Synthesis and reactivity of low-valent uranium and neptunium complexes

Abstract

Chapter 1 reports the synthesis and characterization of U(IV) and Np(IV) selenium bis(phenolate) complexes. The reaction of the U(IV) complex with half an equivalent of p-benzoquinone results in the formation of a U(V)--U(V) species with a bridging reduced quinone. This represents a rare example of high-valent uranium chemistry as well as a rare example of a neptunium aryloxide complex. In Chapters 2 and 3 the synthesis and characterization of a rare U(III) hydrocarbyl complex, U[[eta]4-Me2NC(H)C6H5]3, and the first structurally characterized transuranic hydrocarbyl complex, Np[[eta]4-Me2NC(H)C6H5]3, complex, has been generated with four equivalents of the K[Me2NC(H)C6H5] ligand. In the analogous Th(IV) reaction, C-H bond activation of a methyl group of one dimethylamine was observed yielding Th[[eta]4-Me2NC(H)C6H5]2[[eta]5-(CH2)MeNC(H)C6H5] with a dianionic DMBA ligand. The utility of these complexes as starting materials has been analyzed using a bulky dithiocarboxylate ligand to yield tetravalent actinide species for U and Th but Np maintains the trivalent oxidation state. Chapter 4 describes the on-going synthesis and reactivity of Np(OAr)3 (Ar = 2,6-di-tert-butylphenoxide) utilizing Np[[eta]4-Me2NC(H)C6H5]3 as a Np(III) starting material. The coordination and oxidation chemistry is explored with [nBu4N]N3, (C6H5CO)2O2 and Ph2S2 resulting in a bridged Np(III)/Np(III) azide complex with an outer sphere nBu4N and Np(IV) species, respectively.