Reductive metalation of the uranyl oxo-groups with main Group-, d- and f-block metals

This thesis describes the reductive functionalisation of the uranyl(VI) dication by metalation of the uranyl oxo-groups (O=UVI=O), using reductants from Group I, Group II, Group IV, Group XII and Group XIII as well as from the lanthanide and actinide series of the periodic table. Chapter 1 introduces uranium and nuclear waste, and gives an introduction into uranium(V) chemistry. It further compares the chemistry of uranyl(V) to neptunyl(V), with a specific focus on solid state interactions. The chemistry of the Pacman calixpyrroles is briefly introduced. These macrocyclic ligands form the basis for the synthesis of uranyl Pacman, which represents the major uranyl complex investigated in this thesis. Chapter 2 describes the reductive and catalytic uranyl oxo-group metalation using Group XIII and Group I reagents. It presents the reductive uranyl alumination using di-(iso-butyl)-aluminium hydride and Tebbe’s reagent to form the first Al(III)- uranyl(V) oxo complexes (AlIII-O-UV=O). The chapter shows how the transmetalation of these aluminated uranyl(V) complexes with alkali metal hydrides and alkyls leads to the formation of mono-metalated alkali metal uranyl(V) complexes (MI-O-UV=O). The combination of these two reactions is developed into a catalytic synthesis of the latter. The use of elemental alkali metals is described as another pathway of accessing alkali metal uranyl(V) complexes, carried out in collaboration with Dr. Rianne M. Lord. Chapter 3 describes the synthesis of the first Group IV uranyl(V) complexes, using low-valent titanium and zirconium starting materials. The chapter includes magnetic measurements on the first Ti(III)-uranyl(V) complex and a comparison of computational results regarding a selection of uranyl(V) complexes from this thesis. The magnetic measurements were carried out by Dr. Alessandro Prescimone, University of Edinburgh, and analysed by Dr. Nicola Magnani, Institute for Transuranium Elements, Karlsruhe, Germany. Theoretical calculations were carried out by Xiaobin Zhang and Prof. Dr. Georg Schreckenbach, University of Manitoba, Canada. The chapter further describes the reductive metalation of uranyl using elemental Mg, Ca and Zn and their respective metal halides. Chapter 4 describes the uranyl functionalisation using f-elements and their complexes. It describes the attempted mono-metalation using lanthanides and the formation of a Sm(III)-bis(uranyl(V)) complex. It further describes the uranyl reduction using actinides and the synthesis of the first U(IV)-uranyl(V) complex. The chapter further describes the first Np(IV)-uranyl(V) complex and the attempted synthesis of a Pu(IV)-uranyl(V) complex. These syntheses were performed in collaboration with Michał S. Dutkiewicz at the Institute for Transuranium Elements (ITU) in Karlsruhe, Germany. This work was carried out with the help of Dr. Christos Apostolidis and Dr. Olaf Walter and supervised by Prof. Dr Roberto Caciuffo. Chapter 5 describes the reductive uranyl functionalisation in a redox-active dipyrromethene ligand, collaboratively carried out with James R. Pankhurst and Lucy N. Platts. The synthetic work and analyses were performed jointly with Lucy N. Platts (master student under the supervision of the author); UV-vis spectra and cyclic voltammograms were recorded by James R. Pankhurst and Lucy N. Platts. The chapter presents the synthesis of a new uranyl(VI) complex and its two-electron reduction to uranium(IV) using a titanium(III) reductant. Additionally the chapter describes the reductive uranyl silylation in a dipyrromethane complex of which the ligand was designed by Dr. Daniel Betz. Section 6 describes the synthetic procedures. Section 7 gives references to the work of others. Section 8 shows the publication related to this thesis. Section 9 is a table of the complexes described in this thesis

Rhodium(III) dihalido complexes: The effect of ligand substitution and halido coordination on increasing cancer cell potency

This work presents the synthesis of eight new rhodium(III) dihalido complexes, [RhX2(L)(LH)] (where X = Cl or I), which incorporate two bidentate N-(3-halidophenyl)picolinamide ligands. The ligands have different binding modes in the complexes, whereby one is neutral and bound via N,N (LH) coordination, while the other is anionic and bound via N,O (L) coordination. The solid state and solution studies confirm multiple isomers are present when X = Cl; however, after a halide exchange with potassium iodide (X = I) the complexes exist exclusively as single stable trans isomers. NMR studies reveal the Rh(III) trans diiodido complexes remain stable in aqueous solution with no ligand exchange reported over 96 h. Chemosensitivity data against a range of cancer cell lines show two cytotoxic complexes, where L = N-(3-bromophenyl)picolinamide ligand. The results have been compared to the analogous Ru(III) complexes and overall highlight the Rh(III) trans diiodido complex to be ∼78× more cytotoxic than the analogous Rh(III) dichlorido complex, unlike the Ru(III) complexes which are equitoxic against all cell lines. Additionally, the Rh(III) trans diiodido complex is more selective toward cancerous cells, with selectivity index (SI) values >25-fold higher than cisplatin against colorectal carcinoma

Ammonium Pertechnetate in Mixtures of Trifluoromethanesulfonic Acid and Trifluoromethanesulfonic Anhydride

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH4)2[TcO(OTf)5]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO3(OTf)], and intermediate TcVI species. 99Tc nuclear magnetic resonance (NMR) has been used to study the TcVII compound and electron paramagnetic resonance (EPR), 99Tc NMR and X-ray absorption near-edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH4)2[TcO(OTf)5] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH4)4[{TcO(TcO4)4}4] ⋅10 H2O. Single-crystal X-ray crystallography was used to determine the solid-state structures. Additionally, UV/Vis absorption and IR spectra as well as quantum chemical calculations confirm the identity of the species

Differential uranyl(v) oxo-group bonding between the uranium and metal cations from groups 1, 2, 4, and 12; a high energy resolution X-ray absorption, computational, and synthetic study

The uranyl(VI) ‘Pacman’ complex [(UO₂)(py)(H₂L)] A (L = polypyrrolic Schiff-base macrocycle) is reduced by Cp₂Ti(η²-Me₃SiC[triple bond, length as m-dash]CSiMe₃) and [Cp₂TiCl]₂ to oxo-titanated uranyl(V) complexes [(py)(Cp₂$Ti^{III}$OUO)(py)(H₂L)] 1 and [(ClCp₂$Ti^{IV}$OUO)(py)(H₂L)] 2. Combination of $Zr^{II}$ and $Zr^{IV}$ synthons with A yields the first $Zr^{IV}$–uranyl(V) complex, [(ClCp₂ZrOUO)(py)(H₂L)] 3. Similarly, combinations of $Ae^{0}$ and $Ae^{II}$ synthons (Ae = alkaline earth) afford the mono-oxo metalated uranyl(V) complexes [(py)₂(ClMgOUO)(py)(H₂L)] 4, [(py)₂(thf)₂(ICaOUO)(py) (H₂L)] 5; the zinc complexes [(py)₂(XZnOUO)(py)(H₂L)] (X = Cl 6, I 7) are formed in a similar manner. In contrast, the direct reactions of Rb or Cs metal with A generate the first mono-rubidiated and mono-caesiated uranyl(V) complexes; monomeric [(py)₃(RbOUO)(py)(H₂L)] 8 and hexameric [(MOUO)(py)(H₂L)]₆ (M = Rb 8b or Cs 9). In these uranyl(V) complexes, the pyrrole N–H atoms show strengthened hydrogen-bonding interactions with the endo-oxos, classified computationally as moderate-strength hydrogen bonds. Computational DFT MO (density functional theory molecular orbital) and EDA (energy decomposition analysis), uranium M₄ edge HR-XANES (High Energy Resolution X-ray Absorption Near Edge Structure) and 3d4f RIXS (Resonant Inelastic X-ray Scattering) have been used (the latter two for the first time for uranyl(V) in 7 (ZnI)) to compare the covalent character in the $U^{V}$–O and O–M bonds and show the 5f orbitals in uranyl(VI) complex A are unexpectedly more delocalised than in the uranyl(V) 7 (ZnI) complex. The $O_{exo}$–Zn bonds have a larger covalent contribution compared to the Mg–$O_{exo}$/Ca–$O_{exo}$ bonds, and more covalency is found in the U–$O_{exo}$ bond in 7 (ZnI), in agreement with the calculations

Ammonium Pertechnetate in Mixtures of Trifluoromethanesulfonic Acid and Trifluoromethanesulfonic Anhydride

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH$_{4}$)$_{2}$ [TcO(OTf) $_{5}$]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO$_{3}$(OTf)], and intermediate Tc$^{VI}$ species. $^{99}$Tc nuclear magnetic resonance (NMR) has been used to study the Tc$^{VII}$ compound and electron paramagnetic resonance (EPR), $^{99}$Tc NMR and X-ray absorption near-edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH$_{4}$)2[TcO(OTf)5] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH$_{4}$)$_{4}$ [{TcO(TcO$_{4}$)$_{4}$}$_{4}$] ⋅10 H$_{2}$O. Single-crystal X-ray crystallography was used to determine the solid-state structures. Additionally, UV/Vis absorption and IR spectra as well as quantum chemical calculations confirm the identity of the species

Pseudo electron-deficient organometallics: limited reactivity towards electron-donating ligands

YesHalf-sandwich metal complexes are of considerable interest in medicine, material, and nanomaterial chemistry. The design of libraries of such complexes with particular reactivity and properties is therefore a major quest. Here, we report the unique and peculiar reactivity of eight apparently 16-electron half-sandwich metal (ruthenium, osmium, rhodium, and iridium) complexes based on benzene-1,2-dithiolato and 3,6-dichlorobenzene-1,2-dithiolato chelating ligands. These electron-deficient complexes do not react with electron-donor pyridine derivatives, even with the strong σ-donor 4-dimethylaminopyridine (DMAP) ligand. The Ru, Rh, and Ir complexes accept electrons from the triphenylphosphine ligand (σ-donor, π-acceptor), whilst the Os complexes were found to be the first examples of non-electron-acceptor electron-deficient metal complexes. We rationalized these unique properties by a combination of experimental techniques and DFT/TDFT calculations. The synthetic versatility offered by this family of complexes, the low reactivity at the metal center, and the facile functionalization of the non-innocent benzene ligands is expected to allow the synthesis of libraries of pseudo electron-deficient half-sandwich complexes with unusual properties for a large range of applications

Fast, facile and solvent‐free dry melt synthesis of oxovanadium(IV) complexes: Simple design with high potency towards cancerous cells

YesA range of oxobis(phenyl‐1,3‐butanedione) vanadium(IV) complexes have been successfully synthesized from cheap starting materials and a simple and solvent‐free one‐pot dry‐melt reaction. This direct, straightforward, fast and alternative approach to inorganic synthesis has the potential for a wide range of applications. Analytical studies confirm their successful synthesis, purity and solid‐state coordination, and we report the complexes’ uses as potential drug candidates for the treatment of cancer. After a 24‐hour incubation of A549 lung carcinoma cells with the compounds, they reveal cytotoxicity values 11‐fold greater than cisplatin, and remain non‐toxic towards normal cell types. Additionally, the complexes are stable over a range of physiological pH values and show the potential for interactions with BSA.University of Bradford. Grant Number: Internal Research Development Fun