkyl terphenyl amide ligand system [R3TerNH]– ([R3TerNH]– = 2,6-(2,4,6-R3C6H2)2C6H3NH–; R = Me, Et, iPr) has proven to be a powerful, tunable scaffold to stabilize U(II) and U(III) complexes, and the research described in this work highlights the impact of this system in studying low-valent uranium species. The steric effects of the substituted terphenyl amide ligand system were investigated to determine the required steric bulk to isolate a neutral U(II) complex. The triisopropyl- (previously reported) and triethyl-substituted ligand were able to stabilize a neutral U(II) complexes (R3TerNH)2U (R = Et, iPr); however, the trimethyl-substituted system yielded a bimetallic “triple-decker” sandwich complex with a doubly reduced terphenyl arenide ligand bridging two U(III) metal centers. The reduction chemistry of the neutral U(II) species  was explored through the oxidative addition of diphenyl dichalcogenides (PhEEPh; E = S, Se, Te) to generate U(IV) bis-(terphenyl amido) bis-(phenyl chalcogenolate) complexes where changes in coordination geometry and complex stability were observed. This library of uranium chalcogenolate species also allows for investigation into the metal-ligand covalency down the chalcogen series. The versatility of the terphenyl amide ligand was further explored in the mixed ligand system Cp*(R3TerNH)UI (R = Me, Et, iPr) where it was determined these species feature a highly functionalizable iodide position. This group can be substituted for [BH4]–, –Me, –Bu, –Bz, –SPh, a bipyridyl organic radical to give rare examples of U(III)–ligand interactions.