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Covalent bond shortening and distortion induced by pressurization of thorium, uranium, and neptunium tetrakis aryloxides
Covalency involving the 5f orbitals is regularly invoked to explain the reactivity, structure and spectroscopic properties of the actinides, but the ionic versus covalent nature of metal-ligand bonding in actinide complexes remains controversial. The tetrakis 2,6-di- tert -butylphenoxide complexes of Th, U and Np form an isostructural series of crystal structures containing approximately tetrahedral MO 4 cores. We show that up to 3 GPa the Th and U crystal structures show negative linear compressibility as the OMO angles distort. At 3 GPa the angles snap back to their original values, reverting to a tetrahedral geometry with an abrupt shortening of the M-O distances by up to 0.1 Å. The Np complex shows similar but smaller effects, transforming above 2.4 GPa. Electronic structure calculations associate the M-O bond shortening with a change in covalency resulting from increased contributions to the M-O bonding by the metal 6d and 5f orbitals, the combination promoting MO 4 flexibility at little cost in energy.
Synthesis, structure, and reactivity of crystalline molecular complexes of the {[C 5 H 3 (SiMe 3 ) 2 ] 3 Th} 1– anion containing thorium in the formal +2 oxidation state
Structural, spectroscopic, and DFT analysis of the first molecular complexes of Th 2+ indicate they have a 6d 2 electron configuration of the type expected for the transactinide ions Rf 2+ and Db 3+ .
Uranium and thorium complexes of the phosphaethynolate ion
New tris -amidinate actinide (Th, U) complexes containing a rare O-bound terminal phosphaethynolate (OCP⁻) ligand were synthesized and fully characterized. The cyanate (OCN⁻) and thiocyanate (SCN⁻) analogs were prepared for comparison and feature a preferential N-coordination to the actinide metals. The Th(amid) 3 (OCP) complex reacts with Ni(COD) 2 to yield the heterobimetallic adduct (amid) 3 Th(μ-η 1 (O):η 2 (C,P)-OCP)Ni(COD) featuring an unprecedented reduced (OCP⁻) bent fragment bridging the two metals.
Uranium(iii) and thorium(iv) alkyl complexes as potential starting materials
The synthesis and characterization of a rare U(iii) alkyl complex, U[η 4 -Me 2 NC(H)C 6 H 5 ] 3 , using the dimethylbenzylamine (DMBA) ligand has been accomplished. While attempting to prepare the U(iv) compound, reduction to the U(iii) complex occurred. In the analogous Th(iv) system, C-H bond activation of a methyl group of one dimethylamine was observed yielding Th[η 4 -Me 2 NC(H)C 6 H 5 ] 2 [η 5 -(CH 2 )MeNC(H)C 6 H 5 ] 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.
Revisiting the bis(dimethylamido) metallocene complexes of thorium and uranium: improved syntheses, structure, spectroscopy, and redox energetics of (C 5 Me 5 ) 2 An(NMe 2 ) 2 (An = Th, U)
In addition to improved syntheses, the solid-state structures, voltammetric data and UV-visible–NIR spectra of (C 5 Me 5 ) 2 An(NMe 2 ) 2 (An = Th, U) complexes are presented for the first time.
Chemical structure and bonding in a thorium( iii )–aluminum heterobimetallic complex
We describe the syntheses of [Th( iii )]–[Al] and [U( iii )]–[Al] bimetallics that demonstrate An→Al interactions where the actinide behaves as an electron donor.
Structural properties of ultra-small thorium and uranium dioxide nanoparticles embedded in a covalent organic framework
ThO 2 and UO 2 nanoparticles synthesized using a COF-5 template exhibit unpassivated surfaces and provide insight into nanoscale properties of actinides.
Photolysis-driven bond activation by thorium and uranium tetraosmate polyhydride complexes
We report the synthesis of actinide–osmium polyhydrides and demonstrate their ability to promote photo-induced intra- and intermolecular C–H activation.
Bond energy of ThN + : A guided ion beam and quantum chemical investigation of the reactions of thorium cation with N 2 and NO
Kinetic-energy dependent reactions of Th + with N 2 and NO are studied using a guided ion beam tandem mass spectrometer. The formation of ThO + in the reaction of Th + with NO is observed to be exothermic and barrierless with a reaction efficiency at low energies of 0.91 ± 0.18. Formation of ThN + in the reactions of Th + with N 2 and NO is endothermic in both cases. The kinetic-energy dependent cross sections for formation of this product ion were evaluated to determine a 0 K bond dissociation energy (BDE) of D 0 (Th + –N) = 6.51 ± 0.08 eV, the first direct measurement of this BDE. Additionally, the reactions were explored by quantum chemical calculations, including a full Feller-Peterson-Dixon composite approach with correlation contributions up to CCSDTQ for ThN and ThN + , as well as more approximate CCSD(T) calculations where a semiempirical model was used to estimate spin-orbit energy contributions. As a result, the ThN + BDE is found to be larger than those of the transition metal congeners, TiN + along with estimated values for ZrN + and HfN + , believed to be a result of the actinide contraction.
Advanced Burner Reactors with Breed-and-Burn Thorium Blankets for Improved Economics and Resource Utilization
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