Catalytic one-electron reduction of uranyl(VI) to Group 1 uranyl(V) complexes via Al(III) coordination.

Markus Zegke,Jason B Love,Gary S Nichol,Polly L Arnold

doi:10.1039/c5cc00867k

Abstract

Reactions between the uranyl(VI) Pacman complex [(UO2)(py)(H2L)] of the Schiff-base polypyrrolic macrocycle L and Tebbe's reagent or DIBAL result in the first selective reductive functionalisation of the uranyl oxo by Al to form [(py)(R2AlOUO)(py)(H2L)] (R = Me or (i)Bu). The clean displacement of the oxo-coordinated Al(III) by Group 1 cations has enabled the development of a one-pot, DIBAL-catalysed reduction of the U(VI) uranyl complexes to a series of new, mono-oxo alkali-metal-functionalised uranyl(V) complexes [(py)3(MOUO)(py)(H2L)] (M = Li, Na, K).

Highlights

The uranyl(VI) dication UO22+ is the most common form of uranium in the environment, and is reduced by minerals and microbes to the less stable uranyl(V) monocation UO2+, the chemistry of which has only recently been investigated in detail.[1,2,3,4]
Due to the increased Lewis basicity of UVO2+ compared to UVIO22+,9 uranyl(V) complexes may be employed to model the behaviour of highly radioactive neptunyl ions NpO22+ which are present in nuclear waste.[10]
We report synthetic routes to the first oxo-aluminated uranyl(V) complexes, transmetalation reactions to the first mono-alkali metal uranyl(V) adducts supported by the Pacman ligand, and a new procedure to alkali-metal functionalised uranyl(V) complexes that is catalytic in the Al(III) reagent

Summary

Introduction

The uranyl(VI) dication UO22+ is the most common form of uranium in the environment, and is reduced by minerals and microbes to the less stable uranyl(V) monocation UO2+, the chemistry of which has only recently been investigated in detail.[1,2,3,4] The [Rn] 5f1-electron configuration of uranyl(V) results in a variety of interesting properties such as cation–cation interactions (CCIs)[5] and single molecule magnetism (SMM),[6] and provides insight into often non-trivial 5f-electron behaviours.[7]. Reactions between the uranyl(VI) Pacman complex [(UO2)(py)(H2L)] of the Schiff-base polypyrrolic macrocycle L and Tebbe’s reagent or DIBAL result in the first selective reductive functionalisation of the uranyl oxo by Al to form [(py)(R2AlOUO)(py)(H2L)] (R = Me or iBu).

Results

Conclusion