U–O_yl Stretching Vibrations as a Quantitative Measure of the Equatorial Bond Covalency in Uranyl Complexes: A Quantum-Chemical Investigation

The molecular structures of a series of uranyl (UO₂²⁺) complexes in which the uranium center is equatorially coordinated by a first-row species are calculated at the density functional theory level and binding energies deduced. The resulting electronic structures are investigated using a variety of density-based analysis techniques in order to quantify the degree of covalency in the equatorial bonds. It is shown that a consideration of the properties of both the one-electron and electron-pair densities is required to understand and rationalize the variation in axial bonding effected by equatorial complexation. Strong correlations are found between density-based measures of the covalency and equatorial binding energies, implying a stabilizing effect due to covalent interaction, and it is proposed that uranyl U–O_yl stretching vibrational frequencies can serve as an experimental probe of equatorial covalency

Dithio- and Diselenophosphinate Thorium(IV) and Uranium(IV) Complexes: Molecular and Electronic Structures, Spectroscopy, and Transmetalation Reactivity

We report a comparison of the molecular and electronic structures of dithio- and diselenophosphinate, (E₂PR₂)^1– (E = S, Se; R = ^<i>i</i>Pr, ^<i>t</i>Bu), with thorium­(IV) and uranium­(IV) complexes. For the thorium dithiophosphinate complexes, reaction of ThCl₄(DME)₂ with 4 equiv of KS₂PR₂ (R = ^<i>i</i>Pr, ^<i>t</i>Bu) produced the homoleptic complexes, Th­(S₂P^<i>i</i>Pr₂)₄ (<b>1S-Th-</b>^{<i><b>i</b></i>}<b>Pr</b>) and Th­(S₂P^<i>t</i>Bu₂)₄ (<b>2S-Th-</b>^{<i><b>t</b></i>}<b>Bu</b>). The diselenophosphinate complexes were synthesized in a similar manner using KSe₂PR₂ to produce Th­(Se₂P^<i>i</i>Pr₂)₄ (<b>1Se-Th-</b>^{<i><b>i</b></i>}<b>Pr</b>) and Th­(Se₂P^<i>t</i>Bu₂)₄ (<b>2Se-Th-</b>^{<i><b>t</b></i>}<b>Bu</b>). U­(S₂P^<i>i</i>Pr₂)₄, <b>1S-U-</b>^{<i><b>i</b></i>}<b>Pr</b>, could be made directly from UCl₄ and 4 equiv of KS₂P^<i>i</i>Pr₂. With (Se₂P^<i>i</i>Pr₂)^1–, using UCl₄ and 3 or 4 equiv of KSe₂P^<i>i</i>Pr₂ yielded the monochloride product U­(Se₂P^<i>i</i>Pr₂)₃Cl (<b>3Se-U</b>^{<i><b>i</b></i><b>Pr</b>}<b>-Cl</b>), but using UI₄(1,4-dioxane)₂ produced the homoleptic U­(Se₂P^<i>i</i>Pr₂)₄ (<b>1Se-U-</b>^{<i><b>i</b></i>}<b>Pr</b>). Similarly, the reaction of UCl₄ with 4 equiv of KS₂P^<i>t</i>Bu₂ yielded U­(S₂P^<i>t</i>Bu₂)₄ (<b>2S-U-</b>^{<i><b>t</b></i>}<b>Bu</b>), whereas the reaction with KSe₂P^<i>t</i>Bu₂ resulted in the formation of U­(Se₂P^<i>t</i>Bu₂)₃Cl (<b>4Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Cl</b>). Using UI₄(1,4-dioxane)₂ and 4 equiv of KSe₂P^<i>t</i>Bu₂ with UCl₄ in acetonitrile yielded U­(Se₂P^<i>t</i>Bu₂)₄ (<b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b>). Transmetalation reactions were investigated with complex <b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b> and various CuX (X = Br, I) salts to yield U­(Se₂P^<i>t</i>Bu₂)₃X (<b>6Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Br</b> and <b>7Se-U</b>^{<b><i>t</i>Bu</b>}<b>-I</b>) and 0.25 equiv of [Cu­(Se₂P^<i>t</i>Bu₂)]₄ (<b>8Se-Cu-</b>^{<i><b>t</b></i>}<b>Bu</b>). Additionally, <b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b> underwent transmetalation reactions with Hg₂F₂ and ZnCl₂ to yield U­(Se₂P^<i>t</i>Bu₂)₃F (<b>6</b>) and U­(Se₂P^<i>t</i>Bu₂)₃Cl (<b>4Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Cl</b>), respectively. The molecular structures were analyzed using ¹H, ¹³C, ³¹P, and ⁷⁷Se NMR and IR spectroscopy and structurally characterized using X-ray crystallography. Using the QTAIM approach, the electronic structure of all homoleptic complexes was probed, showing slightly more covalent bonding character in actinide–selenium bonds over actinide–sulfur bonds

Dithio- and Diselenophosphinate Thorium(IV) and Uranium(IV) Complexes: Molecular and Electronic Structures, Spectroscopy, and Transmetalation Reactivity

We report a comparison of the molecular and electronic structures of dithio- and diselenophosphinate, (E₂PR₂)^1– (E = S, Se; R = ^<i>i</i>Pr, ^<i>t</i>Bu), with thorium­(IV) and uranium­(IV) complexes. For the thorium dithiophosphinate complexes, reaction of ThCl₄(DME)₂ with 4 equiv of KS₂PR₂ (R = ^<i>i</i>Pr, ^<i>t</i>Bu) produced the homoleptic complexes, Th­(S₂P^<i>i</i>Pr₂)₄ (<b>1S-Th-</b>^{<i><b>i</b></i>}<b>Pr</b>) and Th­(S₂P^<i>t</i>Bu₂)₄ (<b>2S-Th-</b>^{<i><b>t</b></i>}<b>Bu</b>). The diselenophosphinate complexes were synthesized in a similar manner using KSe₂PR₂ to produce Th­(Se₂P^<i>i</i>Pr₂)₄ (<b>1Se-Th-</b>^{<i><b>i</b></i>}<b>Pr</b>) and Th­(Se₂P^<i>t</i>Bu₂)₄ (<b>2Se-Th-</b>^{<i><b>t</b></i>}<b>Bu</b>). U­(S₂P^<i>i</i>Pr₂)₄, <b>1S-U-</b>^{<i><b>i</b></i>}<b>Pr</b>, could be made directly from UCl₄ and 4 equiv of KS₂P^<i>i</i>Pr₂. With (Se₂P^<i>i</i>Pr₂)^1–, using UCl₄ and 3 or 4 equiv of KSe₂P^<i>i</i>Pr₂ yielded the monochloride product U­(Se₂P^<i>i</i>Pr₂)₃Cl (<b>3Se-U</b>^{<i><b>i</b></i><b>Pr</b>}<b>-Cl</b>), but using UI₄(1,4-dioxane)₂ produced the homoleptic U­(Se₂P^<i>i</i>Pr₂)₄ (<b>1Se-U-</b>^{<i><b>i</b></i>}<b>Pr</b>). Similarly, the reaction of UCl₄ with 4 equiv of KS₂P^<i>t</i>Bu₂ yielded U­(S₂P^<i>t</i>Bu₂)₄ (<b>2S-U-</b>^{<i><b>t</b></i>}<b>Bu</b>), whereas the reaction with KSe₂P^<i>t</i>Bu₂ resulted in the formation of U­(Se₂P^<i>t</i>Bu₂)₃Cl (<b>4Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Cl</b>). Using UI₄(1,4-dioxane)₂ and 4 equiv of KSe₂P^<i>t</i>Bu₂ with UCl₄ in acetonitrile yielded U­(Se₂P^<i>t</i>Bu₂)₄ (<b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b>). Transmetalation reactions were investigated with complex <b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b> and various CuX (X = Br, I) salts to yield U­(Se₂P^<i>t</i>Bu₂)₃X (<b>6Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Br</b> and <b>7Se-U</b>^{<b><i>t</i>Bu</b>}<b>-I</b>) and 0.25 equiv of [Cu­(Se₂P^<i>t</i>Bu₂)]₄ (<b>8Se-Cu-</b>^{<i><b>t</b></i>}<b>Bu</b>). Additionally, <b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b> underwent transmetalation reactions with Hg₂F₂ and ZnCl₂ to yield U­(Se₂P^<i>t</i>Bu₂)₃F (<b>6</b>) and U­(Se₂P^<i>t</i>Bu₂)₃Cl (<b>4Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Cl</b>), respectively. The molecular structures were analyzed using ¹H, ¹³C, ³¹P, and ⁷⁷Se NMR and IR spectroscopy and structurally characterized using X-ray crystallography. Using the QTAIM approach, the electronic structure of all homoleptic complexes was probed, showing slightly more covalent bonding character in actinide–selenium bonds over actinide–sulfur bonds

Dithio- and Diselenophosphinate Thorium(IV) and Uranium(IV) Complexes: Molecular and Electronic Structures, Spectroscopy, and Transmetalation Reactivity

We report a comparison of the molecular and electronic structures of dithio- and diselenophosphinate, (E₂PR₂)^1– (E = S, Se; R = ^<i>i</i>Pr, ^<i>t</i>Bu), with thorium­(IV) and uranium­(IV) complexes. For the thorium dithiophosphinate complexes, reaction of ThCl₄(DME)₂ with 4 equiv of KS₂PR₂ (R = ^<i>i</i>Pr, ^<i>t</i>Bu) produced the homoleptic complexes, Th­(S₂P^<i>i</i>Pr₂)₄ (<b>1S-Th-</b>^{<i><b>i</b></i>}<b>Pr</b>) and Th­(S₂P^<i>t</i>Bu₂)₄ (<b>2S-Th-</b>^{<i><b>t</b></i>}<b>Bu</b>). The diselenophosphinate complexes were synthesized in a similar manner using KSe₂PR₂ to produce Th­(Se₂P^<i>i</i>Pr₂)₄ (<b>1Se-Th-</b>^{<i><b>i</b></i>}<b>Pr</b>) and Th­(Se₂P^<i>t</i>Bu₂)₄ (<b>2Se-Th-</b>^{<i><b>t</b></i>}<b>Bu</b>). U­(S₂P^<i>i</i>Pr₂)₄, <b>1S-U-</b>^{<i><b>i</b></i>}<b>Pr</b>, could be made directly from UCl₄ and 4 equiv of KS₂P^<i>i</i>Pr₂. With (Se₂P^<i>i</i>Pr₂)^1–, using UCl₄ and 3 or 4 equiv of KSe₂P^<i>i</i>Pr₂ yielded the monochloride product U­(Se₂P^<i>i</i>Pr₂)₃Cl (<b>3Se-U</b>^{<i><b>i</b></i><b>Pr</b>}<b>-Cl</b>), but using UI₄(1,4-dioxane)₂ produced the homoleptic U­(Se₂P^<i>i</i>Pr₂)₄ (<b>1Se-U-</b>^{<i><b>i</b></i>}<b>Pr</b>). Similarly, the reaction of UCl₄ with 4 equiv of KS₂P^<i>t</i>Bu₂ yielded U­(S₂P^<i>t</i>Bu₂)₄ (<b>2S-U-</b>^{<i><b>t</b></i>}<b>Bu</b>), whereas the reaction with KSe₂P^<i>t</i>Bu₂ resulted in the formation of U­(Se₂P^<i>t</i>Bu₂)₃Cl (<b>4Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Cl</b>). Using UI₄(1,4-dioxane)₂ and 4 equiv of KSe₂P^<i>t</i>Bu₂ with UCl₄ in acetonitrile yielded U­(Se₂P^<i>t</i>Bu₂)₄ (<b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b>). Transmetalation reactions were investigated with complex <b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b> and various CuX (X = Br, I) salts to yield U­(Se₂P^<i>t</i>Bu₂)₃X (<b>6Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Br</b> and <b>7Se-U</b>^{<b><i>t</i>Bu</b>}<b>-I</b>) and 0.25 equiv of [Cu­(Se₂P^<i>t</i>Bu₂)]₄ (<b>8Se-Cu-</b>^{<i><b>t</b></i>}<b>Bu</b>). Additionally, <b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b> underwent transmetalation reactions with Hg₂F₂ and ZnCl₂ to yield U­(Se₂P^<i>t</i>Bu₂)₃F (<b>6</b>) and U­(Se₂P^<i>t</i>Bu₂)₃Cl (<b>4Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Cl</b>), respectively. The molecular structures were analyzed using ¹H, ¹³C, ³¹P, and ⁷⁷Se NMR and IR spectroscopy and structurally characterized using X-ray crystallography. Using the QTAIM approach, the electronic structure of all homoleptic complexes was probed, showing slightly more covalent bonding character in actinide–selenium bonds over actinide–sulfur bonds

Dithio- and Diselenophosphinate Thorium(IV) and Uranium(IV) Complexes: Molecular and Electronic Structures, Spectroscopy, and Transmetalation Reactivity

We report a comparison of the molecular and electronic structures of dithio- and diselenophosphinate, (E₂PR₂)^1– (E = S, Se; R = ^<i>i</i>Pr, ^<i>t</i>Bu), with thorium­(IV) and uranium­(IV) complexes. For the thorium dithiophosphinate complexes, reaction of ThCl₄(DME)₂ with 4 equiv of KS₂PR₂ (R = ^<i>i</i>Pr, ^<i>t</i>Bu) produced the homoleptic complexes, Th­(S₂P^<i>i</i>Pr₂)₄ (<b>1S-Th-</b>^{<i><b>i</b></i>}<b>Pr</b>) and Th­(S₂P^<i>t</i>Bu₂)₄ (<b>2S-Th-</b>^{<i><b>t</b></i>}<b>Bu</b>). The diselenophosphinate complexes were synthesized in a similar manner using KSe₂PR₂ to produce Th­(Se₂P^<i>i</i>Pr₂)₄ (<b>1Se-Th-</b>^{<i><b>i</b></i>}<b>Pr</b>) and Th­(Se₂P^<i>t</i>Bu₂)₄ (<b>2Se-Th-</b>^{<i><b>t</b></i>}<b>Bu</b>). U­(S₂P^<i>i</i>Pr₂)₄, <b>1S-U-</b>^{<i><b>i</b></i>}<b>Pr</b>, could be made directly from UCl₄ and 4 equiv of KS₂P^<i>i</i>Pr₂. With (Se₂P^<i>i</i>Pr₂)^1–, using UCl₄ and 3 or 4 equiv of KSe₂P^<i>i</i>Pr₂ yielded the monochloride product U­(Se₂P^<i>i</i>Pr₂)₃Cl (<b>3Se-U</b>^{<i><b>i</b></i><b>Pr</b>}<b>-Cl</b>), but using UI₄(1,4-dioxane)₂ produced the homoleptic U­(Se₂P^<i>i</i>Pr₂)₄ (<b>1Se-U-</b>^{<i><b>i</b></i>}<b>Pr</b>). Similarly, the reaction of UCl₄ with 4 equiv of KS₂P^<i>t</i>Bu₂ yielded U­(S₂P^<i>t</i>Bu₂)₄ (<b>2S-U-</b>^{<i><b>t</b></i>}<b>Bu</b>), whereas the reaction with KSe₂P^<i>t</i>Bu₂ resulted in the formation of U­(Se₂P^<i>t</i>Bu₂)₃Cl (<b>4Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Cl</b>). Using UI₄(1,4-dioxane)₂ and 4 equiv of KSe₂P^<i>t</i>Bu₂ with UCl₄ in acetonitrile yielded U­(Se₂P^<i>t</i>Bu₂)₄ (<b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b>). Transmetalation reactions were investigated with complex <b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b> and various CuX (X = Br, I) salts to yield U­(Se₂P^<i>t</i>Bu₂)₃X (<b>6Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Br</b> and <b>7Se-U</b>^{<b><i>t</i>Bu</b>}<b>-I</b>) and 0.25 equiv of [Cu­(Se₂P^<i>t</i>Bu₂)]₄ (<b>8Se-Cu-</b>^{<i><b>t</b></i>}<b>Bu</b>). Additionally, <b>2Se-U-</b>^{<i><b>t</b></i>}<b>Bu</b> underwent transmetalation reactions with Hg₂F₂ and ZnCl₂ to yield U­(Se₂P^<i>t</i>Bu₂)₃F (<b>6</b>) and U­(Se₂P^<i>t</i>Bu₂)₃Cl (<b>4Se-U</b>^{<b><i>t</i>Bu</b>}<b>-Cl</b>), respectively. The molecular structures were analyzed using ¹H, ¹³C, ³¹P, and ⁷⁷Se NMR and IR spectroscopy and structurally characterized using X-ray crystallography. Using the QTAIM approach, the electronic structure of all homoleptic complexes was probed, showing slightly more covalent bonding character in actinide–selenium bonds over actinide–sulfur bonds

Water Adsorption on AnO₂ {111}, {110}, and {100} Surfaces (An = U and Pu): A Density Functional Theory + <i>U</i> Study

The interactions between water and the actinide oxides UO₂ and PuO₂ are important both fundamentally and when considering the long-term storage of spent nuclear fuel. However, experimental studies in this area are severely limited by the intense radioactivity of plutonium, and hence, we have recently begun to investigate these interactions computationally. In this paper, we report the results of plane-wave density functional theory calculations of the interaction of water with the {111}, {110}, and {100} surfaces of UO₂ and PuO₂, using a Hubbard-corrected potential (PBE + <i>U</i>) approach to account for the strongly correlated 5f electrons. We find a mix of molecular and dissociative water adsorption to be most stable on the {111} surface, whereas the fully dissociative water adsorption is most stable on the {110} and {100} surfaces, leading to a fully hydroxylated monolayer. From these results, we derive water desorption temperatures at various pressures for the different surfaces. These increase in the order {111} < {110} < {100}, and these data are used to propose an alternative interpretation for the two experimentally determined temperature ranges for water desorption from PuO₂