Publication
Over the past few decades, low oxidation state f-element molecular complexes, including those of lanthanide, uranium, and thorium, have demonstrated high reactivity towards small molecules such as N2 and CO2 due to their unique chemical properties. However, achieving the multiple electron transfers required for small molecule activation remains a challenge in f-element chemistry, which typically involves one-electron transfer processes. The primary objective of this thesis is to design, synthesize, and characterize molecular complexes containing f-block elements capable of multielectron transfer for small molecule activation, and to understand the fundamental principles governing these processes. To facilitate multielectron transfer, two main strategies are employed. The first strategy involves the use of multinuclear complexes, where metal centers cooperatively transfer electrons. This approach has been successfully applied in our group using three different supporting ligands: -OSi(OtBu)3, -OSiPh3, and -N(SiMe3)2, in combination with diuranium complexes and nitride or oxide linkers, leading to N2 activation and azobenzene cleavage. Chapter 2 explores the synthesis, redox properties, characterization, and reactivity of reduced diuranium complexes supported by 2,6-di-tert-butylphenoxide ligands, with a focus on the effects of various linker atoms (N3-, O2-, S2-) bridging two uranium centers. Although this strategy has been extensively used in uranium chemistry, the synthesis of dithorium complexes with bridging linkers in low-valent oxidation states for multielectron transfer has been less explored due to the challenges associated with obtaining low-valent Th(III) starting materials and synthesizing Th(IV) bridging complexes. Chapter 3 addresses this gap by investigating the synthesis and reactivity of two rare examples of thorium bridging azide/nitride complexes generated through the reduction of thorium azide precursors, a route that has previously failed to produce thorium nitrides. The second strategy employs redox-active ligands, which are particularly advantageous for stabilizing highly reactive low-valent metal centers and facilitating cooperative electron transfer with the metal center. In Chapter 4, we demonstrate the use of commercially available naphthalene (C10H8) as a redox-active ligand. We illustrate its role in terminal versus bridging arene binding modes and its ability to facilitate thorium-ligand cooperative two-electron transfers, acting as Th(II) synthons. Chapters 5 and 6 present the utilization of redox-active tripodal frameworks with arene anchors to stabilize unusual Th(II), Ce(II), and Ce(I) synthons. These frameworks enable the implementation of one- and two-electron redox chemistry at thorium and cerium centers while maintaining the ligand framework, thereby expanding the understanding of thorium and cerium redox behavior. Finally, Chapter 7 explores the stabilization of lanthanides in the +IV oxidation state using the