Synthesis and reactivity of actinide phosphorano-stabilized carbene and phosphido complexes

Field of study: Chemistry.Includes vita."Advisor, Justin Walensky" -- Acknowledgements."May 2018."Nuclear power plants have been operated in the United States for over 60 years, generating over 800 terawatt-hours of energy per year. However, there is still no reliable process to recycle the spent nuclear fuel. This dissertation looks at the formation of actinide-ligand multiple bonds, which may give us insights into how to improve the process of separation of actinides from the spent nuclear fuels contaminated with lanthanides. This is because lanthanides cannot participate in multiple bonding and a difference in coordination chemistry between actinides and lanthanides is important in separation methods. This dissertation contains two parts, both of which involve using phosphorus to create new actinide complexes. Chapters 1 and 2 outline the use of phosphorano-stabilized carbene complexes to make short actinide-carbon bonds. In fact, these complexes exhibit the shortest uranium and thorium-carbon bonds reported in the literature. Chapter 3 revolves around investigating the synthesis, characterization, and reactivity of actinide phosphido (monoanionic phosphine) complexes. In this regard, I have synthesized the first trivalent uranium phosphido complex, (C5Me5)2U[P(SiMe3)(2,4,6- Me3C6H2)](THF). The investigation of its reactivity revealed that the complex is capable of 4-electron reduction chemistry. For example, the reaction of (C5Me5)2U[P(SiMe3)(2,4,6-Me3C6H2)](THF) with azidotrimethylsilane, N3SiMe3, produces a U(VI) complex. Three electrons are from the metal center, U(III) to U(VI), and one electron is from reductive coupling of the phosphido ligand. The phosphido chemistry can also be extended to tetravalent uranium and thorium. Chapter 4 outlines the synthesis of thorium phosphido complexes which exhibit an unusual absorption in the visible region which we contributed to a ligand to metal charge transfer. Just by varying the ligand design, we were able to manipulate the HOMO/LUMO gap, which results in an absorption in a different part of the visible region. Appendix A summaries the synthesis of copper(I) complexes with bulky terphenyl ligands. The steric properties of the complex center can be tuned by changing the substituent on the terphenyl. By carefully controlling the steric properties, different coordinating environments around the metal center can be achieved. Finally, Appendix B describes the reactivity of U(IV) phosphido complexes with organic azide and tert-butyl isocyanide.Includes bibliographical references (pages 125-156)

Structure and properties of [(4,6-tBu2C6H2O)2Se]2An(THF)2, An = U, Np, and their reaction with p-benzoquinone.

The synthesis and characterization of U(iv) and Np(iv) selenium bis(phenolate) complexes are reported. The reaction of two equivalents of the U(iv) complex with 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

Coordination Chemistry and QTAIM Analysis of Homoleptic Dithiocarbamate Complexes, M(S2CNiPr2)4, M = Ti, Zr, Hf, Th, U, Np

In a systematic approach to comparing the molecular structure and bonding in homoleptic transition-metal and actinide complexes, a series of dithiocarbamates, M(S2CNiPr2)4 (M = Ti, Zr, Hf, Th, U, Np), have been synthesized. These complexes have been characterized through spectroscopic and X-ray crystallographic analysis, and their bonding has been examined using density functional theory calculations. Computational results indicate that the covalent character associatedSave with the M-S bonds shows the trend of Hf < Zr < Th < Ti < U ≈ Np. © 2018 American Chemical Society

Site-Specific Metal Chelation Facilitates the Unveiling of Hidden Coordination Sites in an Fe II/Fe III -Seamed Pyrogallol[4]arene Nanocapsule

Under suitable conditions, C-alkylpyrogallol­[4]­arenes (PgCs) arrange into spherical metal–organic nanocapsules (MONCs) upon coordination to appropriate metal ions. Herein we present the synthesis and structural characterization of a novel FeII/FeIII-seamed MONC, as well as studies related to its electrochemical and magnetic behaviors. Unlike other MONCs that are assembled through 24 metal ions, this nanocapsule comprises 32 Fe ions, uncovering 8 additional coordination sites situated between the constituent PgC subunits. The FeII ions are likely formed by the reducing ability of DMF used in the synthesis, representing a novel synthetic route toward polynuclear mixed-valence MONCs

Structure of Uranium(V) Methyl and Uranium(IV) Ylide Complexes

Syntheses of rare examples of U(V) methyl and U(IV) ylide complexes are reported. Reaction of the previously reported U(IV) imido complex [(C 5Me 5) 2U(py)(═NMes)] (py = pyridine, and Mes = 2,4,6-Me 3C 6H 2) with CuI forms the U(V) complex [(C 5Me 5) 2U(I)(═NMes)]. Reaction of the iodo complex with MgMe 2 produces the methyl complex [(C 5Me 5) 2U(CH 3)(═NMes)]. The methyl complex was reacted with CH 2PPh 3, surprisingly forming [(C 5Me 5) 2U(CH 2PPh 3)(═NMes)], a U(IV) ylide. This is formed from a disproportionation of a transient U(V) carbene, leading to the U(IV) ylide and a U(VI) bis(imido) complex, [(C 5Me 5) 2U(═NMes) 2]. These complexes were characterized using spectroscopic methods (nuclear magnetic resonance, infrared, and ultraviolet-visible-nean infrared), SQUID magnetometry, and X-ray crystallography, and density functional theory calculations are used to compare the U(V) methyl with the targeted U(V) carbene ligands

Thorium(IV) and Uranium(IV) Phosphaazaallenes

The synthesis of tetravalent thorium and uranium complexes with the phosphaazaallene moiety, [N(tBu)C=P(C6H5)]2&minus;, is described. The reaction of the bis(phosphido) complexes, (C5Me5)2An[P(C6H5)(SiMe3)]2, An = Th, U, with two equivalents of tBuNC produces (C5Me5)2An(CNtBu)[&eta;2-(N,C)-N(tBu)C=P(C6H5)] with concomitant formation of P(SiMe3)2(C6H5) via silyl migration. These complexes are characterized by NMR and IR spectroscopy, as well as structurally determined using X-ray crystallography

Formation of thorium and uranium - phosphorano - stabilized carbene

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Phosphorano-Stabilized Carbene Complexes with Short Thorium(IV)– and Uranium(IV)–Carbon Bonds

While no alkylidene complexes of the f elements are known, the use of phosphorano-stabilized carbene complexes to produce short actinide–carbon bonds has been previously demonstrated. Complexes of the form, (C₅Me₅)₂­An­(X)­(CHPPh₃), with short thorium­(IV)– and uranium­(IV)–carbon­(carbene) bonds have been synthesized from the reaction of (C₅Me₅)₂­An­(X)­(CH₃) (An = Th, U; X = Cl, Br, or I) with the ylide, CH₂​PPh₃. The resulting uranium complexes feature the shortest uranium­(IV)–carbon bonds reported to date. The molecular and electronic structure of the thorium phosphorano-stabilized carbene complexes is detailed using X-ray crystallography, ¹³C NMR spectroscopy, and density functional theory calculations, and compared to thorium methandiide complexes

Phosphorano-Stabilized Carbene Complexes with Short Thorium(IV)– and Uranium(IV)–Carbon Bonds

While no alkylidene complexes of the f elements are known, the use of phosphorano-stabilized carbene complexes to produce short actinide–carbon bonds has been previously demonstrated. Complexes of the form, (C₅Me₅)₂­An­(X)­(CHPPh₃), with short thorium­(IV)– and uranium­(IV)–carbon­(carbene) bonds have been synthesized from the reaction of (C₅Me₅)₂­An­(X)­(CH₃) (An = Th, U; X = Cl, Br, or I) with the ylide, CH₂​PPh₃. The resulting uranium complexes feature the shortest uranium­(IV)–carbon bonds reported to date. The molecular and electronic structure of the thorium phosphorano-stabilized carbene complexes is detailed using X-ray crystallography, ¹³C NMR spectroscopy, and density functional theory calculations, and compared to thorium methandiide complexes

Phosphorano-Stabilized Carbene Complexes with Short Thorium(IV)– and Uranium(IV)–Carbon Bonds

While no alkylidene complexes of the f elements are known, the use of phosphorano-stabilized carbene complexes to produce short actinide–carbon bonds has been previously demonstrated. Complexes of the form, (C₅Me₅)₂­An­(X)­(CHPPh₃), with short thorium­(IV)– and uranium­(IV)–carbon­(carbene) bonds have been synthesized from the reaction of (C₅Me₅)₂­An­(X)­(CH₃) (An = Th, U; X = Cl, Br, or I) with the ylide, CH₂​PPh₃. The resulting uranium complexes feature the shortest uranium­(IV)–carbon bonds reported to date. The molecular and electronic structure of the thorium phosphorano-stabilized carbene complexes is detailed using X-ray crystallography, ¹³C NMR spectroscopy, and density functional theory calculations, and compared to thorium methandiide complexes