Redox-active ligand uranium complexes for approaches to multi-electron chemistry

John J Kiernicki, Purdue University

Abstract

While transition metal complexes are known to participate in multi-electron redox chemistry to facilitate important organometallic transformations, actinides, due to their low redox potentials, have a propensity to perform single electron chemistry. Because of its highly reducing nature, the ability to control the electronics of low-valent uranium is highly sought after as this may lead to unprecedented reactivity. Our lab has specifically been interested in mediating multi-electron transformations at uranium by employing redox-active ligands. Redox-active ligands can be used to facilitate multi-electron processes such as oxidative addition and reductive elimination at single metal centers. Using primarily 2,6-((Mes)N=CMe)2C5H3N) ( MesPDIMe) as a redox-active ligand, highly reduced uranium species bearing bulky cyclopentadienyl-based ancillary ligands, CpxU (MesPDIMe)(L) (x = P (1-(7,7-dimethylbenzyl)), * (1,2,3,4,5-pentamethyl); L = THF, HMPA), have been synthesized. These species have the ability to perform one, two, and four electron reduction of a variety of substrates. For examples, uranium mediated pinacol coupling of carbonylated substrates as well as oxidative addition toward two (X2, PhE-EPh, PhE-X) and four electron (Ar-N=N-Ar’, oxygen-atom transfer reagents) organic oxidants have been studied. with both radical and concerted addition pathways operable. Synthesis of a trans-dioxo species, Cp*UO2(MesPDIMe), has allowed for the study of the activation of the robust U=O double bonds—providing key insights into the necessary components for U=O bond scission. The lessons learned from the reductive silylation of this complex redox-active ligand species has allowed for application of these principles to simple UO 22+ systems.

Degree

Ph.D.

Advisors

Bart, Purdue University.

Subject Area

Chemistry|Inorganic chemistry

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