Synthesis and Characterization of Three-Coordinate Ni(III)-Imide Complexes

A new family of low-coordinate nickel imides supported by 1,2-bis(di-tert-butylphosphino)ethane was synthesized. Oxidation of nickel(II) complexes led to the formation of both aryl- and alkyl-substituted nickel(III)-imides, and examples of both types have been isolated and fully characterized. The aryl substituent that proved most useful in stabilizing the Ni(III)-imide moiety was the bulky 2,6-dimesitylphenyl. The two Ni(III)-imide compounds showed different variable-temperature magnetic properties but analogous EPR spectra at low temperatures. To account for this discrepancy, a low-spin/high-spin equilibrium was proposed to take place for the alkyl-substituted Ni(III)-imide complex. This proposal was supported by DFT calculations. DFT calculations also indicated that the unpaired electron is mostly localized on the imide nitrogen for the Ni(III) complexes. The results of reactions carried out in the presence of hydrogen donors supported the findings from DFT calculations that the adamantyl substituent was a significantly more reactive hydrogen-atom abstractor. Interestingly, the steric properties of the 2,6-dimesitylphenyl substituent are important not only in protecting the Ni═N core but also in favoring one rotamer of the resulting Ni(III)-imide, by locking the phenyl ring in a perpendicular orientation with respect to the NiPP plane

Outcome during and after anticoagulant therapy in cancer patients with incidentally found pulmonary embolism

Publisher Copyright: Copyright © 2016 ERS.Current guidelines suggest treating cancer patients with incidental pulmonary embolism comparably to patients with symptomatic pulmonary embolism. We used the Registro Informatizado de Enfermedad TromboEmbólica (RIETE) registry to compare the rate of major bleeding and symptomatic pulmonary embolism during the course of anticoagulation and after its discontinuation in cancer patients with incidental pulmonary embolism. As of March 2016, 715 cancer patients with incidental pulmonary embolism had been enrolled in RIETE. During the course of anticoagulant therapy (mean 235 days), the rate of major bleeding was higher than the rate of symptomatic pulmonary embolism (10.1 (95% CI 7.48-13.4) versus 3.17 (95% CI 1.80-5.19) events per 100 patient-years, respectively), and the rate of fatal bleeding was higher than the rate of fatal pulmonary embolism (2.66 (95% CI 1.44-4.52) versus 0.66 (95% CI 0.17-1.81) deaths per 100 patient-years, respectively). After discontinuing anticoagulation (mean follow-up 117 days), the rate of major bleeding was lower than the rate of symptomatic pulmonary embolism (3.00 (95% CI 1.10-6.65) versus 8.37 (95% CI 4.76-13.7) events per 100 patient-years, respectively); however, there were no differences in the rate of fatal events at one death each. The risk/benefit ratio of anticoagulant therapy in cancer patients with incidental pulmonary embolism is uncertain and must be evaluated in further studies.publishersversionPeer reviewe

Remote Density Measurements of Molten Salts via Neutron Radiography

With an increased interest in the use of molten salts in both nuclear and non-nuclear systems, measuring important thermophysical properties of specific salt mixtures becomes critical in understanding salt performance and behavior. One of the more basic and significant thermophysical properties of a given salt system is density as a function of temperature. With this in mind, this work aims to present and layout a novel approach to measuring densities of molten salt systems using neutron radiography. This work was performed on Flight Path 5 at the Los Alamos Neutron Science Center at Los Alamos National Laboratory. In order to benchmark this initial work, three salt mixtures were measured, NaCl, LiCl (58.2 mol%) + KCl (41.8 mol%), and MgCl2 (32 mol%) + KCl (68 mol%). Resulting densities as a function of temperature for each sample from this work were then compared to previous works employing traditional techniques. Results from this work match well with previous literature values for all salt mixtures measured, establishing that neutron radiography is a viable technique to measure density as a function of temperature in molten salt systems. Finally, advantages of using neutron radiography over other methods are discussed and future work in improving this technique is covered

Thorium(IV) and Uranium(IV) Halide Complexes Supported by Bulky β‑Diketiminate Ligands

The coordination behavior of the bulky β-diketiminate ligands <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)­pentane-2,4-diiminate (L^Me) and <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)-2,2–6,6-tetramethylheptane-3,5-diiminate (L^tBu) toward ThX₄(THF)₄ (X = Br, I) and UCl₄ has been investigated. The reaction between K­[L^Me] and ThX₄(THF)₄ (X = Br, I) afforded the mono­(β-diketiminate)­thorium­(IV) halide complexes (L^Me)­ThX₃(THF) (X = Br (<b>7</b>), I (<b>8</b>)). The same reaction carried out with the more sterically demanding K­[L^tBu] gave (L^tBu)­ThBr₃(THF) (<b>9</b>) and (L^tBu)­ThI₃ (<b>11</b>). All attempts to install two β-diketiminate ligands on thorium­(IV) were unsuccessful, giving the mono­(β-diketiminate)­thorium­(IV) halide complex and unreacted K­[L^Me] or K­[L^tBu]. However, complex <b>9</b> was shown to react with smaller anions such as K­[C₅H₄Me] to give the mixed-ligand methylcyclopentadienyl β-diketiminate complex (L^tBu)­Th­(C₅H₄Me)­Br₂ (<b>10</b>). Complexes <b>7</b>–<b>11</b> represent rare examples of thorium complexes featuring only one β-diketiminate ligand, and complexes <b>9</b>–<b>11</b> are the first examples of thorium and halide complexes supported by the L^tBu framework. In a similar manner, both K­[L^Me] and K­[L^tBu] were shown to react with UCl₄ to give the corresponding mono­(β-diketiminate)­uranium­(IV) chloride complexes (L^Me)­UCl₃(THF) (<b>12</b>) and (L^tBu)­UCl₃ (<b>13</b>). Complex <b>13</b> represents the first example of a uranium complex featuring the L^tBu framework. Efforts to prepare the bis­(β-diketiminate)­uranium­(IV) complex (L^Me)₂UCl₂ by reacting 2 equiv of K­[L^Me] with UCl₄ led instead to the interesting cationic diuranium complex [{(L^Me)­(Cl)­U}₂(μ-Cl)₃]­[Cl] (<b>14</b>). Complexes <b>7</b>–<b>14</b> have been characterized by a combination of ¹H and ¹³C­{¹H} NMR spectroscopy, elemental analysis, electrochemistry, and UV–visible–near-IR spectroscopy. Several complexes have also been characterized by X-ray crystallography, and a discussion of their structures is presented. NMR spectroscopy and the X-ray structures demonstrate that the β-diketiminate ligand is symmetrically bound to the actinide metal in the L^Me complexes and is asymmetrically bound to the actinide metal in the L^tBu complexes. In all cases the actinide­(IV) metal centers lie out of the plane of the β-diketiminate ligand NCCCN backbone by ∼1–2 Å. The electronic spectroscopy data on K­[L^Me], (L^Me)­ThI₃(THF) (<b>8</b>), and (L^Me)­UCl₃(THF) (<b>12</b>) suggest relatively weak metal–(β-diketiminate) ligand bonding interactions, although small perturbations in the characteristics of the β-diketiminate π–π* bands with changes in the the metal ion are consistent with some metal–ligand orbital interactions. This new class of mono­(β-diketiminate)­thorium and -uranium halide complexes promises to provide a robust platform for developing new chemistry of the actinides

Thorium(IV) and Uranium(IV) Halide Complexes Supported by Bulky β‑Diketiminate Ligands

The coordination behavior of the bulky β-diketiminate ligands <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)­pentane-2,4-diiminate (L^Me) and <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)-2,2–6,6-tetramethylheptane-3,5-diiminate (L^tBu) toward ThX₄(THF)₄ (X = Br, I) and UCl₄ has been investigated. The reaction between K­[L^Me] and ThX₄(THF)₄ (X = Br, I) afforded the mono­(β-diketiminate)­thorium­(IV) halide complexes (L^Me)­ThX₃(THF) (X = Br (<b>7</b>), I (<b>8</b>)). The same reaction carried out with the more sterically demanding K­[L^tBu] gave (L^tBu)­ThBr₃(THF) (<b>9</b>) and (L^tBu)­ThI₃ (<b>11</b>). All attempts to install two β-diketiminate ligands on thorium­(IV) were unsuccessful, giving the mono­(β-diketiminate)­thorium­(IV) halide complex and unreacted K­[L^Me] or K­[L^tBu]. However, complex <b>9</b> was shown to react with smaller anions such as K­[C₅H₄Me] to give the mixed-ligand methylcyclopentadienyl β-diketiminate complex (L^tBu)­Th­(C₅H₄Me)­Br₂ (<b>10</b>). Complexes <b>7</b>–<b>11</b> represent rare examples of thorium complexes featuring only one β-diketiminate ligand, and complexes <b>9</b>–<b>11</b> are the first examples of thorium and halide complexes supported by the L^tBu framework. In a similar manner, both K­[L^Me] and K­[L^tBu] were shown to react with UCl₄ to give the corresponding mono­(β-diketiminate)­uranium­(IV) chloride complexes (L^Me)­UCl₃(THF) (<b>12</b>) and (L^tBu)­UCl₃ (<b>13</b>). Complex <b>13</b> represents the first example of a uranium complex featuring the L^tBu framework. Efforts to prepare the bis­(β-diketiminate)­uranium­(IV) complex (L^Me)₂UCl₂ by reacting 2 equiv of K­[L^Me] with UCl₄ led instead to the interesting cationic diuranium complex [{(L^Me)­(Cl)­U}₂(μ-Cl)₃]­[Cl] (<b>14</b>). Complexes <b>7</b>–<b>14</b> have been characterized by a combination of ¹H and ¹³C­{¹H} NMR spectroscopy, elemental analysis, electrochemistry, and UV–visible–near-IR spectroscopy. Several complexes have also been characterized by X-ray crystallography, and a discussion of their structures is presented. NMR spectroscopy and the X-ray structures demonstrate that the β-diketiminate ligand is symmetrically bound to the actinide metal in the L^Me complexes and is asymmetrically bound to the actinide metal in the L^tBu complexes. In all cases the actinide­(IV) metal centers lie out of the plane of the β-diketiminate ligand NCCCN backbone by ∼1–2 Å. The electronic spectroscopy data on K­[L^Me], (L^Me)­ThI₃(THF) (<b>8</b>), and (L^Me)­UCl₃(THF) (<b>12</b>) suggest relatively weak metal–(β-diketiminate) ligand bonding interactions, although small perturbations in the characteristics of the β-diketiminate π–π* bands with changes in the the metal ion are consistent with some metal–ligand orbital interactions. This new class of mono­(β-diketiminate)­thorium and -uranium halide complexes promises to provide a robust platform for developing new chemistry of the actinides